Javascript 无法获取属性';订阅';指未定义的或空的引用
在订阅HTML页面中的下拉值更改时,我遇到了一个实现knockout Js的问题。这是我的HTMLJavascript 无法获取属性';订阅';指未定义的或空的引用,javascript,knockout.js,Javascript,Knockout.js,在订阅HTML页面中的下拉值更改时,我遇到了一个实现knockout Js的问题。这是我的HTML <div> <span>Request Types : </span> <select data-bind="options: requestTypes, optionsText: 'Name', optionsCaption: '--Selec
<div>
<span>Request Types : </span>
<select data-bind="options: requestTypes,
optionsText: 'Name',
optionsCaption: '--Select--',
value: selectedRequestType">
</select>
</div>
只有在加载泛型名称下拉列表值后,才会填充请求类型下拉列表值。用户必须首先选择泛型名称。在页面加载时,它抛出一个错误“无法获取未定义或空引用的属性‘subscribe’”
非常感谢您提供的任何帮助,因为我是javascript MVVM框架新手。您已将viewModel声明为wd.viewModel=function(){},这是一个构造函数,您需要在绑定或订阅之前创建它的新实例。如果您添加以下内容:
wd.viewModel=new wd.viewModel()代码>
在这条线之前,它应该能工作
var myName=wd.viewModel.selectedGenericName.subscribe(函数(){
当您尝试初始化myName时,似乎wd.viewModel.selectedGenericName未定义。ko.observable(“”
)的预期值是多少?是wd.viewModel.selectedGenericName在页面加载时未定义,请参见下面的HTML代码(通用名称:)页面加载标题显示在ko的通用名称下拉列表controlvalue中。observable(“”)是一个可观察的函数(即函数observable(){if(arguments.length>0){//Write//Ignore writes,如果值没有更改,如果(observable.isDifferent(_latestValue,arguments[0]){observable.valueWillMutate();)
wd.viewModel = function () {
var data = {};
var self = this;
var url = '';
var selectedRequestingCountry = ko.observable("");
self.optionsProvider = new wd.optionsProvider(self);
self.objGenralInfo = new wd.GI_form(data);
/* For Requesting Country */
url = wd.ConfigObject.baseUrl + wd.ConfigObject.masterServiceUrl + wd.ConfigObject.category.importingCountries; // Fetch Requesting Countries
self.importingCountries = self.optionsProvider.get("importingCountries", url, {});
self.selectedRequestingCountry = ko.observable("");
this.requestingCountryArea = ko.observable("");
/* For Generic Name*/
url = wd.ConfigObject.baseUrl + wd.ConfigObject.masterServiceUrl + wd.ConfigObject.category.genericNames; // Fetch Generic Names
self.genericNames = self.optionsProvider.get("genericNames", url, {});
self.selectedGenericName = ko.observable("");
/* Override Requesting Country Address */
self.IsOverride = ko.observable(false);
/* For Request Types */
self.selectedRequestType = ko.observable("");
self.selectedTradeName = ko.observable("");
};
// Whenever the selected Generic Name changes, populate the Request Type
var myName = wd.viewModel.selectedGenericName.subscribe(function () {
wd.viewModel.url = wd.ConfigObject.baseUrl + wd.ConfigObject.masterServiceUrl + wd.ConfigObject.category.requestTypes + "/" +
wd.viewModel.selectedGenericName().Name;
wd.viewModel.requestTypes = wd.viewModel.optionsProvider.get("requestTypes", url, ''); // Fetch request types based on generic name
}, wd.viewModel);
$(function () {
ko.applyBindings(wd.viewModel);
});