Feature #16460
Updated by harrisonb (Hazel Bachrach) over 4 years ago
Hello! This is my first time filing an issue and I was unable to find anything similar. I apologize if one already exists.
In other languages (such as JavaScript, Swift, and Crystal), it is possible to have two names for a given keyword argument: one that is used in method invocation, and one used in the method definition. Here is an example from Crystal (which has syntax very similar to Ruby):
```crystal
def increment(value, by amount)
value + amount
end
increment(value: 5, by: 10)
```
This helps create more readable method invocations and definitions. It would be especially helpful in Ruby as the language lacks a destructuring syntax for hashes/keyword args. This is unlike JavaScript, where you can do something like:
```javascript
const { nameOfOneProperty: newNameForTheProperty, nameOfAnotherProperty: newNameForTheOtherProperty } = foo;
```
where `foo` is a JavaScript Object that has the properties `nameOfOneProperty` or `nameOfAnotherProperty` (If it did not have either of them, the corresponding identifiers (newNameForTheProperty and newNameForTheOtherProperty would be initialized to undefined).
I'm thinking that such a change would pair nicely with the new 3.0 keyword argument changes.
Others have A suggested that this could also syntax might be helpful if the keyword params collide with reserved keywords in Ruby, e.g.:
```ruby
def reserve_appointment(when:)
Appointment.create(time: when) #=> SyntaxError: unexpected `when', expecting `end'
end
```
Currently, one must use `local_variable_get` to get around this issue, e.g.:
```ruby
def reserve_appointment(when:)
time = local_variable_get(:when)
Appointment.create(time: time)
end
```
---
## Syntax options:
1. No arrow syntax (original proposal)
```ruby
def name(external_name internal_name: default_value) internal_name:)
# ...
end
# Example
def move(from source: 'src/', to destination: 'dist/', at time:)
# ...
end
```
1. Infix arrow syntax
```ruby
def name(external_name => internal_name: default_value)
# ...
end
# Example
def move(from => source: 'src/', to => destination: 'dist/', at => time:)
# ...
end
```
1. Postfix arrow syntax (suggested by zverok (Victor Shepelev))
```ruby
def name(external_name: default_value => internal_name)
# ...
end
# Example
def move(from: 'src/' => source, to: 'dist/' => destination, at: => time)
# ...
end
```