Is it wrong to give permission other classes to change fields ?

Question

Hello everybody

I know that each class should to do its own job. So i always try process my fields by only in class's methods.If another class processing on my public fields i feel that there is something wrong but is it always right thing to make define private fields ? Would be bad design or code If i let other classes to change my public fields ?

By the way is there name about this design or term word ?

Answer 1

Yes, it's considered bad design leaving fields public. Keep your fields private, and make use of public properties instead.

class Graph
{
    /// <summary>
    /// A field of the Graph by list of points
    /// </summary>
    private List<Point> lineGraph = new List<Point>();

    /// <summary>
    /// A Property to get and set the Graph
    /// </summary>
    public List<Point> LineGraph
    {
        get { return this.lineGraph; }
        set { this.lineGraph = value; }
    }
}

Answer 2

This is called friend classes.

It is not always a bad design principle, but you really have to ask yourself why you would like to expose a field directly and not through a method. If you have a good reason, then you can expose the field directly. However, in most cases such reason does not exist