[ruby-core:41688] Re: Documentation of the language itself (syntax, meanings, etc)

On Dec 15, 2011, at 10:39 PM, Rodrigo Rosenfeld Rosas wrote:
> If returning from another method was possible, the framework could =
make the render method return automatically after being called, for =
example. That way, you would be able to simply write:
>=20
> def action
>    render text: "failure while creating post" unless =
Post.create(params)
>    expire_cache_from_post_list
>    render view: 'list'
> end
>=20
> And this is much more readable to me from the perspective of someone =
used to web programming. It would be implicit to the developer that =
either "return" or "render" would stop the method execution. In =
frameworks that don't support rendering by convention (you must call =
render explicitly) it wouldn't even make sense to see a return in such =
action methods.

Even if it were possible, you are suggesting that there should be a way =
for a regular method call (render in your example) to never return but =
instead for control to be passed back to the caller of action.  I think =
that sort of "magic" would be very difficult to work with.  There is =
nothing visible in the code you gave to indicate that the flow of =
control is radically different than what is normally expected.  This =
seems like poor cost/benefit trade off to me.

Of course there is already a standard mechanism for unwinding the stack, =
exceptions.

By using exceptions you can sort of create the control flow you are =
looking for.  At least this way the rescue clause is there to give the =
reader a hint that something unusual is happening.  In this example, =
render_then_raise would raise ReturnNowException (yeah, bad name) to =
bypass the remainder of action.

def action
  render_then_raise text: "failure while creating post" unless =
Post.create(params)
  expire_cache_from_post_list
  render view: 'list'
rescue ReturnNowException
  return
end

Still, I don't like using exceptions as a control flow mechanism for =
entirely un-exceptional situations.

Gary Wright=