Method Arguments: Keyword Argument vs Hash

Problem Statement

In Rails, you might see:

validates :name, presence: true

Is presence: true a keyword argument or a hash?

Answer

Ruby allows both keyword arguments and regular arguments, including hashes. Before Ruby 2.7, keyword arguments were just hashes passed as the last argument. From Ruby 2.7 and especially Ruby 3.0 onward, keyword arguments are now strictly separated from positional hashes.

So depending on the Ruby version, this line:

Could be interpreted as:

• Ruby < 2.7: presence: true is just a Hash.
• Ruby ≥ 2.7: presence: true is a keyword argument unless the method explicitly accepts a trailing Hash.

In Rails, most DSL methods like validates are designed to work with either form.

Rails Example

Rails defines validates like this:

Here, the presence: true part is extracted as a hash from the arguments array.

General Rule

• *args + extract_options! → handles trailing hashes
• **kwargs → handles keyword arguments explicitly

Conclusion

In most Rails DSLs, options like presence: true are passed as trailing hashes. No need to worry unless you’re designing custom APIs or methods.

Also Read:

Ruby on Rails Active Storage