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Encapsulation in OOP?

Anonymous User255612-Jun-2013

I am studying about OOP concepts. As I understood from the documents I have read, I wrote an example program for encapsulation concept in OOP. I pasted my code below. Is my concept about encapsulation is correct ?.


Default.aspx

<asp:Button ID="showBtn" Text="Show Student details." runat="server"/>


Default.aspx.cs

public partial class _Default : System.Web.UI.Page
{
Student stu;
 
protected void Page_Load(object sender, EventArgs e)
{
    stu = new Student();
    stu.SetStudentID(001);
    stu.SetStudentFee(5000);
    stu.StudentName = "Rob";
    stu.StudentAge = 26;
 
    showBtn.Click += new EventHandler(showBtn_Click);
}
 
void showBtn_Click(object sender, EventArgs e)
{
    stu.ShowStudentDetails();
}
}



Class Student


class Student
{
private int stuId;
private int stuFee;
private string stuName;
private int stuAge;
 
public void SetStudentID(int id)
{
    stuId = id; //Mutator
}
 
public void SetStudentFee(int fee)
{
    stuFee = fee;  //Mutator
}
 
public int GetStudentID()
{
    return stuId;  //Accessor
}
 
public int GetStudentFee()
{
    return stuFee;  //Accessor
}
 
public string StudentName
{
    get { return stuName; }   //Accessor
    set { stuName = value; }  //Mutator
}
 
public int StudentAge
{
    get { return stuAge; }  //Accessor
    set { stuAge = value; } //Mutator
}
 
private void ShowDetails()
{
    HttpContext.Current.Response.Write(this.GetStudentID() + " : " + this.StudentName + " : " + this.StudentAge + " : " + this.GetStudentFee());
}
 
public void ShowStudentDetails()
{
    ShowDetails();
}
}


My main doubt is about the way I called the ShowDetails() method in the

Student. Is this a good way to hide the method ShowDetails() ?.

oopsoops 
Updated on 12-Jun-2013
Anonymous User

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1 Answers

Vijay Shukla

Vijay Shukla

12-Jun-2013

From an OO perspective, your ShowDetails method is doing two very different things.

  •   Creating a string that represents the object
  •    Outputting the string to the HttpResponse.

Now The first task does belong to the class Student, you need to know what an Student is to be able to create a string that is representative of the object. In fact in .net this is such a common thing, there is in fact a "overridable" or "virtual" function called Object.ToString().

The second task has absolutely nothing to do with the class Student, and A LOT to do with strings and HttpResponses (and in this case how we get the HttpResponse, which is to get it from the HttpContext, which means we MUST be on a webserver in a HttpRequest). With all these assumptions, it is extremely unsafe in an all purpose "data" or "domain" class.

This is how I would refactor this.

class Student
{
    private int stuId;
    private int stuFee;
    private string stuName;
    private int stuAge;
 
    public void SetStudentID(int id)
    {
        stuId = id; //Mutator
    }
 
    public void SetStudentFee(int fee)
    {
        stuFee = fee;  //Mutator
    }
 
    public int GetStudentID()
    {
        return stuId;  //Accessor
    }
 
    public int GetStudentFee()
    {
        return stuFee;  //Accessor
    }
 
    public string StudentName
    {
        get { return stuName; }   //Accessor
        set { stuName = value; }  //Mutator
    }
 
    public int StudentAge
    {
        get { return stuAge; }  //Accessor
        set { stuAge = value; } //Mutator
    }
 
    public override string ToString()
    {
        return this.GetStudentID() + " : " + 
            this.StudentName + " : " + 
            this.StudentAge + " : " + 
            this.GetStudentFee();
    }
 
 
}


and

public partial class _Default : System.Web.UI.Page
{
    Student stu;
 
    protected void Page_Load(object sender, EventArgs e)
    {
        stu = new Student();
        stu.SetStudentID(001);
        stu.SetStudentFee(5000);
        stu.StudentName = "Rob";
        stu.StudentAge = 26;
 
        showBtn.Click += new EventHandler(showBtn_Click);
    }
 
    void showBtn_Click(object sender, EventArgs e)
    {
        HttpContext.Current.Response.Write(stu.ToString());
    }
}

Since we KNOW for sure that there is a valid HttpContext.Current on the webpage. Thus Students don't need to know about the internet, and would equally be able to work on a WinForm application.

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