String concatenation vs. interpolation in Ruby

Whenever TIMTOWTDI (there is more than one way to do it), you should look for the pros and cons. Using "string interpolation" (the second) instead of "string concatenation" (the first):

Pros:

• Is less typing
• Automatically calls to_s for you
• More idiomatic within the Ruby community
• Faster to accomplish during runtime

Cons:

• Automatically calls to_s for you (maybe you thought you had a string, and the to_s representation is not what you wanted, and hides the fact that it wasn't a string)
• Requires you to use " to delimit your string instead of ' (perhaps you have a habit of using ', or you previously typed a string using that and only later needed to use string interpolation)

Both interpolation and concatination has its own strength and weakness. Below I gave a benchmark which clearly demonstrates where to use concatination and where to use interpolation.

require 'benchmark'iterations = 1_00_000firstname = 'soundarapandian'middlename = 'rathinasamy'lastname = 'arumugam'puts 'With dynamic new strings'puts '===================================================='5.times do  Benchmark.bm(10) do |benchmark|    benchmark.report('concatination') do      iterations.times do        'Mr. ' + firstname + middlename + lastname + ' aka soundar'      end    end    benchmark.report('interpolaton') do      iterations.times do        "Mr. #{firstname} #{middlename} #{lastname} aka soundar"      end    end  end  puts '--------------------------------------------------'endputs 'With predefined strings'puts '===================================================='5.times do  Benchmark.bm(10) do |benchmark|    benchmark.report('concatination') do      iterations.times do        firstname + middlename + lastname      end    end    benchmark.report('interpolaton') do      iterations.times do        "#{firstname} #{middlename} #{lastname}"      end    end  end  puts '--------------------------------------------------'end

And below is the Benchmark result

Without predefined strings====================================================                 user     system      total        realconcatination  0.170000   0.000000   0.170000 (  0.165821)interpolaton  0.130000   0.010000   0.140000 (  0.133665)--------------------------------------------------                 user     system      total        realconcatination  0.180000   0.000000   0.180000 (  0.180410)interpolaton  0.120000   0.000000   0.120000 (  0.125051)--------------------------------------------------                 user     system      total        realconcatination  0.140000   0.000000   0.140000 (  0.134256)interpolaton  0.110000   0.000000   0.110000 (  0.111427)--------------------------------------------------                 user     system      total        realconcatination  0.130000   0.000000   0.130000 (  0.132047)interpolaton  0.120000   0.000000   0.120000 (  0.120443)--------------------------------------------------                 user     system      total        realconcatination  0.170000   0.000000   0.170000 (  0.170394)interpolaton  0.150000   0.000000   0.150000 (  0.149601)--------------------------------------------------With predefined strings====================================================                 user     system      total        realconcatination  0.070000   0.000000   0.070000 (  0.067735)interpolaton  0.100000   0.000000   0.100000 (  0.099335)--------------------------------------------------                 user     system      total        realconcatination  0.060000   0.000000   0.060000 (  0.061955)interpolaton  0.130000   0.000000   0.130000 (  0.127011)--------------------------------------------------                 user     system      total        realconcatination  0.090000   0.000000   0.090000 (  0.092136)interpolaton  0.110000   0.000000   0.110000 (  0.110224)--------------------------------------------------                 user     system      total        realconcatination  0.080000   0.000000   0.080000 (  0.077587)interpolaton  0.110000   0.000000   0.110000 (  0.112975)--------------------------------------------------                 user     system      total        realconcatination  0.090000   0.000000   0.090000 (  0.088154)interpolaton  0.140000   0.000000   0.140000 (  0.135349)--------------------------------------------------

Conclusion

If strings already defined and sure they will never be nil use concatination else use interpolation.Use appropriate one which will result in better performance than one which is easy to indent.

@user1181898 - IMHO, it's because it's easier to see what's happening. To @Phrogz's point, string interpolation automatically calls the to_s for you. As a beginner, you need to see what's happening "under the hood" so that you learn the concept as opposed to just learning by rote.

Think of it like learning mathematics. You learn the "long" way in order to understand the concepts so that you can take shortcuts once you actually know what you are doing. I speak from experience b/c I'm not that advanced in Ruby yet, but I've made enough mistakes to advise people on what not to do. Hope this helps.