1
2
3
4
5
6
7
8
9

NSInteger x = 0;
 
// Increment x
x += 1;
 
...
 
// Decrement x
x -+ 1;

One small problem here, there is a typo in the code for decrementing x, which is easy to do given the + and = are on the say key.

It took some time to track down this problem as the compiler does not provide a warning for operations such as this that don’t have any effect.

Let’s add a compiler option so we receive a warning when we write a statement has no effect.

Option #1: User Defined GCC Options

- Make sure the Active SDK is set to one of the Simulator options
- Expand the Target option in the project settings
- Right click on the target
- Choose the Build settings
- Scroll to the bottom to the user defined settings
- Add an entry: GCC_WARN_UNUSED_VALUE and set the value to YES

Option #2: GCC Warning Options

- Make sure the Active SDK is set to one of the Device options
- Expand the Target option in the project settings
- Right click on the target
- Choose the Build settings
- Scroll to the section GCC 4.0 – Warnings
- Select the entry Unused Values

Either of the above will suffice, it just depends on what you have set as the Active SDK.

Upon making this change, for statements that have no effect, you will now get a warning generated by the compiler:

In an upcoming post I’ll show you how to set this as an option for all project templates.

As an example, begin by entering ifelse into Xcode and follow this by pressing Control . (control period) and you’ll see the following code block inserted:

At this point you can add code into the placeholder fields, moving from one field to the next using Control / (control forward-slash).

If you enter a code snippet in which there is more than one possible match, you can cycle through the options by pressing F5 which will bring up a list of options in a popup window, or pressing Command . will cycle through the choices inline in your code.

For example, if you enter if and follow this by pressing F5, you will be shown the window below:

List of Available Macros

The Xcode documentation includes a list of macros available for C, C++ and Objective-C. Some of the macros I use on a regular basis are shown below:

• nss -> NSString
• nsms -> NSMutableString
• nsd -> NSDictionary
• nsmd -> NSMutableDictionary
• a -> array (press Control-. to toggle through options)
• log -> NSLog
• if -> if else (press Control-. to toggle through options)

Text Macros from the Menu System
Xcode includes a menu of text macros for C, C++, HTML among others. You can find these macros in the Edit menu under Insert Text Macro.

Let’s say I want to insert a CGRectMake method. I can begin by typing CG and pressing F5 (or Option-esc), which will popup a list of possible matches:

If I choose an entry from this list, Xcode takes care of the rest. If I continue to type characters (instead of hitting F5), Xcode will further narrow the available matches (assuming there is more than one). Again, at any point I can press F5 to bring up the matching list.

As an alternative to using F5 for a list of suggestions, I can hit tab at any point and Xcode will insert the matched text currently displayed. For example, in the figure below I entered CGRe and Xcode inserted the suggestion shown below:

If I’d like to go with this suggestion, pressing the Tab key will insert the code.

Filling in Placeholder Fields
The next step is to fill in any required fields that Xcode has recognized. If there are parameters, Xcode will highlight the first field as shown:

Enter the value you want in the field and press Control / to move to the next field.

Code Sense Preference Settings
If you have any trouble getting these suggestions to work, I’ve included a screenshot of the Code Sense settings that I have configured in Xcode:

In the next post I’ll show how you can use various built-in macros to quickly insert blocks of code.

Two of the settings that I have configured are to beep when a left bracket ( ] ) is entered without a matching right bracket, and second, to increase the number of entries in the recent projects menu (File menu, Recent Projects).

From a terminal window, here are the commands I ran to set each preference:

defaults write com.apple.Xcode PBXBeepOnNoMatchingBrace YES
defaults write com.apple.Xcode NSRecentDocumentsLimit 20

You can see the entire list of available settings by reading the document Xcode Expert Preferences Notes (see the Bookmarks section in the Xcode documentation window).

By default, Xcode inserts a company name something similar to the following in all new source files (.m .h etc):

Copyright (c) 2009 MyCompanyName. All rights reserved.

Changing this reference is as simple as entering the following from within a terminal window, replacing “YourNameHere” with the text you prefer. Also, make sure this is all entered on one line in the terminal.

defaults write com.apple.Xcode PBXCustomTemplateMacroDefinitions 
   '{ORGANIZATIONNAME="YourNameHere";}'

// TODO:

This tag is handy for reminding yourself of things that you need to get back to at some point. I generally into these statements at the top of the source file within the main comment block to remind me of features I need to update or add. Here is how this might look in a code block:

//  BirdBookAppDelegate.m
//
// TODO: Check for existence of files
// TODO: Refactor code for NSNotification
#pragma mark -

// FIXME:

Another useful tag, this one calls out code that needs to be re-visited for changes/fixes. The code below shows one example of how this looks, and the figure above shows how this appears inside the Functions menu in Xcode.

  // FIXME: Change memory mgmt handling in this block.
  // Create portrait window and content view (to hold other views)
  UIWindow *localPortraitWindow;

// ??? and /// !!!:

These two tags I don’t use as frequently as those above, however, they do have there place. I use the former when I’m not sure how something works and I need to come back another time to dig a little deeper. The later is nice if you need a reminder of a significant task to perform, for example, verifying that all objects are released inside the dealloc() method. The following code shows both tags inside a source file:

- (void) applicationDidFinishLaunching:(UIApplication *)application
{
  // ???: How does this work?
  [segmentedControl addTarget:self action:@selector(segmentAction:) forControlEvents:UIControlEventValueChanged];
  ...
  ...
- (void) dealloc
{
  // !!!: Verify that all objects are accounted for
  [tabBarController release];
...

The tags for the above would look as follows inside the Functions menu:

Once you get accustomed to using #pragma and one or more of the tags above, it becomes second nature to insert these as you write code. And trust me, these are of great help as the size and complexity of your projects grows.

At one point in the process he opted to remove the Xcode developer tools and start the configuration from the beginning. Which leads to the tip: should you ever find the need to remove Xcode, run the following from within a terminal window to make it happen:

sudo <Xcode>/Library/uninstall-devtools --mode=all

<Xcode> is the directory where the tools are installed. For typical installations the full path is /Developer/Library/uninstall-devtools

Easy enough, just make sure this is what you really intend to do as once it’s gone, it’s gone.

#pragma mark -
#pragma mark Initialization

Once this is in place, the Functions Menu (in the navigation bar) which shows a list of locations within a source file (e.g. definitions of classes, functions and methods) will display a new marker with the label "Initialization." The code in line 1 will add a line separator inside the Functions Menu, in this example, with the line appearing above the "Initialization" marker.

The figure that follows shows an example of how you might use #pragma mark to divide up various sections of your code.

Two notes:

1. You cannot have a space after the "-" in the #pragma mark -
2. If your code does not appear as expected (e.g. the separator does not appear), check that ‘Sort list alphabetically’ is not checked in the Code Sense preference settings.

When inside a debugger and stepping through code, line be line, have you ever wanted to move to the top of a loop and restart, including resetting counters, without having to restart the application/debugger? Here’s a cool trick you can use within Xcode to do just that. In the figure below, notice that the current value of the variable name is America/Antigua.

Also notice in the figure above that the current point of execution (the red arrow) is inside the for loop. In the next figure, notice that America/Antigua is fourth down in the list of known time zones. Therefore, we know that this is our fourth time through the for loop.

Here’s the tip: we can click/drag the red arrow in the debugger and move it back up to line 117. By doing so, we can start the for loop again from the beginning.

See the figure below and notice that this time through the loop the variable name is Europe/Andora , the first entry in the list.

Rather than restart a debugging session to reset a variable or begin at the top of a loop, try this approach instead. This is one of many good tips you’ll find in the book Xcode 3 Unleashed .

This is a two part series on creating a new class that wraps NSLog to add several additional debugging features including output of the filename/path, line number information and the option to turn debug messages off/on.

You can read the rest of the tip on the iPhone Developer Tips blog.