Concatenating strings

I was looking at some Railscasts.com podcasts and Bryan is using an interesting way to concatenate 2 strings, using an array and a join operation.

def full_name
  [first_name, last_name].join(' ')
end

Now, I was wondering if this was a bit overkill since it has to allocate an Array, then loop through it and build the string. So I ran Benchmark on three different ways to concatenate.

require 'benchmark'
include Benchmark

def using_array(a,b)
  [a,b].join(' ')
end

def using_format(a,b)
  "#{a} #{b}"
end

def using_concat(a,b)
  a+' '+b
end

Benchmark.benchmark " "*7 + CAPTION, 7, FMTSTR do |x|
  a = 'We all'
  b = 'love Ruby on Rails'

  n = 300000

  x.report("Array: ") { n.times do; using_array(a,b); end }
  x.report("Format:") { n.times do; using_format(a,b); end }
  x.report("Concat:") { n.times do; using_concat(a,b); end }
end

And the results speaks for themselves. As in other languages, the less memory allocations you do, the more performance you will get.

             user     system      total        real
Array:   1.810000   0.020000   1.830000 (  2.395285)
Format:  1.450000   0.010000   1.460000 (  1.634995)
Concat:  1.670000   0.020000   1.690000 (  1.974156)

As you can see, using the format string is really a better approach and I find it easier to read as well.