Abstract Base Constructor Question

[Randy]

Problem reduced to simplist form:

abstract class myBase
{
myBase(int x)
{
Console.Writeline("x = {0}", x);
}
}
class mySubClass : myBase
{
mySubClass() {}
}

Yields the following error: "No overload for method 'myBase' takes '0'
arguments"

Any ideas on what I have to do to mySubClass to get this to compile?

Thanks,
Randy

[Daniel O'Connell [C# MVP]]

"Randy" <rb***@sumaria.net> wrote in message
news:md*******************@nwrdny03.gnilink.net...

Problem reduced to simplist form:

abstract class myBase
{
myBase(int x)
{
Console.Writeline("x = {0}", x);
}
}
class mySubClass : myBase
{
mySubClass() {}
}

Yields the following error: "No overload for method 'myBase' takes '0'
arguments"
basically
class mySubClass : myBase
{
mySubClass() : base(10) {}
}

in other words, you have to specifiy a value for the base constructor. Any ideas on what I have to do to mySubClass to get this to compile?

Thanks,
Randy

[Rob Windsor [MVP]]

You're derived class needs to call the base classes constructor which
requires one parameter of type int. You need to modify the constructor of
the derived class to look like

mySubClass() : base(<some hard coded integer value here>) {}
or
mySubClass(int x) : base(x) {}

--
Rob Windsor [MVP-VB]
G6 Consulting
Toronto, Canada
"Randy" <rb***@sumaria.net> wrote in message
news:md*******************@nwrdny03.gnilink.net...

Problem reduced to simplist form:

abstract class myBase
{
myBase(int x)
{
Console.Writeline("x = {0}", x);
}
}
class mySubClass : myBase
{
mySubClass() {}
}

Yields the following error: "No overload for method 'myBase' takes '0'
arguments"

Any ideas on what I have to do to mySubClass to get this to compile?

Thanks,
Randy

[Pete Davis]

In myBase, the only constructor you have takes a single argument. In
mySubClass, the only constructor takes no arguments. For inheritance to
work, the sub classed constructor must somehow call the base class
constructor. if there's no argument to pass, it doesn't know how.

If you change mySubClass to:

class mySubClass : myBase
{
mySubClass(int x) {}
}

that will work.

Optionally, you can specify which base class constructor to call and do
something like:

class mySubClass : myBase
{
mySubClass() : base(4) {}
}

In this case, we're passing the constant integer 4 to the base class
constructor.
Pete

--
http://www.petedavis.net
"Randy" <rb***@sumaria.net> wrote in message
news:md*******************@nwrdny03.gnilink.net...

Problem reduced to simplist form:

abstract class myBase
{
myBase(int x)
{
Console.Writeline("x = {0}", x);
}
}
class mySubClass : myBase
{
mySubClass() {}
}

Yields the following error: "No overload for method 'myBase' takes '0'
arguments"

Any ideas on what I have to do to mySubClass to get this to compile?

Thanks,
Randy

[Doug Erickson [MS]]

Yes. You need to pass the constructor parameters up to the parent class
constructor, like so:

abstract class myBase
{
myBase(int x)
{
Console.Writeline("x = {0}", x);
}
}
class mySubClass : myBase
{
mySubClass(int x): base(x) {}
}

Hope this helps!

--
----
Doug Erickson [MSFT], Platform SDK UA
This posting is provided "AS IS" with no warranties, and confers no rights.
You assume all risk for your use. 2003 Microsoft Corporation. All rights
reserved.
"Randy" <rb***@sumaria.net> wrote in message
news:md*******************@nwrdny03.gnilink.net...

Problem reduced to simplist form:

abstract class myBase
{
myBase(int x)
{
Console.Writeline("x = {0}", x);
}
}
class mySubClass : myBase
{
mySubClass() {}
}

Yields the following error: "No overload for method 'myBase' takes '0'
arguments"

Any ideas on what I have to do to mySubClass to get this to compile?

Thanks,
Randy

[Mattias Sjögren]

Randy,

In addition to what the others said, you also have to make the base
constructor accessible to the derived class. It's currently private,
so it can't be used by mySubClass. Make it at least protected.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[Randy]

mySubClass():base(4) {} works! Many thanks to all.

Randy

"Randy" <rb***@sumaria.net> wrote in message
news:md*******************@nwrdny03.gnilink.net...

Problem reduced to simplist form:

abstract class myBase
{
myBase(int x)
{
Console.Writeline("x = {0}", x);
}
}
class mySubClass : myBase
{
mySubClass() {}
}

Yields the following error: "No overload for method 'myBase' takes '0'
arguments"

Any ideas on what I have to do to mySubClass to get this to compile?

Thanks,
Randy