Does double less than minus "<<-" sign mean anything in ruby?

Question

I am trying to get myself familiar with ruby syntax and coding styles(i am a newbie). I came across a code that uses <<-, what does this mean in Ruby? Code is

  def expectation_message(expectation)     <<-FE       #{expectation.message}       #{expectation.stack}     FE   end 

This is just a section of the whole code. Any help would be appreciated.

Answer 1

There are various ways to define multi-line string in Ruby. This is one of them.

> name = 'John' > city = 'Ny' > multiline_string = <<-EOS > This is the first line > My name is #{name}. > My city is #{city} city. > EOS  => "This is the first line\nMy name is John.\nMy city is Ny city.\n"  > 

the EOS in above example is just a convention, you can use any string you like and its case insensitive. Normally the EOS means End Of String

Moreover, even the - (dash) is not needed. However, allows you to indent the "end of here doc" delimiter. See the following example to understand the sentences.

2.2.1 :014 > <<EOF 2.2.1 :015"> My first line without dash 2.2.1 :016">         EOF 2.2.1 :017"> EOF  => "My first line without dash\n        EOF\n"    2.2.1 :018 > <<-EOF 2.2.1 :019"> My first line with dash. This even supports spaces before the ending delimiter. 2.2.1 :020">    EOF  => "My first line with dash. This even supports spaces before the ending delimiter.\n"  2.2.1 :021 >  

for more info see https://cbabhusal.wordpress.com/2015/10/06/ruby-multiline-string-definition/