63 (OC) * NSAutoreleasePool autorelease pool

table of Contents

 

text

1: NSAutorelease implementation principle

1: Starting from the main function

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // insert code here...
        NSLog(@"Hello, World!");
    }
    return 0;
}

 

2: @autoreleasepool

2.1：@autoreleasepool what exactly is it? We use the command line  for the compiler to rewrite the file: clang -rewrite-objc main.m

$ clang -rewrite-objc main.m

 

int main(int argc, const char * argv[]) {
    /* @autoreleasepool */ { __AtAutoreleasePool __autoreleasepool; 

        NSLog((NSString *)&__NSConstantStringImpl__var_folders_49_sdbnp0nd07q4m_sh4_gw52r40000gn_T_main_9e48ee_mi_0);
    }
    return 0;
}

In this file, there is a very strange  structure body , wrote the previous comment  . That   it is converted to: __ structure of AtAutoreleasePool. __AtAutoreleasePool/* @autoreleasepopl */@autoreleasepool {}

 

2.2: can be found by comparing apples around @autoreleasepool is replaced by a structure type __AtAutoreleasePool declare a local variable of type __AtAutoreleasePool

struct __AtAutoreleasePool { 
  __AtAutoreleasePool () {atautoreleasepoolobj = objc_autoreleasePoolPush ();}
   ~ __AtAutoreleasePool () {objc_autoreleasePoolPop (atautoreleasepoolobj);}
   Void * atautoreleasepoolobj; 
};

can be seen:

__AtAutoreleasePool () constructor calls objc_autoreleasePoolPush (),

~ __AtAutoreleasePool () calls the destructor objc_autoreleasePoolPop ()

 

2.3: This shows that our  main function is actually this:

int main(int argc, const char * argv[]) {
    {
        void * atautoreleasepoolobj = objc_autoreleasePoolPush();
        
        // do whatever you want
        
        objc_autoreleasePoolPop(atautoreleasepoolobj);
    }
    return 0;
}

@autoreleasepool Help us less just two lines of code to write, to make the code look more beautiful, then you want to analyze the automatic release of the pool according to the above two methods

 

to sum up