checking if params exists in rails

Question

This is what I'd like to do:

I have this piece of code:

customer = Customer.find(:first, :conditions => {:siteId => params[:siteId], :customerCode => params[:id]})

If :customerCode is null, I'd like to use :temporaryCode instead. But I don't know how. Thanks in advance.

you use params[:id] in customercode if params id is null then what would you use instead of params[:id] for temporarycode? — urjit on rails, Jun 04 '12 at 05:44
@xdazz: `params.has_key? :id` would be better since that is exactly what you mean. — mu is too short, Jun 04 '12 at 05:45
@muistooshort Won't `if (params[:id])` be enough in most situations? — xdazz, Jun 04 '12 at 05:47
@xdazz: There is a possibility that someone is preprocessing `params` so `nil` could be a valid value for `params[:id]`. I think it is best to say exactly what you mean rather than making assumptions. — mu is too short, Jun 04 '12 at 05:50
@muistooshort can you elaborate further about params.has_key? :id? I'm new to that concept. Thank you. If you can give me an example that would really be great. — Aldrin Dela Cruz, Jun 04 '12 at 06:04
[`Hash#has_key?`](http://ruby-doc.org/core-1.9.3/Hash.html#method-i-has_key-3F) returns `true` if the Hash has the key you're asking about and `false` otherwise. I don't think that's what you're looking for here though, you seem to want to use a different column in the database if `customercode` is NULL, you'd use `has_key?` to ask `params` if it contains a certain key. — mu is too short, Jun 04 '12 at 06:23
@xdazz: I think they want to use `:customerCode` if that column isn't NULL and `:temporaryCode` if `:customerCode` is NULL. — mu is too short, Jun 04 '12 at 06:25
@muistooshort yes, actually that's what i'm really looking for. I'm testing the answer you gave me right now — Aldrin Dela Cruz, Jun 04 '12 at 06:58

score 1 · Answer 1 · answered Jun 04 '12 at 07:04

1

customer   = Customer.find_by_siteid_and_customercode  params[:siteId], params[:id]
customer ||= Customer.find_by_siteid_and_temporarycode params[:siteId], params[:id]

making use of finders is most safer, cleaner

answered Jun 04 '12 at 07:04

Amol Pujari

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mu is too short · Answer 2 · 2012-06-04T15:42:57.193

0

I'm pretty sure you want to use COALESCE inside the database:

customer = Customer.where(:siteId => params[:siteId])
                   .where('coalesce(customercode, temporarycode) = ?', params[:id])
                   .first

The SQL COALESCE function returns the first of its arguments that isn't NULL. For example:

coalesce(column1, column2)

gives you column1 if column1 isn't NULL and column2 if column1 is NULL.

If you're using Rails2 then something like this should work:

Customer.find(:first, :conditions => [
    'siteid = ? and coalesce(customercode, temporarycode) = ?',
    params[:siteId], params[:id]
])

edited Jun 04 '12 at 15:42

answered Jun 04 '12 at 06:21

mu is too short

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@Sagiv: true but that's a pretty safe assumption unless stated otherwise. – mu is too short Jun 04 '12 at 07:11
the .where is not available in rails 2. So i tried this instead: – Aldrin Dela Cruz Jun 04 '12 at 08:47
@AldrinDelaCruz: I added a Rails2 option, you should indicate in your question that you're using Rails2 now that it is getting rather old. – mu is too short Jun 04 '12 at 15:43

checking if params exists in rails

2 Answers2