how to append a string to a variable that either exists or not?

my solution is like

if (not (defined?(@results).nil?))
  @results += "run"
else
  @results = "run"
end

but I believe th开发者_JAVA技巧at there is something simpler ...

I would probably do it like this:

@results = @results.to_s + "run"

This works because NilClass defines a #to_s method that returns a zero-length String, and because instance variables are automatically initialized to nil.

You're right:

(@results ||= "") << "run"

To clarify, a || b is a ? a : b, meaning that it tries to use the value a if a is "truthy" (not false or nil) but uses b if a is "falsey". Using ||= hence only updates a variable if the variable is nil. Then, << appends the string.