This pronoun
Description
The pronoun This in
a PowerBuilder script refers to the window, user object, menu, application
object, or control that owns the current script.
Usage
Why include This
Using This allows you to make ownership
explicit. The following statement refers to the current object’s
X property:
|
1 |
This.X = This.X + 50 |
When optional but helpful
In the script for an object or control, you can refer to the
properties of the object or control without qualification, but it
is good programming practice to include This to
make the script clear and easy to read.
When required
There are some circumstances when you must use This. When
a global or local variable has the same name as an instance variable, PowerBuilder
finds the global or local variable first. Qualifying the variable with This allows
you to refer to the instance variable instead of the global variable.
EAServer restriction
You cannot use This to pass arguments in EAServer components.
Examples
Example 1
This statement in a script for a menu places a check mark
next to the menu selection:
|
1 |
This.Check( ) |
Example 2
In this function call, This passes a reference
to the object containing the script:
|
1 |
ReCalc(This) |
Example 3
If you omit This, “x” in
the following statement refers to a local variable x if there is
one defined (the script adds 50 to the variable x, not to the X
property of the control). It refers to the object’s X property
if there is no local variable:
|
1 |
x = x + 50 |
Example 4
Use This to ensure that you refer to the
property. For example, in the following statement in the script
for the Clicked event for a CommandButton, clicking the button changes
the horizontal position of the button (changes the button’s
X property):
|
1 |
This.x = This.x + 50 |