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comp.lang.ruby

Passing a hash of args

Jonathan Leighton

1/8/2006 10:56:00 PM

Is there a way to pass each item is a hash as a successive argument to a
function?

ie:

time = {
:year => 2003
:month => 03
:day => 24
}
Time.local(time)

(that wouldn't work but you get the idea)

Cheers

--
Jonathan Leighton
http://turnips... | http://jonathanlei... | http://digital-...
8 Answers

Marcel Molina Jr.

1/8/2006 11:00:00 PM

0

On Mon, Jan 09, 2006 at 07:55:42AM +0900, Jonathan Leighton wrote:
> Is there a way to pass each item is a hash as a successive argument to a
> function?
>
> ie:
>
> time = {
> :year => 2003
> :month => 03
> :day => 24
> }
> Time.local(time)
>
> (that wouldn't work but you get the idea)

Hashes aren't ordered. Otherwise you could just do Time.local(*time.values).

Time.local(*[:year, :month, :day].map {|key| time[key]}) is DRYer but more
typing than Time.local(time[:year], time[:month], time[:day])

I look forward to someone else coming up with something clever.

marcel
--
Marcel Molina Jr. <marcel@vernix.org>

Daniel Harple

1/8/2006 11:01:00 PM

0

Jonathan Leighton wrote:

> Is there a way to pass each item is a hash as a successive argument
> to a
> function?
>
> ie:
>
> time = {
> :year => 2003
> :month => 03
> :day => 24
> }
> Time.local(time)
>
> (that wouldn't work but you get the idea)
>
> Cheers
>
> --
> Jonathan Leighton
> http://turnips... | http://jonathanlei... | http://
> digital-proof.org/
>
>

Time.local(*time.values.reverse)

-- Daniel

James Gray

1/8/2006 11:01:00 PM

0

On Jan 8, 2006, at 4:55 PM, Jonathan Leighton wrote:

> Is there a way to pass each item is a hash as a successive argument
> to a
> function?
>
> ie:
>
> time = {
> :year => 2003
> :month => 03
> :day => 24
> }
> Time.local(time)

Well, Hashes are unordered by definition, but as long as we declare
an order it's doable:

>> time = {
?> :year => 2003,
?> :month => 03,
?> :day => 24
>> }
=> {:month=>3, :year=>2003, :day=>24}
>> Time.local(*time.values_at(:year, :month, :day))
=> Mon Mar 24 00:00:00 CST 2003

Hope that helps.

James Edward Gray II

Ross Bamford

1/8/2006 11:09:00 PM

0

On Sun, 08 Jan 2006 23:00:42 -0000, Daniel Harple
<dharple@generalconsumption.org> wrote:

> Jonathan Leighton wrote:
>
>> Is there a way to pass each item is a hash as a successive argument to a
>> function?
>>
>> ie:
>>
>> time = {
>> :year => 2003
>> :month => 03
>> :day => 24
>> }
>> Time.local(time)
>>
>> (that wouldn't work but you get the idea)
>>
>
> Time.local(*time.values.reverse)
>

Pretty sure that'd only work with some hashes, and only if you had less
than a bucketful of entries?

Cheers,

--
Ross Bamford - rosco@roscopeco.remove.co.uk

Daniel Harple

1/8/2006 11:34:00 PM

0


On Jan 9, 2006, at 12:18 AM, Ross Bamford wrote:

> On Sun, 08 Jan 2006 23:00:42 -0000, Daniel Harple
> <dharple@generalconsumption.org> wrote:
>
> Pretty sure that'd only work with some hashes, and only if you had
> less than a bucketful of entries?
>
> Cheers,
>
> --
> Ross Bamford - rosco@roscopeco.remove.co.uk
>

Yes, my mistake. (too late to be thinking here...)

James's suggestion seems to be the best.

-- Daniel

Jonathan Leighton

1/9/2006 12:04:00 AM

0

On Mon, 2006-01-09 at 08:01 +0900, James Edward Gray II wrote:
> Well, Hashes are unordered by definition, but as long as we declare
> an order it's doable:
>
> >> time = {
> ?> :year => 2003,
> ?> :month => 03,
> ?> :day => 24
> >> }
> => {:month=>3, :year=>2003, :day=>24}
> >> Time.local(*time.values_at(:year, :month, :day))
> => Mon Mar 24 00:00:00 CST 2003

Cool. Thanks everyone. I didn't realise you could do *myvar when calling
a method as well as when defining them. I was basically looking for a
way to do the following (which I've managed to solve without use of a
hash):

class Time
UNITS = [ :year, :month, :day, :hour, :min, :sec, :usec ]

def to_precision(unit)
args = []
0.upto(UNITS.index(unit)) { |unit| args <<
method(UNITS[unit]).call }
Time.local(*args)
end
end

Is that a sensible way to do it?

Cheers

--
Jonathan Leighton
http://turnips... | http://jonathanlei... | http://digital-...

dblack

1/9/2006 1:27:00 AM

0

Jonathan Leighton

1/9/2006 5:25:00 PM

0

On Mon, 2006-01-09 at 10:26 +0900, dblack@wobblini.net wrote:
> > class Time
> > UNITS = [ :year, :month, :day, :hour, :min, :sec, :usec ]
> >
> > def to_precision(unit)
> > args = []
> > 0.upto(UNITS.index(unit)) { |unit| args <<
> > method(UNITS[unit]).call }
> > Time.local(*args)
> > end
> > end
> >
> > Is that a sensible way to do it?
>
> I would do:
>
> send(UNITS[unit])
>
> in preference to the method/call thing. Maybe:
>
> args = (0..UNITS.index(unit)).map { |unit| send(UNITS[unit]) }

Awesome, thanks. I did feel the method/call bit was slightly ugly.

Cheers

--
Jonathan Leighton
http://turnips... | http://jonathanlei... | http://digital-...