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Archived:Using RProperty for publishing

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m (Protected "Publish and Subscribe: Using RProperty for publishing" [edit=sysop:move=sysop])

Revision as of 09:02, 22 April 2008


ID   Creation date April 15, 2008
Platform S60 3rd Edition, FP1 Tested on devices Nokia N93
Category Symbian C++ Subcategory Files/Data


Keywords (APIs, classes, methods, functions): RProperty, RProperty::Define(), RProperty::Delete(), RProperty::Attach(), RProperty::Set(), RProperty::Close()

Overview

This snippet shows how the class RProperty can be used to publish user defined properties with Symbian's IPC Publish and Subscribe mechanism.

A property is published using the RProperty::Set() function. This means that the value of property is updated. Whenever a property is published, all outstanding subscriptions are completed.

There is also an another snippet "Publish and Subscribe: Using RProperty for subscribing" to subscribe these user defined properties. The property definitions are shared between a publisher and a subscriber through the common header file ExampleProperties.h

#ifndef EXAMPLEPROPERTIES_H_
#define EXAMPLEPROPERTIES_H_
 
const TInt KMaxStrLen = 10;
const TUid KExampleProperty = {0xED1917A8};
enum TExamplePropertyKeys { EIntProperty, EStrProperty };
 
#endif /*EXAMPLEPROPERTIES_H_*/

This snippet can be self-signed.

MMP file

The following libraries are required:

LIBRARY  euser.lib

Preconditions

The publisher or the subscriber thread can be the one to define properties, by calling RProperty::Define(). The user defined properties persist in the kernel until the operating system reboots or the properties are deleted.

TInt ret=RProperty::Define(KExampleProperty,EIntProperty,RProperty::EInt);
if (ret != KErrAlreadyExists)
{
User::LeaveIfError(ret);
}
 
ret= RProperty::Define(KExampleProperty,EStrProperty,RProperty::EByteArray,KMaxStrLen);
if (ret != KErrAlreadyExists)
{
User::LeaveIfError(ret);
}


Source file

#include <e32base.h>
#include <e32property.h>
 
#include "exampleproperties.h"
 
LOCAL_C void SetExamplePropertiesL()
{
TInt err(KErrNone);
 
// Use handle to publish EIntProperty
RProperty intProperty;
err = intProperty.Attach(KExampleProperty, EIntProperty, EOwnerThread);
User::LeaveIfError(err);
err = intProperty.Set(123);
User::LeaveIfError(err);
intProperty.Close();
 
// Use category and key to publish EStrProperty
err=RProperty::Set(KExampleProperty,EStrProperty,_L("321"));
User::LeaveIfError(err);
}
 
// Global Functions
GLDEF_C TInt E32Main()
{
// Create cleanup stack
__UHEAP_MARK;
CTrapCleanup* cleanup = CTrapCleanup::New();
 
// Run application code inside TRAP harness
TRAPD(mainError, SetExamplePropertiesL());
if (mainError)
{
//SetExamplePropertiesL leaves...
}
else
{
//Properties updated ok
}
delete cleanup;
__UHEAP_MARKEND;
return KErrNone;
}

Postconditions

Two example properties are published using the class RProperty.

If the publisher thread was the one that defined properties it is also capable of deleting properties by using the RProperty::Delete(), as follows:

TInt err(KErrNone);
 
err = RProperty::Delete(KExampleProperty,EIntProperty);
if (err != KErrNotFound)
{
User::LeaveIfError(err);
}
err = RProperty::Delete(KExampleProperty,EStrProperty);
if (err != KErrNotFound)
{
User::LeaveIfError(err);
}

When properties are deleted, any outstanding subscriptions will be completed with KErrNotFound.

See also

Publish and Subscribe: Using RProperty for subscribing

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