I’ll take the opposite stance. Why limit this to initialization? I’d love to be
able to guard assignments to *any* variable, whether it’s a property or not:
func foo() {
let bar: String
if someCondition {
guard bar = mightReturnOptional() else {
return
}
} else {
bar = wontReturnOptional()
}
self.doSomethingWith(bar)
}
As opposed to:
func foo() {
let bar: String
if someCondition {
guard let _bar = mightReturnOptional() else {
return
}
bar = _bar
} else {
bar = wontReturnOptional()
}
self.doSomethingWith(bar)
}
Charles
> On Jul 25, 2017, at 4:13 PM, Niels Andriesse via swift-evolution
> <[email protected]> wrote:
>
> Although I have come across this problem as well (particularly when
> initializing from JSON), I don't think the solution is to fundamentally
> change initialization behavior like this, because 1. ) that is probably going
> to break a good deal of existing code and 2. ) I think that the introduction
> of the Codable protocol in Swift 4 will eliminate most cases where this is
> really a problem.
> On Wed, 26 Jul 2017 at 02:30 Taylor Swift via swift-evolution
> <[email protected] <mailto:[email protected]>> wrote:
> I’d be in favor of this.
>
> On Tue, Jul 25, 2017 at 5:44 AM, philohan95 via swift-evolution
> <[email protected] <mailto:[email protected]>> wrote:
> I think the current way to initiate models in a Failable Initializer
> `init?()` is overly verbose and should be shortened down so less boilerplate
> should be needed.
>
> The current way:
>
> ```
> let someProperty: Any
> let anotherProperty: Any
>
> init?(data: [String: Any]) {
> guard
> let someProperty = data["some_key"],
> let anotherProperty = data["another_key"]
> else {
> return nil
> }
>
> self. someProperty = someProperty
> self. anotherProperty = anotherProperty
> }
> ```
>
> As you can see we had to use the properties twice (this would also be the
> case of `if let`) making the initializer twice as long as necessary and
> becomes a pain to implement when having more than 1 property.
>
> My idea is extending the power of the `guard` statement
>
> Idea:
> init?(data: [String: Any]) {
> guard
> someProperty = data["some_key"], // Currently fails
> because `self` us used before all stored properties are initialized
> anotherProperty = data["another_key"]
> else {
> return nil
> }
> }
> }
>
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