Csharp/CSharp Tutorial/struct/struct
Содержание
A simple struct with method
<source lang="csharp">using System; struct Fraction {
public int numerator;
public int denominator;
public void Print( ) {
Console.WriteLine( "{0}/{1}", numerator, denominator );
}
} public class MainClass {
public static void Main( ) {
Fraction f;
f.numerator = 5;
f.denominator = 10;
f.Print( );
Fraction f2 = f;
f.Print( );
f2.numerator = 1;
f.Print( );
f2.Print( );
}
}</source>
5/10 5/10 5/10 1/10
class vs struct
<source lang="csharp">using System; using System.Collections.Generic; using System.Text;
class MyClass {
public int val;
} struct myStruct {
public int val;
} class Program {
static void Main(string[] args) {
MyClass objectA = new MyClass();
MyClass objectB = objectA;
objectA.val = 10;
objectB.val = 20;
myStruct structA = new myStruct();
myStruct structB = structA;
structA.val = 30;
structB.val = 40;
Console.WriteLine("objectA.val = {0}", objectA.val);
Console.WriteLine("objectB.val = {0}", objectB.val);
Console.WriteLine("structA.val = {0}", structA.val);
Console.WriteLine("structB.val = {0}", structB.val);
}
}</source>
Declare a simple struct
<source lang="csharp">struct Fraction {
public int numerator; public int denominator;
} public class MainClass {
public static void Main( ) {
Fraction f;
f.numerator = 5;
f.denominator = 10;
}
}</source>
Difference between class and struct during the reference passing
<source lang="csharp">using System; using System.Collections.Generic; using System.Linq; using System.Text;
class MyClass
{
public int val;
}
struct myStruct
{
public int val;
}
class Program
{
static void Main(string[] args)
{
MyClass objectA = new MyClass();
MyClass objectB = objectA;
objectA.val = 10;
objectB.val = 20;
myStruct structA = new myStruct();
myStruct structB = structA;
structA.val = 30;
structB.val = 40;
Console.WriteLine("objectA.val = {0}", objectA.val);
Console.WriteLine("objectB.val = {0}", objectB.val);
Console.WriteLine("structA.val = {0}", structA.val);
Console.WriteLine("structB.val = {0}", structB.val);
}
}</source>
Reference value type in a struct
<source lang="csharp">using System; struct Point {
public int X; public int Y;
} class MainClass {
static void Main()
{
Point p1, p2, p3;
p1.X = 10; p1.Y = 10;
p2.X = 20; p2.Y = 20;
p3.X = p1.X + p2.X;
p3.Y = p1.Y + p2.Y;
Console.WriteLine("p1: {0}, {1}", p1.X, p1.Y);
Console.WriteLine("p2: {0}, {1}", p2.X, p2.Y);
Console.WriteLine("p3: {0}, {1}", p3.X, p3.Y);
}
}</source>
p1: 10, 10 p2: 20, 20 p3: 30, 30
Structures
A struct is similar to a class, but is a value type, not a reference type.
Here is the general form of a struct:
<source lang="csharp">struct name : interfaces {
// member declarations }</source>
- Structures cannot inherit other structures or classes
- Structures cannot be used as a base for other structures or classes.
- A structure can implement one or more interfaces.
- Structure members can be methods, fields, indexers, properties, operator methods, and events.
- Structures can also define constructors, but not destructors.
- You cannot define a default (parameterless) constructor for a structure.
- A default constructor is automatically defined for all structures, and this default constructor can"t be changed.
- Structure members cannot be specified as abstract, virtual, or protected.
- When new is used, the specified constructor is called.
- When new is not used, the object is still created, but it is not initialized.
- When you assign one structure to another, a copy of the structure object is made.
struct with value types
<source lang="csharp">using System; struct PointerStruct {
public int x, y;
} class MainClass {
public static void Main(string[] args)
{
PointerStruct f1 = new PointerStruct();
f1.x = 100;
f1.y = 100;
PointerStruct f2 = f1;
Console.WriteLine("F1.x = {0}", f1.x);
Console.WriteLine("F1.y = {0}", f1.y);
Console.WriteLine("F2.x = {0}", f2.x);
Console.WriteLine("F2.y = {0}", f2.y);
Console.WriteLine("-> Changing f2.x");
f2.x = 900;
Console.WriteLine("F2.x = {0}", f2.x);
Console.WriteLine("F1.x = {0}\n", f1.x);
}
}</source>
F1.x = 100 F1.y = 100 F2.x = 100 F2.y = 100 -> Changing f2.x F2.x = 900 F1.x = 100
struct with value types and ref types
<source lang="csharp">using System; class MyClass {
public string x;
public MyClass(string s) {
x = s;
}
} struct MyStruct {
public MyClass refType; // Ref type.
public int valueType; // Val type
public MyStruct(string s)
{
refType = new MyClass(s);
valueType = 9;
}
} class MainClass {
public static void Main(string[] args)
{
MyStruct valWithRef = new MyStruct("Initial value");
valWithRef.valueType = 6;
MyStruct valWithRef2;
valWithRef2 = valWithRef;
valWithRef2.refType.x = "I am NEW!";
valWithRef2.valueType = 7;
Console.WriteLine("Values after change:");
Console.WriteLine("valWithRef.refType.x is {0}", valWithRef.refType.x);
Console.WriteLine("valWithRef2.refType.x is {0}", valWithRef2.refType.x);
Console.WriteLine("valWithRef.valueType is {0}", valWithRef.valueType);
Console.WriteLine("valWithRef2.valueType is {0}", valWithRef2.valueType);
}
}</source>
Values after change: valWithRef.refType.x is I am NEW! valWithRef2.refType.x is I am NEW! valWithRef.valueType is 6 valWithRef2.valueType is 7
