Re: Barcode reader and Receipt printer - C# Discussion Boards

8-Aug-03 17:13

hi,

QUESTION 1: i understand you can add modifier to interface:

public interface IA
{
public void DoA(); //Yes, I understand this is INVALID - so, I didnt do this.
void DoB();
void DoC();

double salary
{
get;
}

}

But I thought access modifier is OK when you declare implementation in class? I tried access access modifier in class but the compiler keep bitching that it's NOT legal to do so - and it didnt provide error code (like C1324)! See "QUESTION" below:

public class Capitalist : IA, IB, ICapitalist //QUESTION 2: Can you specify public/private... in interface inheritance? How?
{
//Implement interface IA:
public void IA.DoA() //QUESTION 1: compiler complained here!!
{
Console.WriteLine("Capitalist.IA.DoA");
return;
}

void IA.DoB() //This, on the other hand, is oK.
{
Console.WriteLine("Capitalist.IA.DoB");
return;
}
... and the rest of it ...
}

THanks!

norm

Nish Nishant8-Aug-03 17:28

Nish Nishant

8-Aug-03 17:28

Puzzling indeed. The following code compiled for me without errors :-

public interface IAbc
{
    void Hello();
    string GetName(int y);
}

public class CAbc : IAbc
{
    public void Hello()
    {
    }

    public string GetName(int y)
    {
        return y.ToString();
    }
}

Extending MFC Applications with the .NET Framework [NW] (My book with Tom)
Summer Love and Some more Cricket [NW] (My first novel)
Shog's review of SLASMC [NW]
Come with me if you want to live

found it!

devvvy8-Aug-03 21:10

8-Aug-03 21:10

You can append access modifer when you implement it in a class, PROVIDED that the interface is not the base interface of another interface that the class implements.

Using example below, IAccMaintenance is the base interface of IAccManager:

interface IAccMaintenance
{
int EditAccProfile(...); //DO NOT append access modifer to this method when you implement it.
}

interface IAccManager : IAccMaintenance
{
...
}

Now, when you implement it in a class:
class SiteManager : IAccManager
{
public int IAccManager.CreateAcc(...) {...} //That's OK. You can use access modifier here.
public int EditAccProfile(...) {...} //ERROR: You can't use access modifier - the method comes from an interface that's not directly inherited. But why would .NET team design it this way???

...
}

***********************************************************************
In case you want to just compile the code and see...
using System;

namespace try_interface2
{
public interface IAccMaintenance
{
int EditAccProfile(int accID);
}

public interface IOldAccMaintenance
{
int EditAccProfile(int accID);
}

public interface IAccManager : IAccMaintenance, IOldAccMaintenance
{
int CreateAcc(string accType, int accID);
int DestroyAcc(int accID);

int numAccount
{
get;
set;
}
}

interface IConnManager
{
int Connect(string Destination, int connID);
int Disconn(int connID);
}

class CSiteManager : IAccManager, IConnManager
{
protected int m_numAccount;

//(1) Implementing IAccManager interface:
public int CreateAcc(string accType, int accID)
{
Console.WriteLine("CreateAcc... account type: {0}, account ID: {1}", accType, accID.ToString());
return 1;
}

public int DestroyAcc(int accID)
{
Console.WriteLine("Destroy Acc... account ID: {0}", accID.ToString());
return 1;
}

public int numAccount
{
get{ return m_numAccount; }
set{ m_numAccount=value; }
}

int IAccMaintenance.EditAccProfile(int accID)
{
int err=0;
Console.WriteLine("edit acc profile ver 0. accID: {0}", accID);
return err;
}

int IOldAccMaintenance.EditAccProfile(int accID)
{
int err=0;
Console.WriteLine("edit acc profile ver 0. accID: {0}", accID);
return err;
}

//(2) Implementing IConnManager interface (Default method access modifier: private):
int IConnManager.Connect(string Destination, int connID)
{
int err=0;
Console.WriteLine("Connect... destination: {0} connID: {1}", Destination, connID);
return err;
}

int IConnManager.Disconn(int connID)
{
int err=0;
Console.WriteLine("Disconn... connID: {0}", connID);
return err;
}

}

///

/// Summary description for Class1.
///

class AppClass
{
///

/// The main entry point for the application.
///

[STAThread]
static void Main(string[] args)
{
CSiteManager siteManager = new CSiteManager();
siteManager.CreateAcc("developer_premimum", 731);
siteManager.DestroyAcc(423);
siteManager.numAccount = 14302;
Console.WriteLine("Number of registered accounts: {0}", siteManager.numAccount);

}
}
}

norm

Jim Stewart8-Aug-03 19:37

Jim Stewart

8-Aug-03 19:37

From MSDN[^]:
All interface members implicitly have public access. It is a compile-time error for interface member declarations to include any modifiers. In particular, interfaces members cannot be declared with the modifiers abstract, public, protected, internal, private, virtual, override, or static.

Hope this helps.

α.γεεκ

Fortune passes everywhere.
Duke Leto Atreides

devvvy8-Aug-03 19:56

8-Aug-03 19:56

i know. That's why I didn't add any access modifier in interface declaration. But in the class that implements it... the code is below, compile it and see for yourself:

using System;

namespace deda
{ //namespace deda

public interface IA
{
void DoA();
void DoB();
void DoC();

double salary
{
get;
}

}

public interface IB : IA
{
new void DoA();
}

public interface ICapitalist
{
void HireSlave();
void FireSlave();
}

public class Capitalist : IA, IB, ICapitalist
{
//Implement interface IA:
public void IA.DoA()
{
Console.WriteLine("Capitalist.IA.DoA");
return;
}

void IA.DoB()
{
Console.WriteLine("Capitalist.IA.DoB");
return;
}

void IA.DoC()
{
Console.WriteLine("Capitalist.IA.DoC");
return;
}

public double salary {
get{ return m_salary;}
}

//Implement interface IB:
void IB.DoA()
{
Console.WriteLine("Capitalist.IB.DoA");
return;
}

//Implement interface ICapitalist:
void ICapitalist.HireSlave(){
Console.WriteLine("Capitalist hiring");
return;
}

void ICapitalist.FireSlave(){
Console.WriteLine("Capitalist layoff people");
return;
}

//Class' protected attributes:
protected double m_salary;
}

} //namespace deda

norm

separate method declaration and implementation

Bo Hunter8-Aug-03 19:38

Bo Hunter

8-Aug-03 19:38

I think one is called implicit implementation.
Like this
IA.Dob()
{
}

if you want to use access modifiers then
like he said.
public void Dob()
{
}

Bo Hunter

devvvy8-Aug-03 16:42

8-Aug-03 16:42

Hi, just want to know how to separate method declaration and implementation.

Example:

namespace anothersucker
{

public class SomeClass : IA, IB, IC
{
//QUESTION: How can I do implementation elsewhere so I can separate declaration and implementation like we do in C++
public void DoA() {return;}
protected void DoB() {return;}
public void DoC() {return;}
public void DoD() {return;}
}

}

norm

Nish Nishant8-Aug-03 16:58

Nish Nishant

8-Aug-03 16:58

I don't think that you can do this with C#

Nish

p.s. You could switch to MC++ if this bothers you a lot

Extending MFC Applications with the .NET Framework [NW] (My book with Tom)
Summer Love and Some more Cricket [NW] (My first novel)
Shog's review of SLASMC [NW]
Come with me if you want to live

devvvy8-Aug-03 17:17

8-Aug-03 17:17

that's lame.

norm

Nish Nishant8-Aug-03 17:23

Nish Nishant

8-Aug-03 17:23

What's lame? MC++?

Nish

Extending MFC Applications with the .NET Framework [NW] (My book with Tom)
Summer Love and Some more Cricket [NW] (My first novel)
Shog's review of SLASMC [NW]
Come with me if you want to live

devvvy8-Aug-03 17:52

8-Aug-03 17:52

no, .NET is not lame at all, big step forward from the lame MFC. i was just bitching that you can't separate declaration and implementation in C#.

.net framework is so much more intuitive and organized and with much shorter learnign curve than MFC/WIN32. documentation is much better.. just so much better.

norm

J. Dunlap8-Aug-03 18:08

J. Dunlap

8-Aug-03 18:08

I'll agree with that. I'll be most happy if/when they finally make C# be a language that keeps up with modern concepts (which it does now), does not have the excess baggage/clutter of C++ (C# is good here), AND has the power that C++ achieves (they have a ways to go here). It's definitely not too hard to accomplish.

"Blessed are the peacemakers, for they shall be called sons of God." - Jesus

"You must be the change you wish to see in the world." - Mahatma Gandhi

devvvy8-Aug-03 19:59

8-Aug-03 19:59

despite all .net languages compile to MSIL, i thought managed C++ has more optimized IL than others?

norm

J. Dunlap8-Aug-03 20:11

J. Dunlap

8-Aug-03 20:11

No, it doesn't. But you can mix managed and unmanaged code in Managed C++.

BTW, what makes managed code slower than unmanaged code is that it has to be compiled at runtime.

"Blessed are the peacemakers, for they shall be called sons of God." - Jesus

"You must be the change you wish to see in the world." - Mahatma Gandhi