Block correlation (1)

Block’s trick

Xcode has a built-in Block Snippet, just type inline and it will appear.

C Inline Block as Variable – Save a block to a variable to allow reuse or passing it as an argument.

returnType(^blockName)(parameterTypes) = ^(parameters){
    statements 
};Copy the code

But this is actually not the way to define a complete Block, if you want to define a complete Block.

returnType(^blockName)(parameterTypes) = ^returnType(parameters){
    statements 
};Copy the code

Block Common Scenarios

1. Block Is used temporarily

[myArray enumerateObjectsUsingBlock:^(id object, NSUInteger index, BOOL*stop) {    
    [self doSomethingWith:object];
}];
[myArray enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(idobj, NSUInteger idx, BOOL *stop) {    
    [self doSomethingWith:object];
}];Copy the code

NSArray* enumerateArray = @[@"1 🐶"The @"2 🐱"The @"3 🐭"The @"Four 🐹"The @"Five 🦊" ]; 
[enumerateArray enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(id obj, NSUInteger idx, BOOL *stop) { 
    NSLog(@"% @ % @", obj, [NSThread currentThread]); 
}];Copy the code

It is important to note that this option can be executed concurrently or in reverse.

NSEnumerationOptions
    -> NSEnumerationConcurrent
    -> NSEnumerationReverseCopy the code

NSEnumerationConcurrent takes special note

2. Blocks are used for short periods, but are stored (e.g., they need to be stored, but are called only once, or have a completion period. For example, an animation of UIView, after the animation is done, you need to notify the outside world with a block. Once the block is called, the block can be deleted.

[UIView animateWithDuration:0.2 animations:^{// animations go here}]; [UIView animateWithDuration:0.2 animations:^{// animations go here} completion:^(BOOL finished) {// Block Fires WHEN animation has finished } ]; [UIView animateKeyframesWithDuration: delay 0.2:0.0 options: UIViewKeyframeAnimationOptionCalculationModeLinear animations:^{ // animations go here } completion:^(BOOL finished) { // block fires when animaiton has finished } ];Copy the code

3. Long term use of a Block (eg as an attribute)

// block instead of delegate- (void) viewDidLoad {
    [super viewDidLoad];
    Person* person = [[Person alloc] init];
    person.run = ^(){
        NSLog(@ "running 🏃 ‍ came ️ 🏃 ‍ came ️"); }; _p = person; } - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    self.p.run();
}Copy the code