问题
If I have three or more objects like so:
a = 4
b = 4
c = 4
d = 2
what would be a clean ruby-style way of determining whether they are all equal? Any bespoke methods for running equality tests on three or more elements?
I suppose I could do something like this:
arrays = [a,b,c,d].map{|x| [x]}
arrays.first == arrays.reduce(:&) ? true : false
which appears to work, but feels sort of ham handed, and might be difficult for other developers to read.
回答1:
[a,b,c,d].any?{|x| x != a}
or
array.any?{|x| x != array.first}
Alternatively, the #all? method may read more intuitively for some:
array.all? {|x| x == array.first }
回答2:
[a, b, c, d].group_by(&:itself).length == 1
# => false
or
[a, b, c, d].chunk(&:itself).to_a.length == 1
# => false
or
[a, b, c, d].chunk_while(&:==).to_a.length == 1
# => false
or the naive:
[a, b, c, d].uniq.length == 1
I was reminded of one?. Provided that you do not have any falsy element, the above can be written:
[a, b, c, d].uniq.length.one?
回答3:
I think the answer by @kipar is better by all means, but for the sake of “doing it the way you started” I would post this here:
[a, b, c, d].reduce { |r, e| r == e && r } && true
来源：https://stackoverflow.com/questions/35295181/equality-test-on-three-or-more-objects