ruby check if data exist in database

Question

Im new with ruby on rails and I'm again blocked on something really similar as the last time.. I have a User table, a Course table and a Mark table. I can create a Mark with a user_id, a course_id and a grade.

In my models i have :

/* Mark model */ class Mark < ActiveRecord::Base belongs_to :user belongs_to :course end /* Course model */ class Course < ActiveRecord::Base has_many :marks end /* User model */ class User < ActiveRecord::Base has_many :marks end

So what I want to do is when I created a new mark, with my form I want that my form disappear and display a button destroy ! Like this :

<% if @mark.course_ids.include?(@course.id) and @mark.user_ids.include?(user.id) # Button destroy <% else %> <%= form_for Mark.new do |f| %> <%= hidden_field_tag :course_id, @course.id %> <%= hidden_field_tag :user_id, user.id %> Grade: <%= number_field_tag :grade, nil, min: 0, max: 100 %> <%= f.submit %> <% end %> <% end %>

The goal is to avoid the form when the mark just be added previously.. But here obviously @mark.course_ids and @mark.user_ids doesn't exist !!

Thanks for you help !

"similar as the last time" – are you referring to another question? If so, provide a link, please. — Stefan
– Stefan, Commented Apr 12, 2017 at 12:44
@mark contains course_id and user_id. So you may write if @mark.course_id == @course.id && @mark.user_id == user.id — Ilya Lavrov
– Ilya Lavrov, Commented Apr 12, 2017 at 12:56
@Velantin Mark belongs to user and Mark belongs to course . it means Mark will always have only one course and user. right ? — Vishal
– Vishal, Commented Apr 12, 2017 at 12:58
My view will be a show on my course so example : course/1. I find the @mark by making a findall where course_id: params[:id] ! This is to get every @mark in my table link to this course. So @mark is a table and can't call method user_id or course_id without a .each ! — Valentin Ferey
– Valentin Ferey, Commented Apr 12, 2017 at 13:03

Ahmad Al-kheat · Accepted Answer · 2017-04-12 13:21:24Z

First, I suggest you rethink your tables, maybe take a look at the many-to-many relationship.

Regarding your question, you want to know if there exists a mark that belongs to a specific course for a specific user, so you would need something like this :

Mark.where(course_id: @course.id, user_id: current_user.id).any?

This will return true if such a record exists.

This could work but my User_id is not the current_user ! This is a id of every user in this course this need a .each method ...

Zain · Accepted Answer · 2017-04-13 13:47:16Z

A belongs_to association sets up a one-to-one connection with the other models. Rails then creates a singular utility method (among others) in your model.

For example, According to your model associations, a Mark belongs_to a Course and a User. Rails will create the following utility methods in your Mark model:

@mark.course @mark.user

So the statement:

@mark.course_ids.include?(@course.id) and @mark.user_ids.include?(user.id)

is incorrect. Those methods do not exist in the Mark model.

Try this:

Controller

@marks = Mark.where(course_id: params[:id])

This will get all the marks for that course so the mark will definitely have a course associated with it (there's no need to make that check in your view).

View

Render a form for each mark:

<% @marks.each do |mark| %> <% unless mark.user.exists? %> <%= form_for Mark.new do |f| %> <%= hidden_field_tag :course_id, @course.id %> <%= hidden_field_tag :user_id, user.id %> Grade: #{number_field_tag :grade, nil, min: 0, max: 100}#{f.submit} <% end %> <% end %> <% end %>

Thanks for you answer ! But If i want to use @mark.course for exemple, what shoul i have in my controller? Actually I have this @mark = Mark.where(course_id: params[:id]) but this is an array :/
@ValentinFerey .where will always return a collection of records. Also, a single course can have multiple marks so it makes sense that it returns an array of marks for the course. You have to loop through each one and display a form for it. Check my updated answer.
WoooW ! Thanks a lot !! Of course I new that was the only solution but I just didn't know about the "Unless" tag ! With this I can fix all my problems ! Thanks a lot ! I never heard about unless before ROR ...

Collectives™ on Stack Overflow

ruby check if data exist in database

2 Answers 2

1 Comment

3 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

3 Comments

Linked

Related