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---
type: reference, dev
stage: none
group: Development
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/product/ux/technical-writing/#assignments
---
# Ruby style guide
This is a GitLab-specific style guide for Ruby code. Everything documented in this page can be [reopened for discussion](https://about.gitlab.com/handbook/values/#disagree-commit-and-disagree).
We use [RuboCop](../rubocop_development_guide.md) to enforce Ruby style guide rules.
Where a RuboCop rule is absent, refer to the following style guides as general guidelines to write idiomatic Ruby:
- [Ruby Style Guide](https://github.com/rubocop/ruby-style-guide).
- [Rails Style Guide](https://github.com/rubocop/rails-style-guide).
- [RSpec Style Guide](https://github.com/rubocop/rspec-style-guide).
Generally, if a style is not covered by existing RuboCop rules or the above style guides, it shouldn't be a blocker.
Some styles we have decided [no one should not have a strong opinion on](#styles-we-have-no-opinion-on).
See also:
- [Guidelines for reusing abstractions](../reusing_abstractions.md).
- [Test-specific style guides and best practices](../testing_guide/index.md).
## Styles we have no rule for
These styles are not backed by a RuboCop rule.
For every style added to this section, link the discussion from the section's [version history note](../documentation/versions.md#add-a-version-history-item) to provide context and serve as a reference.
### Instance variable access using `attr_reader`
> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/52351) in GitLab 14.1.
Instance variables can be accessed in a variety of ways in a class:
```ruby
# public
class Foo
attr_reader :my_var
def initialize(my_var)
@my_var = my_var
end
def do_stuff
puts my_var
end
end
# private
class Foo
def initialize(my_var)
@my_var = my_var
end
private
attr_reader :my_var
def do_stuff
puts my_var
end
end
# direct
class Foo
def initialize(my_var)
@my_var = my_var
end
private
def do_stuff
puts @my_var
end
end
```
Public attributes should only be used if they are accessed outside of the class.
There is not a strong opinion on what strategy is used when attributes are only
accessed internally, as long as there is consistency in related code.
### Newlines style guide
In addition to the RuboCops `Layout/EmptyLinesAroundMethodBody` and `Cop/LineBreakAroundConditionalBlock` that enforce some newline styles, we have the following guidelines that are not backed by RuboCop.
#### Rule: separate code with newlines only to group together related logic
```ruby
# bad
def method
issue = Issue.new
issue.save
render json: issue
end
```
```ruby
# good
def method
issue = Issue.new
issue.save
render json: issue
end
```
#### Rule: newline before block
```ruby
# bad
def method
issue = Issue.new
if issue.save
render json: issue
end
end
```
```ruby
# good
def method
issue = Issue.new
if issue.save
render json: issue
end
end
```
##### Exception: no need for a newline when code block starts or ends right inside another code block
```ruby
# bad
def method
if issue
if issue.valid?
issue.save
end
end
end
```
```ruby
# good
def method
if issue
if issue.valid?
issue.save
end
end
end
```
## Styles we have no opinion on
If a RuboCop rule is proposed and we choose not to add it, we should document that decision in this guide so it is more discoverable and link the relevant discussion as a reference.
### Quoting string literals
Due to the sheer amount of work to rectify, we do not care whether string
literals are single or double-quoted.
Previous discussions include:
- <https://gitlab.com/gitlab-org/gitlab-foss/-/issues/44234>
- <https://gitlab.com/gitlab-org/gitlab-foss/-/issues/36076>
- <https://gitlab.com/gitlab-org/gitlab/-/issues/198046>
### Type safety
Now that we've upgraded to Ruby 3, we have more options available
to enforce [type safety](https://en.wikipedia.org/wiki/Type_safety).
Some of these options are supported as part of the Ruby syntax and do not require the use of specific type safety tools like [Sorbet](https://sorbet.org/) or [RBS](https://github.com/ruby/rbs). However, we might consider these tools in the future as well.
For more information, see [Type safety](https://gitlab.com/gitlab-org/gitlab/-/tree/master/ee/lib/remote_development#type-safety) in the `remote_development` domain README.
### Functional patterns
Although Ruby and especially Rails are primarily based on [object-oriented programming](https://en.wikipedia.org/wiki/object-oriented_programming) patterns, Ruby is a very flexible language and supports [functional programming](https://en.wikipedia.org/wiki/Functional_programming) patterns as well.
Functional programming patterns, especially in domain logic, can often result in more readable, maintainable, and bug-resistant code while still using idiomatic and familiar Ruby patterns.
However, functional programming patterns should be used carefully because some patterns would cause confusion and should be avoided even if they're directly supported by Ruby. The [`curry` method](https://www.rubydoc.info/stdlib/core/Method:curry) is a likely example.
For more information, see:
- [Functional patterns](https://gitlab.com/gitlab-org/gitlab/-/tree/master/ee/lib/remote_development#functional-patterns)
- [Railway-oriented programming and the `Result` class](https://gitlab.com/gitlab-org/gitlab/-/tree/master/ee/lib/remote_development#railway-oriented-programming-and-the-result-class)
|
