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
end
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...
end
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...
end
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)
...or...
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)
to
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."
else
return results.first
end
end
end
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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