Objective-C animation chaining utility

BARAnimation.h

@interface BARAnimation : NSObject

/*! Just start to construct your animation from this method. */
+ (instancetype)construct;

/*! Before all animations will execute this block. */
- (instancetype)initially:(void (^)(void))initiallyBlock;

/*! Add animations and link it with each other. */
- (instancetype)animationWithDuration:(NSTimeInterval)duration
				  animationConditions:(void (^)(void))conditions
						   animations:(void (^)(void))animations;

/*! Add animations with parameters and link it with each other. */
- (instancetype)animationWithDuration:(NSTimeInterval)duration
								delay:(NSTimeInterval)delay
							  options:(UIViewAnimationOptions)options
				  animationConditions:(void (^)(void))conditions
						   animations:(void (^)(void))animations;

/*! After completion all of animation block this block will be called. */
- (instancetype)finally:(void (^)(void))finallyBlock;

/*! When you construct your animation, just run it. */
- (void)run;

/*! Just syntax sugar for linking animations. You don't need to use it. */
- (instancetype)then;

@end

BARAnimation.m

#import "BARAnimation.h"

@interface BARAnimationBlock : NSObject

@property (nonatomic, copy, readonly) dispatch_block_t conditions;
@property (nonatomic, copy, readonly) dispatch_block_t animations;
@property (nonatomic, assign, readonly) NSTimeInterval duration;
@property (nonatomic, assign, readonly) NSTimeInterval delay;
@property (nonatomic, assign, readonly) UIViewAnimationOptions options;

- (instancetype)initWithDuration:(NSTimeInterval)duration
						   delay:(NSTimeInterval)delay
						 options:(UIViewAnimationOptions)options
			 animationConditions:(void (^)(void))conditions
					  animations:(void (^)(void))animations;

@end

@implementation BARAnimationBlock

- (instancetype)initWithDuration:(NSTimeInterval)duration
						   delay:(NSTimeInterval)delay
						 options:(UIViewAnimationOptions)options
			 animationConditions:(void (^)(void))conditions
					  animations:(void (^)(void))animations
{
	self = [super init];
	if (self == nil) return nil;

	_duration = duration;
	_delay = delay;
	_options = options;
	_conditions = [conditions copy];
	_animations = [animations copy];

	return self;
}

@end


@interface BARAnimation ()

@property (nonatomic, strong, readonly) NSMutableArray<BARAnimationBlock *> *animationBlocks;
@property (nonatomic, copy, readonly) dispatch_block_t finallyBlock;
@property (nonatomic, copy, readonly) dispatch_block_t initiallyBlock;

@end

@implementation BARAnimation

+ (instancetype)construct
{
	return [[BARAnimation alloc] init];
}

- (instancetype)init
{
	self = [super init];
	if (self == nil) return nil;

	_animationBlocks = [NSMutableArray array];

	return self;
}

- (instancetype)animationWithDuration:(NSTimeInterval)duration
				  animationConditions:(void (^)(void))conditions
						   animations:(void (^)(void))animations
{
	[self.animationBlocks addObject:[[BARAnimationBlock alloc] initWithDuration:duration
																		  delay:0.0
																		options:0
															animationConditions:conditions
																	 animations:animations]];

	return self;
}

- (instancetype)animationWithDuration:(NSTimeInterval)duration
								delay:(NSTimeInterval)delay
							  options:(UIViewAnimationOptions)options
				  animationConditions:(void (^)(void))conditions
						   animations:(void (^)(void))animations
{
	[self.animationBlocks addObject:[[BARAnimationBlock alloc] initWithDuration:duration
																		  delay:delay
																		options:options
															animationConditions:conditions
																	 animations:animations]];

	return self;
}

- (instancetype)then
{
	return self;
}

- (instancetype)finally:(void (^)(void))finallyBlock
{
	_finallyBlock = [finallyBlock copy];

	return self;
}

- (instancetype)initially:(void (^)(void))initiallyBlock
{
	_initiallyBlock = [initiallyBlock copy];

	return self;
}

- (void)run
{
	if (self.initiallyBlock)
	{
		self.initiallyBlock();
	}

	[self runAnimationWithIndex:0];
}

// Recursive call animations
- (void)runAnimationWithIndex:(NSUInteger)index
{
	if (self.animationBlocks.count > index)
	{
		BARAnimationBlock *block = self.animationBlocks[index];
		if (block.conditions)
		{
			block.conditions();
		}

		[UIView animateWithDuration:block.duration delay:block.delay options:block.options animations:^{
			if (block.animations)
			{
				block.animations();
			}
		} completion:^(BOOL finished) {
			if (finished)
			{
				[self runAnimationWithIndex:index + 1];
			};
		}];
	}
	else
	{
		if (self.finallyBlock)
		{
			self.finallyBlock();
		}
	}
}

@end

Description

Simple class for chaining animations in functional style for iOS.

Why?

For example, look at the chained animations below:

dispatch_block_t animationsBlock = ^{
        [self.view updateConstraintsIfNeeded];
        [self.view layoutIfNeeded];
    };

    [gridView mas_updateConstraints:^(MASConstraintMaker *make) {
        make.top.equalTo(imageView).with.offset(32.0);
    }];

    [UIView animateWithDuration:0.425 animations:animationsBlock
        completion:^(BOOL finished) {
        if (finished)
        {
            [gridView mas_updateConstraints:^(MASConstraintMaker *make) {
                make.top.equalTo(imageView).with.offset(0.0);
            }];

            [UIView animateWithDuration:0.425 animations:animationsBlock
                completion:^(BOOL finished) {
                if (finished)
                {
                    [gridView mas_updateConstraints:^(MASConstraintMaker *make) {
                        make.top.equalTo(imageView).with.offset(-32.0);
                    }];

                    [UIView animateWithDuration:0.425 animations:animationsBlock
                        completion:^(BOOL finished) {
                        if (finished)
                        {
                            [gridView mas_updateConstraints:^(MASConstraintMaker *make) {
                                make.top.equalTo(imageView).with.offset(0.0);
                            }];

                            [UIView animateWithDuration:0.425 animations:animationsBlock
                                completion:^(BOOL finished) {
                                if (finished)
                                {
                                    [UIView animateWithDuration:0.8 animations:^{
                                        foreView.alpha = 1.0;
                                    } completion:^(BOOL finished) {
                                        if (finished)
                                        {
                                            [self.didEndSubject sendNext:[RACUnit defaultUnit]];
                                            [self.didEndSubject sendCompleted];
                                        }
                                    }];
                                }
                            }];
                        }
                    }];
                }
            }];
        }
    }];

Looks terrible, yeah? Just imagine how will you change this animation for a new product purpose.

And you can rewrite it with BARAnimation like that:

dispatch_block_t animationsBlock = ^{
        [self.view updateConstraintsIfNeeded];
        [self.view layoutIfNeeded];
    };

    [[[[[[[[[BARAnimation construct]
        initially:animationsBlock]
        animationWithDuration:0.425 animationConditions:^{
            [gridView mas_updateConstraints:^(MASConstraintMaker *make) {
                make.top.equalTo(imageView).with.offset(32.0);
            }];
        } animations:animationsBlock]
        animationWithDuration:0.425 animationConditions:^{
            [gridView mas_updateConstraints:^(MASConstraintMaker *make) {
                make.top.equalTo(imageView).with.offset(0.0);
            }];
        } animations:animationsBlock]
        animationWithDuration:0.425 animationConditions:^{
            [gridView mas_updateConstraints:^(MASConstraintMaker *make) {
                make.top.equalTo(imageView).with.offset(-32.0);
            }];
        } animations:animationsBlock]
        animationWithDuration:0.425 animationConditions:^{
            [gridView mas_updateConstraints:^(MASConstraintMaker *make) {
                make.top.equalTo(imageView).with.offset(0.0);
            }];
        } animations:animationsBlock]
        animationWithDuration:0.8 animationConditions:nil animations:^{
            foreView.alpha = 1.0;
        }]
        finally:^{
            [self.didEndSubject sendNext:[RACUnit defaultUnit]];
            [self.didEndSubject sendCompleted];
        }]
        run];

So, I can add some animations or remove any parts of them any time when I want.

Just hit the star if you like it)
Cheers.