The word unowned doesnt probably reflects the meaning at all by itself. Maybe
'weak' is more accurate.
The thing is that an object you don't own can be corrupted at any time. So you
don't own it, and anybody else can free it, trash it or modify it.
It has nothing to do if it comes from a library or what. Think like this in C:
char *unowned() {
static char ret[128];
strncpy (ret, getenv ("FOO"), sizeof (ret)-1);
return ret;
}
char *owned() {
return strdup (getenv ("FOO"));
}
Maybe my definition is not accurate at all but hope if helps to understand the
problem :)
On 29/10/2011, at 22:53, bsquared <[email protected]> wrote:
>
> LoveBug356 <[email protected]>
> writes:
>
>> Hi,
>>
>> On Sat, 2011-10-29 at 09:44 -0700, bsquared wrote:
>>> Hello,
>>>
>>> I am refactoring some of my test code into a class and have run
>>> into a problem with unowned strings.
>>>
>>> I have a class that has several methods that return strings. These
>>> methods get their value form the response buffer of a Soup Message.
>>>
>>> public string send_misc_method (MiscMethod mm) {
>>> [...]
>>> debug ("send_misc_method: %s",
>>> (string) message.response_body.flatten ().data); // OK
>>> return (string) message.response_body.flatten ().data
>>> }
>>>
>>> public unowned string get_motd () {
>>> string s = send_misc_method (MiscMethod.MOTD);
>>> debug ("get_motd: %s", s); // OK
>>> return s.to_string (); // transfers ownership?
>>> }
>>
>> This looks wrong. You are creating a new unowned string from a string
>> wich you will drop te ownership at the end of the function. So this
>> unowned string will always be wrong. Probably there is no reason here to
>> return a unowned string.
>>
>> Gr,
>> Thijs
>>
>>> main (string[] args) {
>>> [...]
>>> debug ("main - get_motd: %s", server.get_motd ()); // !OK
>>> // var s = server.get_motd ();
>>> // debug ("main - get_motd: %s", s); // also !OK
>>> }
>>>
>>> output:
>>> ** (process:28697): DEBUG: couchdb-server-api.vala:90:
>>> send_misc_method: {"couchdb":"Welcome","version":"1.2.0a-"}
>>>
>>> ** (process:28697): DEBUG: couchdb-server-api.vala:104:
>>> get_motd: {"couchdb":"Welcome","version":"1.2.0a-"}
>>>
>>> ** (process:28697): DEBUG: couchdb-server-api.vala:146:
>>> main - get_motd : \xc0\xa0\u0004uchdb":"Welcome","version":"1.2.0a-"}
>>>
>>> So, what have I done wrong?
>>>
>>> Thank you.
>>>
>
>
> Thanks.
>
> I am confused by the ownership. I am referencing other vapi files
> and guessed that the string should be unowned if it is returned from a
> library.
>
>
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>
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