Ruby on Rails：下拉菜单中元素的唯一性

Question

I'm very new to ROR, and I'm having a problem making the elements in my drop down menu be unique. The menu allows the user to select a Company from a database. At the moment, the menu is listing every Company in the database, because the database holds the same company many times, and I only want that one company to show up once.

<%= f.label :company_name %><br />
<%= f.select( :company_name, Company.all.map {|c| [c.company_name]} ) %>

I know this should be quite simple to fix, but I can't seem to find an answer. Hopefully someone can help.

Thanks in advance.

Answer 1

Rather than calling uniq! on a fetched array, i would rather use a scope to do that... In your model:

named_scope :unique_by_name, :select => 'DISTINCT name', :order => 'name ASC'

Then you can use:

Company.unique_by_name.map { |company| company.name }

Doing so has the advantage to select the unique companies as unique directly from your database backend, rather than expensively retrieving them all and filtering them afterwards with the uniq! method.

Answer 2

You could use:

Company.all.map {|c| c.company_name}.uniq!

But be careful with the id's of the companies and how you're going to use them.

Hope it helps!