How to correctly iterate through params

Question

How do I loop through params in my controller so that I can change their values?

This:

...
params[:contact][:relationships_attributes].each do |rel|
  rel[:contact_ids] = [rel[:contact_ids]]
end
...

Returns an Error of:

# can't convert Symbol into Integer

To provide more context I am using a single select box in place of a multi-select. So the controller is expecting an array but instead its getting a single value.

Here Are My Params:

{"utf8"=>"✓",
"_method"=>"put",
"authenticity_token"=>"8FrW59t9vzSep+jEGceMdE/b5q69i5hrEp08yZJJk0o=",
"contact"=>
  {"first_name"=>"John",
   "last_name"=>"Smith",
   "email_addresses_attributes"=>
    {"0"=>
      {"value"=>"[email protected]",
       "type"=>"Home",
       "_destroy"=>"false",
       "id"=>"4f4eea6dbe5a2ccf03000031"
      },
       "1"=>{"value"=>"[email protected]",
       "type"=>"Home",
       "_destroy"=>"false",
       "id"=>"4f4eea7dbe5a2ccf03000035"
      }
    },
  "phone_numbers_attributes"=>
    {"0"=>
      {"value"=>"555-334-5959",
       "type"=>"Home",
       "_destroy"=>"false",
       "id"=>"4f4eea64be5a2ccf0300002c"}
    },
  "addresses_attributes"=>
    {"0"=>
      {"type"=>"Home",
       "street_address"=>"12345 Any Rd",
       "city"=>"Anytown",
       "state"=>"CO",
       "country"=>"United States",
       "_destroy"=>"false",
       "id"=>"4f4eea64be5a2ccf0300002d"
      }
    },
  "relationships_attributes"=>
    {"1330623965418"=>
      {"contact_ids"=>"4f4e6696be5a2ca2a7000045",
       "title"=>"Wife",
       "_destroy"=>"false"
      }
    }
  },
  "commit"=>"Update Contact",
  "id"=>"4f4e6696be5a2ca2a7000045"
}

Solution

When you use each on a Hash like this:

params[:contact][:relationships_attributes].each do |rel|

the block argument, rel, is actually a two element Array with the key at position 0 and the value at position 1. Then your block tries to access the Array as though it was a Hash:

rel[:contact_ids]

and that explains your error message: you can't index an Array with a Symbol.

I think you want to do something more like this:

params['contact']['relationships_attributes'].each do |k, v|
  v['contact_ids'] = [ v['contact_ids'] ] unless v['contact_ids'].is_a?(Array)
end

That will give you a structure like this:

{
  :contact => {
    :relationships_attributes => {
      '1330623965418' => {
        :contact_ids => ['4f4e6696be5a2ca2a7000045']
        :title => 'Wife',
        :_destroy => 'false'
      }
      ...