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Defining the Converter Class

While connecting ConverterController’s outlets, you probably noticed that one outlet remains unconnected: converter. This outlet identifies an instance of the Converter class in the Currency Converter application, but this instance doesn’t exist yet.

The Converter implements a model object. Model objects contain special knowledge and expertise. They hold data and define the logic that manipulates that data. For example, a customer object, common in business applications, is a model object. Since instances of this type of class don’t communicate directly with the user interface, there is no need for outlets or actions. Here are the steps to be completed:

1. In the Classes pane in the nib file window, create a subclass of java.lang.Object named “Converter”. See “Specify the ConverterController Class” for details.

   
   
   

2. Instantiate the Converter class. See “Create an Instance of the ConverterController Class” for details.

   
   
   

3. Connect the converter outlet of the ConverterController instance to the Converter instance, as shown in Figure 1-22.

   
   

   Figure 1-22  Connecting ConverterController.converter to the Converter instance

   

4. Save the nib file.

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