Category Archives: iOS

So… suppose that you have a container view. And for some reason, you need to remove the subviews that match any given criteria.

The straightforward solution would be to write a foreach loop, by hand, and remove the target subviews with a method call. Guess what!. There is a kung fu solution to this..!!. Check this out:

[cc lang=”objc”]
NSPredicate* predicate = [NSPredicate predicateWithFormat:@”self isKindOfClass: %@”, [SomeView class]];
NSArray* viewsToRemove = [[self subviews] filteredArrayUsingPredicate:predicate];
[viewsToRemove makeObjectsPerformSelector:@selector(removeFromSuperview)];
[/cc]

Less code is better. Always.

This one is a quick and easy trick. How do you detect taps in any UIView?.
Simple. You need to use the UITapGestureRecognizer class… this way:

[cc lang=”objc”]
// Alloc the gesture recognizer
UITapGestureRecognizer* tapGestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(viewTapped)];
[tapGestureRecognizer setNumberOfTapsRequired:1];
[anyRandomView addGestureRecognizer:tapGestureRecognizer];
[anyRandomView setUserInteractionEnabled:YES];

[tapGestureRecognizer release];
tapGestureRecognizer = nil;
[/cc]

Time to invoke some… dark magic. For some reason, UILabel doesn’t support stroke. So, if you’re… by chance… working on a videogame, or a simple iOS app, and you actually need to render an UILabel with a stroke, in a given color, you have come to the right place.

Let’s begin with the header file:

[cc lang=”objc”]
@interface LAStrokeLabel : UILabel
{
NSUInteger _strokeWidth;
   UIColor* _strokeColor;
}

@property (nonatomic, assign) NSUInteger strokeWidth;
@property (nonatomic, retain) UIColor* strokeColor;

@end
[/cc]

So far so good… right?. Nothing weird. Just a simple UILabel subclass, with two extra properties.

Now, let’s get to business. We’re gonna need to link ‘CoreGraphics’ framework. Otherwise this won’t work. The .m file should look like this:

[cc lang=”objc”]
static NSUInteger kDefaultStrokeWidth = 1;

@implementation LAStrokeLabel

@synthesize strokeWidth = _strokeWidth;
@synthesize strokeColor = _strokeColor;

-(void)dealloc
{
[_strokeColor release];
_strokeColor = nil;

[super dealloc];
}

-(id)init
{
if((self = [super init]))
{
_strokeWidth = kDefaultStrokeWidth;
_strokeColor = [[UIColor blackColor] retain];
}

return self;
}

-(id)initWithFrame:(CGRect)frame
{
if((self = [super initWithFrame:frame]))
{
_strokeWidth = kDefaultStrokeWidth;
_strokeColor = [[UIColor blackColor] retain];
}

return self;
}

-(void)awakeFromNib
{
_strokeWidth = kDefaultStrokeWidth;
_strokeColor = [[UIColor blackColor] retain];

[super awakeFromNib];
}

-(void)drawTextInRect:(CGRect)rect
{
CGSize shadowOffset = self.shadowOffset;
UIColor* textColor = self.textColor;
BOOL highlighted = self.highlighted;

CGContextRef c = UIGraphicsGetCurrentContext();

// Draw the stroke
if( _strokeWidth > 0 )
{
CGContextSetLineWidth(c, _strokeWidth);
CGContextSetTextDrawingMode(c, kCGTextStroke);

self.textColor = _strokeColor;
self.shadowColor = _strokeColor;
self.shadowOffset = CGSizeMake(0, 0);
self.highlighted = NO;

[super drawTextInRect:rect];
}

// Revert to the original UILabel Params
self.highlighted = highlighted;
self.textColor = textColor;

// If we need to draw with stroke, we’re gonna have to rely on the shadow
if(_strokeWidth > 0)
{
self.shadowOffset = CGSizeMake(0, 1); // Yes. It’s inverted.
}

// Now we can draw the actual text
CGContextSetTextDrawingMode(c, kCGTextFill);
[super drawTextInRect:rect];

// Revert to the original Shadow Offset
self.shadowOffset = shadowOffset;
}

@end
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If you figured out… you just got an extra point. Yes. For some reason, CoreGraphics’s stroke wasn’t drawing anything ‘below the bottom line’. That’s the reason why i’ve implemented a workaround: the ‘bottom’ of the stroke is actually a shadow.

A bit hacky, but i promess, it will work great.

Suppose the following scenario. You need to display a modal UIViewController whenever the user presses a specific button in a UITabBar.

The trick is pretty simple. First, add an empty UIViewController, wich will serve as placeholder for the ‘modal tab’:

[cc lang=”objc”]
UIViewController* someViewController    = [[UIViewController alloc] init];
[someViewController setTitle:NSLocalizedString(@”Modal Tab”, nil)];
[someViewController.tabBarItem setImage:[UIImage imageNamed:@”modal.png”]];
[/cc]

Then, setup the UITabBarController’s delegate:

[cc lang=”objc”]
[_tabBarController setDelegate:self];
[/cc]

At last… you need to implement the UITabBarControllerDelegate protocol. Specifically, something that looks like this:

[cc lang=”objc”]
– (BOOL)tabBarController:(UITabBarController*)tabBarController shouldSelectViewController:(UIViewController*)viewController

{
BOOL isModalTab = ([[viewController title] isEqualToString:NSLocalizedString(@”Modal Tab”, nil)]);

if(isModalTab)
   {
UIViewController* modalViewController = [[[ModalViewController alloc] init] autorelease];
[self presentModalViewController:modalViewController animated:YES];
}

return !isModalTab;
}
[/cc]

That would do the trick..!

What if you need to write a completely dynamic app, and you need to have the ability of updating the App’s contents remotely, without the need of pushing a new build to the AppStore?.

What if you need to write javascript code, which needs to interact with your iOS code?.
Yeah. I had that problem. Long short story, i’m testing a nice framework called clutch.

Clutch has a nice JavaScript and iOS SDK, which smoothens the interaction between those two technologies. When you ship the app, you bundle a version of the webApp in it.

If the app has no internet access, it will rely on that bundled web. And as soon as you launch it, it gets sync’ed with the backend. (You can actually push ‘new version’ to the Clutch backend).

So far… i’m loving it. Go, try it… and let me know what you think!.

If you just need to build a dumb iOS and JS bridge, i suggest you also check out this github project, and this one.