app/controllers/crud_controller.rb
# Abstract controller providing basic CRUD actions.
#
# Some enhancements were made to ease extensibility.
# The current model entry is available in the view as an instance variable
# named after the +model_class+ or in the helper method +entry+.
# Several protected helper methods are there to be (optionally) overriden by
# subclasses.
# With the help of additional callbacks, it is possible to hook into the
# action procedures without overriding the entire method.
class CrudController < ListController
class_attribute :permitted_attrs
# Defines before and after callback hooks for create, update, save and
# destroy actions.
define_model_callbacks :create, :update, :save, :destroy
# Defines before callbacks for the render actions. A virtual callback
# unifiying render_new and render_edit, called render_form, is defined
# further down.
define_render_callbacks :show, :new, :edit
before_action :entry, only: %i[show new edit update destroy]
helper_method :entry, :full_entry_label
############## ACTIONS ############################################
# GET /entries/1
# GET /entries/1.json
#
# Show one entry of this model.
def show; end
# GET /entries/new
# GET /entries/new.json
#
# Display a form to create a new entry of this model.
def new
assign_attributes if params[model_identifier]
end
# GET /entries/1/edit
#
# Display a form to edit an exisiting entry of this model.
def edit; end
# POST /entries
# POST /entries.json
#
# Create a new entry of this model from the passed params.
# There are before and after create callbacks to hook into the action.
#
# To customize the response for certain formats, you may overwrite
# this action and call super with a block that gets the format and
# success parameters. Calling a format action (e.g. format.html)
# in the given block will take precedence over the one defined here.
#
# Specify a :location option if you wish to do a custom redirect.
def create(**options, &block)
model_class.transaction do
assign_attributes
created = with_callbacks(:create, :save) { entry.save }
respond(created,
**options.merge(status: :created, render_on_failure: :new),
&block)
raise ActiveRecord::Rollback unless created
end
end
# PUT /entries/1
# PUT /entries/1.json
#
# Update an existing entry of this model from the passed params.
# There are before and after update callbacks to hook into the action.
#
# To customize the response for certain formats, you may overwrite
# this action and call super with a block that gets the format and
# success parameters. Calling a format action (e.g. format.html)
# in the given block will take precedence over the one defined here.
#
# Specify a :location option if you wish to do a custom redirect.
def update(**options, &block)
model_class.transaction do
assign_attributes
updated = with_callbacks(:update, :save) { entry.save }
respond(updated,
**options.merge(status: :ok, render_on_failure: :edit),
&block)
raise ActiveRecord::Rollback unless updated
end
end
# DELETE /entries/1
# DELETE /entries/1.json
#
# Destroy an existing entry of this model.
# There are before and after destroy callbacks to hook into the action.
#
# To customize the response for certain formats, you may overwrite
# this action and call super with a block that gets format and
# success parameters. Calling a format action (e.g. format.html)
# in the given block will take precedence over the one defined here.
#
# Specify a :location option if you wish to do a custom redirect.
def destroy(**options, &block)
model_class.transaction do
destroyed = run_callbacks(:destroy) { entry.destroy }
respond(destroyed,
**options.merge(status: :no_content),
&block)
raise ActiveRecord::Rollback unless destroyed
end
end
private
############# CUSTOMIZABLE HELPER METHODS ##############################
# Main accessor method for the handled model entry.
def entry
model_ivar_get || model_ivar_set(params[:id] ? find_entry : build_entry)
end
# Creates a new model entry.
def build_entry
model_scope.new
end
# Sets an existing model entry from the given id.
def find_entry
model_scope.find(params[:id])
end
# Assigns the attributes from the params to the model entry.
def assign_attributes
entry.attributes = model_params
end
# The form params for this model.
def model_params
params.require(model_identifier).permit(permitted_attrs)
end
# Path of the index page to return to.
def index_path
polymorphic_path(path_args(model_class), returning: true)
end
# Path of the show page.
def show_path
path_args(entry)
end
def respond(success, **options)
respond_to do |format|
yield(format, success) if block_given?
if success
format.html { redirect_on_success(**options) }
format.json { render_success_json(options[:status]) }
else
format.html { render_or_redirect_on_failure(**options) }
format.json { render_failure_json }
end
end
end
# If the option :render_on_failure is given, render the corresponding
# template, otherwise redirect.
def render_or_redirect_on_failure(**options)
if options[:render_on_failure]
render options[:render_on_failure]
else
redirect_on_failure(**options)
end
end
# Perform a redirect after a successfull operation and set a flash notice.
def redirect_on_success(**options)
location = options[:location] ||
(entry.destroyed? ? index_path : show_path)
flash[:notice] ||= flash_message(:success)
redirect_to location
end
# Perform a redirect after a failed operation and set a flash alert.
def redirect_on_failure(**options)
location = options[:location] ||
request.env['HTTP_REFERER'].presence ||
index_path
flash[:alert] ||= error_messages.presence || flash_message(:failure)
redirect_to location
end
# Render the show json with the given status or :no_content
def render_success_json(status)
if status == :no_content
head :no_content
else
render :show, status: status, location: show_path
end
end
# Render a json with the errors.
def render_failure_json
render json: entry.errors, status: :unprocessable_entity
end
# Get an I18n flash message.
# Uses the key {controller_name}.{action_name}.flash.{state}
# or crud.{action_name}.flash.{state} as fallback.
def flash_message(state)
scope = "#{action_name}.flash.#{state}"
keys = [:"#{controller_name}.#{scope}_html",
:"#{controller_name}.#{scope}",
:"crud.#{scope}_html",
:"crud.#{scope}"]
I18n.t(keys.shift, model: full_entry_label, default: keys)
end
# A label for the current entry, including the model name.
def full_entry_label
# rubocop:disable Rails/OutputSafety
"#{models_label(plural: false)} <i>#{ERB::Util.h(entry)}</i>".html_safe
# rubocop:enable Rails/OutputSafety
end
# Html safe error messages of the current entry.
def error_messages
# rubocop:disable Rails/OutputSafety
escaped = entry.errors.full_messages.map { |m| ERB::Util.html_escape(m) }
escaped.join('<br/>').html_safe
# rubocop:enable Rails/OutputSafety
end
# Class methods for CrudActions.
class << self
# Convenience callback to apply a callback on both form actions
# (new and edit).
def before_render_form(*methods)
before_render_new(*methods)
before_render_edit(*methods)
end
end
end