@x = 'Hello world'
def printMe
puts @x
end
int the above code section when a call printMe method it behaves as
expected. However if I remove the '@' symbol making x as a local
variable it throws an undefined name error. which is also as expected.
But can anyone explain me in the previous case, what is the class for
@x.
Please explain me in details
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Manav Gupta wrote in post #1035910:
@x = 'Hello world'
def printMe
puts @x
endint the above code section when a call printMe method it behaves as
expected. However if I remove the '@' symbol making x as a local
variable it throws an undefined name error. which is also as expected.
But can anyone explain me in the previous case, what is the class for
@x.Please explain me in details
You can find the current object by calling 'self'. If you open irb:
1.9.3p0 :001 > self
=> main
1.9.3p0 :002 > self.class
=> Object
1.9.3p0 :003 > self.instance_variables
=> [:@prompt]
1.9.3p0 :004 > @x = "hello"
=> "hello"
1.9.3p0 :005 > self.instance_variables
=> [:@prompt, :@x]
You can see @x becomes an instance variable of 'self', which is an
instance of the class Object.
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To expand on the nice diagnostic suggestion in the foregoing post, x and
@x are not the same variable, and they do not have the same scope.
If your program consists entirely of this code:
@x = 'hello'
def printMe
puts x
puts @x
end
@x is an instance variable of self (the Object instance that is your
program). It is visible to all methods of self.
printMe() is a method you've added to self. It can see the value of @x.
x is a local variable whose scope is limited to printMe(), and is
undefined.
(That, at any rate, is how I understand it.)
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Why does it (again) sound like a school assignment?
http://ruby.runpaint.org/methods#global
kaspar
On 09.12.11 13:01, Manav Gupta wrote:
@x = 'Hello world'
def printMe
puts @x
endint the above code section when a call printMe method it behaves as
expected. However if I remove the '@' symbol making x as a local
variable it throws an undefined name error. which is also as expected.
But can anyone explain me in the previous case, what is the class for
@x.Please explain me in details
This can be a bit tricky b/c the toplevel namespace doesn't behave like
this code would if it were defined within a `class...end`, which is more
typical.
In this case @x belongs to `main` which is a special object that also
proxy's certain calls to Object class.
In the more typical case:
class X
@x = 'Hello World'
def printMe
puts @x
end
end
The @x in the class scope is not the same as the @x in the method (instance
scope). Rather:
class X
@x = 'Hello World'
def self.printMe
puts @x #=> 'Hello World'
end
end
@x is visible at the class level (the `self.` makes this a class method
instead of an instance method).
On Friday, December 9, 2011 7:01:24 AM UTC-5, Manav Gupta wrote:
@x = 'Hello world'
def printMe
puts @x
endint the above code section when a call printMe method it behaves as
expected. However if I remove the '@' symbol making x as a local
variable it throws an undefined name error. which is also as expected.
But can anyone explain me in the previous case, what is the class for
@x.Please explain me in details
La Wi wrote in post #1036024:
If your program consists entirely of this code:
@x = 'hello'
def printMe
puts x
puts @x
end
...
x is a local variable whose scope is limited to printMe(), and is
undefined.
No, that's not quite right. x here is a method call, not a local
variable, because there has been no assignment to x earlier in the scope
(in this case the body of method 'printMe'). That is:
puts x
is interpreted as if you had written
puts self.x
or puts x()
However, if you had written instead:
def printMe
if false
x = 123
end
puts x
end
then x would indeed be a local variable, and its value is 'nil' (because
the assignment which occurs earlier in the scope is not actually
executed)
Regards,
Brian.
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