Rails undefined method for array

Question

In my controller I am trying to run a query to get all of the id's not referenced in another table like so:

@vlan_numbers = ActiveRecord::Base.connection.execute("SELECT pop_vlans.id, vlan_number FROM pop_vlans WHERE pop_vlans.id NOT IN (SELECT logical_interfaces.vlan_id FROM logical_interfaces) AND pop_id != " + @pop_id.to_s)

Then in my view I am trying to use collection_select to show these in a dropdown menu:

but the error I get is undefined method 'vlan_number' for [2, "2"]:Array where those values are just the first row of results from the query.

This is a diagram of the two tables involved:

logical_interfaces | pop_vlans
-------------------|-----------
     vlan_id-------|----->id
       ....        |  vlan_number

and the relationships in the models are:

pop_vlan.rb

belongs_to :logical_interface

logical_interface.rb

# no relationship defined

Update

This is how the form is generated:

<%= form_tag :controller => "circuit", :action => "update" %>
    # other inputs
    <%= select_tag options_for_select(@vlan_numbers) %>
    # other inputs
 </form>

j03w · Accepted Answer · 2013-08-14 09:38:43Z

4

You can use select with options_for_select(@vlan_numbers) instead of collection_select

results from ActiveRecord::Base.connection.execute doesn't get loaded into a model

Instead you could try YourModelName.find_by_sql(...) If you want to play with your model

UPDATE Assuming the name of your attribute you want this select_tag to populate is vlan_id so:

<%= form_tag :controller => "circuit", :action => "update" %>
  # other inputs
  <%= select_tag 'vlan_id', options_for_select(@vlan_numbers) %>
  # other inputs
</form>

edited Aug 14, 2013 at 9:38

answered Aug 14, 2013 at 8:53

j03w

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7 Comments

martincarlin87 Over a year ago

thanks but using <%= select options_for_select(@vlan_numbers) %> gives the following error message - wrong number of arguments (1 for 3)

j03w Over a year ago

or select_tag may be… depends on how you're building your form if you are using form_for then f.select :vlan_id, options_for_select(@vlan_numbers) given that f is the instance of your form builder

martincarlin87 Over a year ago

do you mean <%= select_tag options_for_select(@vlan_numbers) %>? Using that, my select menu isn't populated with any options.

j03w Over a year ago

can you provide us some snippets on how you are generating your form?

martincarlin87 Over a year ago

@jo3w, I've updated the question, each input is just manually inserted into the view via an appropriate helper function such as text_field or check_box

|

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

ActiveRecord::Base.connection.execute returns Mysql2::Result not array of object as Arel/AR query does.

So it returns array of arrays containing pop_vlans.id, vlan_number. So have to use first or last in your collection_select instead of something.vlan_number

So you have to use `options_for_select` instead of `collection_select` like:

options_for_select(@vlan_numbers.collect{|v| v.first})

edited Jun 20, 2020 at 9:12

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answered Aug 14, 2013 at 8:50

Muntasim

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4 Comments

martincarlin87 Over a year ago

thanks but I'm not quite sure what you mean, do you have an example?

Muntasim Over a year ago

sample output of

@vlan_numbers = ActiveRecord::Base.connection.execute("SELECT pop_vlans.id, vlan_number FROM pop_vlans WHERE pop_vlans.id NOT IN (SELECT logical_interfaces.vlan_id FROM logical_interfaces) AND pop_id != " + @pop_id.to_s)

could be [[1,3], [2,3], [4,5], [3,1]]. so if you use [[1,3], [2,3], [4,5], [3,1]] in collection_select you have to operate on array so you should not find vlan_number in array

martincarlin87 Over a year ago

I think I know what you mean now, so, next question would be, how to get the last member of each array? e.g. using your example, 3,3,5,1 but bearing in mind I would need the first member of each array to act as the value of the select.

j03w Over a year ago

@martincarlin87 see the api api.rubyonrails.org/classes/ActionView/Helpers/…

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Rails undefined method for array

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So you have to use `options_for_select` instead of `collection_select` like:

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So you have to use options_for_select instead of collection_select like:

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So you have to use `options_for_select` instead of `collection_select` like: