Greetings > 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?
Unless I'm missing something, can't you just call the closure that you passed to the init ? Or do you want to use a different closure ? You could always have a var that is a tuple, with one part being the value and the other the closure. Joanna -- Joanna Carter Carter Consulting _______________________________________________ swift-users mailing list swift-users@swift.org https://lists.swift.org/mailman/listinfo/swift-users