Paper Clip Gem

Paper Clip Gem - Review

https://github.com/thoughtbot/paperclip


Paperclip is a gem used for attaching to Rails applications.

Show View
<%= image_tag @user.user_photo.url %>
<%= image_tag @user.user_photo.url(:medium) %>
<%= image_tag @user.user_photo.url(:thumb) %>

Important Finds

:thumb => "200x200#"
The # signifies that this image is going to be saved as as a square on the inside of the photo. This is very useful for user profile pictures.

:medium => "300>x300"
This ensures that the image will have a a width greater than 300 px. 

Profile Pictures

User has_many UserPhotos

- I started by saving a bolean field on the UserPhoto to check if there is a default photo.
- I later found out that it is better to save a link on the user model



How to Link to AWS Account

- It is a a bad idea to save images to the project. Amazon Web Server and Heroku work well together in order to save files at a cheap fast cost.

https://devcenter.heroku.com/articles/paperclip-s3

Class Instance Variables

Use Class instance Variables

We all know that class variables such as @@ are dangerous to use due to their leaky inheritance.


<script src="https://gist.github.com/surgentt/9464842.js"></script>class Presentaion < Document


WHAT IS GOING ON HERE

 The class << self syntax opens up a classes singleton class.
  This allows you to specialize the behavior of methods called on that specific object.

http://stackoverflow.com/questions/2505067/class-self-idiom-in-ruby

Object
    ^
     |
  <Singleton Class>
    ^
    |
Instance

Singleton Method is a method that is defined for exactly one object instance.


The <Singleton Class> is only invoked when it is filled with something.

  - An example of this is a method on an instance variable.

hand_built_stub_printer = Object.new def hand_built_stub_printer.avaiable? true end