阻止作为局部变量

returnType (^blockName)(parameterType1, parameterType2, ...) = ^returnType(argument1, argument2, ...) {...};    

float (^square)(float) = ^(float x) {return x*x;};

square(5); // resolves to 25
square(-7); // resolves to 49

这是一个没有返回且没有参数的示例：

NSMutableDictionary *localStatus;
void (^logStatus)() = ^(void){ [MYUniversalLogger logCurrentStatus:localStatus]};

// Insert some code to add useful status information
// to localStatus dictionary 

logStatus(); // this will call the block with the current localStatus