Initial values for variables – PB Docs 2021

When you declare a PowerScript variable, you can accept the
default initial value or specify an initial value in the
declaration.

Default values for
variables

If you do not initialize a variable when you declare it,
PowerBuilder sets the variable to the default value for its datatype
as shown in the following table.

Specifying a literal as a initial
value

To initialize a variable when you declare it, place an equal
sign (=) and a literal appropriate for that variable datatype after
the variable. For information about literals for specific datatypes,
see Standard
datatypes.

Although you can use global system functions or expressions to
initialize variables with compile time values in a variable
declaration statement, for runtime value assignments, you must also
declare variables and assign their values in separate
statements.

This example declares li_count as an integer whose value is
5:

This example declares li_a and li_b as integers and initializes
li_a to 5 and li_b to 10:

This example initializes ls_method with the string “UPS”:

This example initializes ls_headers to three words separated by
tabs:

This example initializes li_a to 1 and li_c to 100, leaving li_b
set to its default value of zero:

This example declares ld_StartDate as a date and initializes it
with the date February 1, 2004:

Specifying an expression as an initial
value

You can initialize a variable with the value of an existing
variable or expression, such as:

When you do this, the second variable is initialized with the
value of the expression when the script is compiled. The
initialization is not reevaluated at runtime.

If the expression’s value changes

Because the expression’s value is set to the variable when the
script is compiled (not at runtime) make sure the expression is not
one whose value is based on current conditions. If you want to specify
an expression whose value will be different when the application is
executed, do not initialize the variable in the declaration. For such
values, declare the variable and assign the value in separate
statements.

In this declaration, the value of d_date is the date the script
is compiled:

In contrast, these statements result in d_date being set to the
date the application is run:

How shared variables are
initialized

When you use a shared variable in a script, the variable is
initialized when the first instance of the object is opened. When the
object is closed, the shared variable continues to exist until you
exit the application. If you open the object again without exiting the
application, the shared variable will have the value it had when you
closed the object.

For example, if you set the shared variable Count to 20 in the
script for a window, then close the window, and then reopen the window
without exiting the application, Count will be equal to 20.

How instance variables are
initialized

When you define an instance variable for a window, menu, or
application object, the instance variable is initialized when the
object is opened. Its initial value is the default value for its
datatype or the value specified in the variable declarations.

When you close the object, the instance variable ceases to
exist. If you open the object again, the instance variable is
initialized again.

When to use multiple instances of windows

When you build a script for one of multiple instances of a
window, instance variables can have a different value in each instance
of the window. For example, to set a flag based on the contents of the
instance of a window, you would use an instance variable.

When to use shared variables instead

Use a shared variable instead of an instance variable if you
need a variable that: