bug in ruby

[sairam MP]

class Foo
attr_accessor :bar


def foo
self.bar = 1


if false
bar = 2 # never executed
end


p self.bar # prints 1
p bar # prints nil
end
end

 

[dblack]

Hi --

class Foo
attr_accessor :bar


def foo
self.bar = 1


if false
bar = 2 # never executed
end


p self.bar # prints 1
p bar # prints nil
end
end

That's not a bug. The parser sees:

bar = 2

and that triggers the allocation of bar. Since the expression is
inside of the if false block, it never gets executed, so bar is nil.


David

--
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A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
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A. Ruby Power and Light, LLC (http://www.rubypal.com)

 

[Mike Cahill]

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[Peter Hickman]

if false
bar = 2 # never executed
end

There is no way that this conditional will be triggered.

if expr
...
end

will only execute the body of the if statement if expr is true. False is
never true (outside of politics), hence it is never executed.

 

[Brian Candler]

class Foo
attr_accessor :bar


def foo
self.bar = 1


if false
bar = 2 # never executed
end


p self.bar # prints 1
p bar # prints nil
end
end

This is a bug in your understanding of the language, not in the language
itself. You've not said exactly what you think it *should* do instead of
what it does, so it's hard to give an answer tailored to improving your
understandly.

But briefly: an assignment like "bar = 2" is seen at the time the program is
*parsed* and means that an unqualified "bar" is treated as a local variable
from that point onwards until the end of that scope. Whether or not it is
actually *executed* makes no difference.

When you write "self.bar" or "self.bar=" you are explicitly making a method
call to a method "bar" or "bar=" on the current object; this is never
treated as a local variable.

If you write "bar" by itself, this is treated as a method call on the
current object *unless* an assignment of the form "bar = x" has been seen by
the parser earlier in the scope.

Regards,

Brian.

 

[Robert Klemme]

This is a bug in your understanding of the language, not in the language
itself. You've not said exactly what you think it *should* do instead of
what it does, so it's hard to give an answer tailored to improving your
understandly.

But briefly: an assignment like "bar = 2" is seen at the time the program is
*parsed* and means that an unqualified "bar" is treated as a local variable
from that point onwards until the end of that scope. Whether or not it is
actually *executed* makes no difference.

When you write "self.bar" or "self.bar=" you are explicitly making a method
call to a method "bar" or "bar=" on the current object; this is never
treated as a local variable.

If you write "bar" by itself, this is treated as a method call on the
current object *unless* an assignment of the form "bar = x" has been seen by
the parser earlier in the scope.

Additional reference material:

http://www.ruby-doc.org/docs/ProgrammingRuby/html/language.html#UO

Kind regards

robert

 

[Bob Showalter]

[ snip ]

A gentle suggestion:

"Don't claim that you have found a bug"

http://www.catb.org/~esr/faqs/smart-questions.html#id270918

 

[Wolfgang Nádasi-Donner]

Additional reference material:

http://www.ruby-doc.org/docs/ProgrammingRuby/html/language.html#UO

It should be added in the documentation, that such an uninitialized local
variable is set to the initial value "nil".

Wolfgang Nádasi-Donner