iOS7 only returns 'NSInvalidArgumentException', reason: '-[__NSCFString containsString:]: [duplicate]

Answer 1

The problem is that containsString: is an iOS8 API and thus crashing under iOS7. You could just replace

[wordModel.word containsString:tappedSentence]

with

[wordModel.word rangeOfString:tappedSentence].location != NSNotFound