Group.find results in "Coudn't find Group with 'id'" - ruby-on-rails

Question

Let me say something to begin with - I am very new to ruby on rails as a lot of users here are. So don't throw stones at me, please :)
I am trying to create an API application on Ruby for my android application. Here what I have a problem with:
user.rb Model
class User < ApplicationRecord
belongs_to :group
has_many :tasks
has_secure_password
end
And here is group.rb Model:
class Group < ApplicationRecord
has_many :users, dependent: :destroy
end
And UserController.rb
class UsersController < ApplicationController
def new
#user = User.new
end
def create
#group = Group.find(params.require(:user).permit(:group))
#user = User.new(user_params)
#group.users.create(#user)
#group.users.save
# #user.save!
render json: #user
end
private
def user_params
params.require(:user).permit(:name, :email, :password)
end
end
where I want to create a new user.
I've already tried to create user with #user.create(user_params) but it says, that group doesn't exist, so now I am trying to do that via #group.users.create but exception ActiveRecord::RecordNotFound in UsersController#create keeps coming up, saying that it couldn't find Group with id={"id"=>1020};
The last thing I have to show is JSON that i send:
{
"group": {
"id":1020
},
"user": {
"name": "volkeee",
"email": "test#gmail.com",
"password": "123",
"repeat_password": "123"
}
}

Answer 1

Firstly create a new private method for group params like
def group_params
params.require(:group).permit(:id)
end
replace
#group = Group.find(params.require(:user).permit(:group))
with
#group_params = group_params
#group = Group.find(#group_params[:id])
I'm not in front of a PC so cant actually test. But this should work. Let me know if this doesn't.
A better approach
Replace
#user = User.new(user_params)
#group.users.create(#user)
#group.users.save
with
#user = #group.users.new(user_params)
#user.save
This is a much cleaner and rails way

Answer 2

Change your create method like below
def create
#group = Group.find_or_create_by(params[:group][:id]) do | group |
group.assign_attributes(group_params)
end
#user = #group.users.create(user_params)
render json: #user
end
create private method
def group_params
params.require(:group).permit(:id, :name, :has_subgroups, :created_at, :updated_at)
end
NOTE: user table should have group_id column