带委托参考的Swift默认参数值

Question

I am trying to do dependency injection in my code without using any framework, while refactoring I tried to pass dependency from outside. Now issue which I am facing is declaration of delegate which is needed for default parameter value.

init(service : MYService = MYService(withDelegate: self)) {

}

In above snippet, above object creation needs delegate from outside to transfer results. In Swift is their any way to declare that self reference in parameter.

Technically it seems like at this point self is not created as this is init method, now I have another option which I would like to go with if there is no another way for achieving it.

That is creating MYService object without delegate and I have to expose another method for accepting delegate.

Answer 1

It seems a good approach to inject any service as i hope the MYService class also conform to some protocol so that any service can be injected that conform to that protocol . Specific to this question i would like to recommend keep the delegate also as an injectable object as below,

init(service: MYService = MYService(), serviceDelegate: MyServiceDelegate? = nil) {
   if let delegate = serviceDelegate {
      service.delegate = delegate
   } else {
      service.delegate = self
   }
}

For this, you have to expose service delegate which should be totally fine as this is how we have in Swift ( UITableView , UITextField etc)

As i think you want to make the class that owns service as default delegate so i made the delegate as optional so that if its not there, this class will be the delegate otherwise if it will be the delegate passed along initialization .