Setting up rom-http relation for REST CRUD - ruby

Question

I'm trying to set up a rom-http relation for basic REST CRUD, but I find the documentation to be pretty scarce for a beginner, and a little too complex when digging in. What I've tried so far is this:
rom = ROM.container(:http, uri: 'http://localhost:8000', handlers: :json) do |conf|
conf.relation(:users) do
schema(:users) do
end
end
end
This queries the URI http://localhost:8000/users, but how do I configure prefixes, parameters and related resources?
What I'd like to accomplish is being able to consume a URI such as http://localhost:8000/users/1/posts?start=0&size=10 where we have
a global prefix (api)
a version prefix (v1, could be part of the global prefix)
a parent resource (users/1)
a child resource (posts)
query parameters (bonus points if they can be chained like .offset(0).limit(10))
Is this possible with the current implementation? The documentation could use a deeper example, without forcing newcomers to dig into the architecture - which is without doubt brilliant, but complex for someone coming from the ease of use (and the pitfalls) of ActiveRecord. :-)

Answer 1

Sorry that nobody has replied to this yet, the current built-in json handler is a bit broken at the moment, it builds the uri manually when it should just use it from the dataset, you can achieve what you want with something like the following:
NOTE: I only called .dataset.uri to show an example of the URI that would be queried, as I don't have a compatible API running locally.
NOTE: For anything beyond playing around with the library, you'll probably want to use a custom adapter anyway.
require 'bundler/inline'
gemfile(true) do
gem 'rom'
gem 'rom-http'
end
class MyJSONRequest
def self.call(dataset)
uri = dataset.uri
http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl = true if uri.scheme.eql?('https')
request_class = Net::HTTP.const_get(ROM::Inflector.classify(dataset.request_method))
request = request_class.new(uri.request_uri)
dataset.headers.each_with_object(request) do |(header, value), request|
request[header.to_s] = value
end
http.request(request)
end
end
class MyJSONResponse
# Handle JSON responses
#
# #param [Net::HTTP::Response] response
# #param [Dataset] dataset
#
# #return [Array<Hash>]
#
# #api public
def self.call(response, dataset)
Array([JSON.parse(response.body, symbolize_names: true)]).flatten(1)
end
end
ROM::HTTP::Handlers.register(
:my_json,
request: MyJSONRequest,
response: MyJSONResponse
)
rom = ROM.container(:http, uri: 'http://localhost:8000/api', handlers: :my_json) do |conf|
conf.relation(:users) do
schema('v1/users') do
attribute :id, ROM::Types::Integer.meta(
primary_key: true
)
attribute :name, ROM::Types::String
end
def by_id(id)
append_path(id)
end
def offset(offset)
add_params(start: offset)
end
def limit(limit)
add_params(size: limit)
end
end
conf.relation(:posts) do
schema('v1/posts') do
attribute :id, ROM::Types::Integer.meta(
primary_key: true
)
attribute :name, ROM::Types::String
end
def by_user(user_id)
with_options(
base_path: 'v1/users',
path: "#{user_id}/posts"
)
end
end
end
users = rom.relations[:users]
posts = rom.relations[:posts]
users.offset(0).limit(10).dataset.uri
# => #<URI::HTTP http://localhost:8000/api/v1/users?start=0&size=10>
posts.by_user(1).dataset.uri
# => #<URI::HTTP http://localhost:8000/api/v1/users/1/posts>
Also, for nested resources, ROM can query those automatically, check the (out-dated) example sections below to see how that works.
https://github.com/rom-rb/rom-http/blob/57ca3703bf82bc9d7b2c3304752947de2c6d6dea/examples/repository_with_combine.rb#L49-L51
https://github.com/rom-rb/rom-http/blob/57ca3703bf82bc9d7b2c3304752947de2c6d6dea/examples/repository_with_combine.rb#L66-L71
https://github.com/rom-rb/rom-http/blob/57ca3703bf82bc9d7b2c3304752947de2c6d6dea/examples/repository_with_combine.rb#L81-L83