如何创建嵌套的 Encodable class 并从 Swift 中的 function 返回它？

Question

In my iOS project, I want to do the following:

• create an Encodable class (named ChannelAnswer ) which has multiple attributes, including another generic Encodable object
• pass an instance of that class as an argument of a function or return it from a function

Here is what I tried:

class ChannelAnswer<T> : Encodable where T : Encodable
{
    let errorCode: String?
    let data: T?
    let origin: Int = 2

    init(_ errorCode: String?, _ data: T? = nil)
    {
        self.errorCode = errorCode
        self.data = data
    }
}

Now, if I want to return an instance of that class from a function, like the following:

func test() -> ChannelAnswer
{
    ...
    return ChannelAnswer("abc", anyEncodableObject)
}

I get the following error:

Reference to generic type 'ChannelAnswer' requires arguments in <...>

The thing is: the data attribute could be of any type , I only know that that type is Encodable (the test() function above is just an example for the sake of simplicity).

So how can I create my ChannelAnswer class and successfully pass it as an argument of a function or return it from a function?

Thanks.

Answer 1

What you need is a generic method.

func test<T: Encodable>(data: T) -> ChannelAnswer<T> {
    // ...
    return ChannelAnswer("abc", data)
}