You can download older versions of Xcode by logging into Apple Developer Connection – Downloads and ADC Program Assests (http://connect.apple.com) – You will need to be a member of the developer program to login.

Once on the site, from the Downloads section, choose Developer Tools – you will be shown with a list of all Xcode versions, back to 1.0 released in October of 2004.

Install Multiple Versions of Xcode

To keep from overwriting an existing installation, you can specify the path for Xcode during the install process. For example, the default location is /Developer, to install an older version you could instruct Xcode to install into a simliar name such as /Developer-3.1

To change the install path, click on the Location header in the install dialog:

Choose a new path for the Essentials Package:

Base SDK

The Base SDK is the version of SDK that will be used when compiling your application – the compiler will use the headers and libraries of this specific SDK. For example, in the image below notice that there are only two choices for the Base SDK for both the device and simulator, versions 3.2 and 4.0.

However, we have an issue here, if you build an application with the latest SDK and deploy on a device with an earlier OS, chances are your application will crash if you reference any code in a 4.x API while running the application on a 3.x device. Also, the 3.2 SDK is for the iPad only, so this isn’t an option when deploying to an iPhone or iPod touch.

iPhone OS Deployment Target

To specify which OS version is the minimum that your application will support, you set the deployment target. Your application will then run on this minimum OS as well as all later versions.

This is all well and good, however, the obvious question is how to deploy on an earlier OS version yet take advantage of features for those devices that are running a later OS?

Check for Feature Availability Not OS Version

When targeting an earlier OS as mentioned above, yet you want to take advantage of features of a later OS for devices that support it, you can use the method respondsToSelector to check if the receiver implements or inherits a method that can respond to a specified message. This approach follows Apple’s recommendation to check for availability of features versus a specific OS version.

In the example below the code will check if the object returned by [UIDevice currentDevice] will respond to the selector shown, if so, you can write relevant multi-tasking code:

if ([[UIDevice currentDevice] respondsToSelector:@selector(isMultitaskingSupported)])
{
  // Multi-tasking code for supported devices
}
else
{
  // Devices without multi-tasking support
}

Another time when that you may choose to use respondsToSelector is for cases when the implementation of the same API has changed with a later OS version. I ran into this particular case when writing code for displaying movies using the MPMoviePlayerController. In the 4.x SDK the notifications have changed slightly – in 2.0 to 3.1 MPMoviePlayerContentPreloadDidFinishNotification was the notification you would use to receive notice that a movie was ready to play. With 3.2 (iPad) and later, MPMoviePlayerContentPreloadDidFinishNotification has been deprecated and MPMoviePlayerLoadStateDidChangeNotification has taken its place.

The code example below shows how you may go about using respondsToSelector to figure out which notification you should request based on the whether or not the movie player can return information about its load state:

MPMoviePlayerController *mp = 
   [[MPMoviePlayerController alloc] initWithContentURL:movieURL];
 
// This method is available on 3.2 and greater...
 if ([mp respondsToSelector:@selector(loadState)]) 
{
  // Register to receive notification when load state changed
  // (check for playable, stalled...)
  [[NSNotificationCenter defaultCenter] addObserver:self 
                       selector:@selector(moviePlayerLoadStateChanged:) 
                       name:MPMoviePlayerLoadStateDidChangeNotification 
                       object:nil];
 
}
else
{
  // Register to receive a notification when the movie is ready to play.
  [[NSNotificationCenter defaultCenter] addObserver:self 
                         selector:@selector(moviePreloadDidFinish:) 
                         name:MPMoviePlayerContentPreloadDidFinishNotification 
                         object:nil];
 
}

Check for Function Availability

Beyond working with objects, if you need to check for the availability of a specific function, you do so by comparing the function to NULL. In the example below I check for a function related to creating a PDF-based graphics context (available in 3.2 and later).

if (UIGraphicsBeginPDFContextToFile != NULL)
{
  // The function is available
}

Testing Across OS Versions

Unfortunately, with the upgrade to the latest Xcode (3.2.3) there are no simulators for 3.1.x and earlier OS versions. Although it has always been recommended to test your apps on device, at this point it becomes a necessity.

Renaming an Xcode Project

First, click on the Project menu and select Rename:

From there, fill in the new name, I’d also recommend creating a snapshot as a precaution:

Renaming an Xcode project is no longer a mysterious, troublesome endeavor.

Copyright (c) 2010 MyCompanyName. All rights reserved.

Up until Xcode 3.2 to change this value you had to resort to running a command from a terminal, you can see how this was previously done in this tip: Change Company Name in Xcode.

A welcome change with 3.2+ is that this value can now be managed from within Xcode. Even better, the name can be configured on a project by project basis, which is really nice if you need to maintain multiple copyright statements across projects.

Change Company Name within Xcode

In the Groups and Files window, right click on the project name and select Get Info:

In the General Settings tab, near the bottom you’ll see a field for the Organization Name:

Update this field and the new value will be reflected in each source code file you create in the active project.

You may not always prefer this default action – for example, if a JavaScript file is imported, Xcode does not know what to do with this file type so a compile warning is generated, see the example below:

I ran into this recently when I added a JavaScript file that is associated with an Openx ad that I wanted to displayed inside my application, using a UIWebView.

There is a simple fix, drag/drop the offending file(s) from the Compile Sources folder to the Copy Bundle Resources folder within the applications Target, which will simply include the file in the application bundle with no processing of the file (this is where you will typically see image files, sound files, etc).

In the image below, the file foo.js has been moved into the Copy Bundle Resources folder:

This is the first post of what I hope is many where we can share tips and tricks on working with Xcode.

Tip #1 – Split Editor View Vertically

If you like to have multiple code windows open at once, the Split Editor option is your friend (see the little square grid icon shown below).

By default, the windows are split horizontally. If you prefer to view your code side-by-side (nice for comparing), here’s how to tell the split to be vertical

1. Hold down Option key when clicking the Split Window icon

Tip #2 – Comment Out a Block of Code

You can quickly comment out a block of code as follows:

1. Select one or more lines of code to comment
2. Command-/

To uncomment a block of code, repeat the steps above.

Tip #3 – Toggle Between .h and .m Files (aka Switch to Counterpart)

Within your current code window, you can swap between the .h and .m file as follows:

1. Command-Option Up-Arrow

Tip #4 – Map Keys to Actions (Key Bindings)

The Switch to Counterpart tip above is a real time saver. However, I often find that if I map logical key-strokes to actions I’m much more likely to get into the habit of using them. For example, I mapped the Switch to Counterpart to Option-S, as in Swap or Switch.

Here’s how to set key bindings in Xcode

1. From the Xcode menu choose Prefereces
2. Select Key Bindings
3. Click on one of the Actions in the list
4. Tap on the Keys column on the right
5. Enter the keystroke you want to map to the action
6. Click Ok to save your changes

Tip #5 – Jump to API Documentation

Showing relevant API documentation for anything within the SDK(s) is as simple as:

1. Option Double-Click on relevant code

For example, in the screenshot below, after Option double-clicking on UIToolbar, a popup window shows a summary of the class information.

Tip #6 – Traverse File History

As you open and edit various files, Xcode keeps a history list of your actions, not unlike when using a web-browser. You can move through the list using the directional arrows as shown below:

The keystoke equivalent for the above is:

1. Option-Command Left-Arrow goto to previous file
2. Option-Command Right-Arrow goto to next file

Tip #7 – Set a Bookmark

I can’t imagine coding without having the option to set a bookmark as a placeholder for what I’m working on. I do this regularly when I need to segue to another file to find a snippet or otherwise poke around outside the current file I’m working on.

Setting a bookmark is as simple as:

1. Control-D
2. Enter a name for the bookmark

Tip #8 – Jump to Bookmark

There are two options to jump to a bookmark. First, you can select the bookmark icon in the upper right corner of the Editor window.

You can bring up the same menu as shown in the above figure using this keystoke:

1. Control-4

Tip #9 – Indent / Un-indent Code

You can indent a line of code or a selected block of code as follows:

1. Command-[ move code left
2. Command-] move code right

The above works regardless of where you are in a line of code, in other words, you don’t have to be at the beginning of the line.

Tip #10 – Zoom Editor

You can toggle between Detail view and Editor view by clicking the Editor button as shown here:

The keystroke equivalent of the above is:

1. Shift-Command-E

Have an Xcode Tip to Share?

If you have a favorite tip or trick, please post a comment or send tips to me here. Killer Xcode Tips and Tricks – Tips 11 to 20 will be posted next week, and suggestions are welcome!

Path to Xcode Simulator Files

The path to the simulator files is here:

/Users/USER_NAME/Library/Application Support/iPhone Simulator/User/Applications

USER_NAME is the current user logged in on the machine. There is a unique identifier created by the simulator, one value for each application. The figure below shows how this looks on my machine, notice there are two entries in the Applications folder, one for each of the current applications I am working on.

In the application App-Vol1 you can see that I am creating a custom plist file Favorites.plist and storing the file in the Documents directory. This is the file I referred to earlier that I update whenever the user quits the application.

Easy Access to Simulator Files

To make access to the simulator files quick and easy, I keep an entry on the left side of Finder titled iPhone Simulator. Simply navigate your way to the simulator files and drag/drop the folder on the left sidebar. You can rename this folder by right-clicking and choosing Rename.

Static analysis does a deeper parsing of your code than a traditional compilation. It looks through each potential code path and can find potential problems that are not obvious to the compiler (and may be missed by you as well).

How it Works

The code below compiles just fine, no warnings. However, Xcode 3.2 will flag a few potential problems when running an analysis of the code. To run the analyzer, from the Build menu, choose Build and Analyze.

- (BOOL)getSomeValue:(int)x
{
  BOOL positiveFlag;
 
  if (x < 0)   
  {    
   positiveFlag = NO;   
  }   
  else if (x > 0)
  {
    positiveFlag = YES;
  }  
 
  return positiveFlag;
 
}

If you look in the Build Results window, you’ll see more information:

• Variable ‘positiveflag’ declared without an initial value
• Uninitialized or undefined value returned to caller

The problem occurs in this code if the value of x == 0, given the variable positiveflag has no default value set, it may not return what you expect.

Showing Control Flow

Here’s an interesting option you have within the integration of static analysis in Xcode – click on one of the entries in the Build Results window (as shown below):

and Xcode will highlight the flow of the code, and help you pinpoint the potential problem:

Run Static Analysis with Each Build

By default, you request a static analysis of your code by selecting Build and Analyze in the Build menu. If you would like a static analysis run whenever you build a project with the debug configuration, you can check the Run Static Analyzer in the Build Options as shown in the image below:

Let’s start with how to get your system working with Snow Leopard:

Install Xcode/SDK for Snow Leopard

1. Install Snow Leopard from DVD
2. Install Xcode 3.2 from Snow Leopard DVD
3. Download and install iPhone SDK 3.0 for Snow Leopard from Apple Developer Connection

Once installed, upon opening a project you may see something similar to the following (which I received when opening a recent project):

Notice the reference to “iPhone Device 2.2.1 (missing)”. This project was built for 2.2.1 before I upgrade Xcode. On a similar note, if you open the dialog to set the device and distribution settings, here is how things will look:

Again, the references to earlier SDK’s are no longer available.

Targetging 2.2 or Earlier Version of iPhone SDK

The trick to targeting earlier versions of the SDK is now done through the Deployment section in the Build preferences. In the image below you’ll see a reference to iPhone OS Deployment Target along with a list of available OS target options.

Choose the target you need, clean, rebuild, and with that, you should be good to go.

For ad-hoc builds of your application, by default, iTunes will display a generic icon for your application. The default artwork for an ad-hoc build looks as follows:

To add artwork so beta testers will see an icon within iTunes, you add a file with the name iTunesArtwork to your application bundle.

Add iTunes icon to Xcode Project:

* Create a png or jpg file that is 512×512 pixels
* In the Groups & Files list, right click on Resources group
* Choose Add, followed by Existing Files…
* Select the file you created, iTunesArtwork
* In the popup dialog, check Copy items into destination group’s folder
* Click Add

Clean and rebuild your project. When you add the application to iTunes, you should now see the artwork now tied to the application.

Caveats:
So the above sounds simple enough, which it is, however, there are a few gotcha’s that made this simple process go from what should of been 10 minutes of tinkering to an hour of hair pulling.

Let me point out the steps that may trip you up:

#1 – The file must be named iTunesArtwork with no extension, and don’t forget to capitalize the T and A (hmmm, there’s a joke in there somewhere).

#2 – I now know that you can’t start with a filename that has an extension of jpg or png and simply rename the file. For example, I had a 512×512 image that I created for the App Store. Seemed a reasonable assumption that if I renamed the file, everything would be copacetic. I went into Finder, right clicked on the file and removed the extension. No go. I could add to the project as shown above, however, the icon would not show up in iTunes.

After trying various file types (png, jpg), adding the file in different locations (root of the project, resources folder, etc), I decided to create a new image altogether thinking maybe the image was wonky. When saving the image in the image editor, I specified not to add a file extension. Shazam, that was the problem!

You’ll know if you’ve done this correctly as the file within the Resources folder will show up without an extension:

as compared to this:

#3 – There was a known bug within Xcode in an earlier version that generated the error 0xE8000058. This would happen when you switched from creating an ad-hoc build to a debug version and attempted to install on a device.

If you run into this error, remove the file iTunesArtwork from your application bundle (you can leave the file, just delete the reference to it) and rebuild.