Value of type 'T' has no dynamic member 'object' using key path from root type 'T'

Question

I had a class like this:

class ObjectA:ObservableObject { 
  @Published var type:ObjectSheetType = .none
}

and I was using a class like this to process instances of this kind of object:

class ProcessObject {

  @ObservedObject private var object:ObjectA

  init(object:ObjectA) {
    self.object = object
  }

  process() {
    if object.type == .big {
     // bla bla
    }
    ...
  }

Then I have decided to add another class:

class ObjectB:ObservableObject { 
  @Published var type:ObjectSheetType = .none
}

and a protocol

protocol ObjectProtocol {
  var type:ObjectSheetType { get set }
}

This protocol was added to both classes: ObjectA and ObjectB.

Then the class ProcessObject was modified to accept objects of both kinds:

class processObject<T:ObjectProtocol, ObservableObject > {

  @ObservedObject private var object:T

  init(object:T) {
    self.object = object
  }

Error: Referencing subscript 'subscript(dynamicMember:)' requires wrapper 'ObservedObject.Wrapper' Insert '$' Value of type 'T' has no dynamic member 'object' using key path from root type 'T'

error pointing to

if object.type == .big {

but also Xcode wants me to use $ in front of every published properties of object?

How do I solve this?

Answer 1

All you need to do is to fix the protocol conformance of T because now ObservableObject is seen as another generic type and not the protocol.

Use & to say that T should conform to both protocols

class ProcessObject<T: ObjectProtocol & ObservableObject> {

}

Another way is to say that ObjectProtocol inherits from ObservableObject and then only use ObjectProtocol in all the conform declarations

protocol ObjectProtocol: ObservableObject {
    var type:ObjectSheetType { get set }
}

but that changes what ObjectProtocol is and you may not want that tight coupling between the two protocols