ios-給nsdictionary的key添加一個數組

給nsdictionary的key添加一個數組

想給nsdictionary的key添加一個數組,其中每個key都是一個question，每個question對應多個answer：

---

Question1 = [Answer1], [Answer2] , [Answer3];

Question2 = [Answer1], [Answer2] , [Answer3];

---

然後我嘗試用下面的代碼時報錯：

No Visible @interface for NSDictionary declares the selector 'setObject::forKey'

代碼：

//answers
_surveyAnswers1 = [[NSMutableDictionary alloc] init];
NSArray *myArrayAnswers1 = [NSArray arrayWithObjects:@"One",@"Two", nil];
NSArray *myArrayAnswers2 = [NSArray arrayWithObjects:@"Three",@"Four", nil];
[_surveyAnswers1 setObject:myArrayAnswers1 forKey:@"FirstKey"];
[_surveyAnswers1 setObject:myArrayAnswers2 forKey:@"SecondKey"];

不知道怎麼正確添加？

最佳回答：

你好像把_surveyAnswers1聲明為NSDictionary了：

NSDictionary * _surveyAnswers1;

應該聲明為NSMutableDictionary:

NSMutableDictionary * _surveyAnswers1;

編譯器根據聲明的類型來判斷哪些方法是有效的，NSDictionary沒有這個方法setObject:forKey:，因此編譯器會發出警告