Feature #17663
openEnumerator#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 3 years ago
- Description updated (diff)
Updated by RichOrElse (Ritchie Buitre) over 3 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 3 years ago
- Description updated (diff)
Updated by Hanmac (Hans Mackowiak) over 3 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 3 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)