淘汰赛手动订阅不会在下拉列表更改时触发

Question

另一个我似乎无法找到帮助的淘汰赛问题.

我基本上试图实现级联下拉列表.前几天我请求帮助解析我的复杂JSON(来自cakePHP控制器.我前几天收到的帮助非常好,但我遇到了另一个小问题.

我遇到的问题是我在调用JSON以获取国家列表后更新viewModel.一旦我填充下拉列表,我希望显示县列表,最终显示城市列表,但我还没有.不幸的是,当我改变时,我从列表中选择一个国家,我的观察不会触发.我怀疑这是因为我this.selectedCountry = ko.observable()使用映射创建和更新但我不知道这应该是什么有效选项.当然,我也可以成为标志:/

我有以下代码

HTML:

<select id="countries" 
            data-bind='
                options: countries, 
                optionsValue : "Id", 
                optionsText: "country", 
                optionsCaption: "[Please select a country]", 
                value: selectedCountry'>
</select>

<select id="counties" 
                data-bind='
                    options: selectedCountry() ? counties : null, 
                    optionsValue : "Id", 
                    optionsText: "County", 
                    optionsCaption: "[Please select a county]", 
                    value: selectedCounty,
                    visible: (counties() && counties().length > 0)'>
        </select>

使用Javascript

var countryData= {"countries":[{"Country":{"id":"1","country":"England"}},{"Country":{"id":"2","country":"Wales\/Cymru"}},{"Country":{"id":"3","country":"Scotland"}},{"Country":{"id":"4","country":"Republic of Ireland"}},{"Country":{"id":"5","country":"Northern Ireland"}}]};

var countyData= {"country":[{"County":{"id":"1","county":"Essex"}}]};

var countryMappingOptions = {
    'countries': {
        'update': function (options) {
            return ko.mapping.fromJS(options.data.Country);
        },
        'ignore': ["selectedCountry"]
    }
};

 var countyMappingOptions = {
    'counties': {
        'update': function (options) {
            return ko.mapping.fromJS(options.data.County);
        }
    }
};
        var vm= function () {
            this.selectedCountry = ko.observable(); 
            this.selectedCounty =  ko.observable();
            this.countries = ko.mapping.fromJS([]); 
            this.counties =  ko.mapping.fromJS([]);
            // Whenever the continent changes, reset the country selection
            this.selectedCountry.subscribe(function (countryId) {
                alert(countryId);   
                this.selectedCounty(undefined);
                this.counties(undefined);
                if (countryId != null) {
                   ko.mapping.fromJS(countyData, countyMappingOptions,this.viewModel );
              }
            });
            this.selectedCounty.subscribe(function (countryId) {
                alert(countryId);    
            } .bind(this));
        };

        var viewModel = new vm();
        ko.applyBindings(viewModel );
        console.log(viewModel .countries());
        ko.mapping.fromJS(countryData, countryMappingOptions ,viewModel );
        console.log(viewModel .selectedCountry() );

我还创建了一个JSFiddle来演示这里的问题http://jsfiddle.net/jbrr5/21/

再次对这个问题的任何帮助将不胜感激,一旦我获得了淘汰赛,它将变得如此简单.

谢谢

Answer 1

一些问题:

• 你忘记.bind(this)了第一次订阅
• this.viewModel 而不仅仅是 this
• 你有optionsValue: "Id"而不是optionsValue: "id"
• 你有optionsText: "County"而不是optionsText: "county"
• 你countyData的数组被调用country而不是counties

更新小提琴:http://jsfiddle.net/antishok/jbrr5/23/