But the expression that is assigned to the property will be eagerly evaluated
to produce `newValue`. So this will not accomplish what Nevin is trying to do.
> On Sep 11, 2017, at 3:08 PM, Slava Pestov via swift-users
> <swift-users@swift.org> wrote:
>
> You can have valueSource store a closure that captures the autoclosure value.
> For example,
>
> set {
> valueSource = { newValue }
> }
>
> Slava
>
>> On Sep 11, 2017, at 11:04 AM, Nevin Brackett-Rozinsky via swift-users
>> <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:
>>
>> Hi, quick question here:
>>
>> I have a class with a property that needs to be really *really* lazy. So
>> lazy, in fact, that when you assign to that property, the class actually
>> stores a closure of what you assigned, which is only evaluated if and when
>> you actually attempt to read the property.
>>
>> Simplified:
>>
>> class Foo {
>> private var valueSource: () -> Bar
>> private var valueCache: Bar?
>>
>> init(_ v: @escaping @autoclosure () -> Bar) {
>> valueSource = v
>> }
>>
>> var value: Bar {
>> get {
>> if let v = valueCache { return v }
>> let w = valueSource()
>> valueCache = w
>> return w
>> }
>> set {
>> /* ??? */
>> }
>> }
>>
>> // I want this function's logic to go in the setter above
>> func setValue(_ v: @escaping @autoclosure () -> Bar) {
>> valueSource = v
>> valueCache = nil
>> }
>> }
>>
>> The goal is to be able to write things like “someFoo.value = bar1 / bar2”
>> (or even more complex expressions) and not evaluate them until/unless the
>> result is actually needed.
>>
>> Currently I am using “someFoo.setValue( bar1 / bar2 )”, which is not nearly
>> as ergonomic as the assignment syntax. So, is there a way to make this work?
>>
>> Nevin
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>
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