rbs is a header lang created in 2020.
| #1760on PLDB | 3Years Old |
We defined a new language called RBS for type signatures for Ruby 3. The signatures are written in .rbs files which is different from Ruby code. You can consider the .rbs files are similar to .d.ts files in TypeScript or .h files in C/C++/ObjC. The benefit of having different files is it doesn't require changing Ruby code to start type checking. You can opt-in type checking safely without changing any part of your workflow.
# sig/merchant.rbs
class Merchant
attr_reader token: String
attr_reader name: String
attr_reader employees: Array[Employee]
def initialize(token: String, name: String) -> void
def each_employee: () { (Employee) -> void } -> void
| () -> Enumerator[Employee, void]
end