Reactive Cocoa - 以编程方式设置文本时不会调用UITextView的rac_textSignal [英] Reactive Cocoa - UITextView's rac_textSignal doesn't get called when programmatically setting text
问题描述
我正在实施聊天用户界面，并使用Reactive Cocoa根据用户的类型调整聊天气泡的大小。目前，我正在根据textview的 rac_textSignal 更新UI的布局。一切都很好 - 除了一点：当用户发送消息时，我以编程方式清除文本字段：
I'm implementing a chat UI, and using Reactive Cocoa to adjust the chat bubble's size as the user types. Currently, I'm updating the UI's layout based on the textview's rac_textSignal. Everything's working great - except for one bit: when the user sends the message, I programmatically clear the textfield:
_inputTextView.text = @"";
...但是textview的 rac_textSignal 没有不要激活。 我听说这是ReactiveCocoa的一个功能 - 但是构建它的正确方法是什么？我是否需要拥有一个持有 currentlyTypedString 的NSString，并在该字符串更新时驱动UI更改？
... but the textview's rac_textSignal doesn't activate. I hear this is a feature with ReactiveCocoa - but what's the proper way to build this? Do I need to have an NSString holding the currentlyTypedString, and drive the UI changes when that string updates?
推荐答案
是的，这是正确的。
在 MVVM ，视图模型应被视为UI数据和事件的规范来源（这会带来一系列重要的好处，就像更好的可测试性）。您将在视图模型上存储键入的 NSString ，然后将 绑定到UI。
Under MVVM, the view model should be considered the canonical source of UI data and events (which leads to a whole host of important benefits, like better testability). You'd store the typed NSString on the view model, then bind that to the UI.
使用MVC，您必须使用控制器或模型，但原则是相同的：将视图视为瞬态数据并在其他地方执行重要操作。
With MVC, you'd have to use the controller or model instead, but the principle is the same: treat the view as transient data and do the important stuff elsewhere.
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