Using a function call with lazy attribute results in a compile error

Question

When I call the following, the compiler complains that I am missing argument for parameter #1 in call :

import Foundation

class Person {

    func uniqueID() -> String {
        return NSUUID().UUIDString
    }

    lazy var sessionID: String = uniqueID()

}


let p = Person()

p.sessionID
p.sessionID
p.sessionID

When I replace the line with:

lazy var sessionID: String = NSUUID().UUIDString

It works.

What is causing the problem calling the function in a lazy initialization?

Interestingly, calling a closure works, even if the syntax looks clunky and heavy, as I would have to guard it if self is a weak reference:

lazy var sessionID: String = {
    return self.uniqueID()
}()

Marc Khadpe · Accepted Answer · 2015-12-20 03:46:53Z

1

The issue is you're missing the reference to self. You have it in the closure but not in the direct method call.

lazy var sessionID = self.uniqueID()

answered Dec 20, 2015 at 3:46

Marc Khadpe

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2 Comments

John Difool Over a year ago

Thanks. Should I always use self. when I call methods idiomatically? Omitting it on traditional calls seems to work, but 'lazy' behaves differently. Why is that?

Marc Khadpe Over a year ago

Just guessing, but it looks like a lazy initialization is essentially always treated as a closure, so they follow the rule that self must be explicit.

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