Return from initializer without initializing all stored properties

Question

I have a simple class like this.

public class User {
    let id: Int
    let firstName: String
    let lastName: String
    let email: String?

    init(id: Int, firstName: String, lastName: String) {
        self.id = id
        self.firstName = firstName
        self.lastName = lastName
    }
}

This compiled just fine in previous Swift version. In Swift 1.2, I get the following compilation error.

Return from initializer without initializing all stored properties

Why is that and how can I resolve it?

Solution 1

If a property is constant, so created with let, you have to initialize it in place or in the init method, even if it is an Optional. If you want to be able to set email optionally, you should change let to var. In other words, if you are not initializing a variable in either the init method or class body, then the variable must be both a var and an Optional.

Related statements in the docs:

You can assign a value to a constant property at any point during initialization, as long as it is set to a definite value by the time initialization finishes. Once a constant property is assigned a value, it can’t be further modified.

For class instances, a constant property can only be modified during initialization by the class that introduces it. It cannot be modified by a subclass.

Solution 2

The rule of thumb is:

• If you have let, you need to initialize it (even if it is optional). Eg : let email: String
• If you have a non optional var you need to initialize. Eg var email: String
• If you have an optional var you don't need to initialize it. Eg var email: String?

Solution 3

You need to explicitly set a value for email since it is a constant.

public class User {
    let id: Int
    let firstName: String
    let lastName: String
    let email: String?

    init(id: Int, firstName: String, lastName: String) {
        self.id = id
        self.firstName = firstName
        self.lastName = lastName
        self.email = nil // <--------------
    }
}

Or as the others mentioned you can change email to a variable.

Solution 4

Change the email from "let" to "var" as below.

public class User {
    let id: Int
    let firstName: String
    let lastName: String
    var email: String?

    init(id: Int, firstName: String, lastName: String) {
        self.id = id
        self.firstName = firstName
        self.lastName = lastName

    }
}

Solution 5

First of all make it clear that every let variable must be assigned value at declaration time. So your statements will be

let id: Int  = 0
let firstName: String = "test"
let lastName: String = "Test"
let email: String? = "Test"

Secondly in classes, you must have to initialize variables or define them as optional types by either putting '?' or '!' with every variable. Like

let id: Int!
let firstName: String!
let lastName: String!
let email: String?

or

let id: Int?
let firstName: String?
let lastName: String?
let email: String?

But want to say you here that these variables will not be able to change as they are constants. so you must use var with these if you'r not passing value at time of declaration. Your final code in this case will be some kind of this

var id: Int
var firstName: String
var lastName: String
var email: String?

View more solutions

Comments

[Jurik]

It does not matter if you use let or var. You have to set it in initializer to avoid this compile error. I had same error without using any let variables and this error appeared as well. So I had to remove or setup this variables to avoid this compile error.

[Dániel Nagy]

@Jurik in case of 'Optional's, it does matter, otherwise it's true what you stated.

[VKK]

@DánielNagy the way your answer is phrased is a bit misleading because on a quick read, it would lead one to believe changing let to var, would solve the error. In reality, there are two things that are needed: 1) Changing let to var, and 2) Using optionals

[VKK]

@DánielNagy I do realize in the OP's case its his constant Optional email variable that's causing the error, so the only change necessary is changing it to var, but I think its worth clarifying this for other readers who just look at your answer. I modified the answer to make it a little more clear.