How can I update a json file in ruby?

Question

I want to do this in ruby.

Say I have an example.json file that looks like

{
   "name" : "My name is - "
}

and I want to update that to

{
   "name" : "My name is - Chris"
}

I know to do this

require 'json'
json = JSON.parse('example.json')
name = json['name'] + ' Chris'

Now how I write name back into example.json file and save the file, simply like this?

json['name'] = name