http://stackoverflow.com/questions/21268539/nsarraym-objectforkeyedsubscript-unrecognized-selector-sent-to-instance
2. 关于objectforkeyedsubscript
http://nshipster.com/object-subscripting/
3. NSArray Returning String Instead of Dictionary
http://stackoverflow.com/questions/18782053/nsarray-returning-string-instead-of-dictionary
这是由于下面的调用预期返NSDictionary, 然后没有检查返回id 对象的真正类型，而直接
jsonObject[@"key"]; 这样就导致该类的Crash发生。
1 id jsonObject = [NSJSONSerialization JSONObjectWithData:jsonResponse options:kNilOptions error:nil];
iOS.Crash.[__NSArrayM objectForKeyedSubscript:]
原文：http://www.cnblogs.com/cwgk/p/4534216.html