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Thats IMHO a question pointing to design pattern rules. And here we have clearly said that using compositions is prefered before inheritance. This would lead to the following decision: If you can choose to use an abstract class or an interface to implement a specific requirement then choose the interface implementation.Quote:
Originally Posted by bhushan1980
You are right, I've forgotten it. Maybe because I strongly reject to use inheritance as main design approach. I prefer interfaces and composition, so I very rarely come accross the lack of the limitation of inheritance to just one predecestor
Hi. One more addition here. I searched on google and I came to know that we can have an implementation of a function inside an abstract class as well! So first of all let me know if this is true? And if it is, then please tell me how can we call or interact with that function?
Thankyou,
Bhushan.
Sure. An Abstract Class must have at least one Abstract Method, it can have zero or more "Concrete" methods (ie It does not have to be "Pure"). This is the advantage of an Abstract class over an interface.Quote:
Originally Posted by bhushan1980
IF an abstracxt class had to be pure, then it would only have the capabilities of an interface, but with additional restrictions....now very useful... :rolleyes:
Suppose I am implementing an interface in the .NET framework directly and not inheriting from the implementing class in the .NET framework, then as per the rule, do I have to provide an implementation for all the methods? Say for instance:
An interace like ITextEditor has a lot of methods and properties. So am I supposed to implement all of them?Code:// If I am implementing an interface for text-box as
public class MyTextBox : ITextEditor
{
.....
}
Thankyou,
Bhushan.
edit: Me Bad..See Reply #23.... :blush: :blush:
EVERY concrete class MUST provide an implementation of EVERY method and property, either explicitly or in one of it's base CLASSes.
Simple try it. You will see that you can use it the same way as you are using methods of an inherited class. Here is an exampleQuote:
Originally Posted by bhushan1980
And you can call this in any method like thisCode:using System;
using System.Collections.Generic;
using System.Text;
namespace DesignPatternsChapOne {
// Strategiepattern
public interface IWeaponBehaviour {
void UsedWeapon();
}
public abstract class Hero {
public IWeaponBehaviour _weapon;
public void Fight() {
_weapon.UsedWeapon();
}
public void SetWeapon(IWeaponBehaviour wp) {
_weapon = wp;
}
}
// and here the implementations
public class Messer :IWeaponBehaviour {
#region IWeaponBehaviour Member
public void UsedWeapon() {
Console.WriteLine("This is a knife for cutting and stick someone.");
}
#endregion
}
public class BowAndArrow : IWeaponBehaviour {
#region IWeaponBehaviour Member
public void UsedWeapon() {
Console.WriteLine("The arrow goes directly to the heart. ( If you dont miss the target )");
}
#endregion
}
public class Axe : IWeaponBehaviour {
#region IWeaponBehaviour Member
public void UsedWeapon() {
Console.WriteLine("This is a very heavy thing to hit. Orks are using that.");
}
#endregion
}
public class Sword : IWeaponBehaviour {
#region IWeaponBehaviour Member
public void UsedWeapon() {
Console.WriteLine("To use a sword is a special art.");
}
#endregion
}
public class Szepter : IWeaponBehaviour {
#region IWaffenverhalten Member
public void UsedWeapon() {
Console.WriteLine("If it is heavy enough you may kill the person by a hit of its weight.");
}
#endregion
}
// und die Figuren
public class King : Hero {
public King() {
_weapon = new Szepter();
}
}
public class Queen : Hero {
public Queen() {
_weapon = new BowAndArrow();
}
}
public class Troll : Hero {
public Troll() {
_weapon = new Axe();
}
}
public class Knight : Hero {
public Knight() {
_weapon = new Sword();
}
}
}
You will see the king changes his weapon. This is a very useful pattern. Your interface may contain 20 methods. You implement them in a seperated class.like we have a knife class, a sword class... you may have lots of such classes each contains the same methods and properties but each for a different purpose.Code:King myKing = new King();
myKing.Fight();
myKing.SetWeapon(new Messer());
myKing.Fight();
You have a method in your abstract class calling the methods of your interface. So here an abstract class work together with an interface :D
Very funny, very clever :lol: :lol: ;)
Maybe in C++, but in C#, it definitely has not.Quote:
Originally Posted by TheCPUWizard
You are right boudino, look at my workable example in post #22 it has no abstract method in the abstract class.Quote:
Originally Posted by boudino
Quote:
Originally Posted by boudino
Please Reread Post #21.... :D
(Thanks) :wave: :wave:
bhushan1980 == (George2 with humanity upgrade 1.0 installed)? :eek: :ehh: :D
Re the abstraction argument; indeed.. abstract merely requires that a subclass either provide an implementation of that wich is abstract, or defer implementation to antoher subclass
i.e. marking a class as abstract prevents it from being instantiated directly. A subclass must be created
Marking a method as abstract naturally causes the class to become abstract, because the method is not implemented, the class does not represent a complete workable block of code and hence cannot be created.
It thus follows that a class can be abstract (forcing the developer to subclass it in order to instance it) even if none of its members are abstract.
I do think the compiler error "Class XYZ must be marked abstract: it does not implement ABC" is quite succinct at explaining all this, but maybe thats just me
Interesting comment, given that every class you use while youre coding, is way down an inheritance hierarchy already.. ;)Quote:
Originally Posted by boudino
abstract classes can have some ability to function (because they can contain implementatin code), interfaces have no functional code at all. they mostly define what comes in and what goes out so the compiler can do some compile time type checking ;) and other developers know what kind of data to pass aroundQuote:
Originally Posted by bhushan1980
This question doesnt make sense to me.. It's like asking what comes first, a shopping list (interface - defines what goes in and out, doesnt impl) or a box of ready-made cake mix (abstraction of a cake - just add milk). I never needed one before the other.Quote:
In an enterprise development, which one comes first - an abstract class or an interface?
Nonsense question: You cant implement a method that is marked abstractQuote:
What is happens when the keyword abstract is used to declare and implement a method?
You cannot override that method witha new implementation in a subclassQuote:
What happens when a keyword sealed is applied to a method?
Constructors dont really partake in all the usual inheritance shenanigans. They behave like they are new, which is why you must explicitly state base(args) when you want to call the parent cosntructor. You should be aware that if you do not provide a constructor, C# provides a default one (literally inserts it into your code when compiling) that takes no args and calls the base() again with no args. If no base constructor takes no args then you must provide a constructor to get around this behaviour because the error indicating the base class has no matching constructor, is seen.Quote:
Can we have virtual/override/new keywords attached to a contructor in C#?
This is not constructor inheritance..
shared. vb.net's static is for method variables that retain their value between calls, a somewhat dumb and clumsy idea that c# ditched. if you need the functionality, use a class level variable instead; it's how the vb.net compiler fudges it behind the scenesQuote:
What is the analogous of C# static keyword in VB.NET?
this, (not needed; methods can be treated like objects when dealing with delegates), usingQuote:
Is there a C# equivalent for keywords My, AddressOf, With in C#?
read this: http://www.harding.edu/fmccown/vbnet...omparison.html
here's attaching an eventhandler in c#:
obj.Event += Handler(methodName)
vb:
AddHandler obj.Event, AddressOf methodName
neitherQuote:
Which of the ways is cost effective? Boxing or Unboxing?
I always like the cake mix that comes with frosting. I'm not sure if it's IFrosting or FrostingBase, but it's good.Quote:
Originally Posted by cjard
/me munches on a bowl of Reduced Sugar Kelloggs Frosties* and wonders the same thing
*the concept of which i find one of the most amusingly pointless in the breakfast cereal world.. Frosties = cornflakes + sugar, so if you want frosties without sugar.. ;)