Simple If

Ruby
1

Sorry for total newbie question here - in a method a particular id could
be passed as a variable or as part of the has - how what would be the
equivalent in ruby of the following Perl ?

my $id = (exists $hash->{id}) ? $hash->{id} : $_;

Assuming that in Ruby (well Rails). The ID will either be in
params[:id] or params[:country][:id] ?

So if params[:country][:id] contains the value I assign that otherwise I
assign params[:id]

Thanks for helping my small brain!

2

UPDATE:

This works

if params[:country][:id]
  id = params[:country][:id]
else
  id = params[:id]
end

But is there a oneliner equivalent?

3

On Wed, Aug 12, 2009 at 10:14 PM, Pete M.[email protected] wrote:

But is there a oneliner equivalent?
id = params[:country][:id] || params[:id]

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M++ V PS+ PE Y PGP t+ !5 X- R tv b++ DI+ D++ G- e++ h---- r+++ y++++**

http://anthony.mp

4

On Thu, Aug 13, 2009 at 10:18 AM, Anthony E.[email protected]
wrote:

But is there a oneliner equivalent?

id = params[:country][:id] || params[:id]
maybe safer but still not safe

id = params[:country] && params[:country][:id] || params[:id]
Cheers
Robert

5

2009/8/13 Robert D. [email protected]:

end

But is there a oneliner equivalent?

id = params[:country][:id] || params[:id]
maybe safer but still not safe

id = params[:country] && params[:country][:id] || params[:id]

I’d go for

id = (params[:country] || params)[:id]

But, this does not seem to be what OP needs. The Perl code was

my $id = (exists $hash->{id}) ? $hash->{id} : $_;

For me that translates to something like this:

def any_method(some_id_argument)
id = @hash[:id] || some_id_argument
…
end

Kind regards

robert

6

On Thu, Aug 13, 2009 at 5:00 PM, Robert
Klemme[email protected] wrote:

   id = params[:id]

id = (params[:country] || params)[:id]
that is nicely refactored

But, this does not seem to be what OP needs. Â The Perl code was

my $id = (exists $hash->{id}) ? $hash->{id} : $_;

For me that translates to something like this:

def any_method(some_id_argument)
 id = @hash[:id] || some_id_argument
not really, rather
id = @hash.fetch( :id, some_id_argument)
or the fancier
id = @hash.fetch( :id ){ some_id_argument }

just for completeness :wink: of the API. (This is interesting for some use
cases as e.g. throwing an exception in the block, thus

begin
@hash.fetch( :id )
rescue KeyNotFoundIBelieve
raise OMGWhatDidYouDo
end

becomes

@hash.fetch( :id ){ raise OMGWhatDidYouDo, “AGAIN” } :wink:

HTH
Robert

7

2009/8/13 Robert D. [email protected]:

 id = params[:country][:id]

def any_method(some_id_argument)
id = @hash[:id] || some_id_argument
not really, rather
id = @hash.fetch( :id, some_id_argument)

Good point! Even though I brought up Hash#fetch in a recent thread I
forgot it this time. Darn, my memory… :slight_smile:

end

becomes

@hash.fetch( :id ){ raise OMGWhatDidYouDo, “AGAIN” } :wink:

If that should be general behavior then I’d do

@hash = Hash.new { raise OMGWhatDidYouDo, “AGAIN” }

elsewhere and then just

id = @hash[:id]

It depends on whether you want the same behavior for all misses or just
some.

Cheers

robert

8

On Fri, Aug 14, 2009 at 9:02 AM, Robert
Klemme[email protected] wrote:

if params[:country][:id]
id = params[:country] && params[:country][:id] || params[:id]
For me that translates to something like this:
id = @hash.fetch( :id ){ some_id_argument }
becomes

It depends on whether you want the same behavior for all misses or just some.
Right, i.e. a hash implementing parameters will have varying behavior,
depending if the parameter is optional or not.
Maybe we want to add a messgae about the violating key, so elaborate
the useful Hash::new pattern for those who are not familiar with it:

@h = Hash::new{ |_, k| raise OMGDidYouForgetToSetThisKey, “violating key
#{k}” }

R.