问题
What does the to_sym method do? What is it used for?
回答1:
to_sym converts a string to a symbol. For example, "a".to_sym becomes :a.
It's not specific to Rails; vanilla Ruby has it as well.
It looks like in some versions of Ruby, a symbol could be converted to and from a Fixnum as well. But irb from Ruby 1.9.2-p0, from ruby-lang.org, doesn't allow that unless you add your own to_sym method to Fixnum. I'm not sure whether Rails does that, but it doesn't seem very useful in any case.
来源：https://stackoverflow.com/questions/4062929/what-does-the-ruby-method-to-sym-do