Class: ActionController::Parameters

Inherits:
Object
  • Object
show all
Defined in:
lib/rails/pattern_matching.rb

Instance Method Summary collapse

Instance Method Details

#deconstruct_keys(keys) ⇒ Object

Returns a hash of parameters for the given keys. Provides the pattern matching interface for matching against hash patterns. For example:

class PostsController < ApplicationController
  before_action :find_post

  # PATCH /posts/:id
  def update
    case post_params
    in { published: true, ** } if !can_publish?(current_user)
      render :edit, alert: "You are not authorized to publish posts"
    in permitted if @post.update(permitted)
      redirect_to @post, notice: "Post was successfully updated"
    else
      render :edit
    end
  end

  private

  def find_post
    @post = Post.find(params[:id])
  end

  def post_params
    params.require(:post).permit(:title, :body, :published)
  end
end

Note that for security reasons, this method will only deconstruct keys that have been explicitly permitted. This is to avoid the potential accidental misuse of the ‘**` operator.

Note: as an optimization, Hash#deconstruct_keys (and therefore ActiveSupport::HashWithIndifferentAccess#deconstruct_keys) always returns itself. This works because the return value then has #[] called on it, so everything works out. This can yield some somewhat surprising (albeit correct) results if you call this method manually.



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# File 'lib/rails/pattern_matching.rb', line 213

def deconstruct_keys(keys)
  if permitted?
    to_h.deconstruct_keys(keys)
  else
    raise ArgumentError, "Only permitted parameters can be deconstructed."
  end
end