Playing around with Blocks in Objective-C

blocks.m

        @interface Pair : NSObject
                @property (nonatomic, copy) void (^blockAsProperty)(int val);
                +(void) displayBlock:(void(^)(int param))blockAsMethodParameter;
        @end

        @implementation Pair
                +(void) displayBlock:(void(^)(int param)) blockAsMethodParameter{
                        blockAsMethodParameter(10);
                }
        @end
        
        // blocks as typedef
        typedef void(^callback)(BOOL success, id value);

        // block with void return and no arguments
        void(^voidBlock)() = ^{
            NSLog(@"b");
        };
        voidBlock();
        
        // blocks can be stored in arrays
        NSArray *arrayblocks = [NSArray arrayWithObjects:voidBlock, voidBlock, nil];
        for (void (^block)() in arrayblocks) {
            block();
        }
        
        // block with void return and arguments
        // you can extend it to many more arguments
        void(^blockWithParameters)(int a, int b) = ^(int a, int b){
            NSLog(@"a+b=%d", a+b);
        };
        blockWithParameters(10,20);
        
        arrayblocks = [NSArray arrayWithObjects:blockWithParameters, blockWithParameters, nil];
        for (void (^blockWithParameters)(int param1, int param2) in arrayblocks) {
            blockWithParameters(100,20);
        }
        
        // blocks can also be used to return values
        int(^blockWithReturnType)(int a) = ^(int a){
            return a*a;
        };
        
        // assign a value from the block
        int blockReturnValue = blockWithReturnType(100);
        NSLog(@"return value %d", blockReturnValue);
        
        // blocks as property
        Pair *pair = [Pair new];
        [pair setBlockAsProperty:^(int param) {
            NSLog(@"block as property %d", param);
        }];
        pair.blockAsProperty(10);
        
        // blocks as method parameter
        [Pair displayBlock:^(int param) {
            NSLog(@"displayBlock %d",param);
        }];
        
        // copying a block to use it in some other place
        int salt = 42;
        int(^m_storedBlock)(int param) = ^(int incoming){
                return 2 + incoming + salt;
        };
        
        m_storedBlock = [^(int incoming){
            return 2+incoming+salt;
        } copy];
        
        int outputValue = m_storedBlock(5);
        NSLog(@"When we ran our stored block we got back: %d", outputValue);