Software Customisation Guide
Variables, Objects, Functions and Methods : Methods on User-Defined Object Types
Methods on User-Defined Object Types
When the user defines a new object type, they can also define methods which can be used to handle all objects created with the new type. PML Method definitions are stored in the same file as the object definition, after the endobject command.
Here is an example of an object which defines three methods to illustrate the main ideas. Note that within a method, !This represents the object which invoked the method and !This.Answer is the way to refer to member Answer of this object.
The Code
What it Does
define object LIFE
 member .Answer is REAL
endobject
Defines the object, with a single member, Answer.
define method .Life()
 !This.Answer = 42
endmethod
Defines a method with no arguments but the same name as the type of the object is called the default constructor method. If the default constructor method is present, PML will call it automatically to initialise the object whenever an object of that type is created.
define method .Answer() IS REAL
 return !This.Answer
endmethod
define method .Answer( !Value Is REAL)
 !This.Answer = !Value
endmethod
A method may return a result in just the same way as a PML Function using the return command. Set a member of the object using !This.membername.
These methods might be used in the following way:
!Marvin = object LIFE()
 -- The method .Life() was called automatically
!Number = !Marvin.Answer()
 -- !Number is set to the value 42
!Marvin.Answer(40)
!Number = !Marvin.Answer()
 -- !Number now has the value 40
Warning: When the user creates a new object type, or change an existing definition, the user must load the definition by giving the command:
pml reload object _name_
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