Hello Everyone,
I'm trying to make a function take arguments in a particular way.
This is what I want to create:
#Variable argument testing
def function(*sometimes)
if sometimes.nil?
print "Not given!"
else
print "Here!"
end
end
function
[EOF]
As I understand it, the * operator bundles the argument into an array,
so that if test returns true. I know that I can use "if
sometimes.length==0" to get the same behaviour, but that is rather
obscure compared to the first version.
Is there some other way to set up the argument list? (Alas, I have found
nothing in the documentation or the Forum.)
Thank you,
-Ryan
···
--
Posted via http://www.ruby-forum.com/.
Alle domenica 1 luglio 2007, Ryan Allan ha scritto:
Hello Everyone,
I'm trying to make a function take arguments in a particular way.
This is what I want to create:
#Variable argument testing
def function(*sometimes)
if sometimes.nil?
print "Not given!"
else
print "Here!"
end
end
function
[EOF]
As I understand it, the * operator bundles the argument into an array,
so that if test returns true. I know that I can use "if
sometimes.length==0" to get the same behaviour, but that is rather
obscure compared to the first version.
Is there some other way to set up the argument list? (Alas, I have found
nothing in the documentation or the Forum.)
Thank you,
-Ryan
I can't think of any other way to make a method take any number of arguments,
but remember that there's a shorter way to tell whether an array is empty:
the empty? method:
def function(*sometimes)
if sometimes.empty?
print "Not given!"
else
print "Here!"
end
end
This way, it's as clear as what you wanted to use. Besides, even if it had
been possible, your approach would have had a problem: you wouldn't have been
able to distinguish the case of a single nil argument from the case of no
arguments:
function(nil)
function()
The correct approach solves this problem: if no arguments are passed,
sometimes is empty (empty? returns true); otherwise it's not empty, even if
all arguments are nil.
I hope this helps
Stefano
Thank you Stefano.
You're right; the empty? method is nicely obvious.
I do have a further question, however. You've highlighted a problem
with my original idea, but I don't understand it.
Besides, even if it
had been possible, your approach would have had a problem: you wouldn't have
been able to distinguish the case of a single nil argument from the case of
no arguments:
function(nil)
function()
The correct approach solves this problem: if no arguments are passed,
sometimes is empty (empty? returns true); otherwise it's not empty, even
if all arguments are nil.
What is the difference between no arguments and a single nil argument?
It seems to me that the cases are logically equivalent. Ruby treats them
separately?
Thanks again,
-Ryan
···
--
Posted via http://www.ruby-forum.com/\.
Hi --
Thank you Stefano.
You're right; the empty? method is nicely obvious.
I do have a further question, however. You've highlighted a problem
with my original idea, but I don't understand it.
Besides, even if it
had been possible, your approach would have had a problem: you wouldn't have
been able to distinguish the case of a single nil argument from the case of
no arguments:
function(nil)
function()
The correct approach solves this problem: if no arguments are passed,
sometimes is empty (empty? returns true); otherwise it's not empty, even
if all arguments are nil.
What is the difference between no arguments and a single nil argument?
It seems to me that the cases are logically equivalent. Ruby treats them
separately?
Yes, because nil is an object.
def meth(x)
p x
end
meth(1) # 1
meth(nil) # nil
meth # ArgumentError: wrong number of arguments
David
···
On Mon, 2 Jul 2007, Ryan Allan wrote:
--
* Books:
RAILS ROUTING (new! http://www.awprofessional.com/title/0321509242\)
RUBY FOR RAILS (http://www.manning.com/black\)
* Ruby/Rails training
& consulting: Ruby Power and Light, LLC (http://www.rubypal.com)
Thank you David. That makes much more sense now.
···
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