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steve@stevejay.net
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 Posted: Sun Jul 17, 2005 8:30 pm Post subject: What's this C++ design pattern called? |
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Hi there,
This design pattern is a way of avoiding having to have a constructor
with a long parameter list. A separate class is used to deal with
setting the parameter values, using setter functions that return *this
so that as many or as few as are required can be changed together.
Here's just a skeleton of an example:
class parameters
{
public:
parameters () {}
parameters & setting_a () { return *this; }
parameters & setting_b () { return *this; }
};
class something_useful
{
public:
something_useful (const parameters & p) {}
};
Using the above two classes, I can write:
something_useful my_useful (parameters().setting_a().setting_b());
I'd really like to know what this design pattern's "official" name is!
Thanks,
Steve
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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Maciej Sobczak
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| Posted: Mon Jul 18, 2005 1:01 pm Post subject: Re: What's this C++ design pattern called? |
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[email]steve (AT) stevejay (DOT) net[/email] wrote:
| Quote: | This design pattern
|
I would not call it a "design pattern", since there is no real
collaboration between objects that this "pattern" would encapsulate.
It is just a coding technique, with the scope limited to a single
function (note that it does not have to be a constructor for this
technique to be useful).
It is possible that it has some established name, although I'm not aware
of any.
--
Maciej Sobczak : http://www.msobczak.com/
Programming : http://www.msobczak.com/prog/
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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Fabio Fracassi
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| Posted: Mon Jul 18, 2005 1:02 pm Post subject: Re: What's this C++ design pattern called? |
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[email]steve (AT) stevejay (DOT) net[/email] wrote:
| Quote: | Hi there,
class parameters
{
public:
parameters () {}
parameters & setting_a () { return *this; }
parameters & setting_b () { return *this; }
};
class something_useful
{
public:
something_useful (const parameters & p) {}
};
Using the above two classes, I can write:
something_useful my_useful (parameters().setting_a().setting_b());
I'd really like to know what this design pattern's "official" name is!
Thanks,
Steve
|
The C++ FAQ calls this "named parameter ideom".
see http://www.parashift.com/c++-faq-lite/ctors.html#faq-10.18
I think that ideom fits better than design pattern for this, too, but that
is probably a matter of taste.
HTH
Fabio
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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leonardo77
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steve@stevejay.net
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| Posted: Tue Jul 19, 2005 9:29 am Post subject: Re: What's this C++ design pattern called? |
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Hi,
Fabio Fracassi wrote:
That's where I'd seen it discussed! Thanks very much, to you and
leonardo77.
As for the design pattern/idiom thing, I'm just a beginner so the
language of this field is still quite slippery for me.
Bye,
Steve
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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