__NSCFString containsString:]: unrecognized selector sent to instance 0x7f876b79e160

If you want your code to work on iOS 7 as well as iOS 8 you should use one of the rangeOfString calls instead. Basically if the range returned has a length of zero, the substring is not there.
/* These methods return length==0 if the target string is not found. So, to check for containment: ([str rangeOfString:@"target"].length > 0). Note that the length of the range returned by these methods might be different than the length of the target string, due composed characters and such.
*/
- (NSRange)rangeOfString:(NSString *)aString;
- (NSRange)rangeOfString:(NSString *)aString options:(NSStringCompareOptions)mask;
- (NSRange)rangeOfString:(NSString *)aString options:(NSStringCompareOptions)mask range:(NSRange)searchRange;
- (NSRange)rangeOfString:(NSString *)aString options:(NSStringCompareOptions)mask range:(NSRange)searchRange locale:(NSLocale

@implementation NSString (Contains)

- (BOOL)myContainsString:(NSString*)other {
NSRange range = [self rangeOfString:other];
return range.length != 0;
}

@end

原文链接  http://stackoverflow.com/questions/26410420/nsstring-containsstring-crashes