iOS block

定义：

returnType (^funcName)(paramType paraName) = ^(paramType paraName){};

作为方法参数时：

- (void)fun:( returnType (^funcName)(paramType paraName) ) blockName{}

typedef:

typedef returnType (^funcName)(paramType paraName);

防止block发生循环引用：

__weak __typeof(self) weakSelf = self;