如何打印一个块

In C/Obj-C, we do a typedef like this typedef int MYINT; which is clear.

在C/ object -C中，我们使用这种类型定义;这是明确的。

Doing typedef for a block -typedef void (^MyBlock) (int a);

为一块做typedef typedef无效(^ MyBlock)(int);

Now, we can use MyBlock.

现在，我们可以使用MyBlock。

Shouldn't it be like - typedef void (^MyBlock) (int a) MyBlock; similar to #define?

它不应该像typedef空白(^ MyBlock)(int)MyBlock;类似于#定义?

How the syntax works?

语法是如何运作的吗?

2 个解决方案

#1

See Declaring a Block Reference in "Blocks Programming Topics":

参见在“块编程主题”中声明块引用:

Block variables hold references to blocks. You declare them using syntax similar to that you use to declare a pointer to a function, except that you use ^ instead of *.

块变量保存对块的引用。您声明它们使用语法类似于用来声明一个指针指向一个函数,除了你使用^ *。

所以

 typedef void (^myBlock) (int a);

defines a the type of a block using the same syntax as

使用与之相同的语法定义块的类型

 typedef void (*myFunc) (int a);

declares a function pointer.

声明一个函数指针。

See e.g. Understanding typedefs for function pointers in C for more information about function pointers.

要了解更多关于函数指针的信息，请参见C中的函数指针的typedefs。

#2

Also from "Blocks Programming Topics", creating a type for blocks should be like this:

同样，从“块编程主题”中，为块创建类型应该如下所示:

typedef returnType (^blockName)(argument1, argument2, ...)

Below is a very simple practical example:

下面是一个非常简单的实际例子:

typedef float (^MyBlockType)(float, float);
MyBlockType AddTwoFloat = ^(float a, float b) {return a + b;};
MyBlockType MultiplyTwoFloat = ^(float a, float b) {return a * b;};
float c = AddTwoFloat(1, 2); //c = 3
float d = MultiplyTwoFloat(1, 2); //d = 2

#1