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August 29, 2015 13:56
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The idea here is to give you a simple method that can define your ivar for you, protecting against `nil` proactively, and record the location where the ivar was defined. Best part is, if someone looks for where `#expose` is defined, they'll be happy to find out it's not in a gem. Easy to modify/understand.
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# Instead of ditching ivars, just make them easier to discover: | |
class ApplicationController < ActionController::Base | |
private | |
# Expose an object as an ivar to your views. Explodes if you try to assign nil. | |
# | |
# Use: | |
# | |
# admin = Admin.find_by(email: "admin@test.zz") | |
# | |
# expose(admin) # Defines @admin, because admin.class is Admin | |
# expose(admin, as: "@user") # Overrides default ivar name | |
# expose(admin, permit_nil: true) # Does *not* blow up if admin is nil | |
# | |
def expose(object, as: "@#{object.class.name.underscore}", permit_nil: false) | |
if instance_variable_defined?(as) | |
raise "Instance variable #{as} already defined!" | |
end | |
if object.nil? && permit_nil | |
raise "Tried to expose #{as} as nil!" | |
end | |
unless Rails.env.production? | |
exposed_variables[as] = OpenStruct.new(object: object, source: caller_locations[1]) | |
end | |
instance_variable_set as, object | |
end | |
def exposed_variables | |
# Add the underscores before and after to indicate that this variable is srs bsns. | |
@__exposed_variables__ ||= {} | |
end | |
def source_for_ivar(ivar) | |
exposed_variables.find { |k,v| v.object == ivar }.try(:source) | |
end | |
end | |
# Usage | |
class OrdersController < ApplicationController | |
def show | |
order = Order.find(params[:id]) | |
expose order | |
end | |
end | |
# When you want to override the name: | |
class OrdersController < ApplicationController | |
def show | |
order = PaypalOrder.find(params[:id]) | |
expose order, as: "@order" | |
end | |
end | |
# Now, your view can go back to using ivars, knowing that @order will never be nil, | |
# and that if you ever need to know where it came from, you can find it. | |
# app/views/orders/show.html.erb | |
# | |
# <dl> | |
# <dt>Order Number</dt> | |
# <dt><%= @order.id %></dt> | |
# </dl> |
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expose(self)
is probably a bad practice.