Mongoid paper clip photo is removed when parent.update_attributes!(attr) called - ruby-on-rails

Question

I have 2 models
The User model embeds many pictures as follows
class User
include Mongoid::Document
field :user_name, type: String
embeds_many :pictures, cascade_callbacks: true
...
end
The Picture model is implemented as follows
class Picture
include Mongoid::Document
include Mongoid::Paperclip
field :description, type: String
has_mongoid_attached_file :photo,
default_url: '',
default_style: :thumb,
url: "/:attachment/:id/:style.:extension",
styles: {
original: ['2000x1200>', :jpg],
thumb: ['600x400#', :jpg]
},
convert_options: {
all: '-quality 90 -strip -background black -flatten +matte'
}
...
end
The problem is in the user_controller#update
def update
...
#user.update_attributes!(user_params)
...
end
def user_params
params.require(:user).permit(:user_name, pictures:[:id, :description])
end
I expected this #update to update the description of the picture with the id passed... and it does.
but the uploaded picture is removed after this update ?
how do i update the description of the uploaded photo without it getting removed after using #user.update_attributes!(user_params) ?

Answer 1

Not tested!
pictures_params = params[:user].delete(:pictures)
#user.pictures.where(:id.in => pictures_params.map(&:id)).each do |pic|
pic.set(:description, pictures_params.find{|p| p[:id] == pic.id}[:description])
end

Answer 2

I used the following code to solve the problem but i think there is a better approach for solving this issue
# get the user hash to update both pictures and user
user_params_hash = user_params
# remove the picture from the hash to separate the updating of pictures from users
picture_params_hash = user_params_hash.delete 'pictures'
# update each picture description to avoid removing the photo
unless picture_params_hash.nil?
picture_params_hash.each do |picture_hash|
picture = #user.pictures.find_or_create_by(id: picture_hash[:id])
picture.description = picture_hash[:description]
picture.save!
end
end
# update the user attributes only without touching the embedded pictures
#user.update_attributes!(user_params_hash)
end