我在浏览 Apple 的文档时看到了类似这样的内容 (void (^)(void))
。有人能解释一下这句话的意思吗? ^
是异或,对吧? void XOR void
对我来说没有多大意义?
还有类似 (void (^)(BOOL finish))
最佳答案
这些是向 Objective-C 添加匿名函数和函数对象的 block 。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 block 变量:
void (^my_block)(void);
为其分配一个 block 对象:
my_block = ^(void){ printf("hello world\n"); };
调用它:
my_block(); // prints “hello world\n”
接受 block 作为参数:
- (void)doSomething:(void (^)(void))block;
将该方法与内联 block 一起使用:
[obj doSomeThing:^(void){ printf("block was called"); }];
关于objective-c - 类型之间而不是变量之间的插入符,用括号括起来,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/30335045/