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— Statements —

METHOD

`METHOD` `method-name`
`OF` [`INTERFACE`] `interface-name`
`IS` `subprogram-name`
`END-METHOD`

This document covers the following topics:

Function
Syntax Description
Example

For an explanation of the symbols used in the syntax diagram, see Syntax Symbols.

Related Statements: CREATE OBJECT | DEFINE CLASS | INTERFACE | PROPERTY | SEND METHOD

Belongs to Function Group: Component Based Programming

Function

The METHOD statement assigns a subprogram as the implementation to a method, outside an interface definition. It is used if the interface definition in question is included from a copycode and is to be implemented in a class-specific way.

The METHOD statement may only be used within the DEFINE CLASS statement and after the interface definition. The interface and method names specified must be defined in the INTERFACE clause of the DEFINE CLASS statement.

Syntax Description

Syntax Element	Description
`method-name`	Method Name: This is the name assigned to the `method`.
`OF interface-name`	Interface Name: This is the name assigned to the `interface`.
`IS subprogram-name`	IS Clause: This clause can be used to specify the name of the subprogram that implements the method. The name of the subprogram consists of up to 8 characters. The default is `method-name` (if the `IS` clause is not specified).
`END-METHOD`	End of Method Statement: The Natural reserved word `END-METHOD` must be used to end the `METHOD` statement.

Example

The following example shows how the same interface is implemented differently in two classes and how the PROPERTY statement and the METHOD statement are used to achieve this.

The interface Measure is defined in the copycode iface-c. The classes Elephant and Mouse implement both the interface Measure. Therefore, they both include the copycode iface-c. But the classes implement the property Height using different variables from their respective object data areas, and they implement the method Init with different subprograms. They use the PROPERTY statement to assign the selected data area variable to the property and the METHOD statement to assign the selected subprogram to the method.

Now the program prog can create objects of both classes and initialize them using the same method Init, leaving the specifics of the initialization to the respective class implementation.

Example

The following shows the complete contents of the Natural modules used in the example above:

Copycode: iface-c

interface Measure
*
property Height(p5.2)
end-property
*
property Weight(i4)
end-property
*
method Init
end-method
*
end-interface

Class: class1

define class elephant
object using class1-o
interface using iface-c
*
property Height of interface Measure is height
end-property
*
property Weight of interface Measure is weight
end-property
*
method Init of interface Measure is init1-n
end-method
*
end-class
end

LDA Object Data: class1-o

*   *** Top of Data Area ***
  1 HEIGHT                  P 5.2
  1 WEIGHT                  I 2
*   *** End of Data Area ***

Method Subprogram: init1-n

define data
object using class1-o
end-define
*
height := 17.3
weight := 120
*
end

Class: class2

define class mouse
object using class2-o
interface using iface-c
*
property Height of interface Measure is size
end-property
*
property Weight of interface Measure is weight
end-property
*
method Init of interface Measure is init2-n
end-method
*
end-class
end

LDA Object Data: class2-o

*   *** Top of Data Area ***
  1 SIZE                    P 3.2
  1 WEIGHT                  I 1
*   *** End of Data Area ***

Method Subprogram: init2-n

define data
object using class2-o
end-define
*
size := 1.24
weight := 2
*
end

Program: prog

define data local
1 #o handle of object
1 #height(p5.2)
1 #weight(i4)
end-define
*
create object #o of class 'Elephant'
send "Init" to #o
#height := #o.Height
#weight := #o.Weight
write #height #weight
*
create object #o of class 'Mouse'
send "Init" to #o
#height := #o.Height
#weight := #o.Weight
write #height #weight
*
end

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