Would it solve the issue if we had lazy let initialisers as I mentioned?
-----Original Message-----
From: "David Sweeris" <[email protected]>
Sent: 18/05/2016 06:08 AM
To: "Leonardo Pessoa" <[email protected]>
Cc: "Swift-evolution" <[email protected]>
Subject: Re: [swift-evolution] [proposal] Allow "let" for computed
propertieswhich only reference immutable data
`lazy` properties can't be `let`. Personally, I disagree with this — their
initial mutation is transparent, and it's conceptually perfectly valid to have
a value that's, say, too expensive to calculate during every instance's init
and whose value never changes once calculated — but there may well be Very Good
Reasons for needing them to be `var`.
- Dave Sweeris
On May 17, 2016, at 17:23, Leonardo Pessoa <[email protected]> wrote:
David, I'm thinking about the side effects calling a computed property has and
although I see some use cases for let properties I also see workarounds. For
example, a lazy initialiser will solve the issue of running a certain code only
once and caching its value. I also start to think that any case in this
proposal will be solved by lazy initialisers thus rendering it unnecessary.
On 17 May 2016 at 17:50, David Sweeris <[email protected]> wrote:
You can't, if you're extending a pre-existing type.
I'd think that it might be possible to do some caching if the compiler knows
that a computed property is constant, but maybe it doesn't work that way.
- Dave Sweeris
On May 17, 2016, at 14:40, Leonardo Pessoa via swift-evolution
<[email protected]> wrote:
If the value of the property is a constant, shouldn't you just declare it as
one? If you have any sort of computation in it, even concatenating two constant
strings, can you really say this is a constant? And you would also be
overloading the compiler into trying to check for every property you use let if
the overall computation is constant or not. IMO, let isn't really the most
appropriate keyword to use for properties.
- Leonardo
On 13 May 2016 at 04:44, Andru Felipe Zuniga via swift-evolution
<[email protected]> wrote:
It would be useful for clarification of a computed property being constant in
extensions. For example:
extension SKSpriteNode {
static let type: String {
return “Sprite”
}
}
Andru
_______________________________________________
swift-evolution mailing list
[email protected]
https://lists.swift.org/mailman/listinfo/swift-evolution
_______________________________________________
swift-evolution mailing list
[email protected]
https://lists.swift.org/mailman/listinfo/swift-evolution_______________________________________________
swift-evolution mailing list
[email protected]
https://lists.swift.org/mailman/listinfo/swift-evolution
