Servis-Rhino 4211B Betriebsanweisung PDF herunterladen (Seite 148)

instance of a button, nothing at all will be shown in the web page. We haven't told the button where

on the page it should appear. This is a core notion. Creating a widget does not cause it to appear.

We must also tell the widget where on the page it should be located. To do this, we must associate

the widget with a DOM node. Think of the DOM node as being an anchor on the page that

describes where the widget should appear.

We have a couple of ways to associate a widget with the desired target node. The first is to pass the

node as a parameter when the widget is constructed. Most widgets allows a node to be supplied at

this time. It is common that this is the second parameter on the widget's constructor. For example:

var myButton = new Button({label: "Press Me"}, "myNode");

The target node can be supplied either as the "id" of the target node or as a reference to a node

object.

If we don't want to supply the node when the widget is created, we can usually call a method that

will be found on the widget called "placeAt()" which takes as a parameter the node against

which the widget should be placed.

In the example above, we also snuck in a second new concept. Every widget we will work with has

properties associated with it. These properties control how it looks and behaves. When a widget is

constructed, the first parameter on its constructor is a JavaScript object that has properties that will

be used to set the corresponding named properties of the widget. In the example above, the Button

widget has a property called "label" which describes the label shown on the button.

dijit/registry - Dijit and byId

When a Dijit widget is created, it can be supplied an "id" attribute than can then be used to find the

reference to the widget by its id value using registry.byId("<id>"). Note that the id value

has to be unique on the page. If no id value I supplied, Dojo will generate a unique id.

If we don't know the id value, we can still retrieve a reference to the widget if we know the DOM

node against which it is attached. A second function called "registry.byNode(<node>)"

can be used which will return us a reference to the widget if all we know is a DOM node.

Another extremely useful capability of the registry is to create unique Ids. For example:

registry.getUniqueId(this.declaredClass)

Dijits and events

We can connect a Dijit widget to its events. For example:

connect.connect(myButton, "onClick", this, myFunction);

however, this technique is being deprecated. The newer technology is to use the dojo/on

technique.

Servis-Rhino 4211B Betriebsanweisung Seite 148