Question

// stupid title, but I could not think anything smarter

I have a code (see below, sorry for long code but it’s very-very simple):

namespace Option1
{
    class AuxClass1
    {
        string _field1;
        public string Field1
        {
            get
            {
                return _field1;
            }
            set
            {
                _field1 = value;
            }
        }

        // another fields. maybe many fields maybe several properties

        public void Method1()
        {
            // some action
        }

        public void Method2()
        {
            // some action 2
        }
    }

    class MainClass
    {
        AuxClass1 _auxClass;
        public AuxClass1 AuxClass
        {
            get
            {
                return _auxClass;
            }
            set
            {
                _auxClass = value;
            }
        }

        public MainClass()
        {
            _auxClass = new AuxClass1();
        }
    }
}

namespace Option2
{
    class AuxClass1
    {
        string _field1;
        public string Field1
        {
            get
            {
                return _field1;
            }
            set
            {
                _field1 = value;
            }
        }

        // another fields. maybe many fields maybe several properties

        public void Method1()
        {
            // some action
        }

        public void Method2()
        {
            // some action 2
        }
    }

    class MainClass
    {
        AuxClass1 _auxClass;

        public string Field1
        {
            get
            {
                return _auxClass.Field1;
            }
            set
            {
                _auxClass.Field1 = value;
            }
        }

        public void Method1()
        {
            _auxClass.Method1();
        }

        public void Method2()
        {
            _auxClass.Method2();
        }

        public MainClass()
        {
            _auxClass = new AuxClass1();
        }
    }
}

class Program
{
    static void Main(string[] args)
    {
        // Option1
        Option1.MainClass mainClass1 = new Option1.MainClass();
        mainClass1.AuxClass.Field1 = "string1";
        mainClass1.AuxClass.Method1();
        mainClass1.AuxClass.Method2();

        // Option2
        Option2.MainClass mainClass2 = new Option2.MainClass();
        mainClass2.Field1 = "string2";
        mainClass2.Method1();
        mainClass2.Method2();

        Console.ReadKey();
    }
}

What option (option1 or option2) do you prefer ? In which cases should I use option1 or option2 ? Is there any special name for option1 or option2 (composition, aggregation) ?

Answer 1

According to Law of Demeter, Option2. That way you can freely change the implementation of MainClass, You don’t have to worry about calling code relying on details of AuxClass1, and indeed can remove it entirely if needed.