기술 [Pass Reference to Method]-파울로

[Paulo]

일일 결과물
3조	파울로	10-11-11
Pass reference to a method

Introduction

Reference is the intentional use of one thing, a point to indicate something else.

What is a Reference type?

Reference type is a data type that can only be accessed by references.

What is a Value type?

Value type is a correspondence between a set of data and a set of abstract or concrete entities sharing characteristic attributes.

Difference between Value and Reference types.

Value types are referred to structures or structs while Reference types are referred to classes, and the runtime deals with the two in different ways.

When a value type instance is created, a single space in memory is allocated to store the value. primitive types such as int, float, bool, and char are also value types, and work in the same way.

When the runtime deals with a value type, it’s dealing directly with it’s underlying data and this can be very efficient, particularly with primitive types.

Pass reference to methods

Pass-by-Value and Pass-by-Reference

Pass-by-value is also known as pass by copy. What happens here is that a copy of the argument is made and then passed to the receiving method.

 If the caller method modifies the value of the argument inside of its method body, the caller will never see the results of these modifications.

The copy ends up pointing to the same address, true, but the method receiving the argument cannot change our original reference to point at a different object.

Pass-by-reference supplies the caller with a reference to the same location that caller’s argument was pointing to, enabling the method’s body to access the shared reference and even change it to point elsewhere.

If the caller were to pass a reference to one of its data, it would notice updates made by the method body.

Pass by reference is not used as the default in C# and must be explicitly declared by the method and the caller in C# if you intend to use it.

Example: Pass Reference to Methods

class MyClass

    {

        int a, b;

        public MyClass(int i, int j)

        {

            a = i;

            b = j;

        } 

        // Return true if ob contains the same values as the invoking object.

        public bool SameAs(MyClass ob) // ob: Parameter

        {

            if ((ob.a == a) & (ob.b == b))

                return true;

            else return false;

        }

        public void Copy(MyClass ob) // ob: Parameter

        {

            a = ob.a;

            b = ob.b;

        }

        public void show()

        {

            Console.WriteLine("a:{0}, b:{1}", a, b);

        }

    }

    class MainClass

    {

        public static void Main(string[] args)

        {

            MyClass ob1 = new MyClass(4, 5);

            MyClass ob2 = new MyClass(6, 7);

            Console.Write("ob1:\n");

            ob1.show(); // ob1: Local variable

            Console.Write("ob2:\n");

            ob2.show(); // ob1: Local variable

            if (ob1.SameAs(ob2))

                Console.WriteLine("ob1 and ob2 have the same values.\n");

            else

                Console.WriteLine("ob1 and ob2 have different values.\n");

            // Now, make ob1 a copy of ob2

            ob1.Copy(ob2);

            Console.Write("ob1 after copy:\n");

            ob1.show();

            if(ob1.SameAs(ob2))

                Console.WriteLine("ob1 and ob2 have the same values.\n");

            else

                Console.WriteLine("ob1 and ob2 have different values.\n");

        }

    }