Development/Tutorials/Kross/Call Functions in Kross: Difference between revisions

    From KDE TechBase
    m (Text replace - "<code cpp>" to "<syntaxhighlight lang="cpp">")
    m (Text replace - "</code>" to "</syntaxhighlight>")
    Line 21: Line 21:
    kde4_add_executable(krosshello ${krosshello_SRCS})
    kde4_add_executable(krosshello ${krosshello_SRCS})
    target_link_libraries(krosshello ${KDE4_KDEUI_LIBS} ${KDE4_KROSSUI_LIBS})
    target_link_libraries(krosshello ${KDE4_KDEUI_LIBS} ${KDE4_KROSSUI_LIBS})
    </code>
    </syntaxhighlight>


    === main.cpp ===
    === main.cpp ===
    Line 54: Line 54:
         return app.exec();
         return app.exec();
    }
    }
    </code>
    </syntaxhighlight>


    === mainwindow.h ===
    === mainwindow.h ===
    Line 87: Line 87:


    #endif
    #endif
    </code>
    </syntaxhighlight>


    === mainwindow.cpp ===
    === mainwindow.cpp ===
    Line 173: Line 173:
         lblMessage->setText(result.toString());
         lblMessage->setText(result.toString());
    }
    }
    </code>
    </syntaxhighlight>


    == The Script Files ==
    == The Script Files ==
    Line 194: Line 194:
         return s.split("").reverse().join("");
         return s.split("").reverse().join("");
    }
    }
    </code>
    </syntaxhighlight>


    === Testscriptfile.py ===
    === Testscriptfile.py ===
    Line 206: Line 206:
         lineedit.setText(s)
         lineedit.setText(s)
         return s[::-1]
         return s[::-1]
    </code>
    </syntaxhighlight>

    Revision as of 19:42, 29 June 2011

    This tutorial shows how to deal with functions provided by a script. This tutorial is based on the Hello World tutorial and extends the codebase we wrote there with new functionality to outline how calling scripting functions could be done.

    Please note, that it is recommed to use Autoconnected Signals and Slots if you just like to have a bunch of scripting functions within a script that should be called on demand. That way you have a clear interface with signals that are mapped transparent to scripting functions. The "trick" here is, that Kross will automaticly connect each signal a QObject has to a matching scripting function and at the C++ side all what is needed is to emit a signal and behind the scene the arguments will be translated and a possible defined scripting function got called. A good example here is SuperKaramba which uses the signal+slot rather then callFunction() way. All it defines is the rather huge class that inherits QObject (karambainterface.h). The signals within that class are transparent mapped to scripting functions (e.g. template.py and template.js) while the slots are then callable from within the scripting code. Signals and slots are faster and more type-safe then the in this tutorial used callFunction() (see also the Kross::Action class).

    The C++ Code

    The following code is a KDE C++ project to demonstrate how to deal with scripting functions.

    CMakeLists.txt

    We are using cmake to build our small sample project. The CMakeLists.txt file looks like;

    project (krosshello) find_package(KDE4 REQUIRED) include_directories( ${KDE4_INCLUDES} ) set(krosshello_SRCS main.cpp mainwindow.cpp) kde4_add_executable(krosshello ${krosshello_SRCS}) target_link_libraries(krosshello ${KDE4_KDEUI_LIBS} ${KDE4_KROSSUI_LIBS}) </syntaxhighlight>

    main.cpp

    The main.cpp does create the sample application and shows the mainwindow instance.

    #include <QString>
    #include <KApplication>
    #include <KAboutData>
    #include <KMessageBox>
    #include <KCmdLineArgs>
    #include <KLocalizedString>
    #include "mainwindow.h"
    
    int main (int argc, char *argv[]) {
        // Used to store information about a program.
        KAboutData aboutData("krosshello",
            0,ki18n("Kross Hello World"),"1.0",
    	ki18n("Hello World application for Kross"),
    	KAboutData::License_GPL,
    	ki18n("(c) 2007"),ki18n("Some text..."),
    	"http://kross.dipe.org","[email protected]");
        // Access to the command-line arguments.
        KCmdLineArgs::init( argc, argv, &aboutData );
        // Initialize the application.
        KApplication app;
        // Create and show the main window.
        MainWindow* window = new MainWindow();
        window->show();
        // Finally execute the application.
        return app.exec();
    }
    

    mainwindow.h

    This is the main windows class which defines some displayed widgets for our small sample application.

    #ifndef MAINWINDOW_H
    #define MAINWINDOW_H
    
    #include <QComboBox>
    #include <QLabel>
    #include <QLineEdit>
    #include <kross/core/action.h>
    
    // The main window to display our combobox and the label.
    class MainWindow : public QWidget
    {
        Q_OBJECT
        public:
            MainWindow(QWidget *parent=0);
        private Q_SLOTS:
            // This slot is called when the item in the
            // interpreter-combobox is changed.
            void interpreterActivated(const QString &);
        private:
            QLineEdit* txtInputString;
    	QLabel* lblMessage;
    	QComboBox* cmbInterpreters;
    	Kross::Action* action;
    };
    
    #endif
    

    mainwindow.cpp

    The implementation of the main window functionality. We are displaying a QLineEdit that will be passed as first argument to a scripting function named "reverseString". Those function returns a string that will then displayed in a QLabel. Just like at the Kross Hello World tutorial, we also display a QComboBox that does allow to choose an interpreter.

    #include "mainwindow.h"
    #include <QVBoxLayout>
    #include <QDebug>
    #include <kross/core/manager.h>
    #include <kross/core/action.h>
    
    // the constructor.
    MainWindow::MainWindow(QWidget *parent) : QWidget(parent)
    {
        txtInputString = new QLineEdit();
        lblMessage = new QLabel("Hello");
        cmbInterpreters = new QComboBox ();
        cmbInterpreters->addItem("Choose Interpreter", "");
        foreach(QString s, Kross::Manager::self().interpreters())
            cmbInterpreters->addItem(s);
        connect(cmbInterpreters, SIGNAL(activated(const QString &)),
                SLOT(interpreterActivated(const QString &)));
    
        QVBoxLayout *vLayout = new QVBoxLayout;
        vLayout->addWidget(cmbInterpreters);
        vLayout->addWidget(txtInputString);
        vLayout->addWidget(lblMessage);
        setLayout(vLayout);
    
        // Create the Kross::Action instance .
        action = new Kross::Action(this, "MyScript");
    
        // We don't need to publish any QObject instances
        // for this sample.
        //action->addObject(txtInputString, "MyInputString");
        //action->addObject(cmbInterpreters, "MyInterpreter");
        //action->addObject(lblMessage, "MyLabel");
    }
    
    // this slot is called when the active item of the combobox changes.
    void MainWindow::interpreterActivated(const QString &interpr)
    {
        // this time we are using external script files.
        QString filename;
        if(interpr == "python") // Python backend
            filename = "Testscriptfile.py";
        else if(interpr == "javascript") // JavaScript backend
            filename = "Testscriptfile.js";
        else { // no other sample script files
            lblMessage->setText("-");
            return;
        }
    
        // set the script file that should be executed
        action->setFile(filename);
    
        // execute the scripting code, i.e. preload
        // please note, that it's needed to trigger aka
        // execute the script before calling a function
        // using callFunction() or before asking what
        // functions are available using functionNames().
        // also it's only needed to trigger the script
        // once and then call whatever functions should
        // be called or signals emitted or whatever.
        action->trigger();
    
        // The list of arguments passed to the function
        QVariantList args;
    
        // here we pass in the QLineEdit instance
        // as first argument
        QVariant v;
        v.setValue( (QWidget*) txtInputString );
        args << v;
    
        // and the second argument is a string
        args << "Hello World";
    
        // Call the arbitrary function
        QVariant result = action->callFunction("reverseString",args);
    
        // Use the returnvalue of the function call
        lblMessage->setText(result.toString());
    }
    

    The Script Files

    We are then able to use supported scripting backends like Python, Ruby and JavaScript to execute a scripting function named "reverseString" and called in the mainwindow.cpp file. The "reverseString" function has a QLineEdit and a QString as arguments and returns a QString.

    Testscriptfile.js

    The Testscriptfile.js JavaScript file does provide us the reverseString scripting function.

    function reverseString(lineedit, s) {

       println("reverseString lineedit=" + lineedit + " s=" + s);
       s = "JsReverse: " + s;
    
       lineedit.setText(s);
       //MyInputString.text = s;
    
       return s.split("").reverse().join("");
    

    } </syntaxhighlight>

    Testscriptfile.py

    The Testscriptfile.py Python file does provide us the reverseString scripting function.

    def reverseString(lineedit, s):

       print "reverseString lineedit=%s s=%s" % (lineedit,s)
       s = "PyReverse: %s" % s
       lineedit.setText(s)
       return s[::-1]
    

    </syntaxhighlight>