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I have an Array of objects:
[
#<User id: 1, name: "Kostas">,
#<User id: 2, name: "Moufa">,
...
]
And I want to convert this into an Hash with the id as the keys and the objects as the values. Right now I do it like so but I know there is a better way:
users = User.all.reduce({}) do |hash, user|
hash[user.id] = user
hash
end
The expected output:
{
1 => #<User id: 1, name: "Kostas">,
2 => #<User id: 2, name: "Moufa">,
...
}
621
The to_h method is defined in the array class. It works to convert an array to a hash in the form of key-value pairs. The method converts each nested array into key-value pairs. The method also accepts a block.
Creating an array of hashes You are allowed to create an array of hashes either by simply initializing array with hashes or by using array. push() to push hashes inside the array. Note: Both “Key” and :Key acts as a key in a hash in ruby.
To convert an array of objects to a Map , call the map() method on the array and on each iteration return an array containing the key and value. Then pass the array of key-value pairs to the Map() constructor to create the Map object.
With arrays, the key is an integer, whereas hashes support any object as a key. Both arrays and hashes grow as needed to hold new elements. It's more efficient to access array elements, but hashes provide more flexibility.
users_by_id = User.all.map { |user| [user.id, user] }.to_h If you are using Rails, ActiveSupport provides Enumerable#index_by:
users_by_id = User.all.index_by(&:id) You'll get a slightly better code by using each_with_object instead of reduce.
users = User.all.each_with_object({}) do |user, hash|
hash[user.id] = user
end
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