Using send for convenience, from despair and for fun

One of the methods of the Sidekiq library. Smile Explanation

send to Ruby calls object methods by name. Here is the obvious way to use it:

# :   . ,        . user.name = "" user.age = 29 # :    .    . def set(field, value) send("#{field}=", value) end user.set(:name, "") user.set(:age, 29) 

And you probably also saw these lines:

 after_create :send_email 

Yes, callbacks in the rails inside are also implemented using send .

Even through send, when testing, private methods are called. Sandi Metz, author of Practical Object-Oriented Design in Ruby (on private methods from 10:58), talks about whether to test them at all.

Sometimes you can't do without send:

 data_point = OpenStruct.new(:queued? => true) data_point.queued? # -> true data_point.send("queued?=",false) #      data_point.queued? # -> false 

This is an example from the OpenStruct documentation. The example is contrived, but there are also more strange names: take at least the same method from the picture at the beginning of the post.

Continuing the theme of unusual method names.

Often try to quit irb with a better command? Just add the following code to ~/.irbrc :

 module Kernel def  exit end end 

It occurred to me while mulling over examples for the article; added for the sake of the test itself in .irbrc - works. I was going to delete it, then I think: "But it’s convenient the same." While left, let it lie for a week.

 module Kernel def method_missing(method_name, *arguments, &block) return(super) unless contains_russian_letters?(method_name.to_s) possible_meaning = translit(method_name.to_s) send(possible_meaning, *arguments) end private def translit(string) string.chars.map do |char| russian_to_english_mapping[char] || char end.join end def contains_russian_letters?(string) !(string.chars & russian_symbols).empty? end def russian_symbols "".chars end def russian_to_english_mapping english = "qwertyuiop[]asdfghjkl;'zxcvbnm,.".chars russian_symbols.zip(english).to_h end end # : puts(1.inspect) #  1 (1.) #  . ! 

disadvantages

Inaccurate use of send degrades readability. Compare:

 #  1. ,    if params[:sort_by] == "age" users.sort_by_age else users.sort_by_name end #  2. ,   (    ) sorting_method = "sort_by_#{params[:sort_by]}" users.send(sorting_method) #    ,     #  ,  : users.sort_by(params[:sort_by]) 

Let's sum up

Use send if you need:

• Define the name of the method at run time;
• Write your bicycle callbacks;
• Call private methods in tests.

Do not use send unnecessarily.