Course list http://www.c-jump.com/bcc/

Home work project 1: GUI class emulator app

  1. Description
  2. Instructions
  3. How to submit

Description

Instructions

  1. Use c255labs/example/Hwk_01_pointers project as your starting point for this homework.

  2. Apply the following changes to the Window class in window.h: 

    
    // window.h
    // ...
    class Window {
        char* title;
        Input* inp_box;
        Output* out_box;
        Button* btn_set_text;
    public:
        // constructor
        Window( char* title_ );
        // operations
        void click_btn_set_text();
        void show();
        void run();
    };//class Window

  3. With this change, the Window class no longer contains Input, Output, and Button objects. Instead, the objects must be created dynamically. Modify Window constructor as follows: 

    
// window.cpp
// ...
Window::Window( char* title_ )
{
    title = title_;
    inp_box = new Input;        // create Input object dynamically
    out_box = new Output;       // create Output object dynamically
    btn_set_text = new Button;  // create Button object dynamically

    inp_box->value( "12345" );  // use pointer-to-object dereference operators
    out_box->value( "67890" );
}

  4. Carefully examine the rest of the window.cpp file. Replace all member access
    operators ("." dot operators) with the pointer-to-object dereference operator ->. For example, 

    
    Old code            New code
    -----------------   -----------------
    inp_box.value()     inp_box->value()

  5. Compile and run the program.

  6. What happens to dynamically allocated objects at the end of the program? You can use unique_ptr "smart pointer" to automatically delete dynamically allocated objects. Apply the following changes to the Window class in window.h: 

    
    // window.h
    // ...
    #include <iostream>
    #include <memory> // for unique_ptr
    // ...
    class Window {
        char* title;
        std::unique_ptr< Input > inp_box;
        std::unique_ptr< Output > out_box;
        std::unique_ptr< Button > btn_set_text;
    public:
        // constructor
        Window( char* title_ );
        // operations
        void click_btn_set_text();
        void show();
        void run();
    };//class Window

  7. Modify Window constructor as follows: 

    
// window.cpp
// ...
Window::Window( char* title_ )
    :
inp_box( new Input ),
out_box( new Output ),
btn_set_text( new Button )
{
    title = title_;

    // inp_box = new Input;        // create Input object dynamically
    // out_box = new Output;       // create Output object dynamically
    // btn_set_text = new Button;  // create Button object dynamically

    inp_box->value( "12345" );
    out_box->value( "67890" );
}

  8. Compile and run the program.

     

How to submit