How to combine multiple variables in Rails?

Question

I have Sportists with multiple disciplines and each discipline has one record. I'd like to display the record and in db they are saved as m100rec, m200rec and so on. Is there a way I could display them like so:

@discipline + "rec" ? I have saved @discipline in my Controller as an instance variable that contains the session value and that session has the discipline name saved in it.

EDIT

The view as it goes:

<% @sportists.each do |s| %>
 <%= s.m100rec %>
<% end %>

and since there are many disciplines which are all named by the same convention of 'discipline' + 'rec' I would like to make the code more readable and DRY and use just <%= s.discipline+'rec' %> somehow.

You can display it just like you tried, with: `@discipline + 'rec'`. — Marek Lipka, May 07 '14 at 11:24
@MarekLipka then I get this error: `ActionView::Template::Error (/path/to/view.html.erb:137: syntax error, unexpected tIVAR, expecting '(' ...t_buffer.append=( s.@discipline + 'rec' );@output_buffer.saf...` — Xeen, May 07 '14 at 11:38
Just give an example, what do you have and what do you want. — jbmyid, May 07 '14 at 11:43
@Xeen syntax error, it means you must have messed something up. I guess pasting `view.html.erb` content will help me to resolve this issue. — Marek Lipka, May 07 '14 at 11:43
@Xeen Why you are doing `s.@discipline`? What is `s`? Post the full `code` — Pavan, May 07 '14 at 11:52
@Xeen `s.@discipline` call is illegal in Ruby. Did you learn any of Ruby basics? — Marek Lipka, May 07 '14 at 11:53
It should probably be simply `<%= @discipline + 'rec' %>`, as according to OP `@discipline` is controller's instance variable. But I strongly advice learning Ruby basics. — Marek Lipka, May 07 '14 at 11:56
@Xeen What is the `field name` of the record that has `m100rec` value? — Pavan, May 07 '14 at 12:04

DaveMongoose · Accepted Answer · 2014-05-07T16:26:14.967

You can use:

<% @sportists.each do |s| %>
  <%= s.send("#{@discipline}rec") %>
<% end %>

Or

<% @sportists.each do |s| %>
  <%= s.attributes["#{@discipline}rec"] %>
<% end %>

The first will work if m100rec is a field, method or association.
The second will only work if m100rec is a field, but I think it's clearer what the code is doing.

A better way to structure the relation between Sportists and discipline records might be with a join table?

class Sportist < ActiveRecord::Base
  has_many :sportist_disciplines
  has_many :disciplines, :through => :sportist_disciplines
  ...
end

class SportistDiscipline < ActiveRecord::Base
  belongs_to :sportist
  belongs_to :discipline
  ...
end

class Discipline < ActiveRecord::Base
  has_many :sportist_disciplines
  has_many :sportists, :through => :sportist_disciplines
  ...
end

You could then have a field for record in the sportist_disciplines table, and look it up with -

In the controller:

@sportists = Sportist.includes(:sportist_disciplines).where( ... )
@discipline = Discipline.where( ... ).first

In the view:

 <% @sportists.each do |s| %>
   <%= s.sportist_disciplines.where(:discipline => @discipline).record %>
 <% end %>

N.B: This is only a suggestion for the 'rails-y' way to do this - it might not be suitable depending on the rest of the application and/or the source of the data.

`send` accepts a string, you can remove the `.to_sym` – Uri Agassi May 07 '14 at 16:06 — Uri Agassi, May 07 '14 at 16:06
@UriAgassi Good point! Edited. – DaveMongoose May 07 '14 at 16:27 — DaveMongoose, May 07 '14 at 16:27

score 0 · Answer 2 · answered May 07 '14 at 11:06

0

@discipline.map{|e| e + "rec"}

I think you are looking for something like this.

answered May 07 '14 at 11:06

jbmyid

1,985
19
22

That gives me `ActionView::Template::Error (undefined method 'map' for "m100":String):` – Xeen May 07 '14 at 11:18
If you have only one discipline then you can just write `@discipline + "rec"` – jbmyid May 07 '14 at 11:41

How to combine multiple variables in Rails?

2 Answers2