Ruby: How to chain multiple method calls together with "send"

Question

There has to be a built in way of doing this, right?

class Object
  def send_chain(arr)
    o=self
    arr.each{|a| o=o.send(a) }
    return o
  end
end

Sorption

I'm not sure, but I've gone down paths like this before, and I generally find that they lead to a bad implementation of something. What is it you're actually attempting to accomplish? Maybe there is an existing programming pattern that would benefit you more. – Bordelon

Eh, it's just a rake task to output some columns from some ActiveRecord models. It accepts an array of strings, with each string representing either a model's attribute/method or a model's associated model's attribute/method. So, I want to give it something like ["date", "title", "color", "author.name"] for the "Book" model and have it print out the attributes and the associated author's name attribute. I guess I could write out methods for Book that would return self.author.name, but just wanted something quick for this one-off rake output task. – Sorption

Answer 1

I just ran across this and it really begs for inject:

def send_chain(arr)
  arr.inject(self) {|o, a| o.send(a) }
end

Nikethamide

Shorter: arr.inject(self, :send) – Willianwillie

Safer: arr.inject(self, :try) :) – Colic

How can one do this when one of the methods to send takes arguments? – Livraison

Answer 2

Building upon previous answers, in case you need to pass arguments to each method, you can use this:

def send_chain(arr)
  Array(arr).inject(self) { |o, a| o.send(*a) }
end

You can then use the method like this:

arr = [:to_i, [:+, 4], :to_s, [:*, 3]]
'1'.send_chain(arr) # => "555"

This method accepts single arguments as well.

Fionnula

Answer 3

No, there isn't a built in way to do this. What you did is simple and concise enough, not to mention dangerous. Be careful when using it.

On another thought, this can be extended to accept arguments as well:

class Object
  def send_chain(*args)
    o=self
    args.each do |arg|
      case arg
      when Symbol, String
        o = o.send arg # send single symbol or string without arguments
      when Array
        o = o.send *arg # smash the inner array into method name + arguments
      else
        raise ArgumentError
      end
    end
    return o
  end
end

this would let you pass a method name with its arguments in an array, like;

test = MyObject.new
test.send_chain :a_method, [:a_method_with_args, an_argument, another_argument], :another_method

Stoltzfus

Just being nitpicky here, but keeping in line with Ruby idioms, this really should be duck-typed. – Fabricate

@edgerunner. It didn't worked for me sa.grade_accesses.send_chain(:except_grade_k, :except_grade_math_fact) NoMethodError: undefined method `except_grade_k' for #<Array:0x007fed40a2e0d8> – Sharla

@MohitJain all methods should return self. – Discriminating

Answer 4

How about this versatile solution without polluting the Object class:

def chain_try(arr)
  [arr].flatten.inject(self_or_instance, :try)
end

or

def chain_send(arr)
  [arr].flatten.inject(self_or_instance, :send)
end

This way it can take a Symbol, a String or an Array with a mix of both even.🤔

example usage:

• chain_send([:method1, 'method2', :method3])
• chain_send(:one_method)
• chain_send('one_method')

---

Lascivious