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Classification of blocks

2022-07-19 14:37:00 【InfoQ】

Block The classification of

  • NSConcreteGlobalBlock
      Global static  
    block
    , No external variables will be accessed .
  • NSConcreteStackBlock
      In the stack  
    block
    , When the function returns, it is destroyed .
  • NSConcreteMallocBlock
      Kept in a heap  
    block
    , When the reference count is  0  Will be destroyed .
NSConcreteGlobalBlock  Type of  block  The implementation of the
void (^testGlobalBlock)() = ^{
 NSLog(@"hello block");
};
int main(int argc, const char * argv[]) {
 testGlobalBlock();
 return 0;
}

testGlobalBlock Of
isa
Yes
_NSConcreteGlobalBlock
, That is to create... In the global area ,
block
Variables are stored in the global data store
NSConcreteStackBlock  Type of  block  The implementation of the
int main(int argc, const char * argv[]) {
 void (^testStackBlock)() = ^{
 NSLog(@"hello block");
 };
 testStackBlock();
 return 0;
}

testStackBlock Of
isa
Yes
_NSConcreteStackBlock
, That is, create .
NSConcreteMallocBlock  Type of  block  The implementation of the
int main(int argc, const char * argv[]) {
 void (^testStackBlock)() = [^{
 NSLog(@"hello block");
 } copy];
 testStackBlock();
 return 0;
}

NSConcreteMallocBlock
  Type of  
block
  Usually it doesn't appear directly in the source code , Its needs are determined by
_NSConcreteStackBlock
Type of
block
Copy it ( in other words
block
You need to perform
copy
Then it can be stored in the heap ).

Its internal function memmove In the stack
block
The contents of are copied to the heap , And make
isa
Yes
_NSConcreteMallocBlock
.

block
Some of the main knowledge is in the stack
block
To heap
block
In the process of transfer .
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