[shundhammer @ morgul] ~/tmp % cat weird.rb #!/usr/bin/ruby class Weird attr_accessor :foo def initialize @foo = "foo" end def doit1 puts "doit1" puts foo + "bar" end def doit2 puts "doit2" puts foo +"bar" end end weird = Weird.new weird.doit1 weird.doit2 [shundhammer @ morgul] ~/tmp % ./weird.rb doit1 foobar doit2 Traceback (most recent call last): 1: from ./weird.rb:23:in `<main>' ./weird.rb:17:in `doit2': wrong number of arguments (given 1, expected 0) (ArgumentError) What's going on here? Why does it crash? What's the difference between "doit1" and "doit2"? (Spoiler alert: solution after the blank lines) Yes, it's just that one blank after the plus operator, and it makes all the difference. It turns out that some time ago (with Ruby 2.3), the Ruby string class got a brand new unary plus operator (which is what we had all been missing for so long, of course). That unary plus calls String.unfreeze on that string. And in Ruby, the parentheses for a function call are optional. This is an accident waiting to happen, and it happened right here: Ruby interpreted this as a function call because the plus can be interpreted as an unary plus here, so it decided to unfreeze the constant "bar" string and pass it as an argument to the foo() method - which exists; it is the getter to the @foo member variable (implicitly created by attr_accessor: foo). Of course, this getter does not accept any parameter, so it complains. Actually it's pure luck that it does not accept a parameter and complains instead; if it had been a function that can accept a parameter, it would have happily called it with the unfrozen "bar" string and just done random garbage with that unintended parameter. ARGH. This is when "meaning good" (as in "the opposite of doing good") meets duck typing and happily executing any random garbage. If I really want to unfreeze a frozen string, I will happily tell Ruby to do just that. But no, there was a chance to make a cryptic scripting language even more cryptic by introducing stuff like an unary plus operator for strings, of all things. Tricky programming is soooo cool. Readable and maintainable code is sooo overrated. ARGH. Kind regards -- Stefan Hundhammer <shundhammer@suse.de> YaST Developer SUSE Linux GmbH GF: Felix Imendörffer, Jane Smithard, Graham Norton; HRB 21284 (AG Nürnberg) Maxfeldstr. 5, 90409 Nürnberg, Germany -- To unsubscribe, e-mail: yast-devel+unsubscribe@opensuse.org To contact the owner, e-mail: yast-devel+owner@opensuse.org