Hyper-Operation

Hyper-Operation gem

Operations encapsulate business logic. In a traditional MVC architecture, Operations end up either in Controllers, Models or some other secondary construct such as service objects, helpers, or concerns. Here they are first class objects. Their job is to mutate state in the Stores and Models.

  • Hyperloop::Operation is the base class for Operations.
  • An Operation orchestrates the updating of the state of your system.
  • Operations also wrap asynchronous operations such as HTTP API requests.
  • Operations serve the role of both Action Creators and Dispatchers described in the Flux architecture.
  • Operations also serve as the bridge between client and server. An operation can run on the client or the server, and can be invoked remotely.

Documentation and Help

Basic Installation and Setup

The easiest way to install is to use the hyper-rails gem.

«««< HEAD

Installation

Note: only runs with rails currently.

Add gem 'hyper-operation' to your Gemfile Add //= require hyperloop-loader to your application.rb

If you want operations to interact between server and client you will have to pick a transport:

“by

initializers/hyperloop.rb

Hyperloop.configuration do |config|

# to use Action Cable config.transport = :action_cable # for rails 5+

# to use Pusher (see www.pusher.com) config.transport = :pusher config.opts = { app_id: “pusher application id”, key: “pusher public key”, secret: “pusher secret key” }

# to use Pusher Fake (creates a fake pusher service) # Its a bit weird: You have to define require pusher and # define some FAKE pusher keys first, then bring in pusher-fake # the actual key values don’t matter just the order!!! require ‘pusher’
require ‘pusher-fake’ Pusher.app_id = “MY_TEST_ID” # don’t bother changing these strings Pusher.key = “MY_TEST_KEY” Pusher.secret = “MY_TEST_SECRET” require ‘pusher-fake/support/base’ # then setup your config like pusher but merge in the pusher fake # options config.transport = :pusher config.opts = { app_id: Pusher.app_id, key: Pusher.key, secret: Pusher.secret }.merge(PusherFake.configuration.web_options)

# For down and dirty simplicity use polling: config.transport = :simple_poller # change this to slow down polling, default is much faster # and hard to debug config.opts = { seconds_between_poll: 2 } end

“

You will also have to add at least one channel policy to authorize the connection between clients and the server.

“by

app/policies/application_policy.rb

class Hyperloop::ApplicationPolicy # allow any client too attach to the Hyperloop::Application for example always_allow_connection
end

“

See the Channels section for more details on authorization.

Operation Structure

======= 1. Add gem 'hyper-rails' to your Rails Gemfile development section. 2. Install the Gem: bundle install 3. Run the generator: bundle exec rails g hyperloop:install --all 4. Update the bundle: bundle update

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Your Isomorphic Operations live in a hyperloop/operations folder and your server only Operations in app/operations

You will also find an app/policies folder with a simple access policy suited for development. Policies are how you will provide detailed access control to your Isomorphic models.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/ruby-hyperloop/hyper-operation. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Code of Conduct code of conduct.

License

«««< HEAD

“by class AddItemToCart < Hyperloop::Operation param :sku, type: String param qty: 1, type: Integer, min: 1 end

class Cart < Hyperloop::Store receives AddItemToCart do mutate.items[params.sku] += params.qty end end

“

In addition unlike Hyperloop::Component params, Operation params are not reactive, and so you can assign to them as well:

“by params.some_value = 12

“

The parameter filter types and options are taken from the Mutations gem with the following changes:

  • In Hyperloop::Operations all params are declared with the param macro.
  • The type can be specified using the type: option.
  • Array and hash types can be shortened to [] and {}
  • Optional params either have the default value associated with the param name, or by having the default option present.
  • All other Mutation filter options (such as :min) will work the same.

“by # required param (does not have a default value) param :sku, type: String # equivalent Mutation syntax # required { string :sku }

# optional params (does have a default value) param qty: 1, min: 1 # alternative syntax param :qty, default: 1, min: 1 # equivalent Mutation syntax # optional { integer :qty, default: 1, min: 1 }

“

All incoming params are validated against the param declarations, and any errors are posted to the @errors instance variable. Extra params are ignored, but missing params unless they have a default value will cause a validation error.

Defining Execution Steps

Operations may define a sequence of steps to be executed when the operation is run, using the step, failed and async callback macros.

“by class Reset < Hyperloop::Operation step { HTTP.post(‘/logout’) } end

“

  • step: runs a callback - each step is run in order.
  • failed: runs a callback if a previous step or validation has failed.
  • async: will be explained below.

“by step { } # do something step { } # do something else once above step is done failed { } # do this if anything above has failed step { } # do a third thing, unless we are on the failed track failed { } # do this if anything above has failed

“

Together step and failed form two railway tracks. Initially execution proceeds down the success track until something goes wrong, then execution switches to the failure track starting at the next failed statement. Once on the failed track execution continues performing each failed callback and skipping any step callbacks.

Failure occurs when either an exception is raised or a promise fails (more on this in the next section.) The Ruby fail keyword can be used as a simple way to switch to the failed track.

Both step and failed can receive any results delivered by the previous step. If the previous step raised an exception (outside a promise) the failure track will receive the exception object.

The callback may be provided to step and failed either as a block, a symbol (which will name a method), a proc, a lambda, or an Operation.

“by step { puts ‘hello’ } step :say_hello step -> () { puts ‘hello’ } step Proc.new { puts ‘hello’ } step SayHello # your params will be passed along to SayHello

“

FYI: You can also use the Ruby next keyword as expected to leave the current step and move to the next one.

Promises and Operations

Within the browser, code does not wait for asynchronous methods (such as HTTP requests or timers) to complete. Operations use Opal’s Promise library to deal with these situations cleanly. A Promise is an object that has three states: It is either still pending, or has been rejected (i.e. failed), or has been successfully resolved. A promise can have callbacks attached to either the failed or resolved state, and these callbacks will be executed once the promise is resolved or rejected.

If a step or failed callback returns a pending promise then the execution of the operation is suspended, and the Operation will return the promise to the caller. If there is more track ahead, then execution will resume on the next step when the promise is resolved. Likewise if the pending promise is rejected execution will resume on the next failed callback. Because of the way promises work, the operation steps will all be completed before the resolved state is passed along to caller, so everything will execute in its original order.

Likewise the Operation’s dispatch occurs when the promise resolves as well.

The async method can be used to override the waiting behavior. If a step returns a promise, and there is an async callback farther down the track, execution will immediately pick up at the async. Any steps in between will still be run when the promise resolves, but their results will not be passed outside of the operation.

These features make it easy to organize, understand and compose asynchronous code:

“by class AddItemToCart < Hyperloop::Operation step { HTTP.get(‘/inventory/#paramsparams.sku/qty’) } # previous step returned a promise so next step # will execute when that promise resolves step { |response| fail if params.qty > response.to_i } # once we are sure we have inventory we will dispatch # to any listening stores. end

“

Operations will always return a Promise. If an Operation has no steps that return a promise the value of the last step will be wrapped in a resolved promise. This lets you easily chain Operations, regardless of their internal implementation:

“by class QuickCheckout < Hyperloop::Operation param :sku, type: String param qty: 1, type: Integer, minimum: 1

step { AddItemToCart(params) } step ValidateUserDefaultCC step Checkout end

“

You can also use Promise#when if you don’t care about the order of Operations

“by class DoABunchOStuff < Hyperloop::Operation step { Promise.when(SomeOperation.run, SomeOtherOperation.run) } # dispatch when both operations complete end

“

Early Exits with abort! and succeed!

In any step or failed callback, you may do an immediate exit from the Operation using the abort! and succeed! methods. The abort! method returns a failed Promise with any supplied parameters. The succeed! method does an immediate dispatch, and returns a resolved Promise with any supplied parameters. If succeed! is used in a failed callback, it will override the failed status of the Operation. This is especially useful if you want to dispatch in spite of failures:

“by class Pointless < Hyperloop::Operation step { fail } # go to failure track failed { succeed! } # dispatch and exit end

“

The validate and add_error methods

An Operation can also have a number of validate callbacks which will run before the first step. This is a handy place to put any additional validations. In the validate method you can add validation type messages using the add_error method, and these will be passed along like any other param validation failures.

“by class UpdateProfile < Hyperloop::Operation param :first_name, type: String
param :last_name, type: String param :password, type: String, nils: true param :password_confirmation, type: String, nils: true

validate do add_error( :password_confirmation, :doesnt_match, “Your new password and confirmation do not match” ) unless params.password == params.confirmation end

# or more simply:

add_error :password_confirmation, :doesnt_match, “Your new password and confirmation do not match” do params.password != params.confirmation end

… end

“

If the validate method returns a promise, then execution will wait until the promise resolves. If the promise fails, then the current validation fails.

You may also call abort! from within validate or add_error to immediately exit the Operation. Otherwise all validations will be run and collected together and the Operation will move onto the failed track. If abort! is called within an add_error callback the error will be added before aborting.

You can also raise an exception directly in validate if appropriate. If a Hyperloop::AccessViolation exception is raised the Operation will immediately abort, otherwise just the current validation fails.

If you want to avoid further validations if there are any failures in the basic parameter validations you can add do add this

“by validate { abort! if has_errors? }

“efore the first validate or add_error call.

Handling Failed Operations

Because Operations always return a promise, you can use the Promise’s fail method on the Operation’s result to detect failures.

“by QuickCheckout(sku: selected_item, qty: selected_qty) .then do # show confirmation end .fail do |exception| # whatever exception was raised is passed to the fail block end

“ailures to validate params result in Hyperloop::ValidationException which contains a Mutations error object.

“by MyOperation.run.fail do |e| if e.is_a? Hyperloop::ValidationException e.errors.symbolic # hash: each key is a parameter that failed validation, # value is a symbol representing the reason e.errors.message # same as symbolic but message is in English e.errors.message_list # array of messages where failed parameter is # combined with the message end end

“

Running Operations

You can run an Operation by using … + the Operation class name as a method:

“by MyOperation(…params…)

“ the run method:

“by MyOperation.run …params…

“ the then and fail methods, which will dispatch the operation and attach a promise handler:

“by MyOperation.then(…params…) { alert ‘operation completed’ }

“

The Hyperloop::ServerOp class

Operations will run on the client or the server. Some Operations like ValidateUserDefaultCC probably need to check information server side, and make secure API calls to our credit card processor. Rather than build an API and controller to “validate the user credentials” you simply specify that the operation must run on the server by using the Hyperloop::ServerOp class.

“by class ValidateUserCredentials < Hyperloop::ServerOp param :acting_user add_error :acting_user, :no_valid_default_cc, “No valid default credit card” do !params.acting_user.has_default_cc? end end

“

A Server Operation will always run on the server even if invoked on the client. When invoked from the client Server Operations will receive the acting_user param with the current value that your ApplicationController’s acting_user method returns. Typically the acting_user method will return either some User model, or nil (if there is no logged in user.) Its up to you to define how acting_user is computed, but this is easily done with any of the popular authentication gems. Note that unless you explicitly add nils: true to the param declaration, nil will not be accepted.

As shown above you can also define a validation to further insure that the acting user (with perhaps other parameters) is allowed to perform the operation. In the above case that is the only purpose of the Operation. Another typical use would be to make sure the current acting user has the correct role to perform the operation:

“by … validate { raise Hyperloop::AccessViolation unless params.acting_user.admin? } …

“

You can bake this kind logic into a superclass:

“by class AdminOnlyOp < Hyperloop::ServerOp param :acting_user validate { raise Hyperloop::AccessViolation unless params.acting_user.admin? } end

class DeleteUser < AdminOnlyOp param :user add_error :user, :cant_delete_user, “Can’t delete yourself, or the last admin user” do params.user == params.acting_user || (params.user.admin? && AdminUsers.count == 1) end end

“

Because Operations always return a promise, there is nothing to change on the client to call a Server Operation. A Server Operation will return a promise that will be resolved (or rejected) when the Operation completes (or fails) on the server.

Dispatching From Server Operations

You can also broadcast the dispatch from Server Operations to all authorized clients. The dispatch_to will determine a list of channels to broadcast the dispatch to:

“by class Announcement < Hyperloop::ServerOp # no acting_user because we don’t want clients to invoke the Operation param :message param :duration, type: Float, nils: true # dispatch to the builtin Hyperloop::Application Channel dispatch_to Hyperloop::Application end

class CurrentAnnouncements < Hyperloop::Store state_reader all: [], scope: :class receives Announcement do mutate.all « params.message after(params.duration) { delete params.message } if params.duration end def self.delete(message) mutate.all.delete message end end

“

Channels

As seen above broadcasting is done over a Channel. Any Ruby class (including Operations) can be used as class channel. Any Ruby class that responds to the id method can be used as an instance channel.

For example the User active record model could be a used as channel to broadcast to all users. Each user instance could also be a separate instance channel that would be used to broadcast to a specific user.

The purpose of having channels is to restrict what gets broadcast to who, therefore typically channels represent connections to

  • the application (represented by the Hyperloop::Application class)
  • or some function within the application (like an Operation)
  • or some class which is authenticated like a User or Administrator,
  • instances of those classes,
  • or instances of classes in some relationship - like a team that a user belongs to.

You create a channel by including the Hyperloop::Policy::Mixin, which gives you three class methods: regulate_class_connection always_allow_connection and regulate_instance_connections. For example:

“by class User < ActiveRecord::Base include Hyperloop::Policy::Mixin regulate_class_connection { self }
regulate_instance_connection { self } end

“

will attach the current acting user to the User channel (which is shared with all users) and to that user’s private channel.

Both blocks execute with self set to the current acting user, but the return value has a different meaning. If regulate_class_connection returns any truthy value, then the class level connection will be made on behalf of the acting user. On the other hand if regulate_instance_connection returns an array (possibly nested) or Active Record relationship then an instance connection is made with each object in the list. So for example you could add:

“by class User < ActiveRecord::Base has_many chat_rooms regulate_instance_connection { chat_rooms } # we will connect to all the chat room channels we are members of end

“

Now if we want to broadcast to all users our Operation would have

“by dispatch_to { User } # dispatch to the User class channel

“

or to send an announcement to a specific user

“by class PrivateAnnouncement < Hyperloop::ServerOp param :receiver param :message # dispatch_to can take a block if we need to # dynamically compute the channels dispatch_to { params.receiver } end … # somewhere else in the server PrivateAnnouncement(receiver: User.find_by_login(login), message: ‘log off now!’)

“

The above will work if PrivateAnnouncement is invoked from the server, but usually some other client would be sending the message so the operation could look like this:

“by class PrivateAnnouncement < Hyperloop::ServerOp param :acting_user param :receiver param :message validate { raise Hyperloop::AccessViolation unless params.acting_user.admin? } validate { params.receiver = User.find_by_login(receiver) } dispatch_to { params.receiver } end

“

Now on the client we can say:

“by PrivateAnnouncement(receiver: login_name, message: ‘log off now!’).fail do alert(‘message could not be sent’) end

“

and elsewhere in the client code we would have a component like this:

“by class Alerts < Hyperloop::Component include Hyperloop::Store::Mixin # for simplicity we are going to merge our store with the component state alert_messages: [] scope: :class receives PrivateAnnouncement { |params| mutate.alert_messages « params.message } render(DIV, class: :alerts) do UL do state.alert_messages.each do |message| LI do SPAN { message } BUTTON { ‘dismiss’ }.on(:click) { mutate.alert_messages.delete(message) } end end end end end

“

This will (in only 28 lines of code) + associate a channel with each logged in user + invoke the PrivateAnnouncement Operation on the server (remotely from the client) + validate that there is a logged in user at that client + validate that we have a non-nil, non-blank receiver and message + validate that the acting_user is an admin + lookup the receiver in the database under their login name + dispatch the parameters back to any clients where the receiver is logged in + those clients will update their alert_messages state and + display the message

The dispatch_to callback takes a list of classes, representing Channels. The Operation will be dispatched to all clients connected on those Channels. Alternatively dispatch_to can take a block, a symbol (indicating a method to call) or a proc. The block, proc or method should return a single Channel, or an array of Channels, which the Operation will be dispatched to. The dispatch_to callback has access to the params object. For example we can add an optional to param to our Operation, and use this to select which Channel we will broadcast to.

“by class Announcement < Hyperloop::Operation param :message param :duration param to: nil, type: User # dispatch to the Users channel only if specified otherwise announcement is application wide dispatch_to { params.to || Hyperloop::Application } end

“

Defining Connections in ServerOps

The policy methods always_allow_connection and regulate_class_connection may be used directly in a ServerOp class. This will define a channel dedicated to that class, and will also dispatch to that channel when the Operation completes.

“by class Announcement < HyperLoop::ServerOp # all clients will have a Announcement Channel which will # receive all dispatches from the Annoucement Operation always_allow_connection end

“

“by class AdminOps < HyperLoop::ServerOp # subclasses can be invoked from the client if an admin is logged in # and all other clients that have a logged in admin will receive the dispatch regulate_class_connection { acting_user.admin? } param :acting_user validate { param.acting_user.admin? } end

“

Regulating Dispatches in Policy Classes

Regulations and dispatch lists can be grouped and specified in Policy files, which are by convention kept in the Rails app/policies directory.

“by

app/policies/announcement_policy.rb

class AnnouncementPolicy always_allow_connection dispatch_to { params.acting_user } end

app/policies/user_policy.rb

class UserPolicy regulate_instance_connection { self } end

“

Serialization

If you need to control serialization and deserialization across the wire you can define the following class methods:

“by def self.serialize_params(hash) # receives param_name -> value pairs # return an object ready for to_json # default is just return the input hash end

def self.deserialize_params(object) # recieves whatever was returned from serialize_to_server # (param_name => value pairs by default) # must return a hash of param_name => value pairs # by default this returns object end

def self.serialize_response(object) # receives the object ready for to_json # by default this returns object end

def self.deserialize_response(object) # receives whatever was returned from serialize_response # by default this returns object end

def self.serialize_dispatch(hash) # input is always key - value pairs # return an object ready for to_json # default is just return the input hash end

def self.deserialize_dispatch(object) # recieves whatever was returned from serialize_to_server # (param_name => value pairs by default) # must return a hash of param_name => value pairs # by default this returns object end

“

Isomorphic Operations

Unless the Operation is a Server Operation it will run where it was invoked. This can be handy if you have an Operation that needs to run on both the server and the client. For example an Operation that calculates the customers discount, will want to run on the client so the user gets immediate feedback, and then will be run again on the server when the order is submitted as a double check.

Dispatching With New Parameters

The dispatch method sends the params object on to any registered receivers. Sometimes it’s useful for the to add additional outbound params before dispatching. Additional params can be declared using the outbound macro:

“by class AddItemToCart < Hyperloop::Operation param :sku, type: String param qty: 1, type: Integer, minimum: 1 outbound :available

step { HTTP.get(‘/inventory/#paramsparams.sku/qty’) } step { |response| params.available = response.to_i } step { fail if params.qty > params.available } dispatch end

“

Instance Verses Class Execution Context

Normally the Operation’s steps are declared and run in the context of an instance of the Operation. An instance of the Operation is created, runs and is thrown away.

Sometimes it’s useful to run a step (or other macro such as validate) in the context of the class. This is useful especially for caching values between calls to the Operation. You can do this by defining the steps in the class context, or by providing the option scope: :class to the step.

Note that the primary use should be in interfacing to outside APIs. Don’t hide your application state inside an Operation - Move it to a Store.

“by class GetRandomGithubUser < Hyperloop::Operation def self.reload_users @promise = HTTP.get(“https://api.github.com/users?since=#rand(500)”).then do |response| @users = response.json.collect do |user| { name: user[:login], website: user[:html_url], avatar: user[:avatar_url] } end end end self.class.step do # as one big step return @users.delete_at(rand(@users.length)) unless @users.blank? reload_users unless @promise && @promise.pending? @promise.then { run } end end

or

class GetRandomGithubUser < Hyperloop::Operation class « self # as 4 steps - whatever you like step { succeed! @users.delete_at(rand(@users.length)) unless @users.blank? } step { succeed! @promise.then { run } if @promise && @promise.pending? } step { self.class.reload_users } async { @promise.then { run } } end end

“

An instance of the operation is always created to hold the current parameter values, dispatcher, etc. The first parameter to a class level step block or method (if it takes parameters) will always be the instance.

“by class Interesting < Hyperloop::Operation param :increment param :multiply outbound :result outbound :total step scope: :class { @total ||= 0 } step scope: :class { |op| op.params.result = op.params.increment * op.params.multiply } step scope: :class { |op| op.params.total = (@total += op.params.result) } dispatch end

“

The Hyperloop::Application::Boot Operation

Hyperloop includes one predefined Operation, Hyperloop::Application::Boot, that runs at system initialization. Stores can receive Hyperloop::Application::Boot to initialize their state. To reset the state of the application you can simply execute Hyperloop::Application::Boot

Flux and Operations

Hyperloop is a merger of the concepts of the Flux pattern, the Mutation Gem, and Trailblazer Operations.

We chose the name Operation rather than Action or Mutation because we feel it best captures all the capabilities of a Hyperloop::Operation. Nevertheless Operations are fully compatible with the Flux Pattern.

FluxHyperLoop
ActionHyperloop::Operation subclass
ActionCreatorHyperloop::Operation.step/failed/async methods
Action DataHyperloop::Operation parameters
DispatcherHyperloop::Operation#dispatch method
Registering a StoreStore.receives

In addition Operations have the following capabilities:

  • Can easily be chained because they always return promises.
  • Clearly declare both their parameters, and what they will dispatch.
  • Parameters can be validated and type checked.
  • Can run remotely on the server.
  • Can be dispatched from the server to all authorized clients.
  • Can hold their own state data when appropriate.

Documentation and Help

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/ruby-hyperloop/hyper-store. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Code of Conduct code of conduct.

License

=======

14990fb3321e5a8b1cc1cb2d859d747695ffd907 The gem is available as open source under the terms of the MIT License.