Trying to implement an create if not exists else update record in Active Record.
Currently using:
@student = Student.where(:user_id => current_user.id).first
if @student
Student.destroy_all(:user_id => current_user.id)
end
Student = Student.new(:user_id => current_user.id, :department => 1
)
Student.save!
What would be the correct way of updating the record if it exists or else create it?
In Rails 4
Student.
find_or_initialize_by(:user_id => current_user.id).
update_attributes!(:department => 1)
find_or_initialize_by + update_attributes! will do the trick
update_attributes! is a boolean and not the actual record. You can use Student.find_or_initialize_by(...).tap { |e| e.update!(...) }
User.where(email: email).find_or_initialize_by(password: password) would give you an error of columns users.password does not exist (assuming you're sensible and not storing plain passwords in the database).
.update_attributes to .update. It's the idiomatic way of doing it and the source code reveal it's the same as .update_attributes! (it will simply assign the attributes and call .save ... check apidock.com/rails/ActiveRecord/Persistence/update and apidock.com/rails/v3.2.3/ActiveRecord/Persistence/…).
find_or_initialize_by may not trigger any validationYou may be looking for first_or_create or something similar:
http://guides.rubyonrails.org/v3.2.17/active_record_querying.html#first_or_create
update call onto it. See my answer on this page.
first_or_initialize in exactly the same way as first_or_create; but you must call save or update on the result for it to be persisted.
.first_or_create(user_id: current_user.id, department: 1).update(department: 1)::first_or_create (available since v3.2.1) does what it says on the box.
Model.where(find: 'find_value').
first_or_create(create: 'create_value')
# If a record with {find: 'find_value'} already exists:
before #=> #<Model id: 1, find: "find_value", create: nil>
after #=> #<Model id: 1, find: "find_value", create: nil>
# Otherwise:
before #=> nil
after #=> #<Model id: 2, find: "find_value", create: "create_value">
If you also want it to update an already-existing record, try:
Model.where(find: 'find_value').
first_or_create(create: 'create_value').
update(update: 'update_value')
# If one already exists:
before #=> #<Model id: 1, find: "find_value", create: nil, update: nil>
after #=> #<Model id: 1, find: "find_value", create: nil, update: "update_value">
# If it already matches, no UPDATE statement will be run:
before #=> #<Model id: 1, find: "find_value", create: nil, update: "update_value">
after #=> #<Model id: 1, find: "find_value", create: nil, update: "update_value">
# Otherwise:
before #=> nil
after #=> #<Model id: 2, find: "find_value", create: 'create_value', update: "update_value">
EDIT 2016-03-08: As per Doug's comment, if your validations fail between the #create and #update calls, or you want to minimise database calls, you can use ::first_or_initialize instead, to avoid persisting the record on the first call. However, you must make sure you call #save or #update afterwards in order to persist the record (and I'm not sure if #update works on records that haven't been persisted yet):
Model.validates :update, presence: true # The create call would fail this
Model.where(find: 'find_value').
first_or_initialize(create: 'create_value'). # doesn't call validations
update(update: 'update_value')
(NB. There is a method called #create_or_update, but don't be fooled by any documentation you may find on Google; that's just a private method used by #save.)
@student = Student.where(user_id: current_user.id).first
@student ||= Student.new(user_id: current_user.id)
@student.department_id = 1
@student.save
This is prettier if you have an association between a user and a student. Something along the lines of
@student = current_user.student || current_user.build_student
@student.department_id = 1
@student.save
EDIT:
You can also use http://guides.rubyonrails.org/active_record_querying.html#first_or_create as answered by sevenseacat but you still have to deal with different scenarios like update a student's department id.
UPDATE:
You can use find_or_create_by
@student = Student.find_or_create_by(user_id: current_user.id) do |student|
student.department_id = 1
end
In Rails 5
Student.
find_or_initialize_by(:user_id => current_user.id).
update(:department => 1)
(with all credit taken from @Zorayr answer).
Unfortunately I think the cleanest way to do this is:
Student.where(user_id: id).first_or_create(age: 16).update_attribute(:age, 16)
It's find_or_create_by not first_or_create.
Ex:
Client.find_or_create_by(first_name: 'Andy')
Model.where(find: 'find_value').first_or_create(create: 'create_value') is equivalent to Model.find_or_create_by(find: 'find_value') { |r| r.create = 'create_value' }.