ZK Component Reference/Containers/Fragment

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Fragment

• Demonstration: N/A
• Java API: Fragment
• JavaScript API: Fragment
• Style Guide: N/A

Employment/Purpose

Fragment is a ZK component that let developers combine native HTML elements with ZK data binding syntax to make the static page to be dynamic.

Example

<zk>
    <fragment viewModel="@id('vm') @init('org.zkoss.fragment.demo.VM2')" validationMessages="@id('vmsgs')"
              form="@id('fx') @load(vm) @save(vm, before='submit') @validator(vm.formValidator)"
              prop1="@bind(fx.prop1)" prop1err="@bind(vmsgs['fkey1'])"
              prop2="@bind(fx.prop2)" prop2err="@bind(vmsgs['fkey2'])"><![CDATA[
        <p><input type="text" value="@bind(prop1)"/><span textContent="@load(prop1err)"/></p>
        <p><input type="text" value="@bind(prop2)"/><span textContent="@load(prop2err)"/></p>
        <button onclick="@command('submit')">Submit</button>
    ]]></fragment>
</zk>

Data Binding

By binding the properties of ViewModel to a Fragment component, you can use the ZK MVVM data binding syntax on the native HTML elements.

Here is the supported annotations for now:

• @save

 syntax: @save([EL-expression])

• @load

 syntax: @load([EL-expression])

• @bind

 syntax: @bind([EL-expression])

• @command

 syntax: @command([EL-expression], [arbitraryKey]=[EL-expression])

• @global-command

 syntax: @global-command([EL-expression], [arbitraryKey]=[EL-expression])

<zk>
    <fragment viewModel="@id('vm') @init('org.zkoss.zktest.test2.F85_ZK_3681_Command_VM')"
              status="@bind(vm.status)"><![CDATA[
        <div>
            <input type="checkbox" onchange="@command('onCheck', checked=event.checked)" />
            Check this checkbox: <span textContent="@load(status)"/>
        </div>

        <div>
            <button onclick="@global-command('callGlobal', text='Hello', num=1)">Call global (1)</button>
            <button onclick="@global-command('callGlobal', text='World', num=2)">Call global (2)</button>
        </div>
    ]]></fragment>
</zk>

Shadow Elements

In this example, we use if and forEach tags together for condition and collection rendering.

<zk>
    <fragment viewModel="@id('vm') @init('org.zkoss.zktest.test2.F85_ZK_3681_Shadow_VM')"
        issues="@bind(vm.issues)"><![CDATA[
        <section>
            <h1>My Issue List</h1>
            <ul>
                <forEach items="@load(issues)">
                    <!-- There's a pre-defined variable "each" for convenience. -->
                    <li>
                        <!-- @bind(each) is wrong because each is just a temp variable in loops. -->
                        <input type="checkbox" checked="@load(each.isDone)" />
                        <if test="@load(each.isDone)">
                            <strike>[<span textContent="@load(each.id)"/>]
                            <span textContent="@load(each.description)"/></strike>
                        </if>
                        <!-- No else for now. -->
                        <if test="@load(!each.isDone)">
                            [<span textContent="@load(each.id)"/>]
                            <span textContent="@load(each.description)"/>
                        </if>
                    </li>
                </forEach>
            </ul>
        <section>
    ]]></fragment>
</zk>

• For further details, please refer to Shadow components directly.

Data Validation

Server-side Property/Form Validation

To ensure data is correct and useful, we can leverage ZK's validators.

<zk>
    <fragment viewModel="@id('vm') @init('org.zkoss.fragment.demo.VM1')" validationMessages="@id('vmsgs')"
              prop1="@bind(vm.prop1) @validator(vm.validator1)"
              prop1err="@bind(vmsgs['prop1'])"><![CDATA[
        <input type="text" value="@bind(prop1)"/>
        <span textContent="@load(prop1err)"/>
    ]]></fragment>
</zk>

In order to access invalidate messages by HTML elements, simply bind the messages onto Fragment properties.

Here we can use form-binding and form validators to validate all the fields.

<zk>
    <fragment viewModel="@id('vm') @init('foo.BarVM')" validationMessages="@id('vmsgs')"
     form="@id('fx') @load(vm.currentUser) @save(vm.currentUser, before='submit') @validator('formBeanValidator', prefix='p_')"
     name="@bind(fx.name)" nameerror="@bind(vmsgs['p_name'])"><![CDATA[
     <input type="text" value="@bind(name)"/><span textContent="@load(nameerror)"/>
     <button onclick="@command('submit')">Submit</button>
    ]]></fragment>
</zk>

Client-side Property Validation

This component also provides a new @jsvalidator(validation_function_name) syntax to validate at client-side by evaluating your custom JavaScript function. You can use this annotation on HTML elements.

ValidationFunction(val, vmsgs)
* val: The user input data.
* vmsgs: The validation message holder object. 
* Returns: Boolean. True if the data is valid.

You can use an implicit object (vmsgs) to get the client-side invalid messages. The @jsvalidator has its own validation message holder not shared with server-side.

<zk>
    <fragment viewModel="@id('vm') @init('foo.BarVM')" someprop="@bind(vm.prop1)"><![CDATA[
        <input type="text" value="@bind(someprop) @jsvalidator('validateExample')"/>
        <span textContent="@load(vmsgs['foo'])"/>
        <script type="text/javascript">
        function validateExample(val, vmsgs) {
            var isValid = someValidationProcess(val);
            vmsgs['foo'] = isValid ? '' : 'Invalid value';
            return isValid;
        }
        </script>
    ]]></fragment>
</zk>

For security concerns, we recommend you to use server-side @validator in most cases and choose client-side @jsvalidator if the validation needs an instant feedback such as password strength, number range, and so on.

Properties

• content: specify the content of this component.
• src: specify the URI of an external content file. The file encoding is assumed to be UTF-8.

Supported Events

Name	Event Type
onRecover	Event: Event Represents an event sent back to the server caused by an offline recovery.

Supported Children

None

Use Cases

Version	Description	Example Location
8.5+	Data binding, Shadow elements	Client Binding with ZK MVVM for your eyes only
8.5+	Validation, Event handling

Version History

Version	Date	Content
8.5	2017/09/21	Add the new Fragment component