Blocks in Objective-C

blocks_in_objective-c.m

- (void)test
{
    int foo = 1;
    void (^block)() = ^() {
        NSLog(@"%d at %p", foo, &foo); //=> 1 at 0xbfffd65c / エンクロージャの変数fooは参照できる.
        // 以下は 'Variable is not assignable' コンパイルエラー
        // foo = 2;
    };
    block();
    NSLog(@"%d at %p", foo, &foo); //=> 1 at 0xbfffd6ac / block内のfooとはアドレスが違う.
    
    int *bar = malloc(sizeof(int));
    *bar = 1;
    void (^block2)() = ^() {
        NSLog(@"%d at %p, address of bar is %p", *bar, bar, &bar); //=> 1 at 0x4b21d30, address of bar is 0xbfffd658
        *bar = 2;
    };
    block2();
    NSLog(@"%d at %p, address of bar is %p", *bar, bar, &bar); //=> 2 at 0x4b21d30, address of bar is 0xbfffd6a4
    free(bar);
    
    int baz = 1;
    int *_baz = &baz;
    void (^block3)() = ^() {
        NSLog(@"%d", *_baz); //=> 1
        *_baz = 2;
    };
    block3();
    NSLog(@"%d", *_baz); //=> 2
}