my favourite 10 things about xcode/objectivec

My Favourite Ten Xcode Things

Tuesday, October 11, 11

Some of my favourite Xcode and Objective-C type things.

(Or: Please tell me a better way of doing these things)


Three phases of iPhone development:

1. Argh! Square brackets!2. Ok, how do I do this?3. Ok, what’s the BEST way to do this?

The common theme is that each stage is full of puzzles, and puzzles are attractive to certain types of brains. You think, you solve, you get a little rush. Addictive!

Flip between .h and .m

Control + Command + Arrow up

Switch between open tabs

Shift + Command + [ or ]

Find anywhere in project

Shift + Command + F

1. Xcode Keyboard Shortcuts


I spend many hours using Xcode every day. The transition to Xcode 4 wasn’t too bad, although it took a while to get used to the way it splits views. I’m happy enough now though. At least it’s not Eclipse, and when I go back to Visual Studio it irritates me that I need to double-click on things a lot.

Toggle Debug Console

Shift + Command + Y

Open a file

Shift + Command + O

1b. Xcode Keyboard Shortcuts


Open a file is fantastic. Use it.

Hold down Control and drag a control into your .h file, to create actions and properties (and the associated methods in .m).

2. Drag from the NIB editor into .h files


I love this.

-(NSString *)getAxis{! return [NSString stringWithFormat: @"X:%0.2f Y:%0.2f Z:%0.2f", _accelerometer[0], _accelerometer[1], _accelerometer[2]];}

3. Useful NSString initialization


Very nice - and because there is no ALLOC, it’s an autorelease object.Just don’t put a BOOL in there.

BOOL myStatus = TRUE;

-(NSString *)getStatus{

! return [NSString stringWithFormat: @"%@",(myStatus ? @”YES” : @”NO”)]; }

3b. Useful NSString initialization


Handy for NSLog too.

Don’t check to see if a string is empty like this:

if (myString == nil) { NSLog(@"empty!"); }

Use this:

if ([myString isEqualToString:@""]) { NSLog(@"empty!"); }

Or this: if ([myString length] == 0) { NSLog(@"empty!"); }

4. Useful NSString comparisons


But if it’s just whitespace, that might not work..

// Mr. Will Shipleystatic inline BOOL isEmpty(id thing) { return thing == nil || [thing isKindOfClass:[NSNull class]] || ([thing respondsToSelector:@selector(length)] && [(NSData *)thing length] == 0) || ([thing respondsToSelector:@selector(count)] && [(NSArray *)thing count] == 0);}

4b. Useful NSString comparisons


Here’s the 100% best way.

There is no file system. Except there is.

if ([[NSFileManager defaultManager] fileExistsAtPath:[[NSBundle mainBundle] pathForResource:@"picture" ofType:@"jpg"]]) return YES;

5. Testing to see if a file exists


Also, are you using large image files? Tempted to stick with PNG? Try JPG instead.Same quality in photograph images, but can be 1/10th of the size.

-(void) myMethod{ }

[self performSelector:@selector(myMethod) withObject: nil afterDelay: 1.0];

[NSObject cancelPreviousPerformRequestsWithTarget :self selector :@selector(myMethod) object :nil];

6. Time delay before method call


Multithreading for dummies - a great way to get animation working when the main thread would otherwise be blocked. WARNING! Remember to cancel it if you don’t use it before the reference goes away!

// In AppDelegate-(void)callMe{ }

// In some other class- (void)viewDidLoad{ [super viewDidLoad]; [(AppDelegate*) [[UIApplication sharedApplication] delegate] callMe]; }

7. Delegate callback to parent AppDelegate


Just need to add callMe to .h in AppDelegate, and #import that into the other class.However, think about why you are doing this: it’s very likely that a Singleton will be a better idea.

// In the Modal Dialog UIViewController Class, .h file

@interface CityPickerViewController : UIViewController <UIPickerViewDelegate>

{!! id delegate;!}

- (id)delegate;- (void)setDelegate:(id)newDelegate;

@end

8. Using delegates to perform actions when modal dialog closed.


So you want to trigger something when a modal dialog is closed. Use this to allow the Modal dialog UIViewController class to call a method back in the class that called it.

// In the Modal Dialog UIViewController Class, .m file

- (id)delegate { return delegate;}

- (void)setDelegate:(id)newDelegate { delegate = newDelegate;}

-(void) updateCity: (id)sender{! // replaced by delegated call!}

-(void)callWhenDialogClosing{! [[self delegate] updateCity:self];!}

8b. Using delegates to perform actions when modal dialog closed.


So you want to trigger something when a modal dialog is closed. Use this to allow the Modal dialog UIViewController class to call a method back in the class that called it.

// In the class that is calling the modal dialog

-(void) updateCity: (id)sender{! [self drawLocation];! [myPickerView dismissModalViewControllerAnimated:YES];}

-(IBAction) clickNearestCity: (id)sender{ myPickerView = [[CityPickerViewController alloc] initWithNibName:@"CityPickerViewController" bundle:nil];

! myPickerView.delegate = self; ....

8b. Using delegates to perform actions when modal dialog closed.


You can’t keep the pointer to the view nice and local now, as you’ll need to close it yourself in the delegate. Yes, it smells a bit. Suggestions welcome.

[UIView beginAnimations:@"clickBounce" context:tempButton];

[UIView setAnimationDelegate:self];

[UIView setAnimationDuration:0.2]; !

[UIView setAnimationDidStopSelector:@selector(part2:finished:context:)];

[myButton setTransform:CGAffineTransformMakeScale(.9,.9)];

[UIView commitAnimations];

9. Two-part animation block


Blocks have a terribly ugly syntax, but if you can get over it, they are useful. And increasing in importance. If you wanted an animation to have multiple parts, you needed to use the DidStopSelector, and it was a pain.

[UIView animateWithDuration:1.0 animations:^ { myButton.alpha = 1.0; myButton.transform = CGAffineTransformMakeScale(1.5, 1.5); } completion:^(BOOL completed) { myButton.alpha = 0.8; myButton.transform = CGAffineTransformMakeScale(1, 1); }];

9b. Two-part animation block


Much neater, no extra methods, easier to pass values between different components of the animation etc etc

Declare a Collection, and then link all your buttons to it..

IBOutletCollection(UIButton) NSArray *menuButtonsCollection;

10. UICollections, Tags and iOS 5


Piece of cake in NIB editor.

Now you can iterate over them all..

for (UIButton *button in menuButtonsCollection) { [button setImage:[UIImage imageNamed:@"pic.png"] forState:UIControlStateNormal]; }

10b. UICollections, Tags and iOS 5


Handy to programmatically fade out all buttons for example.Remember you can also set TAGS in the NIB editor, and then act on those in the loop.You don’t need to only use one type of object, use (id) for any control.

If you need to change them all at once..

[[UISwitch appearance] setOnTintColor: [UIColor redColor]];

10b. UICollections, Tags and iOS 5


Note: need to re-open the view to see the changes.

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my favourite 10 things about xcode/objectivec

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