How to add new item to hash

Question

I\'m new to Ruby and don\'t know how to add new item to already existing hash. For example, first I construct hash:

hash = {item1: 1}

after

Answer 1

If you want to add new items from another hash - use merge method:

hash = {:item1 => 1}
another_hash = {:item2 => 2, :item3 => 3}
hash.merge(another_hash) # {:item1=>1, :item2=>2, :item3=>3}

In your specific case it could be:

hash = {:item1 => 1}
hash.merge({:item2 => 2}) # {:item1=>1, :item2=>2}

but it's not wise to use it when you should to add just one element more.

Pay attention that merge will replace the values with the existing keys:

hash = {:item1 => 1}
hash.merge({:item1 => 2}) # {:item1=>2}

exactly like hash[:item1] = 2

Also you should pay attention that merge method (of course) doesn't effect the original value of hash variable - it returns a new merged hash. If you want to replace the value of the hash variable then use merge! instead:

hash = {:item1 => 1}
hash.merge!({:item2 => 2})
# now hash == {:item1=>1, :item2=>2}