Ruby: Is there an opposite of include? for Ruby Arrays?
Ruby on-RailsRubyRuby on-Rails Problem Overview
I've got the following logic in my code:
if !@players.include?(p.name)
...
end
@players
is an array. Is there a method so I can avoid the !
?
Ideally, this snippet would be:
if @players.does_not_include?(p.name)
...
end
Ruby on-Rails Solutions
Solution 1 - Ruby on-Rails
if @players.exclude?(p.name)
...
end
ActiveSupport adds the exclude?
method to Array
, Hash
, and String
. This is not pure Ruby, but is used by a LOT of rubyists.
Solution 2 - Ruby on-Rails
Here you go:
unless @players.include?(p.name)
...
end
You might have a look at the Ruby Style Guide for more info on similar techniques.
Solution 3 - Ruby on-Rails
Looking at Ruby only:
TL;DR
Use none?
passing it a block with ==
for the comparison:
[1, 2].include?(1)
#=> true
[1, 2].none? { |n| 1 == n }
#=> false
Array#include?
accepts one argument and uses ==
to check against each element in the array:
player = [1, 2, 3]
player.include?(1)
#=> true
Enumerable#none?
can also accept one argument in which case it uses ===
for the comparison. To get the opposing behaviour to include?
we omit the parameter and pass it a block using ==
for the comparison.
player.none? { |n| 7 == n }
#=> true
!player.include?(7) #notice the '!'
#=> true
In the above example we can actually use:
player.none?(7)
#=> true
That's because Integer#==
and Integer#===
are equivalent. But consider:
player.include?(Integer)
#=> false
player.none?(Integer)
#=> false
none?
returns false
because Integer === 1 #=> true
. But really a legit notinclude?
method should return true
. So as we did before:
player.none? { |e| Integer == e }
#=> true
Solution 4 - Ruby on-Rails
How about the following:
unless @players.include?(p.name)
....
end
Solution 5 - Ruby on-Rails
module Enumerable
def does_not_include?(item)
!include?(item)
end
end
Ok, but seriously, the unless works fine.
Solution 6 - Ruby on-Rails
Use unless
:
unless @players.include?(p.name) do
...
end
Solution 7 - Ruby on-Rails
Try this, it's pure Ruby so there's no need to add any peripheral frameworks
if @players.include?(p.name) == false do
...
end
I was struggling with a similar logic for a few days, and after checking several forums and Q&A boards to little avail it turns out the solution was actually pretty simple.
Solution 8 - Ruby on-Rails
Can you use:
unless @players.include?(p.name) do
...
end
unless
is opposite of if
, or you may use reject
.
You can reject
the not-required elements:
@players.reject{|x| x==p.name}
after the getting the results you can do your implementation.
Solution 9 - Ruby on-Rails
If your objection to the !
-operator is primarily that it needs to be put in front of your check and this breaks your typing flow, then there is the .!
method. You just put it after the check to invert the boolean:
if @players.include?(p.name).!
Solution 10 - Ruby on-Rails
Using unless
is fine for statements with single include?
clauses but, for example, when you need to check the inclusion of something in one Array
but not in another, the use of include?
with exclude?
is much friendlier.
if @players.include? && @spectators.exclude? do
....
end
But as dizzy42 says above, the use of exclude?
requires ActiveSupport
Solution 11 - Ruby on-Rails
Try something like this:
@players.include?(p.name) ? false : true
Solution 12 - Ruby on-Rails
I was looking up on this for myself, found this, and then a solution. People are using confusing methods and some methods that don't work in certain situations or not at all.
I know it's too late now, considering this was posted 6 years ago, but hopefully future visitors find this (and hopefully, it can clean up their, and your, code.)
Simple solution:
if not @players.include?(p.name) do
....
end