Check row exist or not in Ruby on Rails

Question

I am new to Ruby on Rails and I have basic knowledge of mysql. I am using MySQL db. My question is -- how to check if a row is exists or not in a table. I have tried this code but it's not going straight to the else block, not the if block:

@tasks = User.find_by("user_name = ? AND password = ?", params[:user_name], params[:password])
if @tasks
  redirect_to action: 'index', status: 302
else
  redirect_to action: 'detail', status: 302
end

In the future, if something doesn't work as expected, please explain ***in what way*** that it's not working, like if you're getting any error messages, or what the response is, even if it's not the right one. — , Apr 08 '14 at 05:23
#cupcake--I am not getting any error msg. It is going directly into else condition — Sariban D'Cl, Apr 08 '14 at 05:25
`User.find_by_user_name_and_password(params[:user_name], params[:password])` This will work. But use `where` as suggested by @Cupcake. — Vamsi Krishna, Apr 08 '14 at 05:34
@D'Scolz what version of Ruby and Ruby on Rails are you using? — , Apr 08 '14 at 05:37
Try running your find_by statement in ruby console and check if there are any errors. — Vamsi Krishna, Apr 08 '14 at 05:51
ya. got it. @Cupcake edited my question. Now it is working properly. — Sariban D'Cl, Apr 08 '14 at 05:54
`@tasks = User.find_by("user_name = ? AND password = ?", params[:user_name], params[:password])` — Sariban D'Cl, Apr 08 '14 at 05:56
@Cupcake OP meant the removal of string interpolation in the `find_by` — Vamsi Krishna, Apr 08 '14 at 05:58
@D'Scolz by the way, it's a convention in Ruby to use 2-space indent, not 4-space. — , Apr 08 '14 at 06:10

score 2 · Accepted Answer · edited May 23 '17 at 12:07

2

If you want to find if a user with the given name and password exists using Ruby on Rails, then you can do this:

User.where(user_name: params[:user_name], password: params[:password]).exists?

See the RailsGuides: Existence of Objects.

The Cause of the Original Problem?

So this it the code that the original poster originally submitted:

User.find_by("user_name = ? AND password = ?", "#{params[:user_name]}", "#{params[:password]}")

I removed the string interpolation because it was unnecessary

User.find_by("user_name = ? AND password = ?", params[:user_name], params[:password])

and apparently that fixed the problem. I'm not sure why it would make a difference though, the interpolated string should be the same value as the values in the params dictionary.

edited May 23 '17 at 12:07

Community

1
1

answered Apr 08 '14 at 05:21

thanks it is working.. But whatever i have written is it wrong? – Sariban D'Cl Apr 08 '14 at 05:29
@D'Scolz I can't actually tell, what you had originally looks like it should work too. – Apr 08 '14 at 05:36
@D'Scolz there is no `find_by` in rails. – PythonDev Apr 08 '14 at 05:36
1

@akshay actually, [there is](http://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find_by). – Apr 08 '14 at 05:37
@Cupcake please help me on [Twitter-bootstrap-rails](http://stackoverflow.com/questions/22939854/twitter-bootstrap-in-ruby-on-rails) – Sariban D'Cl Apr 09 '14 at 04:11

score 2 · Answer 2 · answered Apr 08 '14 at 05:40

You can use any of these solutions depending on your requirement.

Sol-1:

User.where(user_name: params[:user_name], password: params[:password]).exists?

Sol-2:

User.find_by_user_name_and_password(params[:user_name], params[:password])

where returns an ActiveRecord::Relation (not an array, even though it behaves much like one), which is a collection of model objects. If nothing matches the conditions, it simply returns an empty relation.
find (and its related dynamic find_by_columnname methods) returns a single model object, or possibly a collection of model objects in an Array (not a Relation). If nothing is found, an ActiveRecord::RecordNotFound exception is raised.

So yes, if you only want and expect a single object, using find is easier, as otherwise you must call Model.where.first.

that means ... suppose i have 2 rows in table and both row have same data. in this case if i use **where** then i will get both the values — Sariban D'Cl, Apr 08 '14 at 05:43
Accept one of the answers which you felt helped you most. That would help other users. — Vamsi Krishna, Apr 08 '14 at 05:52

score 1 · Answer 3 · answered Apr 08 '14 at 05:35

1

you can try it as well..

User.find_by_user_name_and_password(params[:user_name], params[:password])

answered Apr 08 '14 at 05:35

PythonDev

4,287
6
32
39

Check row exist or not in Ruby on Rails

3 Answers3

The Cause of the Original Problem?