if condition vs &&, is there any performance gain

Question

I have a condition to check say delete and article if user is owner.

delete_article if user.owner?

Another way is

user.owner? && delete_article

is there any benefit in choosing either of it or is it just a writing style

Answer 1

Performance is unlikely going to be an issue with that statement.

The first one is much better - it's easier to read. Your future self and others who'll get to work on the code will thank you for it.

Answer 2

You can use both styles but there are some differences in the logic.

Used in a method call:

def something
  delete_article if user.owner?
end

would return whatever the the method delete_article returns or nil if the user is not the owner.

With:

def something
  user.owner? && delete_article
end

it would return false if the user is not an owner. If the user is an owner it would return whatever the method delete_article returns.

Performance should be about the same.

Answer 3

Here's some code to test the speed of if vs. &&.

require 'benchmark'

n = 10_000_000

puts RUBY_VERSION, n
puts

Benchmark.bm(2) do |b|
  10.times do
    b.report('if') { n.times { true if true } }
    b.report('&&') { n.times { true && true } }
  end
end

And the output:

1.9.3
10000000

        user     system      total        real
if   0.970000   0.000000   0.970000 (  0.975714)
&&   1.130000   0.000000   1.130000 (  1.127514)
if   0.950000   0.000000   0.950000 (  0.956892)
&&   1.120000   0.000000   1.120000 (  1.124547)
if   0.970000   0.000000   0.970000 (  0.962618)
&&   1.120000   0.000000   1.120000 (  1.129094)
if   0.960000   0.000000   0.960000 (  0.954498)
&&   1.120000   0.000000   1.120000 (  1.125080)
if   0.960000   0.000000   0.960000 (  0.954001)
&&   1.120000   0.000000   1.120000 (  1.126329)
if   0.950000   0.000000   0.950000 (  0.953360)
&&   1.130000   0.000000   1.130000 (  1.122664)
if   0.950000   0.000000   0.950000 (  0.951391)
&&   1.120000   0.010000   1.130000 (  1.123455)
if   0.980000   0.000000   0.980000 (  0.977263)
&&   1.120000   0.000000   1.120000 (  1.126989)
if   0.970000   0.000000   0.970000 (  0.966264)
&&   1.120000   0.000000   1.120000 (  1.123184)
if   0.960000   0.000000   0.960000 (  0.956702)
&&   1.120000   0.000000   1.120000 (  1.124589)