如何将数组添加到nsdictionary中的键

I want to add an array to a key in nsdictionary. Such as each key is a question and each questions has multiple answers.

我想在nsdictionary中为一个键添加一个数组。比如每个键都是一个问题,每个问题都有多个答案。

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

问题1 = [答案1],[答案2],[答案3];

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

问题2 = [答案1],[答案2],[答案3];

With below code I get No Visible @interface for NSDictionary declares the selector 'setObject:forKey:'

使用下面的代码我得到NSVictionary的No Visible @interface声明了选择器'setObject:forKey:'

//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"];

What is correct way to add an array to a key in NSDictionary?

在NSDictionary中向数组添加数组的正确方法是什么?

2 个解决方案

#1

_surveyAnswers1 seems to be declared as an NSDictionary:

_surveyAnswers1似乎被声明为NSDictionary:

NSDictionary * _surveyAnswers1;

You need to declare it as NSMutableDictionary:

您需要将其声明为NSMutableDictionary:

NSMutableDictionary * _surveyAnswers1;

The compiler checks what methods are available on the object based on its declared type; NSDictionary does not have the method setObject:forKey:, so the compiler warns you (under ARC, this is an error) about that. It would work at runtime, because the object actually is an NSMutableDictionary, but you should still fix the declaration.

编译器根据其声明的类型检查对象上可用的方法; NSDictionary没有方法setObject:forKey:,因此编译器会警告您(在ARC下,这是一个错误)。它可以在运行时工作,因为该对象实际上是一个NSMutableDictionary,但你仍然应该修复声明。

#2

Although you are instantiating _surveyAnswers1 as an NSMutableDictionary, it's declared as an NSDictionary type so either change _surveyAnswers1 to be NSMutableDictionary type or cast _surveyAnswers1 to NSMutableDictionary when you call setObject:forKey:

虽然您将_surveyAnswers1实例化为NSMutableDictionary,但它被声明为NSDictionary类型,因此当您调用setObject:forKey时,将_surveyAnswers1更改为NSMutableDictionary类型或将_surveyAnswers1强制转换为NSMutableDictionary:

[((NSMutableDictionary *)_surveyAnswers1) setObject:myArrayAnswers1 forKey:@"FirstKey"];
[((NSMutableDictionary *)_surveyAnswers1) setObject:myArrayAnswers2 forKey:@"SecondKey"];

#1