如何使用ReactiveCocoa 3实现基本的UITextField输入+ UIButton操作场景？ [英] How to implement a basic UITextField input + UIButton action scenario using ReactiveCocoa 3?

问题描述

我同时是Swift和ReactiveCocoa noob。使用MVVM和Reactive Cocoa v3.0-beta.4框架，我想实现此设置，以了解新RAC 3框架的基础知识。

I'm a Swift and ReactiveCocoa noob at the same time. Using MVVM and Reactive Cocoa v3.0-beta.4 framework, I'd like to implement this setup, to learn the basics of the new RAC 3 framework.

I有一个文本字段，我希望文本输入包含3个以上的字母，以进行验证。如果文本通过验证，则应启用下面的按钮。当按钮收到触地事件时，我想使用视图模型的属性触发一个动作。

I have a text field and I want the text input to contain more than 3 letters, for validation. If the text passes the validation, the button underneath should be enabled. When the button receives the touch down event, I want to trigger an action using the view model's property.

由于目前RAC 3.0测试版的资源非常少，我通过阅读框架的Github repo上的QAs来实现以下内容。以下是我到目前为止所能提出的建议：

Since there are very few resources about RAC 3.0 beta at the moment, I implemented the following by reading the QAs on the framework's Github repo. Here's what I could come up with so far:

ViewModel.swift

class ViewModel {

    var text = MutableProperty<String>("")
    let action: Action<String, Bool, NoError>
    let validatedTextProducer: SignalProducer<AnyObject?, NoError>

    init() {
        let validation: Signal<String, NoError> -> Signal<AnyObject?, NoError> = map ({
            string in
            return (count(string) > 3) as AnyObject?
        })

        validatedTextProducer = text.producer.lift(validation)

        //Dummy action for now. Will make a network request using the text property in the real app. 
        action = Action { _ in
            return SignalProducer { sink, disposable in
                sendNext(sink, true)
                sendCompleted(sink)
            }
        }
    }
}

ViewController.swift

class ViewController: UIViewController {

    private lazy var txtField: UITextField = {
        return createTextFieldAsSubviewOfView(self.view)
    }()

    private lazy var button: UIButton = {
        return createButtonAsSubviewOfView(self.view)
    }()

    private lazy var buttonEnabled: DynamicProperty = {
       return DynamicProperty(object: self.button, keyPath: "enabled")
    }()

    private let viewModel = ViewModel()
    private var cocoaAction: CocoaAction?

    override func viewDidLoad() {
        super.viewDidLoad()
        view.setNeedsUpdateConstraints()

        bindSignals()
    }

    func bindSignals() {
        viewModel.text <~ textSignal(txtField)
        buttonEnabled <~ viewModel.validatedTextProducer

        cocoaAction = CocoaAction(viewModel.action, input:"Actually I don't need any input.")
        button.addTarget(cocoaAction, action: CocoaAction.selector, forControlEvents: UIControlEvents.TouchDown)

        viewModel.action.values.observe(next: {value in
            println("view model action result \(value)")
        })
    }

    override func updateViewConstraints() {
        super.updateViewConstraints()

        //Some autolayout code here
    }
}

RACUtilities.swift

func textSignal(textField: UITextField) -> SignalProducer<String, NoError> {
    return textField.rac_textSignal().toSignalProducer()
        |> map { $0! as! String }
        |> catch {_ in SignalProducer(value: "") }
}

使用此设置，当视图模型的文本超过3个字符时，该按钮将启用。当用户点击按钮时，视图模型的动作运行，我可以将返回值设置为true。到目前为止一直很好。

With this setup, the button gets enabled when the view model's text is longer than 3 characters. When the user taps on the button, the view model's action runs and I can get the return value as true. So far so good.

我的问题是：在视图模型的操作中，我想使用其存储的文本属性并更新代码以使用它来发出网络请求。所以，我不需要视图控制器端的输入。我如何不需要输入我的Action属性？

My question is: Inside the view model's action, I want to use its stored text property and update the code to make a network request using it. So, I don't need an input from the view controller's side. How can I not require an input for my Action property?

推荐答案

来自 ReactiveCocoa / CHANGELOG.md ：

一个动作必须指出它接受的输入类型，它产生的输出类型，以及可能发生的错误类型（如果有的话）。

An action must indicate the type of input it accepts, the type of output it produces, and what kinds of errors can occur (if any).

因此，目前无法在没有输入的情况下定义 Action 。

So currently there is no way to define an Action without an input.

我想你可以声明你不关心输入 AnyObject？并创建 CocoaAction 带方便初始值：

I suppose you could declare that you don't care about input by making it AnyObject? and creating CocoaAction with convenience initialiser:

cocoaAction = CocoaAction(viewModel.action)

补充说明

• 我不喜欢使用 AnyObject？代替 Bool for validatedTextProducer 。我想你更喜欢它，因为绑定到 buttonEnabled 属性需要 AnyObject？。我宁愿把它放在那里，而不是牺牲我的视图模型的类型清晰度（见下面的例子）。

  Additional remarks

  • I dont't like using AnyObject? instead of Bool for validatedTextProducer. I suppose you preferred it because binding to the buttonEnabled property requires AnyObject?. I would rather cast it there though, instead of sacrificing type clarity of my view model (see example below).

    你可能想要限制执行<视图模型级别以及UI上的code>操作，例如：

    You might want to restrict execution of the Action on the view model level as well as UI, e.g.:

    class ViewModel {
    
        var text = MutableProperty<String>("")
        let action: Action<AnyObject?, Bool, NoError>
    
        // if you want to provide outside access to the property
        var textValid: PropertyOf<Bool> {
            return PropertyOf(_textValid)
        }
    
        private let _textValid = MutableProperty(false)
    
        init() {
            let validation: Signal<String, NoError> -> Signal<Bool, NoError> = map { string in
                return count(string) > 3
            }
    
            _textValid <~ text.producer |> validation
    
            action = Action(enabledIf:_textValid) { _ in
                //...
            }
        }
    }
    

    绑定到 buttonEnabled ：

    func bindSignals() {
        buttonEnabled <~ viewModel.action.enabled.producer |> map { $0 as AnyObject }
        //...
    }
    

  
  

  这篇关于如何使用ReactiveCocoa 3实现基本的UITextField输入+ UIButton操作场景？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！