Private methods in Ruby

Ruby
1

##Won’t work method #1

class Foobar
private
def foo; p “Foobar”; end
end

class Baz < Foobar
def blah; foo; end
end

baz = Baz.new
baz.foo

Work method #2

class Foobar
private
def foo; p “Foobar”; end
end

class Baz < Foobar
def blah; foo; end
end

baz = Baz.new
baz.blah

PickAxe2:

If a method is private, it may be called only within the context of
the calling object—it is never possible to access another object’s
private methods directly, even if the object is of the same class as
the caller.

So what happens in Method#2, why foo can be easily called, when called
from inside the class Baz? I mean, that method foo should be still
bound to instance baz…so in which context foo gets called in
Method#2.

2

On Tue, 2006-12-12 at 08:28 +0900, hemant wrote:

class Baz < Foobar
private methods directly, even if the object is of the same class as
the caller.

So what happens in Method#2, why foo can be easily called, when called
from inside the class Baz? I mean, that method foo should be still
bound to instance baz…so in which context foo gets called in
Method#2.

I’ll take a stab at this…

since the instance/object baz is of class Baz, inherited from Foobar, it
has the method foo. When you call baz.blah, baz internally calls its
own foo method, which it is allowed to do.

the “even if the object is of the same class…” bit is a little
confusing, but means that if you (somehow) link baz and baz2 (two
different instances) they can’t call each others private methods, even
though they are the same class.

hope that helps

Brian Broom