KnockoutJS ObservableArray数据分组 [英] KnockoutJS ObservableArray data grouping

问题描述

KnockoutJS是否具有功能，而我可以采取类似的方式:

Does KnockoutJS have a feature whereas I could take something like:

    var myArray = ko.observableArray([
      { name: "Jimmy", type: "Friend" },
      { name: "George", type: "Friend" },
      { name: "Zippy", type: "Enemy" }
    ]);

然后在类型"字段中选择不重复"，从而产生如下所示的结果:

Then select distinct on the "type" field, producing a result which looks like this:

(pseudo code)
    var distinct = myArray.distinct('type')
      // Returns array of two arrays
      //  distinct[0] is an array of type=Friend
      //  distinct[1] is an array of type=Enemy 

我知道ko.utils.arrayGetDistinctValues，但这并不能完全满足我的要求.我也知道我可以使用ko.utils.arrayGetDistinctValues编写一些循环来获取我想要的东西，我只是想知道是否有其他东西被我忽略的KnockoutJS烘焙了.

I'm aware of ko.utils.arrayGetDistinctValues, but that doesn't exactly do what I want. I'm also aware that I could write a few loops using ko.utils.arrayGetDistinctValues to get what I want, I'm just wondering if there is something else baked into KnockoutJS that I'm overlooking.

推荐答案

KO中没有其他任何东西可以使这一切变得简单.

There is not anything else built into KO to make this any easier.

有很多方法可以使这项工作.例如，您可以将observableArrays扩展为具有distinct函数.然后，您可以像这样创建observableArray:

There are many ways that you could make this work. For example, you could extend observableArrays to have a distinct function. Then, you can just create your observableArray like:

this.people = ko.observableArray([
       new Person("Jimmy", "Friend"),
       new Person("George", "Friend"),
       new Person("Zippy", "Enemy")
]).distinct('type');

distinct函数可能类似于:

ko.observableArray.fn.distinct = function(prop) {
    var target = this;
    target.index = {};
    target.index[prop] = ko.observable({});    

    ko.computed(function() {
        //rebuild index
        var propIndex = {};

        ko.utils.arrayForEach(target(), function(item) {
            var key = ko.utils.unwrapObservable(item[prop]);
            if (key) {
                propIndex[key] = propIndex[key] || [];
                propIndex[key].push(item);            
            }
        });   

        target.index[prop](propIndex);
    });

    return target;
};    

它支持链接，因此您可以使用不同的属性多次调用distinct.

It supports chaining so you could call distinct multiple times with different properties.

此处提供示例: http://jsfiddle.net/rniemeyer/mXVtN/

这确实会在每次更改时重建索引一次，因此，如果您有大量的项目列表，则可能需要探索其他方法(手动订阅)以从索引"数组中添加/删除项目.

This does rebuild the index once on each change, so if you have a huge list of items, then you would want to potentially explore other ways (manual subscriptions) for adding/removing items from the "index" arrays.

这篇关于KnockoutJS ObservableArray数据分组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！