What's difference?

— test1.rb —

b = 1
puts a if a = b

NameError: undefined local variable or method `a’ for main:Object

— test2.rb —

a = 1 if false
puts defined?(a)

local-variable

###############

Help Me^^

###############

On Aug 18, 2008, at 8:29, Kyung won Cheon wrote:

— test1.rb —

b = 1
puts a if a = b

NameError: undefined local variable or method `a’ for main:Object

Parser peculiarity. You can’t use a local variable defined for the
first time in the clause of an inline-if for that statement. Define a
before it reaches that line, or use this instead:

if a = b then puts a end

Hier from Programming Ruby book. Its not exactly for this case, but i
think it gets close :


When Ruby sees a name such as ``a’’ in an expression, it needs to
determine if it is a local variable reference or a call to a method with
no parameters. To decide which is the case, Ruby uses a
heuristic. As Ruby reads a source file, it keeps track of symbols that
have been assigned to. It assumes that these symbols are variables. When
it subsequently comes across a symbol that might be
either a variable or a method call, it checks to see if it has seen a
prior assignment to that symbol. If so, it treats the symbol as a
variable; otherwise it treats it as a method call.

There is also this example down below :


Note that the assignment does not have to be executed—Ruby just has to
have seen it. This program does not raise an error.

a = 1 if false; a

Greets

On Mon, 18 Aug 2008 15:29:04 +0900

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs