I was going through Apple's documentation and I saw something like this (void (^)(void))
. Can somebody explain what this statement means? ^
is XOR, right? void XOR void
doesn't makes much sense to me?
There was also something like (void (^)(BOOL finished))
These are blocks which add anonymous functions and function objects to Objective-C. See e.g. 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
Declaring a block variable:
void (^my_block)(void);
Assigning a block object to it:
my_block = ^(void){ printf("hello world\n"); };
Invoking it:
my_block(); // prints “hello world\n”
Accepting a block as an argument:
- (void)doSomething:(void (^)(void))block;
Using that method with an inline block:
[obj doSomeThing:^(void){ printf("block was called"); }];
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