About using variables – PB Docs 2019

General information

To use or set a variable’s value in a PowerBuilder script, you
name the variable. The variable must be known to the compiler — in
other words, it must be in scope.

You can use a variable anywhere you need its value — for example,
as a function argument or in an assignment statement.

How PowerBuilder looks for variables

When PowerBuilder executes a script and finds an unqualified
reference to a variable, it searches for the variable in the following
order:

As soon as PowerBuilder finds a variable with the specified name,
it uses the variable’s value.

Referring to global
variables

To refer to a global variable, you specify its name in a script.
However, if the global variable has the same name as a local or shared
variable, the local or shared variable will be found first.

To refer to a global variable that is masked by a local or shared
variable of the same name, use the global scope operator (::) before the
name:

For example, this statement compares the value of local and global
variables, both named total:

Referring to instance variables

You can refer to an instance variable in a script if there is an
instance of the object open in the application. Depending on the
situation, you might need to qualify the name of the instance variable
with the name of the object defining it.

Using unqualified names

You can refer to instance variables without qualifying them with
the object name in the following cases:

For example, if w_emp has an instance variable EmpID, then you can
reference EmpID without qualification in any script for w_emp or its
controls as follows:

Using qualified names

In all other cases, you need to qualify the name of the instance
variable with the name of the object using dot notation:

This requirement applies only to Public instance variables. You
cannot reference Private instance variables outside the object at all,
qualified or not.

For example, to refer to the w_emp instance variable EmpID from a
script outside the window, you need to qualify the variable with the
window name:

There is another situation in which references must be qualified.
Suppose that w_emp has an instance variable EmpID and that in w_emp
there is a CommandButton that declares a local variable EmpID in its
Clicked script. In that script, you must qualify all references to the
instance variable:

Using pronouns as name qualifiers

To avoid ambiguity when referring to variables, you might decide
to always use qualified names for object variables. Qualified names
leave no doubt about whether a variable is local, instance, or
shared.

To write generic code but still use qualified names, you can use
the pronouns This and Parent to refer to objects. Pronouns keep a script
general by allowing you to refer to the object without naming it
specifically.

Window variables in window scripts

In a window script, use the pronoun This to qualify the name of a
window instance variable. For example, if a window has an instance
variable called index, then the following statements are equivalent in a
script for that window, as long as there is no local or global variable
named index:

Window variables in control scripts

In a script for a control in a window, use the pronoun Parent to
qualify the name of a window instance variable — the window is the
parent of the control. In this example, the two statements are
equivalent in a script for a control in that window, as long as there is
no local or global variable named “index”:

Naming errors

If a local or global variable exists with the name “index”, then
the unqualified name refers to the local or global variable. It is a
programming error if you meant to refer to the object variable. You get
an informational message from the compiler if you use the same name for
instance and global variables.