Development/Tutorials/Kross/Scripts-as-Plugins: Difference between revisions

    From KDE TechBase
    (improved the init() sample to show how to pass a QTimer to scripts)
    Line 23: Line 23:
         {
         {
           // Calls the init() scripting function if available.
           // Calls the init() scripting function if available.
           // We pass ourself and an integer as arguments.
           // We pass our used QTimer instance and an integer
           emit init(this, 2000);
          // as arguments.
           emit init(m_timer, 2000);
           // On timeout call the update() scripting function
           // On timeout call the update() scripting function
           // if available.
           // if available.
    Line 44: Line 45:
       Q_SIGNAL:
       Q_SIGNAL:


         // If emitted calls the init(obj,interval) scripting
         // If emitted calls the init(timer,interval) scripting
         // function if available.
         // function if available.
         void init(MyObject* myobj, int interval);
         void init(QTimer* timer, int interval);


         // If emitted calls the update() scripting function
         // If emitted calls the update() scripting function
    Line 82: Line 83:
    We then add our myobject instance to the action. That way scripting code is able to access the publish {{qt|QObject}} instance, call it slots and connect with the signals.
    We then add our myobject instance to the action. That way scripting code is able to access the publish {{qt|QObject}} instance, call it slots and connect with the signals.


    Cause [http://websvn.kde.org/trunk/KDE/kdelibs/kross/core/childreninterface.h?view=markup Kross::ChildrenInterface::AutoConnectSignals] is defined, the init() and the update() signals the myobject instance provides will be automaticaly connected to matching scripting functions.
    Cause [http://websvn.kde.org/trunk/KDE/kdelibs/kross/core/childreninterface.h?view=markup Kross::ChildrenInterface::AutoConnectSignals] is defined, the init(QTimer*,int) and the update() signals the myobject instance provides will be automaticaly connected to matching scripting functions.


    Then the script file that should be executed is set. The used interpreter will be determinated by the file-extension like e.g. *.py for Python or or *.rb for Ruby. You are also able to set the interpreter explicit with e.g. action->setInterpreter("python") or action->setInterpreter("ruby"). You are also able to use action->setCode("print 'hello world'") to set the scripting code direct.
    Then the script file that should be executed is set. The used interpreter will be determinated by the file-extension like e.g. *.py for Python or or *.rb for Ruby. You are also able to set the interpreter explicit with e.g. action->setInterpreter("python") or action->setInterpreter("ruby"). You are also able to use action->setCode("print 'hello world'") to set the scripting code direct.
    Line 113: Line 114:
    # this function got called if the init(MyObject*,int)
    # this function got called if the init(MyObject*,int)
    # signal got emitted.
    # signal got emitted.
    def init(myobj, interval):
    def init(timer, interval):
       # following lines are doing basicly the same while
       # the following line uses the passed QTimer instance
       # the first one uses the passed arguments and the
      # and set's the interval Q_PROPERTY to the as argument
       # second uses the published myobject instance we
      # passed interval integer.
       # just imported before.
      timer.interval = interval
       myobj.setInterval(interval)
     
      # the following lines does basicly the same as above,
       # that is to set the interval the QTimer should use
       # to call our update() signal. But compared to the
       # line above we are doing it by using the setInterval
       # slot the published MyObject instance provides us.
       myobject.setInterval(2000)
       myobject.setInterval(2000)


    Line 124: Line 130:
    # got emitted.
    # got emitted.
    def update():
    def update():
       # just print the interval
       # just print the interval.
       print "interval=%i" % myobject.interval()
       print "interval=%i" % myobject.interval()
    </code>
    </code>
    Line 136: Line 142:
    require 'myobject'
    require 'myobject'


    # this function got called if the init(MyObject*,int)
    # this function got called if the init(QTimer*,int)
    # signal got emitted.
    # signal got emitted.
    def init(myobj, interval)
    def init(timer, interval)
       # following lines are doing basicly the same while
       # the following line uses the passed QTimer instance
       # the first one uses the passed arguments and the
      # and set's the interval Q_PROPERTY to the as argument
       # second uses the published myobject instance we
      # passed interval integer.
       # just imported before.
      timer.interval = interval
       myobj.setInterval(interval)
     
      # the following lines does basicly the same as above,
       # that is to set the interval the QTimer should use
       # to call our update() signal. But compared to the
       # line above we are doing it by using the setInterval
       # slot the published MyObject instance provides us.
       Myobject.setInterval(2000)
       Myobject.setInterval(2000)
    end
    end
    Line 150: Line 161:
    # got emitted.
    # got emitted.
    def update(myobj, interval)
    def update(myobj, interval)
       # just print the interval
       # just print the interval.
       puts "interval=%i" % Myobject.interval()
       puts "interval=%i" % Myobject.interval()
    end
    end
    </code>
    </code>

    Revision as of 19:48, 31 May 2007

    Introduction

    This tutorial provides a step-by-step introduction on how to integrate scripts as plugins into a C++/Qt/KDE application. This way, an application can be extended with plugins written in scripting languages such as Python, Ruby and KDE JavaScript.

    The C++ code

    The following C++ code demonstrates how to execute scripting code in C++ and how to let scripting code deal with QObject instances.

    For this we define the MyObject class that implements some signals and slots we will access from within scripting code. Scripts are able to access such QObject's as there are classinstances, call slots as they are memberfunctions, get and set properties as there are membervariables and connect scripting functions with signals.

    1. include <QObject>
    2. include <QTimer>
    3. include <kross/core/action.h>

    // This is our QObject our scripting code will access class MyObject : public QObject {

     public:
    
       MyObject(QObject* parent)
         : QObject(parent), m_timer(new QTimer(this))
       {
         // Calls the init() scripting function if available.
         // We pass our used QTimer instance and an integer
         // as arguments.
         emit init(m_timer, 2000);
         // On timeout call the update() scripting function
         // if available.
         connect(m_timer, SIGNAL(timeout()), SIGNAL(update()));
         // Start the timer.
         m_timer->start();
       }
    
       virtual ~MyObject() {}
    
     Q_SLOTS:
    
       // Return the timers interval in milliseconds
       int interval() const { return m_timer.interval(); }
    
       // Set the timers interval in milliseconds
       void setInterval(int ms) { m_timer.setInterval(ms); }
    
     Q_SIGNAL:
    
       // If emitted calls the init(timer,interval) scripting
       // function if available.
       void init(QTimer* timer, int interval);
    
       // If emitted calls the update() scripting function
       // if available.
       void update();
    
     private:
       Q_Timer* m_timer;
    

    };

    // Execute a script file. static void execScriptFile(MyObject* myobject, const QString& file) {

     // Create the script container. myobject is the parent QObject,
     // so that our action instance will be destroyed once the myobject
     // is destroyed.
     Kross::Action* action = new Kross::Action(myobject, file);
    
     // Publish our myobject instance and connect signals with
     // scripting functions.
     action->addObject(
       myobject, "myobject",
       Kross::ChildrenInterface::AutoConnectSignals);
    
     // Set the file we like to execute.
     action->setFile(file);
    
     // Execute the script.
     action->trigger();
    

    }

    The execScriptFile function does create an instance of Kross::Action that is used as abstract container to deal with scripts / script files.

    We then add our myobject instance to the action. That way scripting code is able to access the publish QObject instance, call it slots and connect with the signals.

    Cause Kross::ChildrenInterface::AutoConnectSignals is defined, the init(QTimer*,int) and the update() signals the myobject instance provides will be automaticaly connected to matching scripting functions.

    Then the script file that should be executed is set. The used interpreter will be determinated by the file-extension like e.g. *.py for Python or or *.rb for Ruby. You are also able to set the interpreter explicit with e.g. action->setInterpreter("python") or action->setInterpreter("ruby"). You are also able to use action->setCode("print 'hello world'") to set the scripting code direct.

    Finally the script is executed. This is done by triggering the action. Once executed you are also able to use Kross::ErrorInterface to check if the action was executed successfully like demonstrate below.

     if( action->hadError() )
       kDebug() << action->errorMessage() << endl;
    

    The Kross::Manager provides also the option to connect with the started and finished signals that got emitted if a script got executed. connect(&Kross::Manager::self(), SIGNAL( started(Kross::Action*) ),

           this, SLOT( started(Kross::Action*) ));
    

    connect(&Kross::Manager::self(), SIGNAL( finished(Kross::Action*) ),

           this, SLOT( finished(Kross::Action*) ));
    

    The Kross::ActionCollection class manages collections of Kross::Action instances, enables hierachies and implements serializing from/to XML.

    The Python scripting code

    The following Python script demonstrates how a Python plugin looks like. The init() and the update() functions will be called if the matching signals at the myobject instance are emitted.

    First we import myobject module. This module provides us access to the MyObject QObject instance and it's slots, signals and properties. Within the init() Python function we set the interval to 2000 milliseconds = 2 seconds. The QTimer our MyObject instance starts till emit the update() signal then 2 seconds later what in turn calls our update() Python function.

    1. import the published MyObject instance.

    import myobject

    1. this function got called if the init(MyObject*,int)
    2. signal got emitted.

    def init(timer, interval):

     # the following line uses the passed QTimer instance
     # and set's the interval Q_PROPERTY to the as argument
     # passed interval integer.
     timer.interval = interval
    
     # the following lines does basicly the same as above,
     # that is to set the interval the QTimer should use
     # to call our update() signal. But compared to the
     # line above we are doing it by using the setInterval
     # slot the published MyObject instance provides us.
     myobject.setInterval(2000)
    
    1. this function got called if the update() signal
    2. got emitted.

    def update():

     # just print the interval.
     print "interval=%i" % myobject.interval()
    

    The Ruby scripting code

    The following Ruby script does the same as the Python scripting code above except by using the Ruby scripting language. This shows, that the same rich API functionality is accessible independend of the used scripting language.

    1. import the published MyObject instance.

    require 'myobject'

    1. this function got called if the init(QTimer*,int)
    2. signal got emitted.

    def init(timer, interval)

     # the following line uses the passed QTimer instance
     # and set's the interval Q_PROPERTY to the as argument
     # passed interval integer.
     timer.interval = interval
    
     # the following lines does basicly the same as above,
     # that is to set the interval the QTimer should use
     # to call our update() signal. But compared to the
     # line above we are doing it by using the setInterval
     # slot the published MyObject instance provides us.
     Myobject.setInterval(2000)
    

    end

    1. this function got called if the update() signal
    2. got emitted.

    def update(myobj, interval)

     # just print the interval.
     puts "interval=%i" % Myobject.interval()
    

    end