How do I append a key value pair to an existing hash in Ruby?
15,187
Solution 1
There are 3 ways:
.merge(other_hash)
Returns a new hash containing the contents of other_hash and the contents of hsh.
hash = { a: 1 }
puts hash.merge({ b: 2, c: 3 }) # => {:a=>1, :b=>2, :c=>3}
.merge!(other_hash)
Adds the contents of other_hash to hsh.
hash = { a: 1 }
puts hash.merge!({ b: 2, c: 3 }) # => {:a=>1, :b=>2, :c=>3}
And most efficient way is to modify existing hash, setting new values directly:
hash = { a: 1 }
hash[:b] = 2
hash[:c] = 3
puts hash # => {:a=>1, :b=>2, :c=>3}
Corresponding Benchmarks for these methods:
user system total real
0.010000 0.000000 0.010000 ( 0.013348)
0.010000 0.000000 0.010000 ( 0.003285)
0.000000 0.000000 0.000000 ( 0.000918)
Solution 2
You can merge!
the two hashes together:
hash1 = {}
hash1.merge!({"a" => 1, "b" => 2})
Author by
Sean Bernardino
Updated on June 08, 2022Comments
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Sean Bernardino about 2 years
I'm new to Ruby and am trying to 'inject' key/value pairs to an existing hash in Ruby. I know you can do this with << for arrays, for e.g.
arr1 = [] a << "hello"
But could I do something similar for a hash? So something like
hash1 = {} hash1 << {"a" => 1, "b" => 2}
Basically, I'm trying push key value pairs in a loop based on a condition.
# Encoder: This shifts each letter forward by 4 letters and stores it in a hash called cipher. On reaching the end, it loops back to the first letter def encoder (shift_by) alphabet = [] cipher = {} alphabet = ("a".."z").to_a alphabet.each_index do |x| if (x+shift_by) <= 25 cipher = {alphabet[x] => alphabet[x+shift_by]} else cipher = {alphabet[x] => alphabet[x-(26-shift_by)]} #Need this piece to push additional key value pairs to the already existing cipher hash. end end
Sorry for pasting my whole method here. Can anyone please help me with this?
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Sean Bernardino over 9 yearsThank you. This worked well.