Syntax 2: For activating timing objects – PB Docs 2019

Description

Activates a timing object causing a Timer event to occur
repeatedly at the specified interval.

Applies to

Timing objects

Syntax

Return value

Integer.

Returns 1 if it succeeds and -1 if the timer is already running,
the interval specified is invalid, or there are no system timers
available.

Usage

This syntax of the Start function is used to activate a nonvisual
timing object. Timing objects can be used to trigger a Timer event that
is not associated with a PowerBuilder window, and they are therefore
useful for distributed PowerBuilder servers or shared objects that do
not have a window for each client connection.

A timing object is a standard class user object inherited from the
Timing system object. Once you have created a timing object and coded
its timer event, you can create any number of instances of the object
within the constraints of your operating system. An operating system
supports a fixed number of timers. Some of those timers will already be
in use by PowerBuilder and other applications and by the operating
system itself.

To activate an instance of the timing object, call the Start
function, specifying the interval that you want between Timer events.
The Timer event of that instance is triggered as soon as possible after
the specified interval, and will continue to be triggered until you call
the Stop function on that instance of the timing object or the object is
destroyed.

The resolution of the interval depends on your operating
system.

You can determine what the timing interval is and whether a timer
is running by accessing the timing object’s Interval and Running
properties. These properties are read-only. You must stop and restart a
timer in order to change the value of the timing interval.

Examples

Example 1

Suppose you have a distributed application in which the local
client performs some processing, such as calculating the value of a
stock portfolio, based on values in a database. The client requests a
user object on a remote server to retrieve the data values from the
database.

Create a standard class user object on the server called uo_timer,
inherited from the Timing system object, and code its Timer event to
refresh the data. Then the following code creates an instance, MyTimer,
of the timing object uo_timer. The Start function activates the timer
with an interval of 60 seconds so that the request to the server is
issued at 60-second intervals:

Example 2

The following example uses a timing object as a shared object in a
window that has buttons for starting a timer, getting a hit count,
stopping the timer, and closing the window. Status is shown in a single
line edit called sle_state. The timing object, uo_timing, is a standard
class user object inherited from the Timing system object. It has one
instance variable that holds the number of times a connection is
made:

The timing object uo_timing has three functions:

The timer event in uo_timing calls the of_connect function:

When the main window (w_timer) opens, its Open event script
registers the uo_timing user object as a shared object:

The Start Timer button starts the timer with an interval of five
seconds:

The Get Hits button calls the of_hitcount function and writes the
result in a single line edit:

The Stop Timer button stops the timer, re-enables the Start Timer
button, and resets the hit counter:

The Close button checks that the timer has been stopped and closes
the window if it has:

The Close event for the window unregisters the shared timing
object:

The of_converterror window function converts the ErrorReturn
enumerated type to a string. It takes an argument of type
ErrorReturn:

See also

Stop