Hi all, I really like this idea and appreciate the effort. However, I’d rather have a method similar to Ruby Object#tap <http://apidock.com/rails/Object/tap> and not a free function.
Well, since there’s no "Object class" in Swift, the way I see it is through a protocol, much like the Then <https://github.com/devxoul/Then> project is done. — A > On May 25, 2016, at 2:28 PM, Erica Sadun via swift-evolution > <swift-evolution@swift.org> wrote: > > Over the past couple of days, the Twitters have discovered some work I'd done > on closure-based setup. > It's clear that a demand is out there and strong for this kind of behavior, > even without implicit `self` as > part of the mix or cascading. In that light, I've put together the following: > > https://gist.github.com/erica/96d9c5bb4eaa3ed3b2ff82dc35aa8dae > <https://gist.github.com/erica/96d9c5bb4eaa3ed3b2ff82dc35aa8dae> > > If the community demand is this high, I think we should re-consider pushing > it before 3. > Feedback as always welcome, including criticism. > > -- E > > Introducing with to the Standard Library > > Proposal: TBD > Author: Erica Sadun <https://github.com/erica> > Status: TBD > Review manager: TBD > > <https://gist.github.com/erica/96d9c5bb4eaa3ed3b2ff82dc35aa8dae#introduction>Introduction > > This proposal introduces a with function to the standard library to simplify > the initialization and modification of constants and Foundation-sourced > complex objects. > > Swift-evolution thread: What about a VBA style with Statement? > <http://thread.gmane.org/gmane.comp.lang.swift.evolution/14384> > > <https://gist.github.com/erica/96d9c5bb4eaa3ed3b2ff82dc35aa8dae#motivation>Motivation > > Closure-based initialization enables clean and highly directed set-up in > Swift code. Numerous variations on the theme have been introduced on the > Swift Evolution list and in third party github repositories. Although you can > build solutions natively without functions, current Swift technology has > drawbacks: > > let questionLabel: UILabel = { > $0.textAlignment = .Center > $0.font = UIFont(name:"DnealianManuscript", size: 72) > $0.text = questionText > $0.numberOfLines = 0 > return $0 > }(UILabel()) > > let mySwitch : UISwitch = { > view.addSubview($0) > CenterViewInSuperview($0, horizontal: true, vertical: true) > $0.addTarget(self, action: "action", forControlEvents: .TouchUpInside) > return $0 > }(UISwitch()) > Assignment must be explicitly typed. > The source item must be postpended to the set-up closure. > The closure must return the item. > This approach is better suited to setting up Foundation objects than > modifying Swift constants. When duplicating and modifying a constant, the > closure must create a var copy and modify that copy. > While the implementation is imperfect, the wins are notable. Code naturally > groups into a clear set-up sequence. The scoped setup avoids clumpy redundant > lines where the same variable is accessed over and over. > > let questionLabel = UILabel() > questionLabel.textAlignment = .Center > questionLabel.font = UIFont(name:"DnealianManuscript", size: 72) > questionLabel.text = questionText > questionLabel.numberOfLines = 0 > In the case of non-reference types, a constant's fields may be set-up > sequentially without forcing the constant to be a variable. > > > <https://gist.github.com/erica/96d9c5bb4eaa3ed3b2ff82dc35aa8dae#detailed-design>Detailed > Design > > This proposal introduces a with function that enables modification and use of > an instance using positional references. It's not quite as clean as a > solution with implicit self but it offers sufficient utility that a vast > swath of Swift developers have adopted this function in some form or another. > > @discardableResult > public func with<T>(_ item: T, update: @noescape (inout T) throws -> Void) > rethrows -> T { > var this = item; try update(&this); return this > } > In use: > > struct Person { var name: String, favoriteColor: UIColor } > let john = Person(name: "John", favoriteColor: .blueColor()) > let jane = with(john){ $0.name = "Jane" } > print(jane) // Person(name: "Jane", favoriteColor: UIDeviceRGBColorSpace 0 0 > 1 1) > > struct Point { var (x, y) : (Double, Double) } > let p1 = Point(x: 2, y: 3) > let p2 = with(p1){ $0.y = 4 } > print(p1, p2) // Point(x: 2.0, y: 3.0) Point(x: 2.0, y: 4.0) > > <https://gist.github.com/erica/96d9c5bb4eaa3ed3b2ff82dc35aa8dae#impact-on-existing-code>Impact > on Existing Code > > This proposal is purely additive and has no impact on existing code > > > <https://gist.github.com/erica/96d9c5bb4eaa3ed3b2ff82dc35aa8dae#alternatives-considered>Alternatives > Considered > > Not adopting this proposal > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution
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