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Mike Koofer
Mike Koofer

Reputation: 45

Why does let cause this error, but var does not? Class `UIViewController` has no initializers

Alright, so I found this comment:

How to resolve this error? - Class 'ViewController' has no initializers

But no one answered the question. Why does this line cause an error:

let nameOfDelegate : protocolName!

But this one doesn't:

var nameOfDelegate : protocolName!

I understand that var is a mutable property and let is a constant, but both are being initialized, correct?

Upvotes: 1

Views: 63

Answers (3)

Alexandre Fenyo
Alexandre Fenyo

Reputation: 4819

There is no init() function, so none of these class members is initialized when the class is instanciated. But only one MUST be initialized when the class is instanciated: the one that is immutable, because it will not be possible to initialize it later. Therefore, add an initalizer, in an init() function or directly on the line that defines the constant.

Upvotes: 2

ukim
ukim

Reputation: 2477

In Swift optional variables are set to nil by default if you don't provide it with an initial value. Swift does not give constants default values.

Upvotes: 3

Arie Pinto
Arie Pinto

Reputation: 1292

its because its not initialized, since you will need to give it a value later, you wont be able, because its a "let", so you have to make it a var so you can later initialize it

but you could use values that are already initizalized from other places - exmaple: let appDelegate = UIApplication.shared.delegate

Upvotes: 0

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