I just released a ruby gem to use some JSON over HTTP API:
https://github.com/solyaris/blomming_api
My naif ruby code just convert complex/nested JSON data structures returned by API endpoints (json_data) to ruby Hashes ( hash_data), in a flat one-to-one transaltion (JSON to ruby hash and viceversa). Tat's fine, but...
I would like a programming interface more "high level". Maybe instatiating a class Resource for every endpoint, but I'm confused about a smart implementation.
Let me explain with an abstract code.
Let say I have a complex/nested JSON received by an API, usually an Array of Hashes, recursively nested as here below (imagination example):
json_data = '[{
"commute": {
"minutes": 0,
"startTime": "Wed May 06 22:14:12 EDT 2014",
"locations": [
{
"latitude": "40.4220061",
"longitude": "40.4220061"
},
{
"latitude": "40.4989909",
"longitude": "40.48989805"
},
{
"latitude": "40.4111169",
"longitude": "40.42222869"
}
]
}
},
{
"commute": {
"minutes": 2,
"startTime": "Wed May 28 20:14:12 EDT 2014",
"locations": [
{
"latitude": "43.4220063",
"longitude": "43.4220063"
}
]
}
}]'
At the moment what I do, when I receive a similar JSON form an API is just:
# from JSON to hash
hash_data = JSON.load json_data
# and to assign values:
coords = hash_data.first["commute"]["locations"].last
coords["longitude"] = "40.00" # was "40.4111169"
coords["latitude"] = "41.00" # was "40.42222869"
that's ok, but with awfull/confusing syntax. Instead, I probably would enjoy something like:
# create object Resource from hash
res = Resource.create( hash_data )
# ... some processing
# assign a "nested" variables: longitude, latitude of object: res
coords = res.first.commute.locations.last
coords.longitude = "40.00" # was "40.4111169"
coords.latitude = "41.00" # was "40.42222869"
# ... some processing
# convert modified object: res into an hash again:
modified_hash = res.save
# and probably at least I'll recover to to JSON:
modified_json = JSON.dump modified_hash
I read intresting posts: http://pullmonkey.com/2008/01/06/convert-a-ruby-hash-into-a-class-object/ http://www.goodercode.com/wp/convert-your-hash-keys-to-object-properties-in-ruby/
and copying Kerry Wilson' code, I sketched the implementation here below:
class Resource
def self.create (hash)
new ( hash)
end
def initialize ( hash)
hash.to_obj
end
def save
# or to_hash()
# todo! HELP! (see later)
end
end
class ::Hash
# add keys to hash
def to_obj
self.each do |k,v|
v.to_obj if v.kind_of? Hash
v.to_obj if v.kind_of? Array
k=k.gsub(/\.|\s|-|\/|\'/, '_').downcase.to_sym
## create and initialize an instance variable for this key/value pair
self.instance_variable_set("@#{k}", v)
## create the getter that returns the instance variable
self.class.send(:define_method, k, proc{self.instance_variable_get("@#{k}")})
## create the setter that sets the instance variable
self.class.send(:define_method, "#{k}=", proc{|v| self.instance_variable_set("@#{k}", v)})
end
return self
end
end
class ::Array
def to_obj
self.map { |v| v.to_obj }
end
end
#------------------------------------------------------------
BTW, I studied a bit ActiveResource project (was part of Rails if I well understood). ARes could be great for my scope but the problem is ARes have a bit too "strict" presumption of full REST APIs... In my case server API are not completely RESTfull in the way ARes would expect... All in all I would do a lot of work to subclass / modify ARes behaviours and at the moment I discarded the idea to use ActiveResource
QUESTIONS:
- someone could help me to realize the save() method on the above code (I'm really bad with recursive methods... :-( ) ?
Does exist some gem that to the above sketched hash_to_object() and object_to_hash() translation ?
What do you think about that "automatic" objectifying of an "arbitrary" hash coming froma JSON over http APIs ? I mean: I see the great pro that I do not need to client-side static-wire data structures, allowing to be flexible to possible server side variations. But on the other hand, doing this automatic objectify, there is a possible cons of a side effect to allow security issues ... like malicious JSON injection (possible untrasted communication net ...)
What do you think about all this ? Any suggestion is welcome! Sorry for my long post and my ruby language metaprogramming azards :-)
giorgio
UPDATE 2: I'm still interested reading opinions about question point 3: Pros/Cons to create Resource class for every received JSON Pros/Cons to create static (preemptive attributes) / automatich/dynamic nested objects
UPDATE 1: long reply to Simone: thanks, you are right Mash have a sweet .to_hash() method:
require 'json'
require 'hashie'
json_data = '{
"commute": {
"minutes": 0,
"startTime": "Wed May 06 22:14:12 EDT 2014",
"locations": [
{
"latitude": "40.4220061",
"longitude": "40.4220061"
},
{
"latitude": "40.4989909",
"longitude": "40.48989805"
},
{
"latitude": "40.4111169",
"longitude": "40.42222869"
}
]
}
}'
# trasforma in hash
hash = JSON.load json_data
puts hash
res = Hashie::Mash.new hash
# assign a "nested" variables: longitude, latitude of object: res
coords = res.commute.locations.last
coords.longitude = "40.00" # was "40.4111169"
coords.latitude = "41.00" # was "40.42222869"
puts; puts "longitude: #{res.commute.locations.last.longitude}"
puts "latitude: #{res.commute.locations.last.latitude}"
modified_hash = res.to_hash
puts; puts modified_hash
