子类中的 Swift 5.1 泛型用法

Question

I have the following data model class to represent a MyDataModel:

  public class MyDataModel <T> : Codable, Comparable where T:Codable {

   ...
  }

Next I implement a view that holds an instance of MyDataModel. I can not obviously hold a generic parameter in the subclass of UIView so I try to workaround it as follows:

 protocol MyDataProtocol {
    associatedtype T:Codable
     var dataParam:T { get set }
 }

  public class MyDataView: UIView {

      public var myData:some MyDataProtocol?

  }

But I get an error

  An 'opaque' type must specify only 'Any', 'AnyObject', protocols, and/or a base class

So I can use Any? as type for MyDataProtocol but that will still not tell me the param type of MyDataModel. I am wondering what is the solution here and right way to handle this issue.

Answer 1

You should set an object for myData property and the error wouldn't show.

public class MyDataModel <T> : Codable, Comparable where T:Codable {
    
    public static func == (lhs: MyDataModel<T>, rhs: MyDataModel<T>) -> Bool {
        <#code#>
    }
    
    public static func < (lhs: MyDataModel<T>, rhs: MyDataModel<T>) -> Bool {
        <#code#>
    }
    
}


public protocol MyDataProtocol {
    associatedtype T
    var dataParam:T? { get set }
}

class MyData: MyDataProtocol {
    var dataParam: Codable?
    typealias T = Codable
    
    init() {}
}

public class MyDataView: UIView {
    public var myData: some MyDataProtocol = MyData()
}