two parameter in a constructor

**freddyvorhees** · 07-25-2008

what is the syntax for set and get when you want to initialize 2 private string in a constructor?

**manzoor** · 07-25-2008

What do you mean ?

Do you mean how to write a constructor which receives two arguments ?

**freddyvorhees** · 07-25-2008

yeah!!!at last!!!

**anon** · 07-25-2008

How do you write a constructor that receives one argument? Now, add one more argument to it. (They are separated by comma.)

**freddyvorhees** · 07-25-2008

Nice, thanks for that.Another one what is the syntax for two set and get functions?

**cpjust** · 07-25-2008

Originally Posted by freddyvorhees

Nice, thanks for that.Another one what is the syntax for two set and get functions?

The same as any other function. Although Set functions usually take a parameter and return nothing, while a Get function returns something and takes no parameters.

**freddyvorhees** · 07-25-2008

Ok heres my program, whats wrong with it?Its an exercies from C++ How to program 5e.I've just patterned it from the examples and I havent fully grasped the concept yet.So i dont fully understand what I did.

Code:

#include <iostream>
using std::cout;
using std::endl;
#include <string> 
using std::string;

class GradeBook
{
public:
   
    GradeBook( string course, string instructor )                                               
    {                                                                      
       setCourseName( course ); 
	   setInstructorsName( instructor );
    }                                         
    
    void setCourseName( string course )
    {
       courseName = course; 
    } 
     
    string getCourseName()
    {
       return courseName;
	}

    void displaycourse()
    {
		cout <<getCourseName();
         
	}
		void setInstructorsName ( string instructor )
	{
		instructorsName = instructor;
	}

	string getInstructorsName()
	{
		return instructorsName;
	}
    

	void displayinstructor()
	{
		cout <<getInstructorsName();
	}
 private:
    string courseName; 
	string instructorsName;
}; 

 int main()
{
  
    GradeBook namecourse( "# ICST101 Computer Programming I " );
    GradeBook nameinstructors( "Dr. Allan Sioson " );
    
    cout <<"Welcome to the grade book for: " << namecourse.getCourseName();
	cout <<"This course is presented by: "<<nameinstructors.getInstructorsName();
	
	return 0;
 }

**dudeomanodude** · 07-25-2008

For starters, your constructor is defined to take two arguments, yet you only give it one in main().

Second, why bother calling the set functions in your constructor? You should really use an "initialization list". It would look like so:

Code:

class gradebook{
public:

  Gradebook( string one, string two ) : frist( one ), second( two ) {}

  // etc...

  private:

    string first;
    string second;
};

**dudeomanodude** · 07-25-2008

A few more things:

1. It's a little redundant to have a getInstructorName() function and also the display() which simply pipes the getInstructorName() fucntion to cout.

It's only a style thing, but I'd rather do like this:

Code:

class Gradebook{

  public:

     // etc....

    string getInstructorsName(){ return instructorsName; }

   // etc...
};


// And display it in main() like this:

int main(){

  cout << object.getInstructorsName() << "\n";

  // etc...
}

**dudeomanodude** · 07-25-2008

Since I'm really bored at my desk right now, I decided to clean things up for you a bit. Look itover and learn from it...

Code:

#include <iostream>
#include <string>
using std::cout;
using std::endl;
using std::string;


// Much smaller class now
//
class GradeBook
{
  public:
   
    GradeBook( string course, string instructor )                                               
    : courseName( course ), instructorsName( instructor ) {}                                        
     
    string getCourseName()
    {
        return courseName;
    }

    string getInstructorsName()
    {
        return instructorsName;
    }

  private:
    string courseName; 
    string instructorsName;
}; 


// Write display function outside of class:
//
void displayMessage( GradeBook& mBook ) // Note that argument is passed by reference
{
    cout << "Welcome to the grade book for: " << mBook.getCourseName() 
           << "\nThis course is presented by: " << mBook.getInstructorsName();
}


 int main()
{
    // Constructor takes two arguments:
    //
    GradeBook sampleCourse( "# ICST101 - Computer Programming I", "Dr. Allan Sioson" );
    
    displayMessage( sampleCourse ); // sampleCourse is passed by reference

	return 0;
}

Note that by giving the "get" functions in your class allows users to write functions like displayMessage(). Now, that could've just as well been written into the class, I only wanted to illustrate how that works and also wanted you to see passing an object by reference. The point of pass-by-reference is to stop copying of an object as it's passed by simply giving it's memory address ( which is what the "&" does - it requests the refence to that object, in this case "sampleCourse" ).

**freddyvorhees** · 07-25-2008

Thats very nice,it helped me a lot. But it has an intsructions

3.11 (Modifying Class GradeBook) Modify class GradeBook (Figs. 3.113.12) as follows:

1.Include a second string data member that represents the course instructor's name.

2.Provide a set function to change the instructor's name and a get function to retrieve it.

3.Modify the constructor to specify two parametersone for the course name and one for the instructor's name.

4.Modify member function displayMessage such that it first outputs the welcome message and course name, then outputs "This course is presented by: " followed by the instructor's name.

Code:

 1  // Fig. 3.11: GradeBook.h
 2  // GradeBook class definition. This file presents GradeBook's public
 3  // interface without revealing the implementations of GradeBook's member
 4  // functions, which are defined in GradeBook.cpp.
 5  #include <string> // class GradeBook uses C++ standard string class
 6  using std::string;
 7
 8  // GradeBook class definition
 9  class GradeBook
10  {
11  public:
12     GradeBook( string ); // constructor that initializes courseName    
13     void setCourseName( string ); // function that sets the course name
14     string getCourseName(); // function that gets the course name      
15     void displayMessage(); // function that displays a welcome message 
16  private:
17     string courseName; // course name for this GradeBook
18  }; // end class GradeBook

Code:

 1  // Fig. 3.12: GradeBook.cpp
 2  // GradeBook member-function definitions. This file contains
 3  // implementations of the member functions prototyped in GradeBook.h.
 4  #include <iostream>
 5  using std::cout;
 6  using std::endl;
 7
 8  #include "GradeBook.h" // include definition of class GradeBook
 9
10  // constructor initializes courseName with string supplied as argument
11  GradeBook::GradeBook( string name )
12  {
13     setCourseName( name ); // call set function to initialize courseName
14  } // end GradeBook constructor
15
16  // function to set the course name
17  void GradeBook::setCourseName( string name )
18  {
19     courseName = name; // store the course name in the object
20  } // end function setCourseName
21
22  // function to get the course name
23  string GradeBook::getCourseName()
24  {
25     return courseName; // return object's courseName
26  } // end function getCourseName
27
28  // display a welcome message to the GradeBook user
29  void GradeBook::displayMessage()
30  {
31     // call getCourseName to get the courseName
32     cout << "Welcome to the grade book for\n" << getCourseName()
33        << "!" << endl;
34  } // end function displayMessage

And can you include comments like the other one.

**abachler** · 07-25-2008

Do your own homework.

Don't do his homework for him.

**freddyvorhees** · 07-25-2008

Yes...i know.Im not asking for the answer just the correct syntax.I just showed the instructions because i cant explain it my self. Because like I said I havent fully grasped the concept yet. but I would appreciate it if you can explain it to me, maybe use a analogy - thats what my instructor would do but im in awol. So I guess you could be a substitute? please

**dudeomanodude** · 07-25-2008

1.Include a second string data member that represents the course instructor's name.

-It's already there.

2.Provide a set function to change the instructor's name and a get function to retrieve it.

-You had that originally.

3.Modify the constructor to specify two parametersone for the course name and one for the instructor's name.

-It's already there. And I would advise against how you had it originally calling the set functions in the constructor.

4.Modify member function displayMessage such that it first outputs the welcome message and course name, then outputs "This course is presented by: " followed by the instructor's name.

-You should be able to negotiate that with what's there already.

**freddyvorhees** · 07-25-2008

So did my original code followed those instructions?

Thread: two parameter in a constructor

Thread Tools

Search Thread

Display

two parameter in a constructor

Similar Threads

Screwy Linker Error - VC2005

Logical parameter in parent constructor

Dikumud

Please Help - Problem with Compilers

Constructor with Parameter not Firing