Dynamically adding Components

Often you'd want to give your users the ability to add new items to an existing layout. Strelit Layout offers a number of ways to do this.

• You can turn any DOM element on the page into a 'dragSource' that turns into a layoutItem when dragged
• You can let the user select an element and add items to it
• You can add items to a specified element

Creating a layout

For this tutorial we won't insert the layout directly into the body, but rather into a div to leave some space for a component menu.

<div id="wrapper">
    <ul id="menuContainer"></ul>
    <div id="layoutContainer"></div>
</div>

Let's keep things simple: Create a basic layout with two components in a row

var config = {
    content: [{
        type: 'row',
        content: [{
            type:'component',
            componentName: 'example',
            componentState: { text: 'Component 1' }
        },
        {
            type:'component',
            componentName: 'example',
            componentState: { text: 'Component 2' }
        }]
    }]
};

var myLayout = new window.Strelit Layout( config, $('#layoutContainer') );

myLayout.registerComponent( 'example', function( container, state ){
    container.getElement().html( '<h2>' + state.text + '</h2>');
});

myLayout.init();

Creating the "insert component" menu

The "insert component" menu will be created programmatically as well. That's where we'll add the actual insertion code later on

var addMenuItem = function( text ) {
    var element = $( '<li>' + text + '</li>' );
    $( '#menuContainer' ).append( element );

    //insertion code will go here
};

addMenuItem( 'User added component A' );
addMenuItem( 'User added component B' );

Adding items to a layout - in general

Time to write some "add component" functionality. Strelit Layout builds up a tree of items internally that can be accessed through 'myLayout.root' once the layout is initialised. Every one of these items has an addChild method that expects two parameters: itemOrConfig and index.

Nevermind index for now. It's optional and specifies at which position the new child will be added. The important bit for us is itemOrConfig. This can be any kind of item config - which means it's also possible to create / insert a whole tree of new items at once.

Let's prepare a bit of item configuration in our 'addMenuItem' function

var newItemConfig = {
    type: 'component',
    componentName: 'example',
    componentState: { text: text }
};

The tricky bit is not so much creating the item, but selecting the element to which to add the item to. All three approaches we'll cover next are basically just that: different ways of selecting the parent for the new item.

First: The really awesome way

Strelit Layout makes it simple to turn any DOM element into a "dragSource" - which allows for the creation of components by simply dragging the element onto the layout.

All that needs adding to our 'addMenuItem' method is this line:

myLayout.createDragSource( element, newItemConfig );

Works like a charm:

Second: Add items to a selected stack

Strelit Layout supports selecting items by clicking the empty space in the header area. This is however disabled by default. To enable it, simply add this to your config:

var config = {
    settings: {
        selectionEnabled: true
    },
    content: [...]
};

Now if the user clicks a header it turns into a different color, Strelit Layout emits a 'selectionChanged' event and the value of 'myLayout.selectedItem' points to the selected item.

To use this we'll change our insert logic to this:

element.click(function(){
    if( myLayout.selectedItem === null ) {
        alert( 'No item selected' );
    } else {
        myLayout.selectedItem.addChild( newItemConfig );
    }
});

Now clicking a li in the "insert component" menu will add the component to whatever stack is selected - or alert if no selection has been made.

Third: Adding items to a previously specified element

If we don't want to give the user a choice of where to add the new item, we can just specify an element ourselves. Either by using one of the getter-functions, (e.g. myLayout.root.getItemsById( 'someItem' );) or by traversing the item tree.

For instance, if we always want to add items to the topmost row, it would look like this:

element.click(function(){
    myLayout.root.contentItems[ 0 ].addChild( newItemConfig );
});

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