//強(qiáng)制去掉警告信息
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-variable"
NSString *testStr = @"test";
#pragma clang diagnostic pop
push和pop之間為忽略的范圍，如果不寫就是從#pragma clang diagnostic ignored "-Wunused-variable"開始忽略横媚；
"-Wunused-variable"忽略警告的類型，要結(jié)合具體警告
