Property initializers run before 'self' is available

问题

Seems like I'm having a problem with something that shouldn't be the case... But I would like to ask for some help.

There are some explanations here on the Stack I don't get.

Having two simple classes where one refers to another, as per below;

class User {
  lazy var name: String = ""
  lazy var age: Int = 0

  init (name: String, age: Int) {
      self.name = name
      self.age = age
  }
}

class MyOwn {
  let myUser: User = User(name: "John", age: 100)
  var life = myUser.age 
  //Cannot use instance member 'myUser' within property initializer
  //property initializers run before 'self' is available
}

I get the commented compile error. May someone please tell me what should I do to solve the case?

Many thanks to any good man for help!

回答1:

As correctly pointed by vadian you should create an init in such scenarios:

class MyOwn {
    let myUser: User
    var life: Int

    init() {
        self.myUser = User(name: "John", age: 100)
        self.life = myUser.age 
    }
}

You can't provide a default value for a stored property that depend on another instance property.

回答2:

You should declare life like this:

lazy var life:Int = {
    return self.myUser.age
}()

Because you are trying to initialise one property(variable) with another during initialisation process. At this time variables are not available yet.

来源：https://stackoverflow.com/questions/43550813/property-initializers-run-before-self-is-available