A string literal is Ruby source syntax that directly produces a String value. Double-quoted and single-quoted forms look similar, but they differ in interpolation and escape processing. section 8.1.1 section 7.5.1
Choose the notation according to the behavior and layout the string needs:
- Use double quotes when #{...} interpolation or escapes such as \n and \t should be interpreted. section 8.1.1
- Use single quotes when interpolation should remain literal; backslashes generally remain ordinary characters, except when escaping the quote or another backslash. section 8.1.1
- Use percent notation such as %q{}, %Q{}, or %{} when a different delimiter makes embedded quotation marks easier to read. section 8.1.1
- Use heredocs for multiline strings, including SQL, indented text, method arguments, and strings with optional interpolation behavior. section 8.1.1
Interpolation and truthiness
puts "Two plus two is #{2 + 2}." puts 'Two plus two is #{2 + 2}.' The first line prints 4; the second prints the interpolation marker literally. A string literal evaluates to itself and is truthy in an if test, including an empty string. section 8.1.1 section 7.5.1
class RubyWelcomeWagon
def hyphen_message
<<-EOM
Welcome to the world of Ruby!
In this method, the EOM doesn't have to be flush left!
EOM
end
def squiggly_message
<<~EOM
Welcome to the world of Ruby!
We're happy you're here!
EOM
end
end
Compare <<-EOM and <<~EOM heredocs to see how terminator placement and indentation affect the resulting multiline string. section 8.1.1
