Objective-c – type instead of insertion characters between variables, enclose in parentheses

void (^my_block)(void); 
Assign a block object to it:
 
 
my_block = ^(void){ printf("hello world
"); };
Call it:

my_block(); // prints "hello world
"
Accept a block as a parameter:

- (void)doSomething:(void (^)(void))block ;
Use this method with inline blocks:

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

I am reading Apple's documentation and I saw something similar (void(^)(void)). Can someone explain the meaning of this sentence? ? ^It's XOR, right? Void XOR Void does not make much sense to me?

There are similar things (void(^)(BOOL complete))

These are additions to Objective-C Blocks of anonymous functions and function objects. See for example 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

Declare a block variable:

void (^my_block)(void);

Assign a block object to it:< /p>

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

Call it:

< /p>

my_block(); // prints "hello world
"

Accept block as a parameter:

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

Use this method with inline blocks:

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