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Custom Date Formats in Rails

Quick guide on printing pretty dates in Rails

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• Dynamic Dispatch
• Dynamic Method
• Ghost Methods
• Dynamic Proxies
• Blank Slate
• Kernel Method
• Flattening the Scope (aka Nested Lexical Scopes)
• Context Probe
• Class Eval (not really a 'spell' more just a demonstration of its usage)
• Class Macros

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class ActiveRecord::Base
  
  def self.import!(record_list)
    raise ArgumentError "record_list not an Array of Hashes" unless record_list.is_a?(Array) && record_list.all? {|rec| rec.is_a? Hash }
    return record_list if record_list.empty?

    (1..record_list.count).step(1000).each do |start|
      key_list, value_list = convert_record_list(record_list[start-1..start+999])
      sql = "INSERT INTO #{self.table_name} (#{key_list.join(", ")}) VALUES #{value_list.map {|rec| "(#{rec.join(", ")})" }.join(" ,")}"
      self.connection.insert_sql(sql)

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In this article, I'll walk through a basic Rails (3.2.x) setup for creating a nested resource for two models. Nested resources work well when you want to build out URL structure between two related models, and still maintain a RESTful convention. This code assumes you are running RVM to manage Ruby/Gem versions, and Git for version control.

Creating a new Rails project

$ mkdir family # create rvm gemset 
$ echo "rvm use --create ruby-1.9.2@family" > family/.rvmrc 
$ cd family # install rails 
$ gem install rails # create new rails project 
$ rails new . # version control 

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require 'file_size_validator'
class Song < ActiveRecord::Base
  mount_uploader :attachment, AttachmentUploader

  validates :attachment, :presence => true, 
  			:file_size => {:maximum => 2.megabytes.to_i}
end

when I submit form without file or empty form it gives error :