Ruby: How to chain methods specified in an array (or split string) of methods?

Question

How is it possible to chain methods in Ruby when the method calls are specified as an array?

Example:

class String
  def bipp();  self.to_s + "-bippity"; end
  def bopp();  self.to_s + "-boppity"; end
  def drop();  self.to_s + "-dropity"; end
end

## this produces the desired output
##
puts 'hello'.bipp.bopp.drop #=> hello-bippity-boppity-dropity

## how do we produce the same desired output here?
##
methods   =   "bipp|bopp|drop".split("|")
puts 'world'.send( __what_goes_here??__ ) #=> world-bippity-boppity-droppity

[Note to Ruby purists: stylistic liberties were taken with this example. For notes on preferred usage regarding semicolons, parenthesis, comments and symbols, please feel free to consult Ruby style guides (e.g., https://github.com/styleguide/ruby)]

In Ruby style, empty brackets are usually omitted. This makes it much more readable: 'hello'.bipp.bopp.drop This also applies to method definitions. Semicolons at the end of the line are almost always redundant and are a distraction. For me, they're an indication that someone's not too familiar with Ruby and I should pay careful attention to any code they've written. — tadman
– tadman, Commented Apr 15, 2013 at 21:28
@tadman: That's fine as a general-purpose heuristic. This conclusion, however, does not account for cases where the author is fluent with the language and its idioms, but has deliberately chosen to relax one or more conventions for increased suitability for a general audience. For example, one could also argue that Ruby symbols should have been used instead of strings. Nevertheless, lacking familiarity with symbols is not the same thing as deliberately choosing not to use them (even if one can reasonably disagree with the rationale for that choice). — dreftymac
– dreftymac, Commented Apr 15, 2013 at 22:54
String versus symbol is often a matter of preference, where symbols are preferred if used repeatedly. Extraneous empty brackets rubs against many if not most Ruby coding styles. This example just looks out of place. There's no reason to code for a general audience. When in Rome... To code "fluently" in Ruby it's best to do things the Ruby way, no matter how odd they might seem when viewed from another context. It's like real spoken languages and their often quirky pronunciation. If you don't follow convention, you have a heavy accent. — tadman
– tadman, Commented Apr 16, 2013 at 2:15
//There's no reason to code for a general audience.// A fundamental element of effective communication is conveying ideas in a way that will reach the intended target audience. The intended target audience is more than just Ruby programmers. //String versus symbol is often a matter of preference, where symbols are preferred if used repeatedly.// This nicely illustrates the point already made: reasonable people can differ and the personal preferences of one may not suit another. //Extraneous empty brackets rubs against many if not most Ruby coding styles.// Many does not constitute all. — dreftymac
– dreftymac, Commented Apr 16, 2013 at 10:39

Wayne Conrad · Accepted Answer · 2013-04-15 20:54:57Z

12

Try this:

methods   =   "bipp|bopp|drop".split("|")
result = 'world'
methods.each {|meth| result = result.send(meth) }
puts result

or, using inject:

methods = "bipp|bopp|drop".split("|")
result = methods.inject('world') do |result, method|
  result.send method
end

or, more briefly:

methods = "bipp|bopp|drop".split("|")
result = methods.inject('world', &:send)

By the way - Ruby doesn't need semicolons ; at the end of each line!

edited Apr 15, 2013 at 20:54

Wayne Conrad

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answered Apr 15, 2013 at 20:48

Chowlett

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1 Comment

dreftymac Over a year ago

// By the way - Ruby doesn't need semicolons ; at the end of each line! // True, but it helps with the 'yf' command in Vim.

Arup Rakshit · Accepted Answer · 2013-04-15 21:07:45Z

2

methods   =   "bipp|bopp|drop".split("|")
result = 'world'
methods.each {|meth| result = result.method(meth).call }
puts result #=> world-bippity-boppity-dropity

or

methods = "bipp|bopp|drop".split("|")
methods.each_with_object('world') {|meth,result| result.replace(result.method(meth).call)} #=> world-bippity-boppity-dropity

edited Apr 15, 2013 at 21:07

answered Apr 15, 2013 at 20:58

Arup Rakshit

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