Interfaces

[Duncan McNutt .[FTSE]]

Why does code derive from for example, IComparer

ie,

class SomeClass : IComparer
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}
When it just uses that and could have done without deriving ICompare and
got the same result.

class SomeClass
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}

--

Duncan McNutt
Microsoft Product Deactivation Team
--

[Duncan McNutt .[FTSE]]

And another question...

Because SomeClass derives from the IComparer interface
if i use SomeClass as a base of another like...

class SomeNewClass : SomeClass
{
public SomeNewClass()
{
}
}

Would that above fail due to no Compare method as SomeClass is derived from
ICompare and it MUST implement Compare.. like..

class SomeNewClass : SomeClass
{
public SomeNewClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}

The above would work.

Do i understand this correctly?

--

Duncan McNutt
Microsoft Product Deactivation Team
--
" Duncan McNutt .[FTSE]" <pi*******@127. 0.0.701> wrote in message
news:uL******** ******@TK2MSFTN GP09.phx.gbl...

Why does code derive from for example, IComparer

ie,

class SomeClass : IComparer
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}
When it just uses that and could have done without deriving ICompare and got the same result.

class SomeClass
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}

--

Duncan McNutt
Microsoft Product Deactivation Team
--

[Ignacio Machin]

Hi Duncan,

You do not derive from an interface, you implement it, there is a diference,
an interface is like a template, it has no implementation it only assure
that the classes that implement it have a predefined setof methods ( the
interface ) , when you derive from a class you extend that class, add new
functionality. you do not do that with an interface.

Hope this help,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation
" Duncan McNutt .[FTSE]" <pi*******@127. 0.0.701> wrote in message
news:uL******** ******@TK2MSFTN GP09.phx.gbl...

Why does code derive from for example, IComparer

ie,

class SomeClass : IComparer
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}
When it just uses that and could have done without deriving ICompare and got the same result.

class SomeClass
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}

--

Duncan McNutt
Microsoft Product Deactivation Team
--

[Duncan McNutt .[FTSE]]

oh well yeah oops :D wasnt thinking *gets coffee*

So why inherit from ICompare when its just as easy to implement Compare
anyway and its derived.

--

Duncan McNutt
Microsoft Product Deactivation Team
--
"Peter Vidler" <pv*****@gawab. com> wrote in message
news:bj******** ********@newsfe p1-win.server.ntli .net...

Hi,

Would that above fail due to no Compare method as SomeClass is
derived from ICompare and it MUST implement Compare.. like..
No, because SomeNewClass will inherit the implementation from SomeClass.

I'm almost certain of it ;)

Pete

[Duncan McNutt .[FTSE]]

Yeah I understand an Interface is a contract, that must be implemented but I
see code that has implemented that interface but why would it need to when
it can just as easily implement it anyway and not have tim use ICompare in
the class definition.

Whats to stop me just coding a public int Compare(object x, object y) method
anyway without referring to IComapre?

--

Duncan McNutt
Microsoft Product Deactivation Team
--
"Ignacio Machin" <ignacio.mach in AT dot.state.fl.us > wrote in message
news:uL******** ******@tk2msftn gp13.phx.gbl...

Hi Duncan,

You do not derive from an interface, you implement it, there is a diference, an interface is like a template, it has no implementation it only assure
that the classes that implement it have a predefined setof methods ( the
interface ) , when you derive from a class you extend that class, add new
functionality. you do not do that with an interface.

Hope this help,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation
" Duncan McNutt .[FTSE]" <pi*******@127. 0.0.701> wrote in message
news:uL******** ******@TK2MSFTN GP09.phx.gbl...

Why does code derive from for example, IComparer

ie,

class SomeClass : IComparer
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}
When it just uses that and could have done without deriving ICompare

and

got the same result.

class SomeClass
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}

--

Duncan McNutt
Microsoft Product Deactivation Team
--

[Ignacio Machin]

Hi Duncan,
I would suggest you something, if you have this kind of doubt, try it !! ,
do not missunderstand me, I believe that the best way to learn is
experimenting, your code will not fail cause as I explained in the previous
post when you derive you are extending therefore the new class gets all the
parent's functionality.

Hope this help,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation
" Duncan McNutt .[FTSE]" <pi*******@127. 0.0.701> wrote in message
news:ek******** ******@TK2MSFTN GP10.phx.gbl...

And another question...

Because SomeClass derives from the IComparer interface
if i use SomeClass as a base of another like...

class SomeNewClass : SomeClass
{
public SomeNewClass()
{
}
}

Would that above fail due to no Compare method as SomeClass is derived from ICompare and it MUST implement Compare.. like..

class SomeNewClass : SomeClass
{
public SomeNewClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}

The above would work.

Do i understand this correctly?

--

Duncan McNutt
Microsoft Product Deactivation Team
--
" Duncan McNutt .[FTSE]" <pi*******@127. 0.0.701> wrote in message
news:uL******** ******@TK2MSFTN GP09.phx.gbl...

Why does code derive from for example, IComparer

ie,

class SomeClass : IComparer
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}
When it just uses that and could have done without deriving ICompare

and

got the same result.

class SomeClass
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}

--

Duncan McNutt
Microsoft Product Deactivation Team
--

[Peter Vidler]

Hi,

So why inherit from ICompare when its just as easy to implement
Compare anyway and its derived.

Because then you can use an object of that type wherever IComparer is asked
for (i.e. calls to methods, etc). Otherwise there is no way to tell if an
object supports the Compare method without having a reference to the exact
type of the object.

Pete

[Frank Drebin]

The key element is that the purpose of an interface is that you can write
your code to a generic "interface" ..

For example, say you have a Windows app that needs to connect to a
datasource. That datasource could be a real database, a remote web service
and also an offline file. But you want to abstract HOW the datasource gets
it's data. If you couldn't abstract it, you'd have to write 3 versions of
code mixed in with your main application - to do this.

but instead, you could write your application to use the IDataAccess
interface (this is an interface you write, it has Connect() Authenticate(),
etc)..

Then you have classes such as Database, WebService and OfflineAccess that
implement that interface.

So Interfaces aren't so much a small-scale time-saver, they make more and
more sense the larger the app gets - and the purpose is to abstract the
specific of how something gets done.

Using your examples, if you write your application to use the IComparer
interface:

IComparer objMyComparer = new SomeClass();

Since SomeClass implements IComparer - the above is valid. Imagine that you
could have several different KINDS of comparers - and you would only need to
write your new classes to implement that same IComparer interface.

hope that helps..

" Duncan McNutt .[FTSE]" <pi*******@127. 0.0.701> wrote in message
news:uL******** ******@TK2MSFTN GP09.phx.gbl...

Why does code derive from for example, IComparer

ie,

class SomeClass : IComparer
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}
When it just uses that and could have done without deriving ICompare and got the same result.

class SomeClass
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}

--

Duncan McNutt
Microsoft Product Deactivation Team
--

[Duncan McNutt .[FTSE]]

Yeah but why must that class implement ICompare when it can just as easily
make a public Compare (obj , obj) method and be the same.

--

Duncan McNutt
Microsoft Product Deactivation Team
--
"Ignacio Machin" <ignacio.mach in AT dot.state.fl.us > wrote in message
news:uL******** ******@tk2msftn gp13.phx.gbl...

Hi Duncan,

You do not derive from an interface, you implement it, there is a diference, an interface is like a template, it has no implementation it only assure
that the classes that implement it have a predefined setof methods ( the
interface ) , when you derive from a class you extend that class, add new
functionality. you do not do that with an interface.

Hope this help,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation
" Duncan McNutt .[FTSE]" <pi*******@127. 0.0.701> wrote in message
news:uL******** ******@TK2MSFTN GP09.phx.gbl...

Why does code derive from for example, IComparer

ie,

class SomeClass : IComparer
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}
When it just uses that and could have done without deriving ICompare

and

got the same result.

class SomeClass
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}

--

Duncan McNutt
Microsoft Product Deactivation Team
--

[Duncan McNutt .[FTSE]]

yeah I know, i just wasnt thinking, caffine levels droped :D

But my question is, why implement ICompare when I can just as easily make
the method without reference to IComapre at all in the class.

What is the benifit.
--

Duncan McNutt
Microsoft Product Deactivation Team
--
"Ignacio Machin" <ignacio.mach in AT dot.state.fl.us > wrote in message
news:eA******** *****@TK2MSFTNG P10.phx.gbl...

Hi Duncan,
I would suggest you something, if you have this kind of doubt, try it !! , do not missunderstand me, I believe that the best way to learn is
experimenting, your code will not fail cause as I explained in the previous post when you derive you are extending therefore the new class gets all the parent's functionality.

Hope this help,

--
Ignacio Machin,
ignacio.machin AT dot.state.fl.us
Florida Department Of Transportation
" Duncan McNutt .[FTSE]" <pi*******@127. 0.0.701> wrote in message
news:ek******** ******@TK2MSFTN GP10.phx.gbl...

And another question...

Because SomeClass derives from the IComparer interface
if i use SomeClass as a base of another like...

class SomeNewClass : SomeClass
{
public SomeNewClass()
{
}
}

Would that above fail due to no Compare method as SomeClass is derived

from

ICompare and it MUST implement Compare.. like..

class SomeNewClass : SomeClass
{
public SomeNewClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}

The above would work.

Do i understand this correctly?

--

Duncan McNutt
Microsoft Product Deactivation Team
--
" Duncan McNutt .[FTSE]" <pi*******@127. 0.0.701> wrote in message
news:uL******** ******@TK2MSFTN GP09.phx.gbl...

Why does code derive from for example, IComparer

ie,

class SomeClass : IComparer
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}
When it just uses that and could have done without deriving

ICompare and

got the same result.

class SomeClass
{
public SomeClass()
{
}

public int Compare(object x, object y)
{
return someInt;
}
}

--

Duncan McNutt
Microsoft Product Deactivation Team
--