Elixir-like pipes in Ruby to process collections - arrays

Question

In Elixir there is a great pipeline operator working like this:
"hello, world!"
|> String.split(" ")
|> Enum.map(&String.capitalize/1)
|> Enum.join
In Ruby we can use similar syntax:
"hello, world!"
.split(" ")
.map(&:capitalize)
.join
It works only when have all these methods defined for a object itself. If need to call some local method we should use something like:
.map { |el| URI.parse(el) }
But what if we want to make some collection processing (not a single element), for example GZIP Compression:
chars = text
.downcase
.chars
compressed = GZipped.new(chars).bytes
But chain is broken!
I've found some links, but looks not awesome:
pipe_envy - UGLY! no collections
chainable_methods - no collections
How to use chainable_methods
piperator - much better! But looks heavy
In my opinion it would be great to have something like:
text
.split
.pipe(URI.method(:parse))
.map(&:to_s)
.join
.pipe(GZIPped)
.pipe(Base64.method(:encode))
What is the best way to build such pipes in Ruby?
Update 1
Here is an example
class Dedup
def initialize(obj)
#obj = obj
end
def each
Enumerator.new do |y|
prev = nil
#obj.each do |el|
if el != prev
y << el
prev = el
end
end
end
end
end
expect(
"1 1 1 2 2 3"
.split
.then { |obj| Dedup.new(obj).each }
.to_a
).to eq [1, 2, 3]
This chaining looks ugly and unreadable.
Comparing to:
expect(
"1 1 1 2 2 3"
.split
.pipe(Dedup)
.to_a
).to eq [1, 2, 3]

Answer 1

There's already a method like this, at least starting from Ruby 2.5 - yield_self, aliased as then in Ruby 2.6. You can use & operator with any object responding to to_proc to pass it instead of a block.
text
.split
.map(&URI.method(:parse)) # URI#parse expects a string, not an array
.map(&:to_s)
.join
.then(&GZIPped) # not sure what GZIPped is - I'll assume it has .to_proc method
.then(&Base64.method(:encode))
(I should probably mention that the code above will not actually work and honestly I have no clue what it would suppose to do - why would split a string, convert them to into urls and then back again to strings? The only thing this would to is to raise id one of the substrngs were not a valid string? But then you try to read resulting string as a gzipped file... I'm assuming I misunderstood something in your code)
More advanced stuff - one thing that I quite like in elixir was an option to chain methods together with remaining arguments. This also can be simulated in ruby, but requires a bit of work and good think whether it's worth it:
module MyMath
module_function
UNDEFINED = Object.new
def add(a, b = UNDEFINED)
if b == UNDEFINED
return ->(num) { add(a, num) }
end
a + b
end
end
MyMath.add(2,5) #=> 7
[1,2,5,9].map(&MyMath.add(5)] #=> [6,7,10,14]