As title, I wonder what's the difference between Rails flash.discard and flash.delete.
#SteveTurczyn is right.
However, flash.delete is only possible to do in versions of rails previous to 3.1.
As of 3.1, flash.delete doesn't work anymore, an alternative might be flash.clear (check out flash.delete(:notice) not working in Rails 3.1 RC?).
You might also want to check: https://apidock.com/rails/v3.0.0/ActionDispatch/Flash/FlashHash/discard
flash.delete is immediate. flash.discard will remove the flash at the end of the current action.
So using flash.discard you can still examine the flash contents in the current action.
I have another thread trying a different approach to testing that the resource is being loaded and authorized in the controller, but it seems like I am borderline testing CanCan itself. I've looked at the source code for CanCan's load_and_authorize_resource method and it just seems to be adding a before_filter to the controller.
I've tried the following:
Checking for a load_and_authorize_resource before_filter. I find the filters with the _process_action_callbacks method, but I see no CanCan-related filters. I'm not sure if this is due to how the before_filters are being added.
I tried testing MyController.should_receive(:load_and_authorize_resource).with(:network), to no avail.
Any other suggestions? How would you test this?
I'd mock it out using mocha or some other mocking framework, with something like:
CanCan.expects(:load_and_authorize_resource).once.returns(true)
Does Ruby on Rails 3 (3.0.7) offer a mechanism to reload the class cache on demand? I am running some tests where I overwrite some methods in ApplicationController and in some of my models to stub out authentication. For example, I call a method (I'm using Cucumber for testing) in some of my tags (Before('#tag')) that does this:
ApplicationController.send(:define_method, :current_user) do
#current_user ||= User.where(:id => cookies[:user_id]).first
end
...where the actual current_user method in ApplicationController has a different behavior.
This works great until I need to run some tests in which I do not want to stub out those methods. With config.cache_classes = true set in my test environment, ApplicationController is not reinitialized without my monkey patch, making the tests I don't want to stub out fail. With config.cache_classes = false, my monkey patch is forgotten on the next request, causing all of the tests that I need to stub to fail.
Ideally, I would like to be able to erase the class cache in an After('#tag') method, if this is possible. How can I accomplish that? Or is there a better way of stubbing out certain methods in certain scenarios that I am overlooking?
You could take inspiration from this great SO answer, and make good use of ActionDispatch::Callbacks.
ActionDispatch::Reloader.cleanup!
ActionDispatch::Reloader.prepare!
I posted the rationale behind this over here: Why does code need to be reloaded in Rails 3?
If its bad to cross post the same answer, kindly let me know how its preferred to post an answer thats relevant to two questions...I'm happy to oblige.
As of newer Rails (> 4.0), I was able to reload class definitions, in console, for instance, with reload!.
I found the following code, which I guess goes in config/initializers/kernel.rb.
module Kernel
private
def this_method
caller[0] =~ /`([^']*)'/ and $1
end
end
For adding to the log, is this the preferred way to get the current method?
Thanks.
That seems like a decent way to get the calling method and give you the ability to call this_method in your code to add to the log.
If you are using Ruby 1.9.2 you can call __method__ instead and not worry about defining a special method to do so.
I've tried reading through various blog posts that attempt to explain alias_method_chain and the reasons to use it and not use it. In particular, I took heed to:
http://weblog.rubyonrails.org/2006/4/26/new-in-rails-module-alias_method_chain
and
http://yehudakatz.com/2009/03/06/alias_method_chain-in-models/
I still do not see any practical use for alias_method_chain. Would anyone be able to explain a few things.
1 - is it still used at all?
2 - when would you use alias_method_chain and why?
1 - is it still used at all?
Apparently yes, alias_method_chain() is still used in Rails (as of version 3.0.0).
2 - when would you use
alias_method_chain and why?
(Note: the following is largely based on the discussion of alias_method_chain() in Metaprogramming Ruby by Paolo Perrotta, which is an excellent book that you should get your hands on.)
Let's start with a basic example:
class Klass
def salute
puts "Aloha!"
end
end
Klass.new.salute # => Aloha!
Now suppose that we want to surround Klass#salute() with logging behavior. We can do that what Perrotta calls an around alias:
class Klass
def salute_with_log
puts "Calling method..."
salute_without_log
puts "...Method called"
end
alias_method :salute_without_log, :salute
alias_method :salute, :salute_with_log
end
Klass.new.salute
# Prints the following:
# Calling method...
# Aloha!
# ...Method called
We defined a new method called salute_with_log() and aliased it to salute(). The code that used to call salute() still works, but it gets the new logging behavior as well. We also defined an alias to the original salute(), so we can still salute without logging:
Klass.new.salute_without_log # => Aloha!
So, salute() is now called salute_without_log(). If we want logging, we can call either salute_with_log() or salute(), which are aliases of the same method. Confused? Good!
According to Perrotta, this kind of around alias is very common in Rails:
Look at another example of Rails
solving a problem its own way. A few
versions ago, the Rails code contained
many instances of the same idiom: an
Around Alias (155) was used to add a
feature to a method, and the old
version of the method was renamed to
something like
method_without_feature(). Apart from
the method names, which changed every
time, the code that did this was
always the same, duplicated all over
the place. In most languages, you
cannot avoid that kind of duplication.
In Ruby, you can sprinkle some
metaprogramming magic over your
pattern and extract it into its own
method... and thus was born
alias_method_chain().
In other words, you provide the original method, foo(), and the enhanced method, foo_with_feature(), and you end up with three methods: foo(), foo_with_feature(), and foo_without_feature(). The first two include the feature, while the third doesn't. Instead of duplicating these aliases all around, alias_method_chain() provided by ActiveSupport does all the aliasing for you.
alias_method_chain has been deprecated in Rails 5 in favour of Module#prepend.
Pull request: https://github.com/rails/rails/pull/19434
Changelog: https://github.com/rails/rails/blob/b292b76c2dd0f04fb090d49b90716a0e6037b41a/guides/source/5_0_release_notes.md#deprecations-4
I'm not sure if it's gone out of style with Rails 3 or not, but it is still actively used in versions before that.
You use it to inject some functionality before (or after) a method is called, without modifying any place that calls that method. See this example:
module SwitchableSmtp
module InstanceMethods
def deliver_with_switchable_smtp!(mail = #mail)
unless logger.nil?
logger.info "Switching SMTP server to: #{custom_smtp.inspect}"
end
ActionMailer::Base.smtp_settings = custom_smtp unless custom_smtp.nil?
deliver_without_switchable_smtp!(mail = #mail)
end
end
def self.included(receiver)
receiver.send :include, InstanceMethods
receiver.class_eval do
alias_method_chain :deliver!, :switchable_smtp
end
end
end
That's an addition to ActionMailer to allow swapping out of the SMTP settings on each call to deliver!. By calling alias_method_chain you are able to define a method deliver_with_switchable_smtp! in which you do your custom stuff, and call deliver_without_switchable_smtp! from there when you're done.
alias_method_chain aliases the old deliver! to your new custom method, so the rest of your app doesn't even know deliver! now does your custom stuff too.
is it used at all?
Seems so. It's a common practice among Rails developers
when would you use alias_method_chain and why?
Despite the warnings, alias_method_chain is still the main strategy used when injecting functionality to an existing method, at least was in Rails 2.x and is followed by many people extending it. Yehuda ought to remove alias_method_chain from rails 3.0 to say from his posts and comments in Rails tickets. It is still used by many extensions that add custom behavior at certain points of the execution, such as loggers, error reporters, benchmarking, data injection, etc.
IMO, the best alternative is to include a module, thus you have decoration over delegation. (For example, follow example 4 in this post). That way you can alter the objects even individually if you'd like, without polluting the class' methods. The downside to this is that the method lookup chain increases for each module you inject, but this is what modules are for anyway.
Very interesting question, will keep a look on what other people think about it.