Compiler error when using function in lazy stored property

Question

I am getting an error that says "Cannot convert value of type 'String' to argument type 'Test'" when trying to return a value from a function in lazy stored property. I am not able to spot any issue in the lazy var's closure.

import UIKit

public struct Value {}

public class Test {

    var id: String = ""

    public func getValueById(id: String) -> Value {
        return Value()
    }

    public lazy var value: Value = {
        // Compiler error: Cannot convert value of 'String' to expected argument type 'Test'
        return getValueById(self.id)
    }() 
}

Eric Aya · Accepted Answer · 2015-11-26 18:36:08Z

2

The compiler is confused about getValueById and the error message is meaningless - if not misleading.

What you need is to add self in front of getValueById(self.id) inside the closure:

public struct Value {}

public class Test {

    var id: String = ""

    public func getValueById(id: String) -> Value {
        return Value()
    }

    public lazy var value: Value = {
        return self.getValueById(self.id)
    }() 
}

edited Nov 26, 2015 at 18:36

answered Nov 26, 2015 at 18:25

Eric Aya

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1 Comment

zrzka Over a year ago

That's correct.Here's the quote from the ARC chapter, section Resolving Strong Reference Cycles for Closures (The Swift Programming Language) - Swift requires you to write self.someProperty or self.someMethod() (rather than just someProperty or someMethod()) whenever you refer to a member of self within a closure. This helps you remember that it’s possible to capture self by accident.

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