In Ruby, how would I return true if a string is not in an array of options?
# pseudo code
do_this if current_subdomain not_in ["www", "blog", "foo", "bar"]
...or do you know of a better way to write this?
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possible duplicate of Test if variable matches any of several strings w/o long if-elsif chain, or case-whenAndrew Grimm– Andrew Grimm2011-04-16 05:16:27 +00:00Commented Apr 16, 2011 at 5:16
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5 Answers
do_this unless ["www", "blog", "foo", "bar"].include?(current_subdomain)
or
do_this if not ["www", "blog", "foo", "bar"].include?(current_subdomain)
I'm using the Array#include? method.
However using unless is a fairly big ruby idiom.
1 Comment
Ivan Chau
do_this if !["www", "blog", "foo", "bar"].include?(current_subdomain) works. For complex conditions, example one: && ! example two: and not.You can try exclude? method instead of include?
Example:
do_this if ["www", "blog", "foo", "bar"].exclude?(current_subdomain)
Hope this help...Thanks
Edited: This function is applicable only for Rails (ActiveSupport), not native Ruby.
Besides using an array, you can also do this:
case current_subdomain
when 'www', 'blog', 'foo', 'bar'; do that
else do this
end
This is actually much faster:
require 'benchmark'
n = 1000000
def answer1 current_subdomain
case current_subdomain
when 'www', 'blog', 'foo', 'bar'
else nil
end
end
def answer2 current_subdomain
nil unless ["www", "blog", "foo", "bar"].include?(current_subdomain)
end
Benchmark.bmbm do |b|
b.report('answer1'){n.times{answer1('bar')}}
b.report('answer2'){n.times{answer2('bar')}}
end
Rehearsal -------------------------------------------
answer1 0.290000 0.000000 0.290000 ( 0.286367)
answer2 1.170000 0.000000 1.170000 ( 1.175492)
---------------------------------- total: 1.460000sec
user system total real
answer1 0.290000 0.000000 0.290000 ( 0.282610)
answer2 1.180000 0.000000 1.180000 ( 1.186130)
Benchmark.bmbm do |b|
b.report('answer1'){n.times{answer1('hello')}}
b.report('answer2'){n.times{answer2('hello')}}
end
Rehearsal -------------------------------------------
answer1 0.250000 0.000000 0.250000 ( 0.252618)
answer2 1.100000 0.000000 1.100000 ( 1.091571)
---------------------------------- total: 1.350000sec
user system total real
answer1 0.250000 0.000000 0.250000 ( 0.251833)
answer2 1.090000 0.000000 1.090000 ( 1.090418)
1 Comment
cbliard
In
answer2, defining the array ["www", "blog", "foo", "bar"] as a constant outside the method is faster, but still slower than using when.do this if not ["www", "blog", "foo", "bar"].include?(current_subdomain)
or you can use grep
>> d=["www", "blog", "foo", "bar"]
>> d.grep(/^foo$/)
=> ["foo"]
>> d.grep(/abc/)
=> []
Comments
I find this approach most readable !'foo'.in?(['bar', 'baz'])
Comments
