iOS7.0以下『containsString』报 __NSCFString containsString:]: unrecognized selector sent to instance
-(BOOL)containsString:(NSString*)strNS_AVAILABLE(10_10,8_0);containsString方法在iOS8.0才可用,7.x运行时会报错__NSCFStringcontainsString:]:unrecognizedselectorsenttoinstance在自己写的NSString扩展中NSString+Extension.h重写系统的