Knockout，选择所有复选框并查看选择复选框列表

Question

我有一个带有复选框的列表，当我点击其中一个复选框时，它会显示在SelectedUsers中，正常工作，复选框data-bind="checked: AllChecked"也会被选中，但不应该。

<div data-bind="foreach: SelectedUsers">
    <p>
        <span data-bind="text: userName" ></span>
    </p>
</div>

但是，当我使用data-bind="checked: AllChecked"时，SelectedUsers中不会显示任何内容，之后，当我单击某个复选框时，列表中的所有项目都被选中，SelectedUsers 中也不会显示任何信息

怎么了？示例：http://jsfiddle.net/falkone/cr763bfj/

<div id="sideB">
    <div data-bind="foreach: AllUsers">
        <label>
            <input type="checkbox" name="checkedUser" data-bind="value: userName, checked:$root.selectedUserNames" />
            <span data-bind="text: userName" ></span>
        </label> 
    </div>
    Selected
    <div data-bind="foreach: SelectedUsers">
        <p>
            <span data-bind="text: userName" ></span>
        </p>
    </div>
        <label><input type="checkbox" data-bind="checked: AllChecked" />Check all</label>
</div>

击倒-3.3.0:

function User(data) {
this.userName = ko.observable(data.userName);
this.selected = ko.observable(data.selected);
}
var dataSource = [new User({userName: "Bill", selected: false}),
    new User({userName: "Andrii", selected: false})
    ];
function UsersViewModel() {
    var self = this;
    self.AllUsers = ko.observableArray(dataSource);
    self.SelectedUsers = ko.observableArray([]);
self.selectedUserNames = ko.observableArray([]);
self.selectedUserNames.subscribe(function(newValue) {
    var newSelectedUserNames = newValue;
    var newSelectedUsers = [];
    ko.utils.arrayForEach(newSelectedUserNames, function(userName) {
        var selectedUser = ko.utils.arrayFirst(self.AllUsers(), function(user) {
            return (user.userName() === userName);
        });
        newSelectedUsers.push(selectedUser);
    });
    self.SelectedUsers(newSelectedUsers);
});
self.AllChecked = ko.computed({
    read: function() {
        var firstUnchecked = ko.utils.arrayFirst(dataSource, function(item) {
            return self.selectedUserNames() == false;
        });
        return firstUnchecked == null;
    },
    write: function(value) {
        ko.utils.arrayForEach(dataSource, function(item) {
            self.selectedUserNames(value);
        });
    }
})
}
ko.applyBindings(new UsersViewModel(), document.getElementById('sideB'));

Answer 1

调用write时传递给computed的值不是用户名，而是指示复选框状态的true / false布尔值。

此外，由于selectUserNames是observableArray，因此需要push()作为新的userName，而不是替换整个数组数据。

试试这个：

read: function() {
        var firstUnchecked = ko.utils.arrayFirst(dataSource, function(item) {
            return self.selectedUserNames().indexOf(item.userName()) == -1;
        });
        return firstUnchecked == null;
    },
write: function(value) {
        if (value) {
            ko.utils.arrayForEach(dataSource, function(item) {
               if (self.selectedUserNames().indexOf(item.userName()) == -1)
                   self.selectedUserNames.push(item.userName());
            });
        }
        else {
            self.selectedUserNames.removeAll();
        }
    }

更新（根据您的评论）：

还需要改变read以使用indexOf:检查第一个未检查的userName的存在

var firstUnchecked = ko.utils.arrayFirst(dataSource, function(item) {
    return self.selectedUserNames().indexOf(item.userName()) == -1;
});

参见修改后的Fiddle