Why won't code that initializes a variable interface property in init block compile?

Question

interface A { var a: Int } class AJunior : A { override var a: Int init { a = 3 } }

It won't compile because

Property must be initialized or be abstract

But it is initialized. I know I can write:

override var a: Int = 3

But why won't the first example compile? My guess would be that it is a bug or an intentional limitation to simplify compiler implementation, but I'm not sure.

I see no reason for that not to work. Think it's a bug

voddan
– voddan

2015-12-02 12:41:48 +00:00
Commented Dec 2, 2015 at 12:41 — voddan
– voddan, Commented Dec 2, 2015 at 12:41

Mibac · Accepted Answer · 2017-09-19 20:36:13Z

1

I reported this as a bug, but turns out this behavior is by design because:

you could have code in the init block that could observe the property in its uninitialized state

edited Sep 19, 2017 at 20:36

Mibac

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answered Dec 2, 2015 at 14:59

gvlasov

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2 Comments

eski Over a year ago

I'm wondering about the same question you asked in that ticket, why would the val case work. If you try to reference 'a' before it's initialized in the init block you get the error 'Variable 'a' must be initialized.' I don't see any reason it wouldn't be the same for a var.

gvlasov Over a year ago

@eski You might want to join the discussion at the bug tracker.

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