如何从knockout.js observableArray中获取所选菜单选项？ [英] How to get selected menu option from a knockout.js observableArray?

问题描述

我觉得我缺少一些非常基本的东西，但是我不能得到一个下拉菜单来工作，因为我期望使用Knockout.js。

我有一组要在菜单中显示的对象，我需要找到所选的选项并将其发布到服务器。我可以让菜单渲染，但似乎无法获取所选项目的值。我的视图模型看起来像这样：

  function ProjectFilterItem（name，id）{
 this.Name = name; 
 this.Id = id; 
} 
 
函数FilterViewModel（）{
 this.projectFilters = ko.observableArray（[
 new ProjectFilterItem（foo，1），
 new ProjectFilterItem（bar，2），
 new ProjectFilterItem（baz，3）
]）; 
 this.selectedProject = ko.observable（）; 
} 
 
 ko.applyBindings（new FilterViewModel（））; 
  

，我的视图标记如下所示：

 < select 
 id =projectMenu
 name =projectMenu
 data-bind =
 options：projectFilters，
 optionsText：'Name'，/ *我必须引用这个值，或者我得到一个JS错误* / 
 optionsValue：'Id'，/ *如果我把'selectedProject'放在这里，以下* / 
 optionsCaption：' - 选择项目 - '

>< / select> 
 
< b>所选项目：< / b> < span data-bind =text：selectedProject>< / span> 
  

如何将选定的菜单项显示在span中，并发布到服务器？ （我假设我在span中渲染的可见性与我发布的一样）。我需要在 ProjectFilterItem 中的另一个属性，像这个.selected = ko.observable（false）; ？如果是这样，我如何将其声明为该值的目标？

解决方案

您只需使用 值绑定绑定所选值：

从 选项文档：

注意：对于多选列表，要设置哪些选项是
，或者选择哪个的选项被选中，使用
selectedOptions绑定。对于单选列表，您还可以阅读
并使用值绑定写入选定的选项。

在你的例子中：

 < select 
 id =projectMenu
 name =projectMenu
 data-bind =
 value：selectedProject，
 options：projectFilters，
 optionsText：'Name'，
 optionsValue：'Id'，
 optionsCaption：' - 选择项目 - '

>< / select> 
  

请参阅演示。

I feel like I'm missing something very basic, but I can't get a dropdown menu to work as I expect using Knockout.js.

I have a set of objects I want to present in a menu, and I need to find the selected option and post that to the server. I can get the menu to render, but can't seem to get the value of the selected item. My view model looks like this:

function ProjectFilterItem( name, id ) {
    this.Name = name;
    this.Id   = id;
}

function FilterViewModel() {
    this.projectFilters = ko.observableArray([
        new ProjectFilterItem( "foo", "1" ),
        new ProjectFilterItem( "bar", "2" ),
        new ProjectFilterItem( "baz", "3" )
    ]);
    this.selectedProject = ko.observable();
}

ko.applyBindings( new FilterViewModel() );

and my view markup looks like this:

<select 
    id        = "projectMenu"   
    name      = "projectMenu"
    data-bind = "
        options:        projectFilters,
        optionsText:    'Name', /* I have to enquote the value or I get a JS error */
        optionsValue:   'Id',   /* If I put 'selectedProject here, nothing is echoed in the span below */
        optionsCaption: '-- Select Project --'
    "
></select>

<b>Selected Project:</b> <span data-bind="text: selectedProject"></span>

How do get the selected menu item to display in the span, and to post to the server? (I assume the observable I render in the span is the same one I'd post.) Do I need another property in the ProjectFilterItem, like this.selected = ko.observable(false); ? If so, how would I declare it as the target of the value?

解决方案

You just need use with the value binding to bind the selected value:

From the options documentation:

Note: For a multi-select list, to set which of the options are selected, or to read which of the options are selected, use the selectedOptions binding. For a single-select list, you can also read and write the selected option using the value binding.

In your example:

<select 
    id        = "projectMenu"   
    name      = "projectMenu"
    data-bind = "
        value: selectedProject,
        options:        projectFilters,
        optionsText:    'Name',
        optionsValue:   'Id',
        optionsCaption: '-- Select Project --'
    "
></select>

See Demo.

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