CODEWITHSUNDEEP
c#
Chris Merck
Chris Merck

Reputation: 454

How to Avoid Assignment of Private Members in Constructor

I often find myself doing this:

class MyClass
{
    public MyClass(int x)
    {
        this.x = x;
    }        
    private int x;

    ...
}

Every time I add a new private member variable for configuration, I need to add it to the constructor's parameter list, to the constructor body, and to the class as a member. Is there a good programming pattern for avoiding the extra typing?

Upvotes: 1

Views: 127

Answers (2)

Chris Merck
Chris Merck

Reputation: 454

I find that I can abuse inheritance to accomplish my goal. I set up a "Loader" subclass that has the sole purpose in life of plugging in the dependencies of the base class. Then we can work with the base class and forget about the loader.

Then again, this has the horrible side-effect of preventing use of these protected member variables in the base constructor -- we need to use a .Start() function or something like that instead. So, this is a pretty bad solution, although saving some keystrokes.

public class MyClass
{
    protected int param1;
    protected int param2;

    public void DoStuff()
    {
        Console.WriteLine(param1 + param2);
    }
}


public class MyClassLoader : MyClass
{
    public MyClassLoader()
    {
        param1 = 1;
        param2 = 2;
    }
}

class Program
{
    static void Main(string[] args)
    {

        MyClass myObj = new MyClassLoader();
        myObj.DoStuff();

        Console.WriteLine("Press any key to quit.");
        Console.ReadKey();
    }
}

Upvotes: 0

Sam I am says Reinstate Monica
Sam I am says Reinstate Monica

Reputation: 31194

Generally speaking, If you instantiate a class with a bunch of private members that you have to pass into the constructor, you're doing something problematic already. 

MyClass myClass = new MyClass(x, y, z, 7, 'c', someOtherClass)

If appropriate, you can encapsulate related fields into a struct or a different class like so

class MyClass
{
    public MyClass(Coordinates coords)
    {
        this.coords = coords;
    }
    private Coordinates coords;

}

public struct Coordinates
{
     public int X{get; set;}
     public int Y{get; set;}
     public int z{get; set;}
}

and then you can instanciate it with

MyClass myClass = new MyClass(new Coordinates() { X = 1, Y = 2, Z = 3 });

Without a particular implementation, It's kinda hard to determine the optimal solution, but if you don't actually have to set the fields from outside your class, you can do something like

class MyClass
{
    public MyClass()
    {

    }        
    private int x = 2;

    ...
}

or

class MyClass
{
    public MyClass()
    {
        this.x = 2;
    }        
    private int x;

    ...
}

Upvotes: 2

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