Iphone – Performant way to build long strings in a loop

No, foo is variable holding a pointer to an NSString. The assignment foo = @"bar" sets the value stored by the pointer foo to the address of the NSString @"bar". There is no copy made. If foo already pointed to an other NSString instance that was not a string constsant (i.e. like @"bar") and there are no other references to that instance, then you have a memory leak. You would

[foo release];
foo = @"bar";

in that case. You do not need to retain or release string constants like @"bar".

String constants cannot be mutated, so you will get a runtime error if you try to modify the value of a constant string. There's no difference between assigning @"bar" to an NSString* vs an NSMutableString*. Of course, you won't be able to use the mutating methods of the NSMutableString without a runtime error just because you assign the address of @"bar" (an NSString instance) to a variable of type NSMutableString*. If you want to mutate the string, you would do

NSMutableString *mutableFoo = [@"bar" mutableCopy];

In this case, a copy is obviously made and you are responsible for releasing mutableFoo when you're done with it.

Since I am using a background image, none of these solutions worked well for me. Here is a solution that does some fun objective-c magic and offers a drop in solution with minimal code.

First, add a category to UIButton that overrides the hit test and also adds a property for expanding the hit test frame.

UIButton+Extensions.h

@interface UIButton (Extensions)

@property(nonatomic, assign) UIEdgeInsets hitTestEdgeInsets;

@end

UIButton+Extensions.m

#import "UIButton+Extensions.h"
#import <objc/runtime.h>

@implementation UIButton (Extensions)

@dynamic hitTestEdgeInsets;

static const NSString *KEY_HIT_TEST_EDGE_INSETS = @"HitTestEdgeInsets";

-(void)setHitTestEdgeInsets:(UIEdgeInsets)hitTestEdgeInsets {
    NSValue *value = [NSValue value:&hitTestEdgeInsets withObjCType:@encode(UIEdgeInsets)];
    objc_setAssociatedObject(self, &KEY_HIT_TEST_EDGE_INSETS, value, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

-(UIEdgeInsets)hitTestEdgeInsets {
    NSValue *value = objc_getAssociatedObject(self, &KEY_HIT_TEST_EDGE_INSETS);
    if(value) {
        UIEdgeInsets edgeInsets; [value getValue:&edgeInsets]; return edgeInsets;
    }else {
        return UIEdgeInsetsZero;
    }
}

- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event {
    if(UIEdgeInsetsEqualToEdgeInsets(self.hitTestEdgeInsets, UIEdgeInsetsZero) || !self.enabled || self.hidden) {
        return [super pointInside:point withEvent:event];
    }

    CGRect relativeFrame = self.bounds;
    CGRect hitFrame = UIEdgeInsetsInsetRect(relativeFrame, self.hitTestEdgeInsets);

    return CGRectContainsPoint(hitFrame, point);
}

@end

Once this class is added, all you need to do is set the edge insets of your button. Note that I chose to add the insets so if you want to make the hit area larger, you must use negative numbers.

[button setHitTestEdgeInsets:UIEdgeInsetsMake(-10, -10, -10, -10)];

Note: Remember to import the category (#import "UIButton+Extensions.h") in your classes.