In the second part of the self-study series, we figure out that the responsible Render name is stored in Button control's metadata:

In this part, we will concentrate on the Button metadata.

How can I get control data in the runtime

Since we already have the button control instance returned by new keyword, simply call its function getMetadata() and that's it.

You can find there are lots of useful information stored in the metadata. I will go through the most important fields one by one.

aAllPublicMethods

When you type "oButton1." in Console, you find lots of methods available in the list. Where do them come from? From the control metadata, stored in this array aAllPublicMethods.

From this array, we find there are totally 110 public methods. However if you check the source code Button.js, you can not find most of those methods defined there. The prototype chain works here again. Most of the methods are defined not in Button.js itself, but in the Button control's ancestor node in the prototype chain.

if you type the code below in console, you will get result: false.

oButton1.hasOwnProperty("getText");

The public methods of a given control is an union of its own public methods defined in its JS file and the public methods belonging to all its ancestors in the prototype chain:

aPublicMethods

A subset of aAllPublicMethods, defined in the metadata.publicMethods area. See one example below for EventProvider:

In the runtime, they are parsed as below:

mAllAggregations

List all available Aggregation. One example is tooltip. It gives hint that the button tooltip is stored as an aggregation, and its value could be queried out via the sGetter: getTooltip:

That's the reason we type the following code in console and we can get the tooltip as expected.

mProperties

List all the properties together with their Getter and Setter. Keep in mind this is the metadata, so you can not expert that the text we specified in the JS code "Button" could be found here. The "mProperties" here just stores the metadata of properties, not the instance data.

oParent

Points to its ancestor's metadata.

There are two ways to get the total number of all public methods of Button control: 110.

approach1: its direct parent's all public methods + its public method.

For button control, it is 75 + 35 = 110.

approach2: accumulate public methods number of each node in the prototype chain.

Keep in mind this prototype chain as always:

BaseObject -> EventProvider -> ManagedObject -> Element -> Control

In the next blog, I will study the instance data of Button control. I will use the setText and getText as example for research.