select - 如何从 knockout.js observableArray 中获取选定的菜单选项？

Question

我觉得我错过了一些非常基本的东西，但我无法使用 Knockout.js 使下拉菜单按照我的预期工作。

我有一组想要在菜单中显示的对象，我需要找到选定的选项并将其发布到服务器。我可以渲染菜单，但似乎无法获取所选项目的值。我的 View 模型如下所示:

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() );

我的 View 标记如下所示:

<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>

如何让选定的菜单项显示在范围中，并发布到服务器？ (我假设我在跨度中渲染的可观察值与我发布的相同。)我是否需要在 ProjectFilterItem 中使用另一个属性，例如 this.selected = ko.observable(false) ; ?如果是这样，我如何将其声明为值的目标？

Answer 1

您只需要与 value binding 一起使用绑定(bind)所选值:

来自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.

在您的示例中:

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

参见Demo .