Deep Convert OpenStruct to JSON

There is no default methods to accomplish such task because the built-in #to_hash returns the Hash representation but it doesn't deep converts the values.

If a value is an OpenStruct, it's returned as such and it's not converted into an Hash.

However, this is not that complicated to solve. You can create a method that traverses each key/value in an OpenStruct instance (e.g. using each_pair), recursively descends into the nested OpenStructs if the value is an OpenStruct and returns an Hash of just Ruby basic types.

Such Hash can then easily be serialized using either .to_json or JSON.dump(hash).

This is a very quick example

def openstruct_to_hash(object, hash = {})
  object.each_pair do |key, value|
    hash[key] = value.is_a?(OpenStruct) ? openstruct_to_hash(value) : value
  end
  hash
end

openstruct_to_hash(OpenStruct.new(foo: 1, bar: OpenStruct.new(baz: 2)))
# => {:foo=>1, :bar=>{:baz=>2}}

Fixes to above solution to handle arrays

def open_struct_to_hash(object, hash = {})
  object.each_pair do |key, value|
    hash[key] = case value
                  when OpenStruct then open_struct_to_hash(value)
                  when Array then value.map { |v| open_struct_to_hash(v) }
                  else value
                end
  end
  hash
end