Tag: XML

<== Lesson 5 || Overview || Lesson 7 ==>

This lesson takes advantage of the server script to select mountains based on their elevation.The script returns mountains that exceed an elevation value you provide as part of the URL request made to the web server.

This means you cannot use a static XML file for the UI and code that is added in this section. If you cannot provide a server, you could proceed by skipping this lesson and ignoring the code and UI added. But the code and UI will appear in all future lessons and may serve to confuse you. Best approach is to put the provided PHP script and data file in a folder on a web server and continue with these. These files are included as a part of all the lesson downloads since lesson 2.

The tasks in this lesson are more in adding the UI to provide the user with suitable information to understand what to do with very little screen space. This example choose to use a bit more screen space to help make the selection of an elevation more informative.

Source Download

1. Starting XCode 4 Project. This is the lesson 5 project completed.
2. PHP and CSV Files. Script to read data file and selects by elevation and returns XML. See Lesson 2.
3. Completed XCode 4 Project

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Step 1: MainViewController.h – Add the Slider and Slider Label

Download and uncompress the Starting XCode Project file and open in XCode.

Open the MainViewController.h in the project navigator window.

Lines 13 and 27 are the UILabel that will appear above the slider. The label shows the value in the slider. You will change the label as the slider is changed.

Lines 14 and 28 are the UISlider.

Line 39 is a IBAction method you link up in the UI to receive messages when the slider is changed.

Remember to change line 4 to include your url.

//
//
//
#define kTextURL    @"http://YOUR_DOMAIN/PATH_IF_ANY_TO_SCRIPT/PHP_SCRIPT_OR_XML_FILE"

#import <UIKit/UIKit.h>

@interface MainViewController : UIViewController <NSXMLParserDelegate, UITableViewDelegate, UITableViewDataSource>
{
    UIButton                *searchButton;
    UIActivityIndicatorView *activityIndicator;
    UITableView             *resultsTableView;
    UILabel                 *elevationLabel;
    UISlider                *elevationSlider;

    NSURLConnection         *urlConnection;
    NSMutableData           *receivedData;

    NSXMLParser             *xmlParser;

    NSMutableArray          *mountainData;

}
@property (nonatomic, retain) IBOutlet UIButton                 *searchButton;
@property (nonatomic, retain) IBOutlet UIActivityIndicatorView  *activityIndicator;
@property (nonatomic, retain) IBOutlet UITableView              *resultTableView;
@property (nonatomic, retain) IBOutlet UILabel                  *elevationLabel;
@property (nonatomic, retain) IBOutlet UISlider                 *elevationSlider;

@property (nonatomic, retain) NSURLConnection *urlConnection;
@property (nonatomic, retain) NSMutableData *receivedData;

@property (nonatomic, retain) NSXMLParser *xmlParser;

@property (nonatomic, retain) NSMutableArray *mountainData;

-(IBAction) startSearch:(id)sender;
- (void) setUIState:(int)uiState;
- (IBAction)sliderChanged:(id)sender;

-(NSString *) getCommaSeparatedFromStringContainingNumber:(NSString *)stringWithNumber;
@end

Step 2: MainViewController.m – Add the Slider, Slider Label and Change Navbar Title

Open the MainViewController.m file in the project explorer.
This step is pretty routine.
You need to add in the new UI variables shown on the highlighted lines 11, 12, 40, 41, 77 and 78. These include them in the class and also take care of memory management.
Line 66 is the NavigationBar title you can change.
//
//
//
#import "MainViewController.h"
#import "MountainItem.h"

@implementation MainViewController
@synthesize searchButton;
@synthesize activityIndicator;
@synthesize resultTableView;
@synthesize elevationLabel;
@synthesize elevationSlider;

@synthesize urlConnection;
@synthesize receivedData;

@synthesize xmlParser;

@synthesize mountainData;

// State is loading data. Used to set view.
static const int LOADING_STATE = 1;
// State is active. Used to set view.
static const int ACTIVE_STATE = 0;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)dealloc
{
    [searchButton release];
    [activityIndicator release];
    [resultTableView release];
    [elevationLabel release];
    [elevationSlider release];
    [urlConnection release];
    [receivedData release];
    [xmlParser release];
    [mountainData release];
    [super dealloc];
}

- (void)didReceiveMemoryWarning
{
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    mountainData = [[NSMutableArray alloc] init];
    [mountainData retain];

    [self setTitle:@"USA Mountains Lesson 6"];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
    self.searchButton = nil;
    self.activityIndicator = nil;
    self.resultTableView = nil;
    self.elevationLabel = nil;
    self.elevationSlider = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

Step 3: MainViewController.m – Add the sliderChanged Method.
Add all the code below in the UI Interface section just before the -(IBAction) startSearch:(id)sender method.
When the user changes the slider, you are updating a label that shows the slider value with a comma separated number. For example Elevation 10,000 feet.
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You can see at the end of line 91 the NSNumber value property provided by the UISlider: elevationSlider.value. Lines 89 to 91 converting that to a NSString formatted with commas to create NSString *formattedNumberString.
Line 92 assembles NSString *formattedNumberString with the words Elevation and feet and updates the UILabel elevationLabel text property.
You end with the cleanup of the NSNumberFormatter used in the process.
#pragma mark - UI Interface
- (IBAction)sliderChanged:(id)sender
{
    NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
    [numberFormatter setPositiveFormat:@"###,##0"];
    NSString *formattedNumberString = [numberFormatter stringFromNumber:[NSNumber numberWithFloat:elevationSlider.value]];
    elevationLabel.text = [[NSString alloc] initWithFormat:@"Elevation %@ feet",formattedNumberString];
    [numberFormatter release];
}

Step 4: MainViewController.m – Modify the URL to Send the Elevation
You need to add a URL query for example: ?elevation_min=10000. This is needed for the PHP script. You do not need to know how to program PHP but it is included here for reference with a few key lines highlighted to illustrate.
<?php
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT" );
header("Last-Modified: " . gmdate( "D, d M Y H:i:s" ) . "GMT" );
header("Cache-Control: no-cache, must-revalidate" );
header("Pragma: no-cache" );
header("Content-Type: text/xml; charset=utf-8");
// XML to return.
$xml = '';
// Counter for number of mountains returned.
$mountain_count = 0;
// Filter mountains equal to or above this value.
$elevation_min = 12000;
// Check for elevation parameter as a integer.
if ($_REQUEST['elevation_min'] && intval($_REQUEST['elevation_min']))
{
	$elevation_min = intval( $_REQUEST['elevation_min']);
}
// Each element contains data for one mountain.
$mountains = array();
// Read a CVS file containing mountain data.
$mountain_data_lines = file('mountain_data.csv');
// Each line read .
foreach($mountain_data_lines as $line)
{
	// Strip newline at end of line and break line by comma delimiter and
	// append to $mountains.
	$mountains[] = explode( ',', rtrim($line));
}
// Each mountain.
foreach ($mountains as $value)
{
	// Mountain elevation equals or exceeds the filter value.
	if ( intval($value[1]) >= $elevation_min  )
	{
		$mountain_count++;
		// Create the mountain_item node.
		$xml .= '<mountain_item ';
		$xml .= 'id = "' . $mountain_count . '" ';
		$xml .= 'name = "' . $value[0] . '" ';
		$xml .= 'elevation = "' . $value[1] . '" ';
		$xml .= 'lat = "' . $value[2] . '" ';
		$xml .= 'lon = "' . $value[3] . '" ';
		$xml .= '/>';

	}
}
// Add mountains close node.
$xml .= '</mountains>';
// Create mountains open node.
$xml_mountains = '<mountains ';
$xml_mountains .= 'source = "http://en.wikipedia.org/wiki/Table_of_the_highest_major_summits_of_the_United_States" ' ;
$xml_mountains .= 'elevation_min = "' . $elevation_min . '" ';
$xml_mountains .= 'count = "' . $mountain_count . '" ';
$xml_mountains .= '>';
// Add mountains open node.
$xml = $xml_mountains . $xml;
// Return xml
echo $xml;
?>

The PHP script provided looks for the elevation_min parameter on lines 14 and 16, absorbs it to the $elevation_min variable and uses $elevation_min on line 33 to filter the returned mountains that have an elevation at or above that value.
A slight modification to the MainViewController.m startSearch method will send the elevation_min parameter to the PHP script.
Line 102 is added to take the slider value and convert to a number.
The single line of code shown on 104 and 105 adds the URL query needed by the PHP script.
-(IBAction) startSearch:(id)sender
{
    //NSLog(@"startSearch");

     // Change UI to loading state
    [self setUIState:LOADING_STATE];
    // Convert the NSSlider elevationValue_ui value to a string
    NSString *elevation = [[NSString alloc ] initWithFormat:@"%.0f", elevationSlider.value];
    // Create the URL which would be http://YOUR_DOMAIN_NAME/PATH_IF_ANY_TO/get_usa_mountain_data.php?elevation=12000
    NSString *urlAsString = [NSString stringWithFormat:
                             @"%@%s%@", kTextURL , "?elevation_min=", elevation];

    //NSLog(@"urlAsString: %@",urlAsString );
    NSURLRequest *req = [[NSURLRequest alloc] initWithURL:[NSURL URLWithString:urlAsString]];
    // Create the NSURLConnection con object with the NSURLRequest req object
    // and make this MountainsEx01ViewController the delegate.
    urlConnection = [[NSURLConnection alloc] initWithRequest:req delegate:self];
    // Connection successful
    if (urlConnection) {
        NSMutableData *data = [[NSMutableData alloc] init];
        self.receivedData=data;
        [data release];
    }
    // Bad news, connection failed.
    else
    {
        UIAlertView *alert = [
                              [UIAlertView alloc]
                              initWithTitle:NSLocalizedString(@"Error", @"Error")
                              message:NSLocalizedString(@"Error connecting to remote server", @"Error connecting to remote server")
                              delegate:self
                              cancelButtonTitle:NSLocalizedString(@"Bummer", @"Bummer")
                              otherButtonTitles:nil
                              ];
        [alert show];
        [alert release];
    }
    [req release];
    [elevation release];
}

The remainder of the code is unchanged and is included here for reference:
-(void) setUIState:(int)uiState;
{
    // Set view state to animating.
    if (uiState == LOADING_STATE)
    {
        searchButton.enabled = false;
        searchButton.alpha = 0.5f;
        [activityIndicator startAnimating];

    }
    // Set view state to not animating.
    else if (uiState == ACTIVE_STATE)
    {
        searchButton.enabled = true;
        searchButton.alpha = 1.0f;
        [activityIndicator stopAnimating];
    }
}

#pragma mark - NSURLConnection Callbacks
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [receivedData setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [receivedData appendData:data];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    [connection release];
    self.receivedData = nil; 

    UIAlertView *alert = [[UIAlertView alloc]
                          initWithTitle:@"Error"
                          message:[NSString stringWithFormat:@"Connection failed! Error - %@ (URL: %@)", [error localizedDescription],[[error userInfo] objectForKey:NSURLErrorFailingURLStringErrorKey]]
                          delegate:self
                          cancelButtonTitle:@"Bummer"
                          otherButtonTitles:nil];
    [alert show];
    [alert release];
    // Change UI to active state
    [self setUIState:ACTIVE_STATE];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    [mountainData removeAllObjects];
    // Convert receivedData to NSString.

    xmlParser = [[NSXMLParser alloc] initWithData:receivedData];
    [xmlParser setDelegate:self];
    [xmlParser parse];

    [self.resultTableView reloadData];

    // Connection resources release.
    [connection release];
    self.receivedData = nil;
    // Change UI to active state
    [self setUIState:ACTIVE_STATE];
}

#pragma mark - NSXMLParser Callbacks
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI
 qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict
{
    //Is a mountain_item node
    if ([elementName isEqualToString:@"mountain_item"])
    {
        MountainItem *mountainItem = [[MountainItem alloc] init];
        mountainItem.name = [attributeDict objectForKey:@"name"];
        mountainItem.elevation = [attributeDict objectForKey:@"elevation"];
        mountainItem.elevationAsString = [self getCommaSeparatedFromStringContainingNumber:[attributeDict objectForKey:@"elevation"]];
        mountainItem.latitude = [attributeDict objectForKey:@"lat"];
        mountainItem.longitude = [attributeDict objectForKey:@"lon"];

        [mountainData addObject:mountainItem];

        [mountainItem release];
        mountainItem = nil;

    }

}
#pragma mark - Table View Data Source Methods
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [self.mountainData count];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *SimpleTableIdentifier = @"SimpleTableIdentifier";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:
							 SimpleTableIdentifier];
    // UITableViewCell cell needs creating for this UITableView row.
    if (cell == nil)
    {
        cell = [[[UITableViewCell alloc]
				 initWithStyle:UITableViewCellStyleDefault
				 reuseIdentifier:SimpleTableIdentifier] autorelease];
    }
    NSUInteger row = [indexPath row];
    if ([mountainData count] - 1 >= row)
    {
        // Create a MountainItem object from the NSMutableArray mountainData
        MountainItem *mountainItemData = [mountainData objectAtIndex:row];
        // Compose a NSString to show UITableViewCell cell as Mountain Name - nn,nnnn
        NSString *rowText = [[NSString alloc ] initWithFormat:@"%@ - %@ feet",mountainItemData.name, mountainItemData.elevationAsString];
        // Set UITableViewCell cell
        cell.textLabel.text = rowText;
        cell.textLabel.font = [UIFont boldSystemFontOfSize:14];
        // Release alloc vars
        [rowText release];
    }
    return cell;
}
#pragma mark - Table Delegate Methods
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    //NSLog(@"%s", __FUNCTION__);

     NSUInteger row = [indexPath row];
     MountainItem *mountainItemData = [mountainData objectAtIndex:row];

     NSString *message = [[NSString alloc] initWithFormat:
                          @"Coordinates\nLatitude: %f\nLongitude: %f", [mountainItemData.latitude floatValue], [mountainItemData.longitude floatValue]];
     UIAlertView *alert = [[UIAlertView alloc]
         initWithTitle:mountainItemData.name
         message:message
         delegate:nil
         cancelButtonTitle:@"Close"
         otherButtonTitles:nil];
     [alert show];

     [message release];
     [alert release];
     [tableView deselectRowAtIndexPath:indexPath animated:YES];

}
#pragma mark - Utilities
-(NSString *) getCommaSeparatedFromStringContainingNumber:(NSString *)stringWithNumber
{
    // Convert the MountainItem.elevation as a NSString to a NSNumber
    NSNumberFormatter * elevationToNumber = [[NSNumberFormatter alloc] init];
    [elevationToNumber setNumberStyle:NSNumberFormatterDecimalStyle];
    NSString *elevation = stringWithNumber;
    NSNumber *myNumber = [elevationToNumber numberFromString:elevation];
    [elevationToNumber release];

    // Format elevation as a NSNumber to a comma separated NSString
    NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
    [numberFormatter setPositiveFormat:@"###,##0"];
    NSString *formattedNumberString = [numberFormatter stringFromNumber:myNumber];
    [numberFormatter release];
    return formattedNumberString;
}

@end

Step 5: MainViewController.xib – Add in the UISlider
Now you can move on to the UI. Refer to the screen shot at the top of the post to keep you on track with the goal of the changes.
Keep in mind, you can do this generally after you have the header definitions in place. You need those so that the Interface Builder part of XCode can display the names of methods and UI components you choose in code. These lessons choose to complete the implementation in the code before moving to UI just to keep the zig zag back and forth that XCode often creates for tutorials. As you get faster, you might want to do the UI right after you do the header files.
Drag a Slider from the Objects library in the bottom right to place it above the Search button.

Fine tune the position and size to match the tutorial:

Then you need to wire the MainViewController to the UISlider elevationSlider property defined in step 1 for the MainViewController header and you need to wire the UISlider valueChanged send event to the sliderChanged method you also defined in step 1.
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You can use the Properties Inspector to get this done. With the Slider you placed in the design window selected open the Property Inspector. Drag from the “Value Changed” Send Event to the File’s Owner and when you release you can select the sliderChanged in the popped menu above the File’s Owner.
Repeat for the “New Referencing Outlet” and when you release the mouse over the File’s Owner icon select elevationSlider.
Another process you see is to control drag from the Slider in the design window to the File’s Owner in the Related Files panel on left and release mouse. You should see sliderChanged appear in a small menu popped over the File’s Owner. Click and select. Then you can repeat the process in the opposite direction and when you release over the Slider, you should see elevationSlider as a menu choice in the popped menu above the Slider.
The end result is shown here:

There are some tweaks needed to make the slider provide the range of elevations and a starting elevation. The range is to match the data available and a starting value to avoid automatic downloads of all the data every time.
So modify the Slider’s Property Inspector as follows:

Step 6: MainViewController.xib – Add in the UILabel Displaying the Slider Value
Next is a Label above the Slider to show the value of the Slider when it changes.
Drag a Label from the Objects library in the bottom right to place it above the Slider.

Fine tune the position and size to match the tutorial:

Set the properties. Note the hard coded match up to display the starting value in the slider.

Finally you got to wire this label so you can update it in the code. In code you are using the elevationLabel property defined in step 1. Open the Connections Inspector with this Label selected. Drag the New Referencing Outlet to the File’s Owner and after you release the mouse select elevationLabel in the menu popped over the File’s Owner.
Here is the result:

Step 7: MainViewController.xib – Add the Minimum and Maximum Labels
This step you add a Label on the left and a Label on the right of the Slider to give the range of elevation values possible. These Labels are static and do not need to be wired to the code.
Drag a Label to the left side of the Slider in the design window:

Tweak size and position as follows:

The text property for this Label is 12,000 ft. You need to tweak the font size to make the text fit.
The properties as set:

Drag a Label to the right side of the Slider in the design window:

Tweak size and position as follows:

The text property for this Label is 12,000 ft. You need to tweak the font size to make the text fit.
The properties as set:

Now try it out in the Simulator.
<== Lesson 5 || Overview || Lesson 7 ==> 





		

<== Lesson 1 || Overview || Lesson 3 ==>

In this lesson you will make a requests for the Mountain data from a web site. The data is returned in an XML format. Then for testing you will display the raw XML on the phone screen and also display the XML data in the XCode console.

The main goal is to learn to use the NSURL, NSURLRequest, NSURLConnection and NSMutableData classes.

NSURL defines a URL for XCode. NSURLConnection establishes a connection to a server and manages the data to and from that server. NSURLRequest defines a network request along with data to send. NSMutableData stores any returning data.

When you load data from the web or any indeterminate process, you will want to include an activity indicator. So we will add a UIActivityIndicatorView that is the common activity indicator for Mac applications.

To see the data on the phone screen, we will use the UITextView which is a scrollable text component. In future lessons, we will replace the UITextView with a scrolling list of mountains in the XML data we receive.

You will need a web server to complete this and all future lessons in this tutorial. The tutorials use a web server with PHP that reads a comma delimited file containing the mountain data. The XML that the PHP script returns is included in this post should you not have PHP on your server. I will show you how to use that instead of the provided PHP script. However in future lessons we will want to ask the server for just partial data and we need a program to do that. Keep in mind you can also put the mountain data into a database on the server.

Source Download

1. Starting XCode Project. This is the lesson 1 project completed.
2. PHP and CSV Files. Script to read data file and selects by elevation and returns XML.
3. Mountain XML Data. Alternative to hosting PHP script.
4. Completed XCode 4 Project

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Step 1: MainViewController.h – Define properties and methods.

Download and uncompress the Starting XCode Project file and open in XCode.

Select the MainViewController.h in the project navigation window on the left and add the highlighted lines.

Line 4 is a constant for the URL to the PHP script or the XML file if you choose not to host the PHP script. More on these choices in this post when we get to those files.

The app will enable and disable the UIButton searchButton, so we need to include it for reference in code.

The UIActivityIndicatorView and UITextView are being added and are also referenced from our UI. The UIActivityIndicatorView will need to be hidden and revealed when we are not and are loading data from the server as well starting and ending its animation. So we need to make it an IBOutlet.

The UITextView will be updated with data coming in from the server and so it also needs to be an IBOutlet.

The MSMutableData is needed to capture the data coming in from the server in a raw format.

Your implementation code will call for disabling and enabling the search button and hiding and unhiding the activity indicator in more than one place in the code. Line 26 defines a method you will use so you do not have to repeat this UI state changing code in more than one place. The method receives an int parameter to define the state of the UI components. You will define their values in the implementation code.

//
//
//
#define kTextURL    @"http://YOUR_DOMAIN/PATH_IF_ANY_TO_SCRIPT/PHP_SCRIPT_OR_XML_FILE"

#import <uikit uikit.h=""></uikit>

@interface MainViewController : UIViewController
{
    UIButton                *searchButton;
    UIActivityIndicatorView *activityIndicator;
    UITextView              *resultsTextView;

    NSURLConnection         *urlConnection;
    NSMutableData           *receivedData;

}
@property (nonatomic, retain) IBOutlet UIButton                 *searchButton;
@property (nonatomic, retain) IBOutlet UIActivityIndicatorView  *activityIndicator;
@property (nonatomic, retain) IBOutlet UITextView               *resultsTextView;

@property (nonatomic, retain) NSURLConnection *urlConnection;
@property (nonatomic, retain) NSMutableData *receivedData;

-(IBAction) startSearch:(id)sender;
- (void) setUIState:(int)uiState;
@end

Step 2: MainViewController.m – Add Properties and Constants
This step basically is the implementation housekeeping prerequisites.
You add the getter and setters for the properties on lines 4 to 9 using synthesize.
Lines 12 and 14 provide constants for states of the view that are used in the setUIState method we defined in the last step. Those places in the code can make the code more readable when calling the setUIState.
#import "MainViewController.h"

@implementation MainViewController
@synthesize searchButton;
@synthesize activityIndicator;
@synthesize resultsTextView;

@synthesize urlConnection;
@synthesize receivedData;

// State is loading data. Used to set view.
static const int LOADING_STATE = 1;
// State is active. Used to set view.
static const int ACTIVE_STATE = 0;


Step 3: MainViewController.m – Memory Management Housekeeping
Add the memory release for the searchButton, activityIndicator, activityIndicator, resultsTextView, urlConnection and receivedData in the dealloc method.

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)dealloc
{
    [searchButton release];
    [activityIndicator release];
    [resultsTextView release];
    [urlConnection release];
    [receivedData release];
    [super dealloc];
}

- (void)didReceiveMemoryWarning
{
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}


Step 4: MainViewController.m – Navigation Top Bar Title Updated
On line 47 you might want to update the title so you are not confused when viewing the app.
#pragma mark - View lifecycle

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    [self setTitle:@"USA Mountains Lesson 2"];
}

Step 5: MainViewController.m – More Memory Management
In the viewDidUnload method add these lines to release the subviews you are going to link to this view in the UI.
- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
    self.searchButton = nil;
    self.activityIndicator = nil;
    self.resultsTextView = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}


Step 6: MainViewController.m – Update the startSearch Method to Fetch Server Data
The startSearch method is already linked to our searchButton from the last tutorial. You have the code below to get the UI in the state for loading in progress, to make a request to the data source on the server and take needed steps based on the success or failure of that connection.
Line 69 is calling a method you will add in the next step to set the UI state. Your constant LOADING_STATE was defined in the last step.
Line 71 creates a NSString for the URL. In a future lesson you are going to concatenate a parameter to send along with the URL and now this line is ready for that.
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The NSURLRequest object named req is created on line 74.
The instance object named urlConnection on line 77 is your NSURLConnection. It does all the work for communicating with the server.
You see on line 77 it is using our NSURLRequest req object and also sending the delegate message to make this class, self, its delegate. That means urlConnection can call NSURLConnection methods you add to this class to take action needed to handle notifications such as successful completion or failure.
For this lesson you need to add four methods to handle the NSURLConnection messages didReceiveResponse, didReceiveData, didFailWithError and connectionDidFinishLoading. You will do that just after creating our setUIState method.
Lines 79 to 83 handle a successful connection. A NSMutableData object is created and assigned to the class receivedData NSMutableData object that in later code you will convert to readable XML for display.
Should the connection fail, lines 85 to 97 display a UIAlertView with the error information. Generally you will want to change that to something more meaningful to the user.
#pragma mark - UI Interface
-(IBAction) startSearch:(id)sender
{
    NSLog(@"startSearch");
     // Change UI to loading state
    [self setUIState:LOADING_STATE];
    // Create the URL which would be http://YOUR_DOMAIN_NAME/PATH_IF_ANY_TO/get_usa_mountain_data.php?elevation=12000
    NSString *urlAsString = [NSString stringWithFormat:@"%@", kTextURL ];

    NSLog(@"urlAsString: %@",urlAsString );
    NSURLRequest *req = [[NSURLRequest alloc] initWithURL:[NSURL URLWithString:urlAsString]];
    // Create the NSURLConnection con object with the NSURLRequest req object
    // and make this MountainsEx01ViewController the delegate.
    urlConnection = [[NSURLConnection alloc] initWithRequest:req delegate:self];
    // Connection successful
    if (urlConnection) {
        NSMutableData *data = [[NSMutableData alloc] init];
        self.receivedData=data;
        [data release];
    }
    // Bad news, connection failed.
    else
    {
        UIAlertView *alert = [
                              [UIAlertView alloc]
                              initWithTitle:NSLocalizedString(@"Error", @"Error")
                              message:NSLocalizedString(@"Error connecting to remote server", @"Error connecting to remote server")
                              delegate:self
                              cancelButtonTitle:NSLocalizedString(@"Bummer", @"Bummer")
                              otherButtonTitles:nil
                              ];
        [alert show];
        [alert release];
    }
    [req release];

}


Step 7: MainViewController.m – Create the UI State Setting Method setUIState
This is your custom method to set the states of the UI components.
The UIButton has an alpha and enabled property. For your UIButton searchButtonobject, the alpha value is toggled between 50% and 100% and its enabled state is also toggled between true and false.
The UIActivityIndicatorView has methods on lines 108 and 116 for starting and stopping their animation. There is also a property hidesWhenStopped that you will set in the UI design that handles the hiding and showing of our UIActivityIndicator.
-(void) setUIState:(int)uiState;
{
    // Set view state to animating.
    if (uiState == LOADING_STATE)
    {
        searchButton.enabled = false;
        searchButton.alpha = 0.5f;
        [activityIndicator startAnimating];

    }
    // Set view state to not animating.
    else if (uiState == ACTIVE_STATE)
    {
        searchButton.enabled = true;
        searchButton.alpha = 1.0f;
        [activityIndicator stopAnimating];
    }
}

Step 8: MainViewController.m – Clear Received Data When Connection Is Established
You learned about pragma marks in the last lesson. You have 4 NSURLConnection related methods to add and this mark on line 119 is an easy way in XCode to get to where you are placing them in the code.
The connection didReceiveResponse method occurs when a connection is established. When that happens, your data communication starts over. To be on the safe side of it occurring more than once, you clear the NSMutableData object from any previous incomplete attempts. Consider this a boilerplate block you always include in code.
#pragma mark - NSURLConnection Callbacks
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [receivedData setLength:0];
}

Step 9: MainViewController.m – Accumulate Data Being Received
The NSURLConnection calls the connection didReceiveData method as data arrives and is ready for use. This is called as often as needed depending on the amount of data. The code you need here is to append the data received to your NSMutableData object.
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [receivedData appendData:data];
}

Step 10: MainViewController.m – Handle Network Connection Failure
The connection didFailWithError NSURLConnection call back method is where you handled the failure of the data transmission. In your case the code displays a UIAlertView with information from the NSError class error object passed in for learning purposes. A better user error should be considered for a released app.
You can use the NSError class to take different action based on the type of error. This is over the scope of this tutorial.
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There is some housekeeping such as calling the connection object release method and terminating the NSMutableData receivedData property.
The last line of code calls the sertUIState method with the ACTIVE_STATE value so the UI again appears available for another search.
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    [connection release];
    self.receivedData = nil; 

    UIAlertView *alert = [[UIAlertView alloc]
                          initWithTitle:@"Error"
                          message:[NSString stringWithFormat:@"Connection failed! Error - %@ (URL: %@)", [error localizedDescription],[[error userInfo] objectForKey:NSURLErrorFailingURLStringErrorKey]]
                          delegate:self
                          cancelButtonTitle:@"Bummer"
                          otherButtonTitles:nil];
    [alert show];
    [alert release];
    // Change UI to active state
    [self setUIState:ACTIVE_STATE];
}


Step 11: MainViewController.m – Handle Network Connection Successful Completion
This final method is called when all the data is successfully loaded. The NSMutableData receivedData object is converted to a NSString on line 147.
On line 151 the UITextView text property resultsTextView is set to the data as a NSString. One the previous line the same is displayed in the XCode console window.
After that the NSURLConnection connection variable is released and the receivedData NSMutable object is truncated.
Your last line has the same task of setting the UI back to a state that the user can search again.
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    // Convert receivedData to NSString.
    NSString *receivedDataAsString = [[NSString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding];

    // Trace receivedData
    NSLog(@"%s - %@", __FUNCTION__, receivedDataAsString);
    resultsTextView.text = receivedDataAsString;
    [receivedDataAsString release];

    // Connection resources release.
    [connection release];
    self.receivedData = nil;
    // Change UI to active state
    [self setUIState:ACTIVE_STATE];
}

Step 12: MainViewController.xib – Add the Activity Indicator
Open the MainViewController.xib in the Project navigator and drag an Activity Indicator from the Objects library in the bottom right to place it under the button with the Search label.

Be sure you keep the Activity Indicator you placed selected while completing the next three tasks.
Select the size panel in the top right and set the x and y values as shown here.

Select the Properties inspector and set the style to Large White and check the Behavior Hides When Stopped.

In the Connections Inspector panel drag from the “New Referencing Outlet” in the “Referencing Outlets” group to the File Owner’s icon and release the mouse. Then select activityIndicator. You defined activityIndicator in your MainViewController code as a UIActivityIndicatorView.
Here is how the Connections Inspector will look when you are done.

Step 13: MainViewController.xib – Add the TextView
You are adding a TextView that in a future tutorial you replace with a TableView. So there is no need to get heavily invested in how it looks.
Now drag a TextView from the Objects library in the bottom right to place it under the button with the Activity Indicator.

Keep the TextView you placed selected while completing the next two tasks.
Select the size panel in the top right and set the X, Y, Width and Height values as shown here.

In the Connections Inspector panel drag from the “New Referencing Outlet” in the “Referencing Outlets” group to the File Owner’s icon and release the mouse. Then select resultsTextView defined activityIndicator in your MainViewController code as a UITextView.
Your Connections Inspector should appear as follows.

Step 14: MainViewController.xib – Review the Changes
First you can check the layout looking as follows.

If you select the Connections inspector and then the File Owner’s icon you should see the following. If so you are good to go.

Step 15: PHP Server Script or XML File
This IPhone app loads XML data from a server. The Source Download includes an XML file you can use for this lesson.
However, the longer term of the Tutorial will request a query of the data from the server and at that point you can use the PHP script provided. I suggest you use that with this lesson so you are set up. But if you do not have a PHP script enabled server, you can use the XML file for a few more lessons.
Detailing how the PHP script works is beyond the scope of this tutorial. However what you should know it reads a CSV file. Here is a snippet of the file. The name used in the PHP script is mountain_data.csv.
Mount McKinley,20320, 63.0690,-151.00063
Mount Saint Elias,18008,60.2927,-140.9307
Mount Foraker,17400,62.9605,-151.3992

Then the PHP script returns XML. This is a snippet of what the XML data looks like when returned.
<!--?xml version="1.0" encoding="UTF-8"?-->
<mountains source="http://en.wikipedia.org/wiki/Table_of_the_highest_major_summits_of_the_United_States" elevation_min="12000" count="100">
  <mountain_item id="1" name="Mount McKinley" elevation="20320" lat=" 63.0690" lon="-151.00063">
  <mountain_item id="2" name="Mount Saint Elias" elevation="18008" lat="60.2927" lon="-140.9307">
  <mountain_item id="3" name="Mount Foraker" elevation="17400" lat="62.9605" lon="-151.3992">
</mountain_item></mountain_item></mountain_item></mountains>

This XML you will learn to parse in a future tutorial.
This is the PHP script. The name I used for the script was get_mountain_data.php. You can name it what you like.
<!--?php
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT" );
header("Last-Modified: " . gmdate( "D, d M Y H:i:s" ) . "GMT" );
header("Cache-Control: no-cache, must-revalidate" );
header("Pragma: no-cache" );
header("Content-Type: text/xml; charset=utf-8");
// XML to return.
$xml = '';
// Counter for number of mountains returned.
$mountain_count = 0;
// Filter mountains equal to or above this value. 
$elevation_min = 12000;
// Check for elevation parameter as a integer.
if ($_REQUEST['elevation_min'] && intval($_REQUEST['elevation_min']))
{
	$elevation_min = intval( $_REQUEST['elevation_min']);
}
// Each element contains data for one mountain.
$mountains = array();
// Read a CVS file containing mountain data.
$mountain_data_lines = file('mountain_data.csv');
// Each line read .
foreach($mountain_data_lines as $line) 
{
	// Strip newline at end of line and break line by comma delimiter and 
	// append to $mountains.
	$mountains[] = explode( ',', rtrim($line));
}
// Each mountain.
foreach ($mountains as $value)
{
	// Mountain elevation equals or exceeds the filter value.
	if ( intval($value[1]) -->= $elevation_min  )
	{
		$mountain_count++;
		// Create the mountain_item node.
		$xml .= '<mountain_item ';="" $xml="" .="id = "" $mountain_count="" '"="" $value[0]="" $value[1]="" $value[2]="" $value[3]="" ;<="" p="">
</mountain_item>

	}
}
// Add mountains close node.
$xml .= '';
// Create mountains open node.
$xml_mountains = '<mountains ';="" $xml_mountains="" .="source = "http://en.wikipedia.org/wiki/Table_of_the_highest_major_summits_of_the_United_States" " ;="" $elevation_min="" '"="" $mountain_count="" ;<br="">
// Add mountains open node.
$xml = $xml_mountains . $xml;
// Return xml
echo $xml;
?>

<== Lesson 1 || Overview || Lesson 3 ==>