I am very new to Ruby array and hash manipulation.
How can I do this simple transformation?
array = [#<struct id=1, car='red'>, #<struct id=2, car='yellow'>, #<struct id=3, car='green'>]
desired output in json:
[{id : 1, car : 'red'} , {id:2, car :'yellow'} ,{id:3 , car: "green"}]
Does anyone have any hints?
array.map { |o| Hash[o.each_pair.to_a] }.to_json
require 'json' to get the to_json function.
.to_h instead.Convert array of struct objects into array of hash, then call to_json. You need to require json (ruby 1.9) in order to use the to_json method.
array.collect { |item| {:id => item.id, :car => item.car} }.to_json
By default a Struct instance will be displayed as a string when encoding to json using the json ruby gem:
require 'json'
array = [#<struct id=1, car='red'>, #<struct id=2, car='yellow'>, #<struct id=3, car='green'>] # assuming real structure code in the array
puts array.to_json
prints
["#<struct id=1, car='red'>", "#<struct id=2, car='yellow'>", "#<struct id=3, car='green'>"]
This is obviously not what you want.
The next logical step is to make sure that your struct instances can be properly serialized to JSON, as well as created back from JSON.
To do this you can alter the declaration of your structure:
YourStruct = Struct.new(:id, :car)
class YourStruct
def to_json(*a)
{:id => self.id, :car => self.car}.to_json(*a)
end
def self.json_create(o)
new(o['id'], o['car'])
end
end
So you can now write the following:
a = [ YourStruct.new(1, 'toy'), YourStruct.new(2, 'test')]
puts a.to_json
which prints
[{"id": 1,"car":"toy"},{"id": 2,"car":"test"}]
and also deserialize from JSON:
YourStruct.json_create(JSON.parse('{"id": 1,"car":"toy"}'))
# => #<struct YourStruct id=1, car="toy">
