使用MVVM光的使者传递到视图模型之间的值 [英] Use MVVM Light's Messenger to Pass Values Between View Model

问题描述

可能有人会这么好心来解释MVVM光的使者给我吗？我在这里读在计算器上一个帖子： MVVM视图模型之间传递值努力得到这个。在MVVM光的文档是不是很大在这一点上，所以我完全不能确定去哪里。

说我有两个的ViewModels和ViewModelLocator。我希望能够通过这三个参数之间没有问题。我怎么会去的使者这样做呢？ ？难道能够说

编辑：这是我的新的实现。截至目前，它看起来好像MessengerInstance并不要求一个令牌。 。我非常困惑

在第一个视图模型：

  MessengerInstance.Send<&的XDocument GT;（SelectedDocument）; 
  

和第二：

  MessengerInstance.Register<&的XDocument GT;（这一点，XDOC => CopySettings（XDOC））; 
  

可能是完全错误的。没有得到一个机会来测试，但视觉工作室变得少跟我生气时，我做这种方式。另外，MessengerInstance并注册发送邮件之前。

解决方案

说我有两个的ViewModels和ViewModelLocator。我希望能够通过这三个参数之间没有问题。我怎么会去的使者这样做呢？难道能够说？

这也正是它的，是的。

要发送消息：

  MessengerInstance.Send（有效载荷，令牌）; 
  

要收到一条消息：

  MessengerInstance.Register< PayloadType>（
本，令牌，有效载荷= GT; SomeAction（负载））; 
  

有很多重载，所以不知道你想通过信使来完成什么，我不会进入所有的人，但上面应覆盖想要发送和接收有效载荷的消息的简单情况。

请注意，令牌可以是真的什么标识消息。虽然字符串经常被用于此，我更喜欢，因为它是一个小更安全，更使智能感知使用一个枚举，发现习惯等。

例如：

 公共枚举MessengerToken 
 {
 BrushChanged，
 WidthChanged，
 HeightChanged 
} 
  

然后您发送/接收会是这样的：

  //发送视图模型
 MessengerInstance.Send（Brushes.Red，MessengerToken.BrushChanged）; 
 
 //接收视图模型
 
 //把这个线在构造函数中
 MessengerInstance.Register<刷>（这一点，道理，刷=> ChangeColor（刷））; 
 
公共无效ChangeColor（刷刷）
 {
 =刷刷; 
} 
  

URL以下改为devuxer的评论：
< A HREF =http://blog.galasoft.ch/posts/2009/09/mvvm-light-toolkit-messenger-v2/相对=nofollow> http://blog.galasoft.ch/posts/2009 / 09 / MVVM光的工具包信使-V2 /

Could someone be so kind as to explain MVVM Light's Messenger for me? I was reading a post on StackOverflow here: MVVM pass values between view models trying to get this. The documentation on MVVM Light's not that great at this point so I'm completely unsure where to go.

Say I have two ViewModels and a ViewModelLocator. I want to be able to pass parameters between all three without issue. How would I go about doing this with the messenger? Is it capable of that?

Edit: Here's my new implementation. As of now, it looks as if MessengerInstance doesn't call for a token. I'm terribly confused.

In the first ViewModel:

MessengerInstance.Send<XDocument>(SelectedDocument);

And in the second:

MessengerInstance.Register<XDocument>(this, xdoc => CopySettings(xdoc));

Could be completely wrong. Haven't gotten a chance to test it, but visual studio gets less angry with me when I do it this way. Also the MessengerInstance does register before the Message is sent.

解决方案

Say I have two ViewModels and a ViewModelLocator. I want to be able to pass parameters between all three without issue. How would I go about doing this with the messenger? Is it capable of that?

That's exactly what it's for, yes.

To send a message:

MessengerInstance.Send(payload, token);

To receive a message:

MessengerInstance.Register<PayloadType>(
    this, token, payload => SomeAction(payload));

There are many overloads, so without knowing exactly what you're trying to accomplish via the messenger, I won't go into all of them, but the above should cover the simple case of wanting to send and receive a message with a payload.

Note that "token" can be really anything that identifies the message. While a string is often used for this, I prefer to use an enum because it's a little safer and enables intellisense, "find usages", etc.

For example:

public enum MessengerToken
{
    BrushChanged,
    WidthChanged,
    HeightChanged
}

Then your send/receive would be something like:

// sending view model
MessengerInstance.Send(Brushes.Red, MessengerToken.BrushChanged);

// receiving view model

// put this line in the constructor
MessengerInstance.Register<Brush>(this, token, brush => ChangeColor(brush));

public void ChangeColor(Brush brush)
{
    Brush = brush;
}

[EDIT] URL to devuxer's comment below changed to: http://blog.galasoft.ch/posts/2009/09/mvvm-light-toolkit-messenger-v2/

这篇关于使用MVVM光的使者传递到视图模型之间的值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！