Custom to_json for nested complex objects in Ruby - ruby

Question

I'm new to Ruby and having a little trouble json. I have inherited my classes with custom made JSONable class, as explained HERE in this answer. I have customized it according to my need, but I couldn't figure out how to make it work with custom nested (complex) objects, according to my requirement. I have following scenario.
First Class:
class Option < JSONable
def IncludeAll=(includeAll) #bool
#includeAll = includeAll
end
def IncludeAddress=(includeAddress) #bool
#includeAddress= includeAddress
end
......
Second Class:
class Search < JSONable
def CustomerId=(customerId)
#customerId = customerId
end
def identifier=(identifier)
#identifier = identifier
end
def Options=(options) #This is expected to be of Class Option, declared above
#options = options
end
Third Class:
class Request < JSONable
def DateTimeStamp=(dateTimeStamp)
#dateTimeStamp = dateTimeStamp
end
def SDKVersion=(sDKVersion)
#sDKVersion = sDKVersion
end
def RequestMessage=(requestMessage) #This is of type Search, declared above
#requestMessage = requestMessage
end
I call it as:
search = Search.new
searchOpts = Options.new
request = Request.new
search.identifier = identifier
searchOpts.IncludeAll = false
searchOpts.IncludeAddress = true
search.Options = searchOpts #setting nested level2 property here
//THE MOST OUTER CLASS OBJECT
request.SDKVersion = "xyz"
request.RequestMessage = search #setting nested level1
My ultimate goal is to send this request object to an API, after converting it to JSON. so i call to_json on request object as:
request.to_json
But here, suggested solution in that post (JSONable) fails in this case, as it can't convert the nested complex objects request.search and request.search.Options to Json.
(gives error: in 'to_json': wrong number of arguments (1 for 0) (ArgumentError)')
What I tried:
class JSONable
def to_json
hash = {}
self.instance_variables.each do |var|
#hash[var] = self.instance_variable_get var #tried to apply following check
if((self.instance_variable_get var).instance_of? Options ||((varVal).instance_of? Search))
varVal = self.instance_variable_get var
hash[var] = varVal.to_json #convert inner object to json
else
hash[var] = self.instance_variable_get var
end
end
hash.to_json
end
.....
This converts the nested model without any problem, but it messes up the 3rd level json. The result is as following:
{"DateTimeStamp":"121212","SDKVersion":"1.5","Culture":"en","RequestMessage":"{\"identifier\":\"851848913\",\"Options\":\"{\\\"IncludeAll\\\":true,\\\"IncludeAssociatedEntities\\\":true,\\\"IncludeAddress\\\":true,\\\"IncludePaymentInstructions\\\":true}\"}"}
And API doesn't respond. It seems as it messes up the boolean variables, which should be something like:
"SearchOption":"{\"IncludeAll\":true,\"IncludeAssociatedEntities\":true,\...
but it gives:
"SearchOption\":\"{\\\"IncludeAll\\\":true,\\\"IncludeAssociatedEntities\\\":true,\\\"Includ...
So the API logic can't cast it to corresponding bool objects anymore. JSON validator also fails to validate this result, i checked online
Questions:
How can I avoid this, and produce valid JSON in this case?
How can I apply generic check to in my JSONable class to check if the object is of some custom class / complex object.
(currently i have checked only for specific classes as:)
if((self.instance_variable_get var).instance_of? Options ||((varVal).instance_of? Search))
Other Info:
It works fine for all complex objects, having no nested objects
API is developed in .NET
I'm not using Rails, its a Ruby console app (I'm new to Ruby)

Answer 1

The answer you referred is dated “Dec 2010.” JSON library is included in ruby stdlib for years already and it perfectly converts Hash instances to json. That said, you just need to construct hashes out of your objects and then call JSON.dump on the resulting hash. I have no idea what JSONable is and you definitely do not need it. Introduce some base class, let’s call it Base:
class Base
def to_h
instance_variables.map do |iv|
value = instance_variable_get(:"##{iv}")
[
iv.to_s[1..-1], # name without leading `#`
case value
when Base then value.to_h # Base instance? convert deeply
when Array # Array? convert elements
value.map do |e|
e.respond_to?(:to_h) ? e.to_h : e
end
else value # seems to be non-convertable, put as is
end
]
end.to_h
end
end
Now just derive your classes from Base to make them respond to to_h, define all your instance variables as you did, and call:
require 'json'
JSON.dump request.to_h # request.to_h.to_json should work as well
The above should produce the nested JSON, hashes are happily converted to json by this library automagically.