Difference between revisions of "UniqueInstance"

Revision as of 04:45, 3 October 2007

UniqueInstance provides an easy way to force only one instance per application running at same time.

Just drop in the main form

Properties:

Enabled: enables/disables the component
Identifier: used to provides a way to identify the application
UpdateInterval: the interval in milliseconds which the component will monitor messages from new instances. Has meaning only under unix

Event

OnOtherInstance: called when another instance is initiated. Receives the parameters passed to that instance.

Add uniqueinstanceraw unit to your uses section.

Call the InstanceRunning function: it will return true if there's already a instance running.

There are two variants:

Without arguments: will use the executable name as identifier and will not send the command line parameters
With two arguments:
- Identifier: the identifier of the application
- SendParameters(default = false): send the command line parameters to the already running instance, if any, before quit.

Tested with win32 (XP SP2) and Linux (Ubuntu Feisty).
Version 0.2 requires fpc 2.2.0
Although it does not use platform dependent code, the callback mechanic used to pass the command line probably won't work in Linux. This occurs because TSimpleIPCServer under Linux does not call the OnMessage event (At least until some months ago when i tested it). Not more true since version 0.2
If you put two TUniqueInstance components in the same application with the same identifier your application won't load.
The Identifier is optional both to the function and the component. In the case it's not used, the executable name is used as an Identifier. The consequence is that if someone changes the exe name another instance will not be identified.
To make sure a application will not avoid other launching you can use a GUID as the Identifier

02/10/07 - Version 0.2
- Based in fpc 2.2.0
- Implemented parameter reception under unix
- General optimizations and code clean up
16/12/06 - Initial release. See my blog to know how it began.

Luiz Américo Pereira Câmara

Modified LGPL

@@ Line 35: / Line 35: @@
 === Remarks ===
 * Tested with win32 (XP SP2) and Linux (Ubuntu Feisty).
+* Version 0.2 requires fpc 2.2.0
 * <strike>Although it does not use platform dependent code, the callback mechanic used to pass the command line probably won't work in Linux. This occurs because TSimpleIPCServer under Linux does not call the OnMessage event (At least until some months ago when i tested it).</strike> Not more true since version 0.2
 * If you put two TUniqueInstance components in the same application with the same identifier your application won't load.