在block函数中规避错误信息 "capturing self strongly in this block is likely to lead to a retain cycle”

以形如

       _fontValueChangedBlock = ^(){
            [self.fontSmallButton addTarget:self action:@selector(btnFontSmallClicked) forControlEvents:UIControlEventTouchUpInside];
        };

的代码为例，这个代码运行会报警告。"capturing self strongly in this block is likely to lead to a retain cycle” 

要想消除这个警告，需要将代码改为如下形式：

        __weak typeof(self) weakSelf = self;
        
        _fontValueChangedBlock = ^(){
            typeof(weakSelf) __strong strongSelf = weakSelf;
            [strongSelf.fontSmallButton addTarget:strongSelf action:@selector(btnFontSmallClicked) forControlEvents:UIControlEventTouchUpInside];
        };

参考 http://stackoverflow.com/questions/16067712/avoiding-the-capturing-self-strongly-in-this-block-is-likely-to-lead-to-a-retai