Re: Cleaning up iterators

[Antonio Vieiro <antonio@...>]

El 27/07/11 03:05, lua-l-request@lists.lua.org escribió:
> Message: 2
> Date: Tue, 26 Jul 2011 22:02:27 +0200
> From: Petite Abeille<petite.abeille@gmail.com>
> Subject: Re: Cleaning up iterators
> To: Lua mailing list<lua-l@lists.lua.org>
> Message-ID:<097DD5DE-4C96-48B7-9628-8FA9E088F888@gmail.com>
> Content-Type: text/plain; charset=us-ascii
>
>
> Well, there is always a way, no?
>
> For example, in the first case, the iterator can automatically clause the result set upon exhausting it.
>
> Say:
>
> local aDB = DB( 'sqlite3://localhost/test.db' )
>
> for aContact in aDB( 'select * from contact' ) do
>      print( aContact.name, aContact.email )
> end


Thanks all for your replies. The fact is that I need the cursor to be 
automatically closed (to avoid programming errors/leaks) as soon as 
possible (because I need to clean-up resources quickly due to high load).

I think I'll use closures instead:

local adb = DB('sqlite3://localhost/test.db')

local antonio_is_there = false

adb:foreachrow( 'select name, email from contact',
  function(aContact)
    print(aContact.name, aContact.email)
    if aContact.name == 'antonio' then
      antonio_is_there = true
      return false -- end iteration
    else
      return true -- continue to next row
    end
  end
)

The 'foreachrow' function will be responsible for:
- sending rows to the function until the function returns false.
- closing the cursor when the function ends (or there're no more rows).

I know it's no so easy to use as a 'for' loop, but it's 'easier' for me 
to always close things no matter what I do.

Cheers,
Antonio