Puoi mescolare le classi derivate e di base in una lista generica in C # di tipo di classe di base?
-
11-12-2019 - |
Domanda
È possibile mescolare le classi derivate e di base in una lista generica in C # di tipo di classe di tipo?Non vedo perché no ... e non vedo una risposta chiara a questo ... ma giocando oggi con un elenco generico di classe base di tipo, che aveva anche nelle classi derivate, non ne ho visto nessunoi problemi.Ma mi chiedo se ci possano essere potenziali problemi, a parte le solite limitazioni upper / downcast che sono sempre inerenti a classi derivate / base.Il motivo per cui chiedo: non so se una lista generica per c # funziona lo stesso di quello che è stato definito un arrayList in C ++, cioè, sia che otterrete reclami durante la compilazione per miscelare "tipi" come questo (base vs classi derivate).Ho corso numerosi esempi oggi senza reclami, ma voglio verificare se c'è un potenziale per un problema.
Soluzione
Quindi sì, va bene.
Altri suggerimenti
using System;
using System.Collections.Generic;
namespace DoFactory.GangOfFour.Composite.Structural
{
/// <summary>
/// MainApp startup class for Structural
/// Composite Design Pattern.
/// </summary>
class MainApp
{
/// <summary>
/// Entry point into console application.
/// </summary>
static void Main()
{
// Create a tree structure
Composite root = new Composite("root");
root.Add(new Leaf("Leaf A")); //1st Add for root
root.Add(new Leaf("Leaf B")); //2nd Add for root
Console.WriteLine(" ....");
root.Display(1);
Console.WriteLine("...........");
Composite comp = new Composite("Composite X");
comp.Add(new Leaf("Leaf XA"));
root.Add(comp); //add comp to root //3rd Add for root
DerivedComposite myDerivedComposite = new DerivedComposite("derived member", 1000);
Console.WriteLine("Show the special int, string for DerivedComposite");
myDerivedComposite.mySpecialVariablesAre();
Console.WriteLine("........");
root.Add(myDerivedComposite); //4th Add for root
Composite SecondRoot = new Composite("SecondRoot");
SecondRoot.Add(new Leaf("Leaf fA"));
SecondRoot.Add(myDerivedComposite); //add to SecondRoot
root.Add(SecondRoot); //add comp to root ; //5th Add for root
//// Recursively display tree again, after adding
root.Display(1);
Console.WriteLine("Now get List read back");
Console.WriteLine("show List elements for root (should be five)");
root.DisplayList();
Console.WriteLine("Show List elements for comp (should be one)");
comp.DisplayList();
Console.WriteLine("Show List ele for SecondRoot (should be 2)");
SecondRoot.DisplayList();
// Wait for user
Console.ReadKey();
}
}
/// <summary>
/// The 'Component' abstract class
/// </summary>
abstract class Component
{
protected string name;
// Constructor
public Component(string name)
{
this.name = name;
}
public abstract void Add(Component c);
public abstract void Remove(Component c);
public abstract void Display(int depth);
public abstract void printSpecialInt();
}
/// <summary>
/// The 'Composite' class
/// </summary>
class Composite : Component
{
private List<Component> _children = new List<Component>();
//This Generic List was potentially troublesome but it executed fine
protected int specialbaseInt;
// Constructor
public Composite(string name)
: base(name)
{
specialbaseInt = -1;
}
public override void Add(Component component)
{
_children.Add(component);
}
public override void Remove(Component component)
{
_children.Remove(component);
}
public override void Display(int depth)
{
Console.WriteLine(new String('-', depth) + name);
// Recursively display child nodes
foreach (Component component in _children)
{
component.Display(depth + 2); //calls .Display again, is recursive
}
}
public void DisplayList()
{
int ijk = _children.Count;
Console.WriteLine("# elements in this List: {0}", ijk);
foreach (Component c in _children)
{
int ii = c.GetHashCode();
Type type = c.GetType();
Console.WriteLine("GetHashCode, Type on list: {0}, {1}", ii, type.FullName);
c.printSpecialInt();
}
}
public override void printSpecialInt()
{
Console.WriteLine("special int (at base class): {0}", specialbaseInt);
}
}
class DerivedComposite : Composite
{
public string myExtraString;
public int mySpecialInt;
public DerivedComposite(string name,int ianint)
: base(name)
{
myExtraString = name;
mySpecialInt = ianint + 10;
specialbaseInt = ianint;
}
public void mySpecialVariablesAre()
{
Console.WriteLine("The string, int, specialbaseInt are!- {0}, {1}, {2}", myExtraString, mySpecialInt, specialbaseInt);
}
public override void printSpecialInt()
{
Console.WriteLine("The string, int, specialbaseInt are (at derived): {0}, {1}, {2}", myExtraString, mySpecialInt, specialbaseInt);
}
}
/// <summary>
/// The 'Leaf' class
/// </summary>
class Leaf : Component
{
// Constructor
public Leaf(string name)
: base(name)
{
}
public override void Add(Component c)
{
Console.WriteLine("Cannot add to a leaf");
}
public override void Remove(Component c)
{
Console.WriteLine("Cannot remove from a leaf");
}
public override void Display(int depth)
{
Console.WriteLine(new String('-', depth) + name);
}
public override void printSpecialInt()
{
Console.WriteLine("at Leaf printSpecialInt");
}
}
/// <summary>
/// The 'Leafail' class //try and make it fail
/// </summary>
class Leafail : Component
{
// Constructor
public Leafail(string name)
: base(name)
{
myExtraString = "Hi, I am Leafail";
mySpecialInt = 123;
}
public string myExtraString;
public int mySpecialInt;
public override void Add(Component c)
{
Console.WriteLine("Cannot add to a leafail");
}
public override void Remove(Component c)
{
Console.WriteLine("Cannot remove from a leafail");
}
public override void Display(int depth)
{
Console.WriteLine(new String('-', depth) + name);
}
public void mySpecialVariablesAre()
{
Console.WriteLine("The string, int are: {0}, {1}", myExtraString,mySpecialInt);
}
public override void printSpecialInt()
{
Console.WriteLine("at Leafail printSpecialInt");
}
}
}
.