objective-c – 类型而不是变量之间的插入字符,用括号括起来

我正在阅读Apple的文档,我看到了类似的东西(void(^)(void)).有人可以解释这句话的含义吗？ ^是XOR,对吗？虚空XOR虚空对我来说没有多大意义？

还有类似的东西(void(^)(BOOL完成))

这些是向Objective-C添加匿名函数和函数对象的块.参见例如 Introducing Blocks and Grand Central Dispatch ：

Block objects (informally, “blocks”) are an extension to C, as well as Objective-C and C++, that make it easy for programmers to define self-contained units of work. Blocks are similar to — but far more powerful than — traditional function pointers. The key differences are:

• Blocks can be defined inline, as “anonymous functions.”
• Blocks capture read-only copies of local variables, similar to “closures” in other languages

声明一个块变量：

void (^my_block)(void);

为其分配块对象：

my_block = ^(void){ printf("hello world\n"); };

调用它：

my_block(); // prints “hello world\n”

接受块作为参数：

- (void)doSomething:(void (^)(void))block;

将该方法与内联块一起使用：

[obj doSomeThing:^(void){ printf("block was called"); }];