ShapeFacory.dart

class ShapeFactory{
  IShape getShape(String shapeType){
    // check for nulls being passed
    if(shapeType == null){
      return null;
    }
    
    // check for types
    var type = shapeType.toLowerCase();
    switch(type){
      case "rectangle":
        return new Rectangle();
        break;
      case "circle":
        return new Circle();
        break;
      case "square":
        return new Square();
        break;
    }
    // we always return null if there are no matches
    return null;
  }
}