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Interfacing to External Code

This example shows some of the techniques that can be used when writing Umple code that will be connected to code written separately, such as code in a GUI library. Use of the:

Example

/*
This example demonstrates an example of using the
internal, depends, external, before and after
keywords to interface umple code to code in
another system.

The internal keyword is suitable for situations
where the developer doesn't want setter/getters
to be generated. GUI windows are an example of
such a case. A GUI window/unit contains several
components but the rest of the program may only
need the value stored within those components. So
it's a good practice to hide UI components from
classes other than the containing one. 

*/

// required to make HelloInternals class a JFrame
external JFrame{}

class HelloInternals {
  // HelloInternals extends JFrame
  isA JFrame;

  // importing required classes
  depend javax.swing.JFrame;
  depend javax.swing.JLabel;

  /* messageLabel is a component of the frame;
  often we don't want sub-components of a GUI unit
  to be settable/gettable. By making them internal
  Umple will avoid generating setter/getter for
  messageLabel. Using lazy Umple will avoid adding
  a constructor parameter for this component */
  lazy internal JLabel messageLabel;
  
  // the contents of messageLabel 
  String message;
  
  /* before getting the message, this code updates
  the message attribute using the text from
  messageLabel */  
  before getMessage {
    message=messageLabel.getText();
  }
  
  /* after setting the messae, this code updates
  messageLabel to contain the newly updated
  message */
  after setMessage {
    messageLabel.setText(message);
  }
  
  // using after constructor is a good way of
  // initiating a GUI unit
  after constructor {
    getContentPane().setLayout(null);
  
    messageLabel=new JLabel(message);
    messageLabel.setBounds(10, 10, 200, 20);
    add(messageLabel);
    
    pack();
    setSize(250, 200);
  }
}


      

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