How to enforce generic constraints on a variable?

Using Swift
1

Hi Swift experts!
I'm looking for some help on how to implement this properly.

I have a protocol for a Command with a strong typed parameter:

 protocol Command {
    associatedtype Parameter

    func canExecute(for: Parameter) -> Bool        
    func execute(with: Parameter) async
}

and I have a protocol for a Command Manager:

protocol CommandManaging {
    associatedtype C where C: Command
    
    var managedCommands: [C] { get }    
    func updateCommands(parameter: C.Parameter)
}

I'd like to implement Command Manager but keep the Parameter generic

class CommandManager<Parameter>: CommandManaging {  
 // How to implement this? 
}

so that other components can use it like this:

let manager: CommandManager<Int> = .init([command1, command2])
manager.updateCommands(parameter: 123)

But I can't find the proper way to implement the CommandManager class.
Is his even possible?

2

Hi, try this code:

struct CommandInt: Command {
  func canExecute(for value: Int) -> Bool { true }
  func execute(with value: Int) async { }
}

class CommandManager<T: Command>: CommandManaging {
  private(set) internal var managedCommands: [T]
  
  init(_ commands: [T]) {
    managedCommands = commands
  }
  
  func updateCommands(parameter: T.Parameter) {
    
  }
}

let manager = CommandManager([CommandInt(), CommandInt()])
manager.updateCommands(parameter: 123)
3

There's more than one way to achieve the effect you're after. The best approach heavily depends on what exactly is the problem you're solving.

For instance, what is a CommandManaging supposed to be in charge of? What does it mean to update commands? Is a command expected to provide a custom interface that needs to be retained when necessary?