I want to rewrite several methods of HighLine to customise my console and at the moment my code looks like this:
cmd = ask("#{#prompt_label} #{#prompt_separator} ", #tab_completion_candidates) do |q|
q.readline = true
# rewriting the Question class to make it do what we want
class << q
HERE I WRITE MY CODE
end
end
I would like to be able to separate my changes from my main console file, so let's say i have a class Console::Question that contains all the changes I want to do in HighLine::Console, I'd like to be able to do something like that:
Console::Question << q
end
But unfortunately that doesn't work :)
Any solution?
Thanks for your time.
If you put your changes in a module rather than a class then you can then do
q.extend(YourModule)
e.g. to override valid_answer?
module QuestionCustomisations
def valid_answer?
# your code here
end
end
q.extend(QuestionCustomisations)
This will apply your changes in just the object instance which is passed to the block.
Related
A bit of context first
I have a class Phone that defines a method advertise like this:
class Phone
def advertise(phone_call)
'ringtone'
end
end
I would like to have some adaptations for this method.
For example when the user is in a quiet environment, the phone should vibrate and not ring.
To do so, I define modules like
module DiscreetPhone
def advertise_quietly (phone_call)
'vibrator'
end
end
Then my program can do
# add the module to the class so that we can redefine the method
Phone.include(DiscreetPhone)
# redefine the method with its adaptation
Phone.send(:define_method, :advertise, DiscreetPhone.instance_method(:advertise_quietly ))
Of course for this example I hardcoded the class and module's name but they should be parameters of a function.
And so, an execution example would give:
phone = Phone.new
phone.advertise(a_call) # -> 'ringtone'
# do some adaptation stuff to redefine the method
...
phone.advertise(a_call) # -> 'vibrator'
Finally coming to my question
I want to have an adaptation that call the original function and append something to its result. I would like to write it like
module ScreeningPhone
def advertise_with_screening (phone_call)
proceed + ' with screening'
end
end
But I don't know what the proceed call should do or even where should I define it.
I'm using Ruby 2.3.0 on Windows.
proceed could be replaced by something else but I'd like to keep it as clean as possible in the module that defines the adaptation.
You can do this by prepending your module instead of including it.
Instead of using define_method as a sort of ersatz alias_method, just call the method advertise in your modules too.
Within your advertise method, you can call super to call up the inheritance hierarchy.
In my opinion, this approach is way too complex, and an inappropriate use of Modules.
I recommend thinking about a simpler way to implement this.
One simple way is to just include all the methods in the Phone class.
Or, you could use a hash as a lookup table for ring strategies:
class Phone
attr_accessor :ring_strategy
RING_STRATEGIES = {
ringtone: -> { ring_with_tone },
discreet: -> { ring_quietly },
screening: -> { ring_with_tone; ring_screening_too }
# ...
}
def initialize(ring_strategy = :ringtone)
#ring_strategy = ring_strategy
end
def ring
RING_STRATEGIES[:ring_strategy].()
end
end
I have a Volt Framework Task that checks and stores information on a directory, e.g.
class DirectoryHelperTask < Volt::Task
def list_contents()
contents = []
Dir.glob("/path/to/files").each do |f|
contents << f
end
return contents
end
end
I would like to call this from a different task, e.g.
class DirectoryRearrangerTask < Volt::Task
dir_contents = DirectoryHelperTask.list_contents()
end
The code above (DirectoryRearranger) throws an error, as does a promise call
DirectoryHelperTask.list_contents().then do |r|
dir_conents = r
end.fail do |e|
puts "Error: #{e}"
end
Could not find a way to call a task from another task in the Volt Framework documentation.
Thanks a lot!
From what I gather, tasks are meant to be run on the server side and then called on the client side, hence the use of the promise object. The promise object comes from OpalRb, so trying to call it from MRI won't work. If you have a "task" that will only be used on the server side, then it doesn't really fit with Volt's concept of a task.
Your first approach to the problem actually does work, except that DirectoryRearrangerTask can't inherit from Volt::Task.
directory_helper_task.rb
require_relative "directory_rearranger_task"
class DirectoryHelperTask < Volt::Task
def list_contents
contents = []
Dir.glob("*").each do |file|
contents << file
end
DirectoryRearrangerTask.rearrange(contents)
contents
end
end
directory_rearranger_task.rb
class DirectoryRearrangerTask
def self.rearrange(contents)
contents.reverse!
end
end
Here is a GitHub repo with my solution to this problem.
You can call tasks from the client or server, but keep in mind that you call instance methods on the class. (So they get treated like singletons) And all methods return a Promise. I think your issue here is that your doing dir_contents = DirectoryHelperTask.list_contents() inside of the class. While you could do this in ruby, I'm not sure its what you want.
Also, where you do dir_contents = r, unless dir_contents was defined before the block, its going to get defined just in the block.
I have a situation in my Rails application where I need to include arbitrary modules depending on the current runtime state. The module provides custom application code that is only needed when certain conditions are true. Basically, I'm pulling the name of a company from the current context and using that as the filename for the module and its definition:
p = self.user.company.subdomain + ".rb"
if File.exists?(Rails.root + "lib/" + p)
include self.class.const_get(self.user.company.subdomain.capitalize.to_sym)
self.custom_add_url
end
My test module looks like this:
module Companyx
def custom_add_url
puts "Calling custom_add_url"
end
end
Now in the console, this actually works fine. I can pull a user and include the module like so:
[1] pry(main)> c = Card.find_by_personal_url("username")
[2] pry(main)> include c.class.const_get(c.user.company.subdomain.capitalize)=> Object
[3] pry(main)> c.custom_add_url
Calling custom_add_url
If I try to run the include line from my model, I get
NoMethodError: undefined method `include' for #<Card:0x007f91f9094fb0>
Can anyone suggest why the include statement would work on the console, but not in my model code?
I'm doing a similar thing. I found this answer useful:
How to convert a string to a constant in Ruby?
Turns out I was looking for the constantize method. This is the line I'm using in my code:
include "ModuleName::#{var.attr}".constantize
Edit:
So ack, I ran into various problems with actually using that line myself. Partially because I was trying to call it inside a method in a class. But since I'm only calling one method in the class (which calls/runs everything else) the final working version I have now is
"ModuleName::#{var.attr}".constantize.new.methodname
Obviously methodname is an instance method, so you could get rid of the new if yours is a class method.
Include is a method on a class.
If you want to call it inside a model, you need to execute the code in the context of its singleton class.
p = self.user.company.subdomain + ".rb"
if File.exists?(Rails.root + "lib/" + p)
myself = self
class_eval do
include self.const_get(myself.user.company.subdomain.capitalize.to_sym)
end
self.custom_add_url
EDIT:
class << self doesn't accept a block; class_eval does, hence it preserves the state of local variables. I've modified my solution to use it.
I have a class, Autodrop, that contains several methods , a.o. 'metadata', that call an external API (dropbox). They are slow.
However, I already often have that metadata around when initializing the AutodropImage, so I should make the methods smarter.
What I have in mind is this:
class Autodrop
include Dropbox
attr_reader :path
def initialize(path)
#path = path
end
def self.from_entry(drop_entry)
#drop_entry = drop_entry
self.initialize(#drop_entry.path)
end
def metadata
if #drop_entry = nil
return heavy_lifting_and_network_traffic
else
return #drop_entry.metadata
end
end
#...
end
Now, I would expect to call
entry = BarEntry.new()
foo = Autodrop.from_entry(entry)
foo.metadata
In order to avoid that heavy lifting and network traffic call.
But this does not work. And somehow, in all my newbieness, I am sure I am goind at this all wrong.
Is there a term I should look for and read about first? How would you go for this?
Note, that the examples are simplified: in my code, I inherit AutodropImage < Autodrop for example, which is called from withing AutodropGallery < Autodrop. The latter already knows all metadata for the AutodropImage, so I mostly want to avoid AutodropImage going over the heavy lifting again.
You are creating an instance variable #drop_entry in your class method from_entry and obviously it wont be available to your object that you are creating in this method. One workaround is to pass it as a parameter when you are initializing the class. It should work if you do the following modifications:
In your from_entry class method change
self.initialize(#drop_entry)
to
new(#drop_entry)
Modify initialize method to:
def initialize(drop_entry)
#drop_entry = drop_entry
#path = #drop_entry.path
end
Or if your class is tied up to pass only the path parameter, ie. you dont want to change the other existing code then you can use an optional parameter drop entry like so
def initialize(path, drop_entry=nil)
You would need to cache the metadata in a class variable.
Edit: Or in a class level instance variable.
Maybe this read will help: http://railstips.org/blog/archives/2006/11/18/class-and-instance-variables-in-ruby/
I want to eliminate "=" sign for a particular reason. It might looks like this:
cat_that_has_name("Kelly").as(:kelly)
kelly.do_something
The "as" method here is used to generate a method "kelly" that reference my cat. Could anyone help me with this?
Any suggestions will be appreciated.
Update:
Jorg was right, I've add a simple test to demonstrate my intention:
require "test/unit"
class AsTest < Test::Unit::TestCase
def setup
#cats = ["Kelly", "Tommy"]
end
def teardown
end
def test_as
kelly1 = get_cat("Kelly")
get_cat("Kelly").as(:kelly2)
assert_equal(kelly1.object_id, kelly2.object_id)
end
private
def get_cat(name)
#cats.each do |cat|
if cat.to_s==name
return cat
end
end
return nil
end
end
It's kind of hard to figure out what you actually want. If you want some sensible answers, you will have to provide a complete code example of what you want to achieve (for example, the code you posted is missing definitions for the cat_that_has_name and so_something methods). You will also need to post a complete specification of what exactly you expect the as method to do, with usage examples and ideally also with a testsuite. After all, how do we know if our answer is correct if you haven't defined what "correct" means?
The best I could decipher from your cryptic question is something like this:
class Object
def as(name)
s = self
Object.send(:define_method, name) { s }
Object.send(:private, name)
end
end
But there is no way of knowing whether this works, because if I try to run your code example, I get a NoMethodError for cat_that_has_name and another NoMethodError for so_something.
Note also that your question is self-inconsistent: in your subject line you ask about a method to replace = (i.e. creating variables) but in your question you talk about creating methods, which would mean that you are looking for a replacement for def and not for =. Again, it would be much easier to answer correctly if there were a testsuite.