Projects/Nepomuk/QuickStart: Difference between revisions
(Re-done most of the page) |
No edit summary |
||
| Line 8: | Line 8: | ||
}} | }} | ||
=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. | 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. | ||
==Some Basics== | |||
Nepomuk is centred around a main 'Resource' class. For simple, non-high performance access to Nepomuk, it is recommended that you use the Resource class. | Nepomuk is centred around a main 'Resource' class. For simple, non-high performance access to Nepomuk, it is recommended that you use the Resource class. | ||
| Line 21: | Line 21: | ||
Every file, folder, contact or tag is a Resource. | Every file, folder, contact or tag is a Resource. | ||
==Dealing with Tags== | |||
Every tag in Nepomuk is a Resource. In fact the Tag class is also derived from the Resource class. | Every tag in Nepomuk is a Resource. In fact the Tag class is also derived from the Resource class. | ||
===Setting Tags=== | |||
<syntaxhighlight lang="cpp-qt"> | <syntaxhighlight lang="cpp-qt"> | ||
| Line 36: | Line 36: | ||
The 'Nepomuk2::Tag' class will automatically look for for a tag called "Awesome-Tag-Name", it is finds it then Tag::exists() will return true. Otherwise, the tag will be saved the first time the tag is used. In our case, when we add the tag to the Resource via Resource::addTag(), the tag will be saved. | The 'Nepomuk2::Tag' class will automatically look for for a tag called "Awesome-Tag-Name", it is finds it then Tag::exists() will return true. Otherwise, the tag will be saved the first time the tag is used. In our case, when we add the tag to the Resource via Resource::addTag(), the tag will be saved. | ||
===Retrieving Tags=== | |||
<syntaxhighlight lang="cpp-qt"> | <syntaxhighlight lang="cpp-qt"> | ||
| Line 50: | Line 50: | ||
Every resource has a predefined function for retrieving all the Tags any resource is tagged with - Resource::tags(). The Resource::genericLabel() function tries to find a presentable name for any resource. In the case of tags, it returns the tags name. | Every resource has a predefined function for retrieving all the Tags any resource is tagged with - Resource::tags(). The Resource::genericLabel() function tries to find a presentable name for any resource. In the case of tags, it returns the tags name. | ||
===Listing all the Tags=== | |||
The simplest way to list all the tags that are present in Nepomuk is via a static function - Tag::allTags(). You, however, need to be careful using this in a production environment as it executes a blocking query in the background. Depending on the number of tags on the system, it could take some time. | The simplest way to list all the tags that are present in Nepomuk is via a static function - Tag::allTags(). You, however, need to be careful using this in a production environment as it executes a blocking query in the background. Depending on the number of tags on the system, it could take some time. | ||
| Line 63: | Line 63: | ||
==Dealing with files== | |||
Every file in Nepomuk is represented as a resource. Since dealing with files is very common, we provide a special File class which is derived from the Resource class. We also provide convenience functions for checking if a resource is a file. | Every file in Nepomuk is represented as a resource. Since dealing with files is very common, we provide a special File class which is derived from the Resource class. We also provide convenience functions for checking if a resource is a file. | ||
| Line 82: | Line 82: | ||
Internally Nepomuk Files are not very different from other Resources. | Internally Nepomuk Files are not very different from other Resources. | ||
==Ratings== | |||
Every resource in Nepomuk can be given a numeric rating. It is generally done on a scale of 0-10. | Every resource in Nepomuk can be given a numeric rating. It is generally done on a scale of 0-10. | ||
| Line 97: | Line 97: | ||
==Includes and Linking== | |||
===Headers=== | |||
For the example you need the following includes: | For the example you need the following includes: | ||
<syntaxhighlight lang="cpp-qt"> | <syntaxhighlight lang="cpp-qt"> | ||
| Line 106: | Line 108: | ||
</syntaxhighlight> | </syntaxhighlight> | ||
===CMake=== | |||
In your CMakeLists.txt, you need the find macro for Nepomuk and link to it of course ;) | In your CMakeLists.txt, you need the find macro for Nepomuk and link to it of course ;) | ||
Revision as of 16:31, 1 August 2012
| Tutorial Series | Nepomuk |
| Previous | Getting started with KDE development |
| 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.
Some Basics
Nepomuk is centred around a main 'Resource' class. For simple, non-high performance access to Nepomuk, it is recommended that you use the Resource class.
Everything in Nepomuk is a Resource. Each Resource has a number of properties associated with it, which are stored as (key, value) pairs. They keys are referred to as properties or predicates, and the values are referred to as the objects.
Every file, folder, contact or tag is a Resource.
Dealing with Tags
Every tag in Nepomuk is a Resource. In fact the Tag class is also derived from the Resource class.
Setting Tags
Nepomuk2::Tag tag( "Awesome-Tag-Name" );
Nepomuk2::Resource res( url );
res.addTag( tag );
The 'Nepomuk2::Tag' class will automatically look for for a tag called "Awesome-Tag-Name", it is finds it then Tag::exists() will return true. Otherwise, the tag will be saved the first time the tag is used. In our case, when we add the tag to the Resource via Resource::addTag(), the tag will be saved.
Retrieving Tags
using namespace Nepomuk2;
Resource res( url );
QList<Tag> tags = res.tags();
foreach(const Tag& tag, tags)
kDebug() << tag.genericLabel();
Every resource has a predefined function for retrieving all the Tags any resource is tagged with - Resource::tags(). The Resource::genericLabel() function tries to find a presentable name for any resource. In the case of tags, it returns the tags name.
Listing all the Tags
The simplest way to list all the tags that are present in Nepomuk is via a static function - Tag::allTags(). You, however, need to be careful using this in a production environment as it executes a blocking query in the background. Depending on the number of tags on the system, it could take some time.
using namespace Nepomuk2;
QList<Tag> tags = Tag::allTags();
foreach(const Tag& tag, tags)
kDebug() << tag.genericLabel();
Dealing with files
Every file in Nepomuk is represented as a resource. Since dealing with files is very common, we provide a special File class which is derived from the Resource class. We also provide convenience functions for checking if a resource is a file.
using namespace Nepomuk2;
File fileRes( urlOfTheFile );
kDebug() << fileRes.url();
Resource res( urlOfTheFile );
if( res.isFile() )
kDebug() << res.toFile().url();
Internally Nepomuk Files are not very different from other Resources.
Ratings
Every resource in Nepomuk can be given a numeric rating. It is generally done on a scale of 0-10.
using namespace Nepomuk2;
File fileRes( urlOfTheFile );
int rating = fileRes.rating();
rating = rating + 1;
fileRes.setRating( rating );
Includes and Linking
Headers
For the example you need the following includes:
#include <Nepomuk2/Tag>
#include <Nepomuk2/Resource>
#include <Nepomuk2/File>
#include <KDebug>CMake
In your CMakeLists.txt, you need the find macro for Nepomuk and link to it of course ;)
find_package(NepomukCore REQUIRED)
target_link_libraries(myfile ${NEPOMUK_CORE_LIBRARY} )