记录群聊天关于block内部引用问题

// %p &testStr 是object自身的内存地址

// %p testStr  是指向的内存地址　

// block本质是对象，访问外部变量当成自己的成员变量

// block内有一个新的引用，指向原对象所指向的内存地址

@autoreleasepool {
        NSMutableString *testStr = [[[NSMutableString alloc]initWithString:@"String"] autorelease];
        NSLog(@" NORMAL : %@, %p, %p", testStr, testStr, &testStr);
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
            [testStr appendString:@" Append"];
            NSLog(@"Bgroud : %@, %p, %p", testStr, testStr, &testStr);
        });
        NSLog(@" Append : %@, %p, %p", testStr, testStr, &testStr);
    }

2014-05-23 09:38:13.772 PPPTest[1839:60b]  NORMAL : String, 0x8e74cd0, 0xbfffc8c4
2014-05-23 09:38:13.772 PPPTest[1839:60b]  Append : String, 0x8e74cd0, 0xbfffc8c4
2014-05-23 09:38:13.772 PPPTest[1839:1303] Bgroud : String Append, 0x8e74cd0, 0x8e74e94

@autoreleasepool {
        __block int nInt = 10;
        NSLog(@"    : %d, %p", nInt, &nInt);
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
            ++nInt;
            NSLog(@"bg : %d, %p", nInt, &nInt);
        });
        ++nInt;
        NSLog(@" ++ : %d, %p", nInt, &nInt);
    }

2014-05-23 09:38:54.446 PPPTest[1851:60b]     : 10, 0xbfffc8c8
2014-05-23 09:38:54.446 PPPTest[1851:60b]  ++ : 11, 0x8d7be50
2014-05-23 09:38:54.446 PPPTest[1851:1303] bg : 12, 0x8d7be50