How do methods use hash arguments in Ruby?

Question

I saw hash arguments used in some library methods as I've been learning.

E.g.,

list.search(:titles, genre: 'jazz', duration_less_than: 270)

Can someone explain how a method uses arguments like this, and how you could create a method that makes use of Hash arguments?

question from:https://stackoverflow.com/questions/16576477/how-do-methods-use-hash-arguments-in-ruby

Answer 1

Example:

def foo(regular, hash={})
    puts "regular: #{regular}"
    puts "hash: #{hash}"
    puts "a: #{hash[:a]}"
    puts "b: #{hash[:b]}"
end

foo("regular argument", a: 12, :b => 13)

I use hash={} to specify that the last argument is a hash, with default value of empty hash. Now, when I write:

foo("regular argument", a: 12, :b => 13)

It's actually a syntactic sugar for:

foo("regular argument", {a: 12, :b => 13})

Also, {a: 12} is syntactic sugar for {:a => 12}.

When all of this is combined together, you get a syntax that looks similar to named arguments in other languages.