Question

I have been reading about Factory pattern a lot lately. I am trying to figure out the best way to implement it. In the book C # Agile Principles patterns and practice the recommendation is to create the Factory like this:

public class ShapeFactoryImplementation : ShapeFactory {
    public Shape Make(string name) {
        if (name.Equals("Circle"))
            return new Circle();
        else if (name.Equals("Square"))
            return new Square();
        else
            throw new Exception("ShapeFactory cannot create: {0}", name);
        }
    }

Rather than…

public class ShapeFactoryImplementation : ShapeFactory {
    public Shape MakeCircle() {
        return new Circle();
    }

    public Shape MakeSquare() {
        return new Square();
    }
}

Please tell me what are your thoughts? Or maybe there is a better way to implement the factory pattern?

Answer 1

The main point of the factory pattern is to de-couple the client from the creation of objects.

In your second example, the client has hard-coded the shape to create, such as MakeCircle, and therefore tightly couples the object creation and the client.