Limiting how often a user can post on a particular person's profile/wall in Rails - ruby-on-rails-3

Question

How can I limit a user to only to being able to post once or twice per day on a particular users's wall? I primarily want to do it in order to limit spam. My code for the wall, models, view, and controllers are below. I don't really know how to go about it as I'm new to rails but I know there is something time.now. I'm not exactly sure how to implement such a feature.
Class UsersController < ApplicationController
def show
#user = User.find(params[:id])
#first_name = #user.first_name
#last_name = #user.last_name
#wallpost = WallPost.new(params[:wall_post])
#showwallposts = #user.received_wallposts
end
def create
#wallpost = WallPost.create(params[:wall_post])
end
models
class WallPost < ActiveRecord::Base
attr_accessible :content, :receiver_id, :sender_id
belongs_to :receiver, :class_name => "User", :foreign_key => "receiver_id"
belongs_to :sender, :class_name => "User", :foreign_key => "sender_id"
end
class User < ActiveRecord::Base
has_many :sent_wallposts, :class_name => 'WallPost', :foreign_key => 'sender_id'
has_many :received_wallposts, :class_name =>'WallPost', :foreign_key => 'receiver_id'
in the view
<%= form_for(#wallpost, :url => {:action => 'create'}) do |f| %>
<%= f.hidden_field :receiver_id, :value => #user.id %>
<%= f.hidden_field :sender_id, :value => current_user.id %>
<%= f.text_area :content, :class => 'inputbox' %>
<%= f.submit 'Post', class: 'right btn' %>
<% end %>

Answer 1

You could create a custom validator which assures maximum DAILY_LIMIT posts have been created on that person's wall that day by that user:
class SpamValidator < ActiveModel::Validator
DAILY_LIMIT = 2
def validate(record)
if similar_posts_today(record).count >= DAILY_LIMIT
record.errors[:spam_limit] << 'Too many posts today!'
end
end
def similar_posts_today(record)
WallPost.where(receiver: record.receiver, sender: record.sender)
.where("DATE(created_at) = DATE(:now)", now: Time.now)
end
end
Then add that validation to your WallPost model:
validates_with SpamValidator
Then it will fail with a validation error when trying to create a wall post beyond the limit set in the constant. You need to handle this case in the create action in your controller. A simple (but not optimal in terms of user experience) way of handling this is:
def create
#wallpost = WallPost.new(params[:wall_post])
flash[:error] = "You've reached the daily posting limit on that wall." unless #wallpost.save
redirect_to user_path(#wallpost.receiver)
end
With that, it'll try to save the new wall post, if it is unable to, it'll set flash[:error] to the error message above. You'd need to show this on your show.html.erb page with <%= flash[:error] if flash[:error] %>.