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If you are here I am guessing that you are interested in iPhone/iTouch development and are looking for a place to start. Due to Apple’s NDA on the iPhone SDK there really isn’t much information out there on getting started with iPhone development, by writing this tutorial I hope to give people the confidence to get started developing on the iPhone and also to help myself get my head around it.
Lets get started

1. Getting your development environment setup

You will need a copy of the iPhone SDK (available for free at http://developer.apple.com/iphone). Once you have downloaded the installer (it is pretty big, 1GB+) you will need to let it run and to install all the required components.

By default the installer doesn’t add any icons to anywhere so you will have to navigate to /Developer/Applications to find the tools that you will need, I suggest that you drag XCode and Interface Builder to your dock as you will be using them alot!

Fire up XCode to make sure that it launches OK, if so then you are ready to get into it!

2. Getting the TouchXML Libraries

As you cannot use the standard NSXML* libraries for iPhone development (they will work in the simulator but not when you try to deploy the app to the real hardware, I found out the hard way after working on an app for days!) we will be using the TouchXML library from TouchCode

You will need to check the latest code out from the TouchXML SVN Repository, if you dont know how to use SVN I have included the required commands below.

Launch a new Terminal window
Create a new folder called “ExtraLibraries” where you would like to keep your iPhone development libraries (I save mine in /Developer/ExtraLibraries/)

mkdir /Developer/ExtraLibraries

Change into the new folder

cd /Developer/ExtraLibraries

Run the SVN checkout code

svn checkout http://touchcode.googlecode.com/svn/trunk/ touchcode-read-only

You will see the filenames scrolling up the screen and it should only take around 30 seconds to grab all the required files.

Now you have the TouchXML libraries on your local machine ready to start creating your first iPhone app.

3. Setting up your New Project

Now its time to get into the hands on development, start up XCode if you haven’t already and click File > New Project and you will see the window below.

Double click on “Navigation-Based Application”, enter name your project “AdvancedBlogTutorial” and click Save.

You should see the following screen appear with all of your project files.

You can lay this screen out any way you wish but my favourite is to make the screen as large as possible and to drag the horizontal resizer all the way to the top to allow for the largest possible “code view” area as possible, like below.

4. Including TouchXML in our project

As we are using TouchXML for our xml parsing, we will need to import the required files and also edit some of the project settings.

In the menu bar click Project > Edit Project Settings and a new window will appear with 4 tabs at the top (General, Build, Configurations and Comments). We are only interested in the “Build” tab at the moment, so go ahead and click the “Build” Tab and the following window will appear.

The settings that we are interested in are “Header Search Paths” and “Other Linker Flags”, you can easily find these by typing the beginning of the name into the “Quick Find” at the top right of the window.

You need to add “/usr/include/libxml2″ to the “Header Search Paths” and you need to add “-lxml2″ to the “Other Linker Flags”.

Once you have done this you can close the settings window and you will be back at your project window.

Now that the libxml2 libraries have been included you will need to import the TouchXML files to your project, to do this simply right click on the “Classes” folder in the left hand pane and click Add > Existing Files…

You will be presented with a finder window and you will need to navigate to the location that you checked the TouchXML files out to (in my case it was /Developer/ExtraLibraries/) and then keep going to the following path “touchcode-read-only/TouchXML/Common/Source/” and select all the files and click “Add”. You will be presented with the following screen:

Leave everything as default and click “Add” .

You should now see the CXML* files in your left hand pane and they are now available for your application to use.

We are now finally setup and ready to get going.

5. Setting up our Variables, Outlets and Classes

As we used the “Navigation-Based Application” template, much of our layout and code structure has already been created for us. We could have started this from scratch but for simplicity sake it is much easy to use one of the default templates.

Open up the “RootViewController.h” file by expanding the “Classes” folder in the left hand pane and clicking once on “RootViewController.h”, you should see the contents of the right hand pane change to that of the file you selected.

By default you will see

//
//  RootViewController.h
//  AdvancedBlogTutorial
//
//  Created by dBlog on 15/09/08.
//  Copyright __MyCompanyName__ 2008. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface RootViewController : UITableViewController {

}

@end

Change the code to the following

#import <UIKit/UIKit.h>
#import "TouchXML.h"

@interface RootViewController : UITableViewController {
    // This is the outlet for the blog view, it will allow the data from the controller to be used in a view
    IBOutlet UITableView *blogTable;

    // blogEntries is used to store the data retrieved from the RSS feed before being added to the view
    NSMutableArray *blogEntries;

    // loadSwirlie will display a loading overlay while the data is downloaded from the RSS feed.
    UIActivityIndicatorView *loadSwirlie;
}
@end

The first line, “#import “TouchXML.h”", will import the TouchXML library for us to use in this Controller, it is very important because if we do not include it here we will not be able to access any of the TouchXML features.

The second line, “IBOutlet UITableView *blogTable;”, will allow our view to access data from the controller, this will be where we add the individual blog entries.

The third line, “NSMutableArray *blogEntries;”, creates a new Mutable Array called blogEntries that will be where we store the RSS feed items.

Finally the forth line “UIActivityIndicatorView *loadSwirlie;”, is a view that will overlay the default “Load Swirlie” while the RSS feed is being downloaded, this is especially helpful when accessing via EDGE or when trying to read large feeds.

Save the file.

6. Digging into the core code!

Now that we have the headers all setup and our TouchXML libraries included we are ready to start on the real workhorse of the application, the RSS reader!

Open up the “RootViewController.m” file the same way that you did in the previous step.

You will see alot more code in this file as when the project was created from the template it also created most of the basic code, we will be using some of the auto-generated code and also adding some of our own.

The first thing that we want to do is to make our RSS grabbing function, to do this just paste the following code below the “@implementation RootViewController” line.

// grabRSSFeed function that takes a string (blogAddress) as a parameter and
// fills the global blogEntries with the entries
-(void) grabRSSFeed:(NSString *)blogAddress {

    // Initialize the blogEntries MutableArray that we declared in the header
    blogEntries = [[NSMutableArray alloc] init];	

    // Convert the supplied URL string into a usable URL object
    NSURL *url = [NSURL URLWithString: blogAddress];

    // Create a new rssParser object based on the TouchXML "CXMLDocument" class, this is the
    // object that actually grabs and processes the RSS data
    CXMLDocument *rssParser = [[[CXMLDocument alloc] initWithContentsOfURL:url options:0 error:nil] autorelease];

    // Create a new Array object to be used with the looping of the results from the rssParser
    NSArray *resultNodes = NULL;

    // Set the resultNodes Array to contain an object for every instance of an  node in our RSS feed
    resultNodes = [rssParser nodesForXPath:@"//item" error:nil];

    // Loop through the resultNodes to access each items actual data
    for (CXMLElement *resultElement in resultNodes) {

        // Create a temporary MutableDictionary to store the items fields in, which will eventually end up in blogEntries
        NSMutableDictionary *blogItem = [[NSMutableDictionary alloc] init];

        // Create a counter variable as type "int"
        int counter;

        // Loop through the children of the current  node
        for(counter = 0; counter < [resultElement childCount]; counter++) {

            // Add each field to the blogItem Dictionary with the node name as key and node value as the value
            [blogItem setObject:[[resultElement childAtIndex:counter] stringValue] forKey:[[resultElement childAtIndex:counter] name]];
        }

        // Add the blogItem to the global blogEntries Array so that the view can access it.
        [blogEntries addObject:[blogItem copy]];
    }
}

Now I know that probably looks quite confusing but I have tried to add detailed commenting to allow you to follow what It does. Basically it sends a request to the address that you specify and pulls back the response into the rssParser object. Once this is done it loops through the <item< nodes and adds it, along with its children to the global blogEntries Array.

Now that we have a function that will request, read and process a RSS feed into an Array we have to actually call it from somewhere.

Enter “viewDidAppear”!

This function will already be in your file as the template would have created it, but it will be commented out. Remove the comment tags and edit the code to look like the following:

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    // Check if blogEntries has already been filled, if not
    // then send the request
    if([blogEntries count] == 0) {
        // Create the feed string, in this case I have used dBlog
        NSString *blogAddress = @"http://dblog.com.au/feed/";

        // Call the grabRSSFeed function with the above
        // string as a parameter
        [self grabRSSFeed:blogAddress];

        // Call the reloadData function on the blogTable, this
        // will cause it to refresh itself with our new data
        [blogTable reloadData];
    }
}

The above code simply checks to see if the item count in blogEntries is zero, if true then it will call the grabRSSFeed function with the supplied URL and then reload the Table Outlet with the new data. You can change the URL to any valid RSS feed and it will work.

We are getting extremely close to a working application now, just a couple more small changes and we are up and running!

Ones of these is the “numberOfRowsInSection” function, if you have a look in your file you will see it up near the top and it will be returning a static value of zero. What this means is, is that every time the table is reloaded it calls this function to see how many cells it needs to draw. Currently this will always return zero and therefore it will never actually draw anything

What you need to do is to make it so when this function is called it returns the count of items in the blogEntries Array, this is very easy to do. Just change the “return 0;” line to the following:

return [blogEntries count];

Now whenever this function is called it will return the correct number of entries, that was easy wasn’t it?

Our final code change will actually generate the cells for the table view, we are just doing a simple cell that shows the title text, but this can be anything including icons, fonts, styles, etc.

Find the “cellForRowAtIndexPath” function in your file, then inside that function find “// Set up the cell” and enter the following code under it.

int blogEntryIndex = [indexPath indexAtPosition: [indexPath length] -1];
[cell setText:[[blogEntries objectAtIndex: blogEntryIndex] objectForKey: @"title"]];

What the above code does is it grabs the index of the item that is being generated and then calls the setText function on the cell with the “title” value of the corresponding entry in blogEntries. You could easily change this to “link”, “pubDate” or any other child node of the node.

Guess what? Its now time to run your application!

7. Running the code for the first time

Make sure that everything is saved and then click Build > Build and Go (Run), you can also press Command + Enter to do the same thing.

You should see the iPhone simulator appear and your application will start up, you should see…nothing!

What? You mean I spent all that time for an application that doesn’t even do anything?

No, no, no, It does do everything that you told it to..BUT, we forgot to link the table display to the blogTable Outlet..doh!

8. Linking the Table in the View to the blogTable Outlet

Double click on the “RootViewController.xib” file in the resources folder in the left hand pane, the “Interface Builder” application will launch with your RootViewController interface in it. You should see something similar to the image below:

Now in the Main window you will see three icons, the “File’s Owner”, “First Responser” and “Table View”. What we need to do is to Control click and drag from the “File’s Owner” to the “Table View” icons, you will see a blue bar appear as you drag and when you let go over the “Table View” icon a little grey window will appear, see below:

You will need to select “blogTable” as that is the Outlet we created in our header file. Once you are done you can save the interface and click “Interface Builder”.

9. The Moment of Truth

If you try to Build and Run your application now you should get some results in the screen, for my blog it looked like the following:

10. Project Files

Here are the source files for this project: Download the project source files

11. What’s Next?

Well currently you can’t really do much with the application apart from read the headers, I intend to create a series of tutorials outlining how to actually read the rest of the feeds on your phone, how to add multiple feeds and even how to add some simple animation to spruce things up. I will also be taking a look at memory management too as this tutorial hasn’t looked into this at all.

This all depends on time and also on how well this first tutorial goes. But hopefully there will be many more to come.

I hope that you all have a better idea of how to work with the iPhone SDK and also how to get the TouchXML library up and running (it took me a fair while to get my head around it!).

If you have any questions or if you find any bugs please let me know!

Until next time, bye bye!

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