Projects/Nepomuk/QuickStart: Difference between revisions
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==Nepomuk Quickstart== | ==Nepomuk Quickstart== | ||
Reading or setting simple metadata in your | Reading or setting simple metadata in your application with Nepomuk, can be very easy. However, keep in mind that the process described here may have performance drawbacks when changing a lot of metadata. | ||
We will now take a look at a simple way to access a resource's metadata. | We will now take a look at a simple way to access a resource's metadata. | ||
===Initializing the Resource Manager=== | ===Initializing the Resource Manager=== | ||
The ResourceManager is the central KMetaData configuration point. | The ResourceManager is the central KMetaData configuration point. For KDE 4.2 and newer, we must explicitly initialize it in order to connect to the Nepomuk service. | ||
<code cppqt> | <code cppqt> | ||
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</code> | </code> | ||
This method returns a bool. If it | This method returns a <i>bool</i>. If it returns <i>true</i>, the connection to the Nepomuk service has been established and we can work with it. If it returns <i>false</i>, the Nepomuk service was unreachable and we can't continue working with any Nepomuk related code--this may occur if the user has disabled the Nepomuk service for his current session. | ||
=== | ===Retrieving Metadata=== | ||
Let's get the metadata for a file | Let's get the metadata for a file, assuming the URL or the file is stored in <i>uri</i>. | ||
<code cppqt> | <code cppqt> | ||
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</code> | </code> | ||
This allows us to obtain all the properties assigned to the file. | |||
We can now use Nepomuk to get human readable labels for the properties and display the properties in a generic way: | We can now use Nepomuk to get human-readable labels for the properties, and display the properties in a generic way: | ||
<code cppqt> | <code cppqt> | ||
| Line 47: | Line 47: | ||
</code> | </code> | ||
=== | ===Setting Metadata=== | ||
Similarly, assume <i>uri</i> is the URL of a file that we want to set some metadata to. This time we want to set a tag and a comment and will do this using two slightly different methods: | |||
Let's start with the tag and use the easy Nepomukish way: | Let's start with the tag and use the easy Nepomukish way: | ||
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</code> | </code> | ||
Simple! Actually if the tag already exists it will be reused. | Simple! Actually, if the tag already exists, it will be reused. | ||
Now let's set a comment for the file without the use of the convenience methods in Nepomuk: | Now let's set a comment for the file without the use of the convenience methods in Nepomuk: | ||
Revision as of 22:58, 21 May 2009
Development/Tutorials/Metadata/Nepomuk/Quickstart
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| Tutorial Series | Nepomuk |
| Previous | None |
| What's Next | Handle Resource Metadata with Nepomuk |
| Further Reading | n/a |
Nepomuk Quickstart
Reading or setting simple metadata in your application with Nepomuk, can be very easy. However, keep in mind that the process described here may have performance drawbacks when changing a lot of metadata. We will now take a look at a simple way to access a resource's metadata.
Initializing the Resource Manager
The ResourceManager is the central KMetaData configuration point. For KDE 4.2 and newer, we must explicitly initialize it in order to connect to the Nepomuk service.
Nepomuk::ResourceManager::instance()->init();
This method returns a bool. If it returns true, the connection to the Nepomuk service has been established and we can work with it. If it returns false, the Nepomuk service was unreachable and we can't continue working with any Nepomuk related code--this may occur if the user has disabled the Nepomuk service for his current session.
Retrieving Metadata
Let's get the metadata for a file, assuming the URL or the file is stored in uri.
Nepomuk::Resource res( uri );
QHash<QUrl, Variant> properties = res.properties();
This allows us to obtain all the properties assigned to the file.
We can now use Nepomuk to get human-readable labels for the properties, and display the properties in a generic way:
for( QHash<QUrl, Variant>::const_iterator it = properties.constBegin();
it != properties.constEnd(); ++it ) {
QUrl propertyUri = it.key();
Variant value = it.value();
Nepomuk::Types::Class propertyType( propertyUri );
someList->appendItem( propertyType.label() + ": " + value.toString() );
}
Setting Metadata
Similarly, assume uri is the URL of a file that we want to set some metadata to. This time we want to set a tag and a comment and will do this using two slightly different methods:
Let's start with the tag and use the easy Nepomukish way:
Nepomuk::Tag tag( "This is my nice tag name" );
Nepomuk::Resource res( uri );
res.addTag( tag );
Simple! Actually, if the tag already exists, it will be reused.
Now let's set a comment for the file without the use of the convenience methods in Nepomuk:
Nepomuk::Resource res( uri );
QString comment = getFancyFileComment();
res.setProperty( Soprano::Vocabulary::NAO::description(), comment );
That's all. The comment is saved and will now be searchable via Nepomuk.