仅从 ko.observableArray 发送更新的对象

Question

如何仅从可观察数组发送更新的模型而不是发送整个数组？

var student = function (){
this.studentId=0;
this.firstName=ko.obserable();
this.lastName=ko.obserable();
}
var course= function (){
this.courseId=0;
this.students=ko.obserableArray([]);
this.Name=ko.obserable();
}

现在，我只想从课程中获取信息已更新的特定学生。假设当我们添加新课程时，我们可以随时随地动态添加新学生。假设您必须在添加新学生之前验证以前的学生。当我得到那个特定的学生时，我想把那个学生信息发送回服务器。

谢谢。

Answer 1

如果我正确理解您的任务，您可以使用"arrayChange"事件类型来获取确切更改(添加/删除)的项目：

sourceArray = ko.observableArray();
sourceArray.subscribe(function (changes) {
changes.forEach(function(arrayChange) {
if(arrayChange.status === 'added') {
// some code on add
} else if(arrayChange.status === 'deleted') {
// some code on delete
}
});
}, null, "arrayChange");

Answer 2

如果要获取已修改的学生列表，可以提供一个标志来标识学生对象中的对象是否已被修改。每当更新值时，使用.subscribe修改该标志。然后使用ko.computed或ko.pureComputed获取该列表。

它也应该是observable.

var student = function (id, firstName, lastName) {
var self = this;
self.hasChanged = ko.observable(false);
var modified = function(){
self.hasChanged(true);
};
self.studentId = ko.observable(id);
self.firstName = ko.observable(firstName);
self.firstName.subscribe(modified);
self.lastName = ko.observable(lastName);
self.lastName.subscribe(modified);
}
var course= function (){
var self = this;
self.courseId = 0;
self.students = ko.observableArray([new student(1, "Cristiano", "Ronaldo"), new student(2, "Lionel", "Messi")]);
self.modifiedStudent = ko.computed(function(){
return ko.utils.arrayFilter(self.students(), function(student) {
return student.hasChanged();
});
}, self);
self.Name = ko.observable("Programming 101");
}  
$(document).ready(function () {
var myViewModel = new course();
ko.applyBindings(myViewModel);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.2.0/knockout-min.js"></script>
List of all students:
<div data-bind="foreach: students">
<div>
<span data-bind="text: studentId"></span>
<input type="text" data-bind="value: firstName" />
<input type="text" data-bind="value: lastName" />
</div>
</div>
<br/>
List of students which has been modified:
<div data-bind="foreach: modifiedStudent">
<div>
<span data-bind="text: studentId"></span>
<input type="text" data-bind="value: firstName" readonly />
<input type="text" data-bind="value: lastName" readonly />
</div>
</div>