How to add to an existing hash in Ruby

user_868090 0
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In regards to adding an key => value pair to an existing populated hash in Ruby, I'm in the process of working through Apress' Beginning Ruby and have just finished the hashes chapter.

I am trying to find the simplest way to achieve the same results with hashes as this does with arrays:

x = [1, 2, 3, 4]
x << 5
p x
hash new-operator ruby
7 Answers

You can use double splat operator which is available since Ruby 2.0:

h = { a: 1, b: 2 }
h = { **h, c: 3 }
p h
# => {:a=>1, :b=>2, :c=>3}
user_18383000 
hash = { a: 'a', b: 'b' }
 => {:a=>"a", :b=>"b"}
hash.merge({ c: 'c', d: 'd' })
 => {:a=>"a", :b=>"b", :c=>"c", :d=>"d"}

Returns the merged value.

hash
 => {:a=>"a", :b=>"b"}

But doesn't modify the caller object

hash = hash.merge({ c: 'c', d: 'd' })
 => {:a=>"a", :b=>"b", :c=>"c", :d=>"d"} 
hash
 => {:a=>"a", :b=>"b", :c=>"c", :d=>"d"}

Reassignment does the trick.

user_27826180
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