Feature #17663
open
Enumerator#with, an alternative to Enumerator#with_object
Description
Enumerator#with yields each element along with the arguments
class Enumerator def with(*options) return to_enum(:with, *options) unless defined? yield each do |entry| yield entry, *options end end end Suppose we have a proc that accepts more than 1 argument.
format = proc do |value, *option| value.to_s(*option) end Normally to apply the argument we enclosed it in a block, like so:
(10..15).map { |n| format.(n, 16) } # => ["a", "b", "c", "d", "e", "f"] I found Enumerator#with_object method awkward to use.
(10..15).each.with_object(16).map(&format) # => ["a", "b", "c", "d", "e", "f"] Tried simplifying this code further, but Enumerator#with_object ignores the given block and just returns the argument.
(10..15).map.with_object(16, &format) # => 16 Compare to how concise this line using Enumerator#with
(10..15).map.with(16, &format) # => ["a", "b", "c", "d", "e", "f"] 
Updated by RichOrElse (Ritchie Buitre) over 4 years ago
- Description updated (diff)
Updated by RichOrElse (Ritchie Buitre) over 4 years ago
- Subject changed from Enumerator#with, an alternative for Enumerator#with_object to Enumerator#with, an alternative to Enumerator#with_object
Updated by RichOrElse (Ritchie Buitre) over 4 years ago
- Description updated (diff)
Updated by Hanmac (Hans Mackowiak) over 4 years ago
i had a similar problem when i wanted to make Symbol to_proc use parameters, i would have done something like :to_s.(16)
for your list of code comparisons:
(10..15).map(&"%x".method(:%)) Updated by RichOrElse (Ritchie Buitre) over 4 years ago
Hanmac (Hans Mackowiak) wrote in #note-4:
i had a similar problem when i wanted to make Symbol to_proc use parameters, i would have done something like
:to_s.(16)
Thanks, the implementation of format proc could be anything other than Integer#to_s.
I usually define to_proc for my classes, in those scenarios I couldn't use Symbol#call, which is not intended for specifying the second parameter without the first.
class UserPresenter < SimpleDelegator def initialize(model, view = nil) @view = view super(model) end def self.to_proc method(:new).to_proc end end # in a controller action @users = User.all.map.with(view_context, &UserPresenter)