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Please make AASM compatible with JSON::Serializable #7

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drhuffman12 opened this issue Jan 23, 2020 · 2 comments · May be fixed by #8
Open

Please make AASM compatible with JSON::Serializable #7

drhuffman12 opened this issue Jan 23, 2020 · 2 comments · May be fixed by #8

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@drhuffman12
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I want to use JSON::Serializable with AASM. In the example below, I get this error: Error: no overload matches 'AASM::StateMachine#to_json' with type JSON::Builder.

Crystal code (having 'aasm' shard already installed in the Crystal app):

require "json"
require "aasm"

struct Foo
  # This is just one set of inputs_given, one set of outputs_guessed, and one set of weights (i.e.: no hidden layers)
  # It can be run (via wrapper?) in states (e.g.: init, load, guess, calc_output_errors, calc_output_deltas, adjust_weights, calc_input_deltas, done)

  include AASM
  include JSON::Serializable

  def act_as_state_machine
    aasm.state :pending, initial: true
  end

  # # NOTE: Initializer must have a param; TODO: Find out why.
  # # .... Otherwise, you get something like:
  #  24 | f = Foo.new
  #               ^--
  # Error: wrong number of arguments for 'Foo.new' (given 0, expected 1)
  #
  # Overloads are:
  #  - Foo.new(pull : ::JSON::PullParser)
  def initialize(@bar : String)
    act_as_state_machine
  end
end

f = Foo.new("test")

f.to_json

... will display:

=> Foo(@aasm=#<AASM::StateMachine:0x7f6e302ae740 @states={:pending => AASM::State(@enter=nil, @guard=nil)}, @events={}, @transition_table={}, @current_state_name=:pending>, @bar="test")
icr(0.32.1) > 
icr(0.32.1) > f.to_json
Showing last frame. Use --error-trace for full trace.

There was a problem expanding macro 'macro_140610915503952'

Code in /home/drhuffman/.anyenv/envs/crenv/versions/0.32.1/share/crystal/src/json/serialization.cr:262:7

 262 | {% begin %}
       ^
Called macro defined in /home/drhuffman/.anyenv/envs/crenv/versions/0.32.1/share/crystal/src/json/serialization.cr:262:7

 262 | {% begin %}

Which expanded to:

 > 28 | 
 > 29 |                 
 > 30 |                   _aasm.to_json(json)
                                ^------
Error: no overload matches 'AASM::StateMachine#to_json' with type JSON::Builder

Overloads are:
 - Object#to_json(io : IO)
 - Object#to_json()
@drhuffman12 drhuffman12 linked a pull request Jan 23, 2020 that will close this issue
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@drhuffman12
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I forked the repo and modified it to look like:

class AASM::StateMachine
  getter current_state_name

  include JSON::Serializable
  def to_json
    {
      states: @states,
      events: @events,
      transition_table: @transition_table,
      current_state_name: @current_state_name
    }.to_json
  end

  def initialize
 ...

.. and added updated spec/aasm/state_machine_spec.cr to like:

require "../spec_helper"

def one_state_machine(enter = ->{}, guard = ->{ true })
...

    end

    describe "#to_json" do
      it "creates a StateMachine based on given json" do

        # s = two_states_machine
        # s.next_state.should eq :active

        s1 = two_states_machine
        s1.fire_event :activate
        s1.next_state.should eq nil

        state_json = s1.to_json

        s2 = two_states_machine.from_json(state_json)
        s2.state.should eq (s1.state)
      end
    end
  end
end

But, this complained that I need to implement AASM::State#to_json. So I made this look like:

struct AASM::State
  include JSON::Serializable
  def to_json
    {
      opts: @opts
      # ,
      # enter: @enter,
      # guard: @guard
    }.to_json
  end

  getter enter : (-> Nil)?
...

This complained with: Error: no overload matches 'Proc(Nil)#to_json' with type JSON::Builder. At this point, I'm kinda our of time for this and not quite sure what the best path forward would be.

See: #8

@veelenga
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Hey, this is a nice idea.

It happens because there is no way to convert a proc to json and back.

Thanks for the investigation, I will take a look at what could be done.

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drhuffman12/enable_json_serializable drhuffman12/aasm.cr
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@drhuffman12 @veelenga