Swift无法通过下标分配：“ peerDeviceSettings”是仅获取属性”

Question

I have this declaration in my class:

var peerDevice: [String: Any]? 

private var peerDeviceSettings:[String:Any]? {
    get {
        if let settings = peerDevice?["settings"] as? [String:Any] {
            return settings
        }

        return nil
    }
}

Now the problem is if I wish to change peerDeviceSettings, such as this:

 fileprivate func set(_ value: Any?, forKey key: Key) {
    if peerDeviceSettings != nil {
        peerDeviceSettings?[key.rawValue] = value
    } 
 }

I get an error

 Cannot assign through subscript: 'peerDeviceSettings' is a get-only property

The point is how do I rearchitect this thing without creating a new mutable variable peerDeviceSettings?

Answer 1

Just add set (setter) to the property and handle it there.

private var peerDeviceSettings:[String:Any]? {
    get {
        if let settings = peerDevice?["settings"] as? [String:Any] {
            return settings
        }

        return nil
    }
    set {

    }
}

Answer 2

your code seems to be fine, since you're creating links to the nested settings dictionary (sounds reasonably)

just add setter:

private var peerDeviceSettings: [String: Any]? {
    get {
        if let settings = peerDevice?["settings"] as? [String:Any] {
            return settings
        }

        return nil
    }
    set { 
      if peerDevice == nil {
        peerDevice = [:] // if it's desired behavior
      }
      peerDevice?["settings"] = newValue 
    }

}

I'd also suggest getting rid of optionality in peerDevice , just initialize it with empty value (if it feets your logic)

Answer 3

You see this error because you declared only getter for your property, you have also add setter

    private var peerDeviceSettings:[String:Any]? {
    get {
        if let settings = peerDevice?["settings"] as? [String:Any] {
            return settings
        }

        return nil
    }
    set {
        peerDevice?["settings"] = newValue
    }
}

UPDATE: to show how it must be in this certain case

Answer 4

You need a setter

private var peerDeviceSettings:[String:Any]? {
    get {
        return  peerDevice?["settings"] as? [String:Any]
    }

    set {
        peerDevice?["settings"] = newValue
    }
}