Why User.count inside this block is always zero? - ruby-on-rails

Question

Only the first created user can be an admin.
I was expecting to achieve that with user.admin = User.count == 0 ? true : false inside the self.from_omniauth(auth) method, but for some reason, it doesn't matter how many users I have, admin is always set to true.
To be sure there are no users:
from rails console
User.destroy_all
User.count
=> 0
user.rb
def self.from_omniauth(auth)
where(provider: auth.provider, uid: auth.uid).first_or_create do |user|
user.email = auth.info.email
user.password = Devise.friendly_token[0,20]
user.email = auth.info.email
user.image = auth.info.image
user.name = auth.info.name
user.nickname = auth.info.nickname
user.admin = User.administrator?
end
end
def self.administrator?
count == 0
end
schema.rb
create_table "users", force: true do |t|
...
t.boolean "admin", default: false
end
Thanks!
Now it's working in the expected way, but the initial question is still unanswered.
Even when I don't really like this solution, at least is working now.
Here I'm creating this user_qty variable outside the block.
def self.from_omniauth(auth)
user_qty = User.count
where(provider: auth.provider, uid: auth.uid).first_or_create do |user|
user.password = Devise.friendly_token[0,20]
user.email = auth.info.email
user.image = auth.info.image
user.name = auth.info.name
user.nickname = auth.info.nickname
user.admin = user_qty == 0
end
end

Answer 1

The code inside of the first_or_create block executes within the current scope. In ActiveRecord::Relation, the first_or_create method calls the create method which uses scoping:
def create(*args, &block)
scoping { #klass.create(*args, &block) }
end
And the scoping method says to run within the current_scope.
A call to User.count within this block is like calling:
User.where(provider: auth.provider, uid: auth.uid).count
If you debug with:
where(provider: auth.provider, uid: auth.uid).first_or_create do |user|
puts "current_scope: #{current_scope}"
You should see something like:
current_scope: SELECT "users".* FROM "users" WHERE "users"."provider" = '<value1>' AND "users"."uid" = '<value2>'
If you wanted to ask for the full count of all users within the first_or_create block you can do something like:
where(provider: auth.provider, uid: auth.uid).first_or_create do |user|
...
user.admin = User.unscoped.count == 0 ? true : false