Object Factory

As seen in the Creating a Widget, a widget may be created using scout.create. When using this function, the call is delegated to the ObjectFactory.

The ObjectFactory is responsible to create and initialize a Scout object. A typical Scout object has an objectType and an init function. But actually any kind of object with a constructor function may be created.

If you use a string based object type, objects are created using naming convention by default. This means when calling scout.create('scout.Table', model), the scout namespace is searched for a class called Table. Since scout is the default namespace, it may be omitted. So calling scout.create('Table', model) has the same effect. If there is such a class found, it will be instantiated and the init function called, if there is one. The model is passed to that init function. So instead of using scout.create you could also use the following code:

Listing 1. Creating an object without the ObjectFactory

import {Table} from '@eclipse-scout/core';
var table = new Table();
table.init(model);

This will work fine, but you will lose the big benefit of the ObjectFactory: the ability to replace existing classes. So if you want to customize the default Table, you would likely extend that table and override some functions. In that case you need to make sure every time a table is created, your class is used instead of the default. To do that you have to register your class in the ObjectFactory with the objectType Table. If scout.create('Table') is called the object factory will check if there is a class registered for the type Table and, if yes, that class is used. Only if there is no registration found, the default approach using the naming convention is performed.

In order to register you class, you need a file called objectFactories and add that to your JavaScript module (e.g. index.js). The content of that file may look as following:

Listing 2. Adding a new object factory registration

import {CustomTable} from './index';
import {scout} from '@eclipse-scout/core';

scout.addObjectFactories({
  'Table': () => new CustomTable()
});

This will simply add a new factory for the type Table the the list of existing factories. From now on yourproject.CustomTable will be instantiated every time a Table should be created.

This replacement also works if scout.create is used with class references (which is the recommended approach). So, scout.create('Table') as well as scout.create(Table) will return a new CustomTable.