On Nov 19, 7:49 pm, Brian <[EMAIL PROTECTED]> wrote:
> ok thanks that got it working. I think I had this working before like
> that, but then changed it because of confusion over the usage of
> self. I thought self was used to define class-level methods.
> Apparently the usage is different in instance methods? It is partly
> addressed here
Self is simple when you get it right. It just means 'the current
object'. The only reason it is relevant here is that when ruby sees
self.foo = bar it can be damn sure you want to call the method foo= on
the current object, whereas with foo= bar you might just want to
create a local variable.
in the same way
def self.foo
end
creates a class method (in the context of a class) because it says
"define a method on the object self" (as opposed to inside the
appropriate class), given that at this point the self object is the
class, this creates a method on that class object.
so for example
class Foo
def self.bar
puts "hi"
end
end
is the same as
class Foo
def Foo.bar
puts "hi"
end
end
is the same (from the point of view of method definition - constant
scopes and so on would be different) as
class Foo
end
def Foo.bar
puts "hi"
end
In the first example self is at that point Foo, which is why it works.
It's more convenient that typing Foo.bar partly because class names
are usually longer, partly because it stands out more and partly
because if you were to rename the Foo class you can leave all of your
def self.bar alone whereas with the second example you would have to
change def Foo.bar to def NewClassName.bar
Fred
>
> http://wiki.rubyonrails.org/rails/pages/RubyHeadScratching
>
> On Nov 19, 1:56 pm, Frederick Cheung <[EMAIL PROTECTED]>
> wrote:
>
> > On Nov 19, 6:19 pm, Brian <[EMAIL PROTECTED]> wrote:
>
> > > thanks for the response, but can anyone provide a simple example of
> > > the proper way to access and change an attribute from within an
> > > instance method?
>
> > You just need to call the accessor methods, same as for people outside
> > the class. the only subtlety is that to set it you need to do
> > self.attribute_name = value (as attribute_name = value would be
> > interpreted as you trying to set a local variable)
>
> > Fred
>
> > > I've worked through AWDwR, re-read the ActiveRecord and Ruby sections,
> > > am currently going through wiki.rubyonrails.org and the Reference
> > > Docs, and still haven't found it.
>
> > > On Nov 19, 11:55 am, Frederick Cheung <[EMAIL PROTECTED]>
> > > wrote:
>
> > > > On 19 Nov 2008, at 16:48, Brian wrote:> What's wrong? I'm assuming I'm
> > > > missing something basic, but it's
> > > > > pretty confusing.
>
> > > > attributes aren't instance variables
>
> > > > Fred
>
> > > > > Thanks
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