public void ContravarianceTest()
{
IContravariance <BaseClass> b = new Contravariance();
// IContravariance<BaseClass> => IContravariance<DerivedClass>로 implicit conversion.
// 반대로는 불가능.
IContravariance <DerivedClass> d = b;
}
static void Main(string[] args)
{
Vehicle v1 = new Car();
//Vehicle v2 = new Car();
//Vehicle v3 = new Aircraft();
Func <Vehicle> func = GetVehicle; //#1
Vehicle v4 = func(); // For Func, input param is covariant and output param is conbtra.
v4.getVehicle(); //Only the Vehicle class properties and methods will be accessiable. Not of Car class.It will peel of anything related to Cars while assigning the object to Vehicle.
Action <Car> action = ParkVehicle;
action(new Car()); //#2 This is called contravariance, because we assigning more derived class to less derived class.
//Action type parameters are IN, means all are contravariant.
ICovariant <Vehicle> covariant = (ICovariant <Car>)null; //#1 Covariant - Assigning more derived class to less derived class.
IContravariance <Car> contravariance = (IContravariance <Vehicle>)null;
}
public void Method()
{
ICovariance <DerivedClass> deriveList1 = null;
ICovariance <BaseClass> baseList1 = deriveList1;
IContravariance <BaseClass> baseList2 = null;
IContravariance <DerivedClass> deriveList2 = baseList2;
Func <object, FileStream> f2 = null;
Func <string, Stream> f1 = null;
f1 += Ment1;
f1 += Ment2;
f1 = f2;
}
static void Main(string[] args)
{
// Covariance:
// ----------
// Derived type assigned to type
ICovariance <TitledMessage> a = new Covariance();
ICovariance <Message> b = a;
Message v = b.Create("Hello world");
Console.WriteLine(v.Content);
// Contravariance:
// -----------
// Less derived type assigned to derived type
IContravariance <Message> d = new Contravariance();
IContravariance <TitledMessage> f = d;
f.Do(new TitledMessage {
Content = "Hello world"
});
}
public static void Main(string[] args)
{
List <int> list = new List <int>();
list.AddRange(new int[] { 1, 2, 3, 4, 5 });
foreach (var item in list)
{
Console.WriteLine(item);
}
MyGeneric <string> myGeneric = new MyGeneric <string>();
myGeneric.SomeProperty = "Hello";
Console.WriteLine(myGeneric.SomeMethod <int>(5));
#region Covariance&Contravariance
ICovariance <Child> covariance = new Covariance();
Child child = covariance.DoSmth();
child.DoSmth();
ICovariance <Parent> covariance2 = covariance;
Parent parent = covariance2.DoSmth();
parent.DoSmth();
child = new Child();
parent = new Parent();
IContravariance <Parent> contravariance = new Contravariance <Parent>();
contravariance.DoSmth(parent);
IContravariance <Child> contravariance2 = contravariance;
contravariance2.DoSmth(child);
#endregion
#region Arrays&Tuples
(int, int)tuple = (1, 4);
Console.WriteLine($"{tuple.Item1} {tuple.Item2}");
var(name, age) = ("Tom", 23);
int[][] jagged = new int[2][];
jagged[0] = new int[3] {
1, 2, 3
};
jagged[1] = new int[2] {
4, 5
};
foreach (var line in jagged)
{
foreach (var item in line)
{
Console.Write($"{item} ");
}
Console.WriteLine();
}
#endregion
#region Enumerable
foreach (var item in new MyEnumerable(7))
{
Console.Write($"{item} ");
}
Console.WriteLine();
foreach (var item in new MyEnumerableYield(7))
{
Console.Write($"{item} ");
}
Console.WriteLine();
foreach (var item in new MyEnumerableYield(15))
{
Console.Write($"{item} ");
}
Console.WriteLine();
#endregion
}