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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