關(guān)閉警告：

#pragma clang diagnostic push

#pragma clang diagnostic ignored "-Warc-performSelector-leaks"

[myObj performSelector:mySelector withObject:name];

#pragma clang diagnostic pop

忽略沒用的變量

#pragma unused (foo)

明確定義錯(cuò)誤和警告

#error Whoa, buddy, you need to check for zero here!

#warning Dude, don't compare floating point numbers like this!