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outer_join.rb

This Ruby code snippet demonstrates how to use the map method and the find method in conjunction with the merge method to create a new array of hashes that combines information from two other arrays.

The first array is an array of users, each represented as a hash with an id key and a name value. The second array is an array of posts, each represented as a hash with an id key, a user_id key, and a title value.

The code uses the map method to iterate over each user in the users array, and for each user it finds the corresponding post in the posts array by using the find method with a block that checks if the user_id key in the post hash matches the id value of the current user. If a match is found, the code uses the merge method to combine the information from the two hashes into a single hash that includes both the user’s name and the title of their post. If no match is found, the code sets the title to nil.

The resulting array contains a new hash for each user, with an additional key-value pair for the title of their post if they have one.

Ruby code snippet

users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' },
  { id: 3, name: 'Charlie' }
]
#=> [{id: 1, name: "Alice"}, {id: 2, name: "Bob"}, {id: 3, name: "Charlie"}]

posts = [
  { id: 1, user_id: 1, title: 'Post 1' },
  { id: 2, user_id: 2, title: 'Post 2' }
]
#=> [{id: 1, user_id: 1, title: "Post 1"}, {id: 2, user_id: 2, title: "Post 2"}]

users.map do |user|
  post = posts.find { |p| p[:user_id] == user[:id] }
  user.merge(post || { title: nil })
end
#=> 
[{id: 1, name: "Alice", user_id: 1, title: "Post 1"},
 {id: 2, name: "Bob", user_id: 2, title: "Post 2"},
 {id: 3, name: "Charlie", title: nil}]

Executed with Ruby 3.4.4.