Hashes

Create a hash

Keys are often symbols in idiomatic Ruby.

user = { name: "Ada", lessons: 4 }
puts user[:name]
user[:lessons] = 5

Read safely

Fetch with a default when a key might be missing.

puts user.fetch(:name)
puts user.fetch(:email, "none")

Iterate

Yield key and value together.

user.each do |key, value|
  puts "#{key}=#{value}"
end

Hash habits

• Symbol keys (:name) are common for fixed fields
• String keys appear often with JSON
• keys and values list contents
• Hashes do not keep numeric indexes like arrays