Best Practices

A guide for programming well.

General

Don't duplicate the functionality of a built-in library.
Don't swallow exceptions or "fail silently."
Don't write code that guesses at future functionality.
Exceptions should be exceptional.
Keep the code simple.

Object-Oriented Design

Avoid global variables.
Avoid long parameter lists.
Limit collaborators of an object (entities an object depends on).
Limit an object's dependencies (entities that depend on an object).
Prefer composition over inheritance.
Prefer small methods. One line is best.
Prefer small objects with a single, well-defined responsibility.
Tell, don't ask.

Ruby

Avoid optional parameters. Does the method do too much?
Avoid monkey-patching.
Prefer classes to modules when designing functionality that is shared by multiple models.
Prefer private when indicating scope. Use protected only with comparison methods like def ==(other), def <(other), and def >(other).

Rails

Don't change a migration after it has been merged into master if the desired change can be solved with another migration.
Validate the associated belongs_to object (user), not the database column (user_id).
Avoid exact version numbers in Gemfile except for non-framework gems.

Bundler

Use the project's Gemfile to specify the Ruby version
Use an exact version in the Gemfile for fragile gems, such as Rails.
Use a pessimistic version in the 'Gemfile' for gems that follow semantic versioning, such as rspec, factory_girl, and capybara.
Use versionless Gemfile declarations for gems that are safe to update often, such as pg, thin, and debugger.

Postgres

Avoid multicolumn indexes in Postgres. It combines multiple indexes efficiently. Optimize later with a compound index if needed.
Consider a partial index for queries on booleans.
Constrain most columns as NOT NULL.

Background Jobs

Store IDs, not ActiveRecord objects for cleaner serialization, then re-find the ActiveRecord object in the perform method.

Email

Use SendGrid or Amazon SES to deliver email in staging and production environments.
Use a tool like mail_view to look at each created or updated mailer view before merging.

Testing

Disable real HTTP requests to external services with WebMock.disable_net_connect!.
Test background jobs with a Delayed::Job matcher.
Use a Fake to stub requests to external services.
Use integration tests to execute the entire app.
Use non-SUT methods in expectations when possible.

Browsers

Don't support clients without Javascript.
Don't support IE6.

Objective-C

Prefer categories on Foundation classes to helper methods.
Prefer string constants to literals when providing keys or key paths to methods.