I Want to Return a Single Result Using .Find() with Ruby on Rails

I want to return a single result using .find() with Ruby on Rails

I am assuming you have a rental object, for which you show the form, I assume it is an instance variable @rental, furthermore I assume that inside your Rental class there is the following relation

class Rental

belongs_to :user


Then you could just write the following:

f.select :user_id, [[@rental.user.user_name, @rental.user.id]]

Hope this helps.

On a related but less important note: it is really weird to have a column called user_name for a user: I would call that column just name, since it is part of a user anyway.

ruby on rails I am trying to use find() to return a single result

You are passing :user_id to the find method, which is a symbol, not a user id.

You have to pass a number to find, then find will search for the record with that id.

Another problem, why are you calling collect on the result of find ? Find return only one row, not an array.

Here is how you should structure your code :

You should get the user variable into the controller, for instance :

@user = User.find(params[:id])

Beware, find throws an exception if the model is not found, as you saw, consider using find_by_id that returns nil if no model is found.

Then, you can use @user in your view.

If you want to display a select tag with only the user in it, do the following :

<%= f.select, :user_id, options_for_select([[@user.user_name, @user.id]]) %>

Check http://guides.rubyonrails.org/form_helpers.html for form helpers.

Checking if ActiveRecord find returns a result

find :all returns an empty array ([]) if no rows are returned, so you can just use it this way:

post = Post.find(:all, :conditions => { :url => params['url'] }, :limit => 1)

unless post.empty?
# do something...

By the way, if you do find :all you're going to get an array, not a single row. If you're trying to get just one Post, it would be cleaner to use the find_by helper or find :first or just first instead:

post = Post.find_by_url params['url']

# or

post = Post.first :conditions => { :url => params['url'] }

# then...

if post
# do something...

Rails return single record using AR find

rating = Rating.where(recommendation_id:1773452, rating_set:18, product_id:2086981).first

rating.label # returns "Fair"

ActiveRecord find and only return selected columns

In Rails 2

l = Location.find(:id => id, :select => "name, website, city", :limit => 1)


l = Location.find_by_sql(:conditions => ["SELECT name, website, city FROM locations WHERE id = ? LIMIT 1", id])

This reference doc gives you the entire list of options you can use with .find, including how to limit by number, id, or any other arbitrary column/constraint.

In Rails 3 w/ActiveRecord Query Interface

l = Location.where(["id = ?", id]).select("name, website, city").first

Ref: Active Record Query Interface

You can also swap the order of these chained calls, doing .select(...).where(...).first - all these calls do is construct the SQL query and then send it off.

Best way to find a single record using ActiveRecord 3 / Arel?

Rails 4 :

Foo.find_by( bar: 'a_value', wibble: 'a wibble value' )

How to always return a JSON array for single result in Ruby On Rails?

Try changing this

render json: Entry.find_by(user: current_user).to_json(include: :user)


render json: Entry.where(user: current_user).to_json(include: :user)

find_by returns an object, whereas where an ActiveRecord::Relation

Ruby find and return objects in an array based on an attribute

array_of_objects.select { |favor| favor.completed == false }

Will return all the objects that's completed is false.

You can also use find_all instead of select.

Rails method for only returning a single record and throwing an exception when multiple are returned

I'm not aware of a built in Active Record method that does what you ask but it wouldn't be hard to write your own. Something like:

class YourModel
def self.find_only_one_by_slug(slug)
results = YourModel.where(slug: slug)
if results.size > 1
raise "There should only be one return value."
return results.first

I haven't tested the above code so there will most certainly be errors but you get the idea. You could even take this a step farther and add a similar method to active record base that all of your models would have access to.

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