Structs

Will · October 24th, 2009, 07:41 AM

I am reading through chapter 5 and I am just not undertsanding structs at all.

A struct in this book is described as:
"data structures composed of several peices of data, possibly of different types. that allow you to define your own types of variables based on this structure"

so then in the following exercise we call upon the same variable

myRoute:

Code:

struct route
    {
        public orientation direction;
        public double distance;
    }

    class Program
    {
        static void Main(string[] args)
        {
            route myRoute;

and then later we use it with two different types:

Code:

myRoute.direction = (orientation)myDirection;
            myRoute.distance = myDistance;

So it seems that a struct just allows you to use the same variable but hold different values in it throughout your code?

Is that a crude way of putting it? I feel like I am missing the point can anyone explain it in another way to me?

Cheers,

amma1505 · January 6th, 2010, 06:53 AM

A Struct type is a value type that is typically used to encapsulate small groups of related variables.

within a struct declaration,fields cannot be initialized unless they are declared as const or static.

A struct may not declare a default constructor or a destructor

struct can be instantiated without using a new operator

Will · January 10th, 2010, 12:00 PM

Thanks for the reply, I have a better understanding of them now.

jawadh_khan786 · January 12th, 2010, 01:33 AM

A struct is a simple user-defined type, a lightweight alternative to a class. They support access modifiers, constructors, indexers, methods, fields, nested types, operators, and properties. They may declare a default constructor (a constructor with no parameters), however you can also declare a custom constructor. Unlike classes, structures do not support compile-time initialization of instance fields, they cannot derive from anything other than System.ValueType and they cannot be the base of another class. However, they may implement an Interface. They can be instantiated without using a new operator.

Structures take up fewer resources in memory than classes, so when you have a small, frequently used class, give some thought to using a struct instead. Note though that performance can suffer when using structures in situations where reference types are expected due to boxing and unboxing.

struct members may not be declared protected.

Declaration

A struct is declared as follows:

Code:

[attributes] [modifiers] struct identifier [:interfaces]
{
  body [;]
}

The attributes is optional and is used to hold additional declarative information.

The modifier is optional. The allowed modifiers are new, static, virtual, abstract, override, and a valid combination of the four access modifiers (public, protected, internal and private).

The keyword struct must be followed by an identifier that names the struct.

The interfaces list is optional. The list contains the interfaces implemented by the struct, all separated by commas.

The body contains the member declarations.

Example 1 - A coordinate

Code:

public struct Coords
{
  public int X, Y;
 
  public Coords(int p1, int p2)
  {
    X = p1;
    Y = p2;
  }
 
  // Override the ToString method so the value appears in text
  public override string ToString()
  {
    return String.Format("({0},{1})", X, Y);
  }
}

Which can be created in the following manner:

Code:

class Program
{
  static void Main(string[] args)
  {
    Coords coord = new Coords(3,4);
    Console.WriteLine(coord.ToString());
    Console.ReadKey();
  }
}

Please do rate my answer

Will · January 12th, 2010, 03:12 PM

Thanks for taking the time to write that out it has definitely helped me.

Cheers