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  ◄Structured Types► ◄Contents► ◄Index►                           ◄Back►
 
  TYPE
    <identifier> = OBJECT[ ( <parent class> ) ]
      <data fields>
      <methods>
    END
 
  Description
 
    A class is a template defining an object. It is an object type. A
    class declares one or more <data fields> and the <methods> that
    manipulate them. A class can inherit the data fields and methods of
    an existing or "parent" class. The name of the parent class is
    given in the optional parentheses after OBJECT. It is an error
    to list more than one class within the parentheses.
 
  <data fields>
 
    The declaration of one or more data structures. Use the same syntax
    that declares the fields of a record.
 
  <methods>
 
    A list of method declarations. Each method declaration is like
    a procedure or function heading except that the name may be
    qualified with the name of the class (class_name.method_name). For
    example, note how each method name in the following shape object
    begins with 'shape.'. Although not required, such a qualification
    is good programming style.
 
    To create an object, first declare a class:
 
       TYPE
           shape = OBJECT
               color : colors;
               height, width : Integer;
               PROCEDURE shape.init;
               PROCEDURE shape.draw;
               PROCEDURE shape.move( horz, vert : Integer );
               FUNCTION  shape.area : Real;
               END;
 
    Then declare an instance of the class:
 
       VAR
           a_shape : shape;
 
    Finally, allocate memory for the new object:
 
       BEGIN
           .
           New( a_shape );
           .
       END.
 
  See also:  INHERITED, Member, OBJECT, OVERRIDE