How to drop columns using Rails migration
remove_column :table_name, :column_name For instance: remove_column :users, :hobby would remove the hobby Column from the users table.
ruby-on-rails
How to “pretty” format JSON output in Ruby on Rails
Use the pretty_generate() function, built into later versions of JSON. For example: require ‘json’ my_object = { :array => [1, 2, 3, { :sample => “hash”} ], :foo => “bar” } puts JSON.pretty_generate(my_object) Which gets you: { “array”: [ 1, 2, 3, { “sample”: “hash” } ], “foo”: “bar” }
How to get a random number in Ruby
Use rand(range) From Ruby Random Numbers: If you needed a random integer to simulate a roll of a six-sided die, you’d use: 1 + rand(6). A roll in craps could be simulated with 2 + rand(6) + rand(6). Finally, if you just need a random float, just call rand with no arguments. As Marc-André Lafortune … Read more
Can’t find the ‘libpq-fe.h header when trying to install pg gem
It looks like in Ubuntu that header is part of the libpq-dev package (at least in the following Ubuntu versions: 11.04 (Natty Narwhal), 10.04 (Lucid Lynx), 11.10 (Oneiric Ocelot), 12.04 (Precise Pangolin), 14.04 (Trusty Tahr) and 18.04 (Bionic Beaver)): … /usr/include/postgresql/libpq-fe.h … So try installing libpq-dev or its equivalent for your OS: For Ubuntu/Debian systems: … Read more
How to rollback a specific migration?
rake db:rollback STEP=1 Is a way to do this, if the migration you want to rollback is the last one applied. You can substitute 1 for however many migrations you want to go back. For example: rake db:rollback STEP=5 Will also rollback all the migration that happened later (4, 3, 2 and also 1). To … Read more
Understanding the Rails Authenticity Token
What happens When the user views a form to create, update, or destroy a resource, the Rails app creates a random authenticity_token, stores this token in the session, and places it in a hidden field in the form. When the user submits the form, Rails looks for the authenticity_token, compares it to the one stored … Read more
Getting error: Peer authentication failed for user “postgres”, when trying to get pgsql working with rails
The problem is still your pg_hba.conf file*. This line: local all postgres peer Should be: local all postgres md5 After altering this file, don’t forget to restart your PostgreSQL server. If you’re on Linux, that would be sudo service postgresql restart. Locating hba.conf Note that the location of this file isn’t very consistent. You can … Read more
How do I get the current absolute URL in Ruby on Rails?
For Rails 3.2 or Rails 4+ You should use request.original_url to get the current URL. Source code on current repo found here. This method is documented at original_url method, but if you’re curious, the implementation is: def original_url base_url + original_fullpath end For Rails 3: You can write “#{request.protocol}#{request.host_with_port}#{request.fullpath}”, since request.url is now deprecated. For … Read more
Why do people use Heroku when AWS is present? What distinguishes Heroku from AWS? [closed]
First things first, AWS and Heroku are different things. AWS offer Infrastructure as a Service (IaaS) whereas Heroku offer a Platform as a Service (PaaS). What’s the difference? Very approximately, IaaS gives you components you need in order to build things on top of it; PaaS gives you an environment where you just push code … Read more
How to understand nil vs. empty vs. blank in Ruby
.nil? can be used on any object and is true if the object is nil. .empty? can be used on strings, arrays and hashes and returns true if: String length == 0 Array length == 0 Hash length == 0 Running .empty? on something that is nil will throw a NoMethodError. That is where .blank? … Read more