Source code of the Hello world example

Browse below the source code for Wt's Hello world example.

  • hello
    • hello.C
    /*
     * Copyright (C) 2008 Emweb bvba, Heverlee, Belgium.
     *
     * See the LICENSE file for terms of use.
     */
    
    #include <Wt/WApplication.h>
    #include <Wt/WBreak.h>
    #include <Wt/WContainerWidget.h>
    #include <Wt/WLineEdit.h>
    #include <Wt/WPushButton.h>
    #include <Wt/WText.h>
    
    /*
     * A simple hello world application class which demonstrates how to react
     * to events, read input, and give feed-back.
     */
    class HelloApplication : public Wt::WApplication
    {
    public:
      HelloApplication(const Wt::WEnvironment& env);
    
    private:
      Wt::WLineEdit *nameEdit_;
      Wt::WText     *greeting_;
    
      void greet();
    };
    
    /*
     * The env argument contains information about the new session, and
     * the initial request. It must be passed to the WApplication
     * constructor so it is typically also an argument for your custom
     * application constructor.
    */
    HelloApplication::HelloApplication(const Wt::WEnvironment& env)
      : WApplication(env)
    {
      setTitle("Hello world");                            // application title
    
      root()->addWidget(Wt::cpp14::make_unique<Wt::WText>("Your name, please ? ")); // show some text
    
      nameEdit_ = root()->addWidget(Wt::cpp14::make_unique<Wt::WLineEdit>()); // allow text input
      nameEdit_->setFocus();                              // give focus
    
      auto button = root()->addWidget(Wt::cpp14::make_unique<Wt::WPushButton>("Greet me."));
                                                          // create a button
      button->setMargin(5, Wt::Side::Left);                   // add 5 pixels margin
    
      root()->addWidget(Wt::cpp14::make_unique<Wt::WBreak>());    // insert a line break
      greeting_ = root()->addWidget(Wt::cpp14::make_unique<Wt::WText>()); // empty text
    
      /*
       * Connect signals with slots
       *
       * - simple Wt-way: specify object and method
       */
      button->clicked().connect(this, &HelloApplication::greet);
    
      /*
       * - using an arbitrary function object, e.g. useful to bind
       *   values with std::bind() to the resulting method call
       */
      nameEdit_->enterPressed().connect(std::bind(&HelloApplication::greet, this));
    
      /*
       * - using a lambda:
       */
      button->clicked().connect([=]() { 
          std::cerr << "Hello there, " << nameEdit_->text() << std::endl;
      });
    }
    
    void HelloApplication::greet()
    {
      /*
       * Update the text, using text input into the nameEdit_ field.
       */
      greeting_->setText("Hello there, " + nameEdit_->text());
    }
    
    int main(int argc, char **argv)
    {
      /*
       * Your main method may set up some shared resources, but should then
       * start the server application (FastCGI or httpd) that starts listening
       * for requests, and handles all of the application life cycles.
       *
       * The last argument to WRun specifies the function that will instantiate
       * new application objects. That function is executed when a new user surfs
       * to the Wt application, and after the library has negotiated browser
       * support. The function should return a newly instantiated application
       * object.
       */
      return Wt::WRun(argc, argv, [](const Wt::WEnvironment &env) {
        /*
         * You could read information from the environment to decide whether
         * the user has permission to start a new application
         */
        return Wt::cpp14::make_unique<HelloApplication>(env);
      });
    }