gistfile1.m

//
//  UIView+TimedAnimations.m
//  Bumper
//
//  Created by Ian Ownbey on 6/30/15.
//  Copyright © 2015 Bumpers Media Inc. All rights reserved.
//

#import "UIView+TimedAnimations.h"
#import <objc/runtime.h>

@interface BPSavedAnimationState: NSObject

@property (strong) CALayer  *layer;
@property (copy)   NSString *keyPath;
@property (strong) id        oldValue;

+ (instancetype)savedStateWithLayer:(CALayer *)layer
                            keyPath:(NSString *)keyPath;

@end

@implementation BPSavedAnimationState

+ (instancetype)savedStateWithLayer:(CALayer *)layer
                            keyPath:(NSString *)keyPath
{
    BPSavedAnimationState *savedState = [BPSavedAnimationState new];
    savedState.layer    = layer;
    savedState.keyPath  = keyPath;
    savedState.oldValue = [layer valueForKeyPath:keyPath];
    return savedState;
}

@end

@implementation UIView (TimedAnimations)

static NSMutableArray *BP_savedAnimationStates = NULL;

+ (void)load
{
    BP_savedAnimationStates = [NSMutableArray array];
    
    SEL originalSelector = @selector(actionForLayer:forKey:);
    SEL extendedSelector = @selector(BP_actionForLayer:forKey:);
    
    Method originalMethod = class_getInstanceMethod(self, originalSelector);
    Method extendedMethod = class_getInstanceMethod(self, extendedSelector);
    
    NSAssert(originalMethod, @"original method should exist");
    NSAssert(extendedMethod, @"exchanged method should exist");
    
    if(class_addMethod(self, originalSelector, method_getImplementation(extendedMethod), method_getTypeEncoding(extendedMethod))) {
        class_replaceMethod(self, extendedSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
    } else {
        method_exchangeImplementations(originalMethod, extendedMethod);
    }

}


static void *BP_currentAnimationContext = NULL;
static void *BP_animationContext = &BP_animationContext;

- (id<CAAction>)BP_actionForLayer:(CALayer *)layer forKey:(NSString *)event
{
    if (BP_currentAnimationContext == BP_animationContext) {
        [BP_savedAnimationStates addObject:[BPSavedAnimationState savedStateWithLayer:layer keyPath:event]];
        
        return [NSNull null];
    }
    
    return [self BP_actionForLayer:layer forKey:event];
}

+ (void)BP_cubicTimedAnimateWithDuration:(NSTimeInterval)duration delay:(NSTimeInterval)delay group:(dispatch_group_t)group animations:(void (^)(void))animations complete:(void (^)(BOOL))complete
{
    [self BP_timedAnimateWithDuration:duration delay:delay timingFunction:[[CAMediaTimingFunction alloc] initWithControlPoints:0.2 : 0.7 : 0.5 : 1] group:group animations:animations complete:complete];
}

+ (void)BP_timedAnimateWithDuration:(NSTimeInterval)duration delay:(NSTimeInterval)delay timingFunction:(CAMediaTimingFunction *)timingFunction group:(dispatch_group_t)group animations:(void (^)(void))animations complete:(void (^)(BOOL))complete
{
    BP_currentAnimationContext = BP_animationContext;
    
    animations();
    
    [BP_savedAnimationStates enumerateObjectsUsingBlock:^(BPSavedAnimationState *savedState, NSUInteger idx, BOOL *stop) {
        CALayer *layer    = savedState.layer;
        NSString *keyPath = savedState.keyPath;
        id oldValue       = savedState.oldValue;
        id newValue       = [layer valueForKeyPath:keyPath];
        
        layer.masksToBounds = NO;
        
        CABasicAnimation *anim = [CABasicAnimation animationWithKeyPath:keyPath];
        
        anim.beginTime = CACurrentMediaTime() + delay;
        anim.duration = duration;
        anim.fromValue = oldValue;
        anim.toValue = newValue;
        anim.timingFunction = timingFunction;
        
        // back to old value without an animation
        [CATransaction begin];
        [CATransaction setDisableActions:YES];
        [layer setValue:oldValue forKeyPath:keyPath];
        [CATransaction commit];
        
        // animate the "pop"
        if (group) {
            dispatch_group_enter(group);
        }
        [CATransaction begin];
        [CATransaction setCompletionBlock:^{
            [layer setValue:newValue forKey:keyPath];
            [layer removeAnimationForKey:keyPath];
            if (complete) {
                complete(YES);
            }
            
            if (group) {
                dispatch_group_leave(group);
            }
        }];
        [layer addAnimation:anim forKey:keyPath];
        [CATransaction commit];
        
    }];
    
    // clean up (remove all the stored state)
    [BP_savedAnimationStates removeAllObjects];
    
    BP_currentAnimationContext = nil;
}
                                                                                                                                                                                        

@end