使用带有基因敲除js绑定的bootstrap-select从4个选项中选择2个

Question

I have made a bootstrap-select picker using knockoutjs custom binding , I am providing it data from my flask view which is the list of users. I need to select 2 out of 4 options only. Please have a look at my select tag

<select data-bind="selectPicker: selectPicking, selectPickerOptions: { options: allusers, optionsText: 'uname', optionsValue: 'uuid' }" data-live-search="true" multiple="true" ></select>

Now I am getting this

I want to select only 2 out of 4 options how can I do this , as such there is no options size attribute in HTML or HTML5 where I can define that I would like to select only 4 users from n number of users. Do i need to write some knockout code or JS code for this.

Answer 1

Here is how you would go about limiting your checkboxes selected count:

Link to a fiddle for this

// Describes what an option is
var option = function(data){
    this.Name = ko.observable(data.Name);
    this.Selected = ko.observable(data.Selected);
}
var optionsVM = function(){
    var self = this;
    // Collection of options
    self.options = ko.observableArray();
    // Find out which items are selected
    self.selectedItems = ko.computed(function(){
        return ko.utils.arrayFilter(self.options(), function(item){
            return item.Selected() === true;
        });
    });
    // Dummy init to put options in the collection
    self.init = function(){
        self.options([
            new option({ Name : "Test 0", Selected: false }),
            new option({ Name : "Test 1", Selected: false }),
            new option({ Name : "Test 2", Selected: false }),
            new option({ Name : "Test 3", Selected: false }),
            new option({ Name : "Test 4", Selected: false })
        ])
    };

    self.canCheck = function(item){
        var _canCheck = self.selectedItems().length < 2;
        if (_canCheck){
            // If it can check then just toggle
            item.Selected(!item.Selected());
            return true;
        }
        if (!_canCheck && item.Selected()){
            // if it can't then only allow deselection
            item.Selected(false);
            return true;
        }
    }
}
var myOptions = new optionsVM();
myOptions.init();
ko.applyBindings(myOptions);

html:

<ul data-bind="foreach: options">
    <li><label><input type="checkbox" data-bind="click: $parent.canCheck, checked: Selected()" /> <span data-bind="text: Name"></span> <span data-bind="text: Selected"></span></label></li>
</ul>

<p data-bind="text: selectedItems().length"></p>

Pay close attention to the fact that I have made the checked binding of the checkbox a one way binding (a read only property) by executing it in the view using ()

There are many ways of doing this and this is only one.