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Exposing things, adequately
Ruby

Merge pull request #22 from plicjo/master

Document Adequate Exposure
latest commit db05385e00
@rwz authored

README.md

Adequate Exposure

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Exposing things, adequately.

Adequate exposure is a lightweight alternative to Decent Exposure. With its narrowly focused api you can get exactly what you need without all the extra dressing.

Note: It is not the intent of the author to imply that Decent Exposure is inadequate.

Installation is as simple as: $ gem install adequate_exposure. Once you have that down we can start talking about the API.

API

The whole API consists of three methods so far: expose, expose!, and exposure_config.

In the simplest scenario you'll just use it to expose a model in the controller:

class ThingsController < ApplicationController
  expose :thing
end

Now every time you call thing in your controller or view, it'll look for an ID and try to perform Thing.find(id). If the ID isn't found, it'll call Thing.new(things_params). The result will be memoized in an @exposed_thing instance variable.

Example Controller

Here's what a standard Rails 4 CRUD controller using Adequate Exposure might look like:

class ThingsController < ApplicationController
  expose :things, ->{ Thing.all }
  expose :thing

  def create
    if thing.save
      redirect_to thing_path(thing)
    else
      render :new
    end
  end

  def update
    if thing.update(thing_params)
      redirect_to thing_path(thing)
    else
      render :edit
    end
  end

  def destroy
    thing.destroy
    redirect_to things_path
  end

  private

  def thing_params
    params.require(:thing).permit(:foo, :bar)
  end
end

Under the Hood

The default resolving workflow is pretty powerful and customizable. It could be expressed with the following pseudocode:

def fetch(scope, id)
  instance = id ? find(id, scope) : build(build_params, scope)
  decorate(instance)
end

def id
  params[:thing_id] || params[:id]
end

def find(id, scope)
  scope.find(id)
end

def build(params, scope)
  scope.new(params) # Thing.new(params)
end

def scope
  model # Thing
end

def model
  exposure_name.classify.constantize # :thing -> Thing
end

def build_params
  if respond_to?(:thing_params, true) && !request.get?
    thing_params
  else
    {}
  end
end

def decorate(thing)
  thing
end

The exposure is also lazy, which means that it won't do anything until you call the method. To eliminate this lazyness you can use expose! macro instead, which will try to resolve the exposure in a before filter.

Each step could be overrided with options. The acceptable options to the expose macro are:

fetch

This is the entry point. The fetch proc defines how to resolve your exposure in the first place.

expose :thing, fetch: ->{ get_thing_some_way_or_another }

Because the above behavior overrides the normal workflow, all other options would be ignored. However, Adequate Exposure is decent enough to actually blow up with an error so you don't accidentally do this.

There are other less verbose ways to pass the fetch block, since you'll probably be using it often:

expose(:thing){ get_thing_some_way_or_another }

Or if you (like me) absolutely hate parens in side-effect methods:

expose :thing, ->{ get_thing_some_way_or_another }

or even shorter

expose :thing, :get_thing_some_way_or_another

There is another shortcut that allows you to redefine the entire fetch block with less code:

expose :comments, from: :post
# equivalent to 
expose :comments, ->{ post.comments }

id

The default fetch logic relies on the presence of an ID. And of course Adequate Exposure allows you to specify how exactly you want the ID to be extracted.

Default behavior could be expressed using following code:

expose :thing, id: ->{ params[:thing_id] || params[:id] }

But nothing is stopping you from throwing in any arbitrary code:

# id is always gonna be the answer to ultimate question of life, the universe,
# and everyting
expose :thing, id: ->{ 42 }

Passing lambdas might not always be fun, so here are a couple of shortcuts that could help make life easier.

expose :thing, id: :custom_thing_id
# equivalent to
expose :thing, id: ->{ params[:custom_thing_id] }

expose :thing, id: [:try_this_id, :or_maybe_that_id]
# equivalent to
expose :thing, id: ->{ params[:try_this_id] || params[:or_maybe_that_id] }

find

If an ID was provided, Adequate Exposure will try to find the model using it. Default behavior could be expressed with this configuration:

expose :thing, find: ->(id, scope){ scope.find(id) }

Where scope is a model scope, like Thing or User.active or Post.published.

Now, if you're using FriendlyId or Stringex or something similar, you'd have to customize your finding logic. Your code might look somewhat like this:

expose :thing, find: ->(id, scope){ scope.find_by!(slug: id) }

Again, because this is likely to happen a lot, Adequate Exposure gives you a decent shortcut so you can get more done by typing less.

expose :thing, find_by: :slug

build

When an ID is not present, Adequate Exposure tries to build an object for you. By default, it behaves like this:

expose :thing, build: ->(thing_params, scope){ scope.new(thing_params) }

build_params

These options are responsible for calulating params before passing them to the build step. The default behavior was modeled with Strong Parameters in mind and is somewhat smart: it calls the thing_params controller method if it's available and the request method is not GET. In all other cases it produces an empty hash.

You can easily specify which controller method you want it to call instead of thing_params, or just provide your own logic:

expose :thing, build_params: :custom_thing_params
expose :other_thing, build_params: ->{ { foo: "bar" } }

private

def custom_thing_params
  # strong parameters stuff goes here
end

scope

Defines the scope that's used in find and build steps.

expose :thing, scope: ->{ current_user.things }
expose :user, scope: ->{ User.active }
expose :post, scope: ->{ Post.published }

Like before, shortcuts are there to make you happier:

expose :post, scope: :published
# equivalent to
expose :post, scope: ->{ Post.published }

and

expose :thing, parent: :current_user
# equivalent to:
expose :thing, scope: ->{ current_user.things }

model

Allows you to specify the model class to use. Pretty straightforward.

expose :thing, model: ->{ AnotherThing }
expose :thing, model: AnotherThing
expose :thing, model: "AnotherThing"
expose :thing, model: :another_thing

decorate

Before returning the thing, Adequate Exposure will run it through the decoration process. Initially, this does nothing, but you can obviously change that:

expose :thing, decorate: ->(thing){ ThingDecorator.new(thing) }

exposure_config

You can pre-save some configuration with exposure_config method to reuse it later.

exposure_config :cool_find, find: ->{ very_cool_find_code }
exposure_config :cool_build, build: ->{ very_cool_build_code }

expose :thing, with: [:cool_find, :cool_build]
expose :another_thing, with: :cool_build

Contributing

  1. Fork it (https://github.com/rwz/adequate_exposure/fork)
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request
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