I know it's possible to require inheriting classes to implement a particular
function or property, but is it possible to require a inheriting class to
implement a constructor of it's own?
Thanks,
Steve
21  10172 
Steve - DND <ng@digitalnoth ing.com> wrote: I know it's possible to require inheriting classes to implement a particular
function or property, but is it possible to require a inheriting class to
implement a constructor of it's own?
No, I'm afraid not.
--
Jon Skeet - <sk***@pobox.co m> http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
Hi Steve,
No, there is no way?
Unless if you declare only protected constructors for the base class.
class Foo
{
protected Foo()
{
}
}
Now if I want to inherit from this class and be able to instatiate objects I
have to declare at least one public constructor. But I cannot force the
inheritors to declare constructor with specific prototype (as I can do with
abstract methods).
class Bar: Foo
{
public Bar()
{
}
}
What do you need that for? I can't think of any useful application of this.
HTH
B\rgds
100
"Steve - DND" <ng@digitalnoth ing.com> wrote in message
news:uL******** ******@TK2MSFTN GP09.phx.gbl... I know it's possible to require inheriting classes to implement a
particular function or property, but is it possible to require a inheriting class to
implement a constructor of it's own?
Thanks,
Steve
100 <10*@100.com> wrote:
<snip> What do you need that for? I can't think of any useful application of this.
I can, very easily: plug-in systems. Basically, sooner or later in any
plug-in framework you need to instantiate a type which you don't know
about at compile-time. You'll have to instantiate it with reflection
anyway, but it would help if the plug-in author got an error when
writing the type if they didn't provide an appropriate constructor.
--
Jon Skeet - <sk***@pobox.co m> http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@msnews.micros oft.com... What do you need that for? I can't think of any useful application of
this. I can, very easily: plug-in systems. Basically, sooner or later in any
plug-in framework you need to instantiate a type which you don't know
about at compile-time. You'll have to instantiate it with reflection
anyway, but it would help if the plug-in author got an error when
writing the type if they didn't provide an appropriate constructor.
Wouldn't you use an interface to define the plugin, then why would you care
about the constructor? What I mean is the functionality of a Foo
constructor Foo(int a, int b); Could simply be Init(int a, int b) in an
interface, ignoring a constructor completely.
-- Alan
You could do this with generics.
But if you need a definatie API, use an interface, or if you need a definate
behaviour, use abstract base classes
"Alan Pretre" <no@spam> wrote in message
news:#k******** ******@TK2MSFTN GP12.phx.gbl... "Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@msnews.micros oft.com... What do you need that for? I can't think of any useful application of this. I can, very easily: plug-in systems. Basically, sooner or later in any
plug-in framework you need to instantiate a type which you don't know
about at compile-time. You'll have to instantiate it with reflection
anyway, but it would help if the plug-in author got an error when
writing the type if they didn't provide an appropriate constructor.
Wouldn't you use an interface to define the plugin, then why would you
care about the constructor? What I mean is the functionality of a Foo
constructor Foo(int a, int b); Could simply be Init(int a, int b) in an
interface, ignoring a constructor completely.
-- Alan
"news.microsoft .com" <di********@dis cussion.microso ft.com> wrote in message
news:OH******** *****@tk2msftng p13.phx.gbl... But if you need a definatie API, use an interface, or if you need a
definate behaviour, use abstract base classes
In this case you could do both. Inherit functionality from PluginBase() and
yet implement IPlugin.
-- Alan
Alan Pretre <no@spam> wrote: "Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@msnews.micros oft.com... What do you need that for? I can't think of any useful application of this. I can, very easily: plug-in systems. Basically, sooner or later in any
plug-in framework you need to instantiate a type which you don't know
about at compile-time. You'll have to instantiate it with reflection
anyway, but it would help if the plug-in author got an error when
writing the type if they didn't provide an appropriate constructor.
Wouldn't you use an interface to define the plugin, then why would you care
about the constructor?
To create an instance of the type that implements the interface.
What I mean is the functionality of a Foo
constructor Foo(int a, int b); Could simply be Init(int a, int b) in an
interface, ignoring a constructor completely.
How do you call Init in the first place? If it's a static method, you
can't specify that in the interface, and if it's an instance method
then you're back to the question of how you create an instance in the
first place.
--
Jon Skeet - <sk***@pobox.co m> http://www.pobox.com/~skeet
If replying to the group, please do not mail me too
"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@msnews.micros oft.com... Wouldn't you use an interface to define the plugin, then why would you
care about the constructor?
To create an instance of the type that implements the interface.
By definition, it would be of the type if it implemented the interface. What I mean is the functionality of a Foo
constructor Foo(int a, int b); Could simply be Init(int a, int b) in an
interface, ignoring a constructor completely.
How do you call Init in the first place? If it's a static method, you
can't specify that in the interface, and if it's an instance method
then you're back to the question of how you create an instance in the
first place.
I mean created with a default constructor then refined based on appropriate
instance methods or overloads or whatever.
-- Alan
Alan Pretre <no@spam> wrote: "Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@msnews.micros oft.com... Wouldn't you use an interface to define the plugin, then why would you
care> about the constructor?
To create an instance of the type that implements the interface.
By definition, it would be of the type if it implemented the interface.
Yes - but you'd need to create an instance of it in order to use it
though, is my point. How do you call Init in the first place? If it's a static method, you
can't specify that in the interface, and if it's an instance method
then you're back to the question of how you create an instance in the
first place.
I mean created with a default constructor then refined based on appropriate
instance methods or overloads or whatever.
That relies on there *being* a parameterless constructor though - and
you can't enforce that. (It would also restrict the plugin to being a
mutable type, which isn't ideal.)
--
Jon Skeet - <sk***@pobox.co m> http://www.pobox.com/~skeet
If replying to the group, please do not mail me too This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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