MESSAGE
| DATE | 2016-12-21 |
| FROM | Ruben Safir
|
| SUBJECT | Subject: [Learn] (fwd) Re: Threads and Object Methods
|
From learn-bounces-at-nylxs.com Wed Dec 21 17:21:37 2016
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From: Ruben Safir
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Date: Wed, 21 Dec 2016 17:20:23 -0500 (EST)
Subject: [Learn] (fwd) Re: Threads and Object Methods
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NNTP-Posting-Date: Sun, 18 Dec 2016 15:40:30 -0600
Subject: Re: Threads and Object Methods
Newsgroups: comp.lang.c++
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From: Vir Campestris
Date: Sun, 18 Dec 2016 21:40:31 +0000
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Xref: panix comp.lang.c++:1126120
On 18/12/2016 14:36, ruben safir wrote:
> On 12/18/2016 06:09 AM, ?? Tiib wrote:
>> On Sunday, 18 December 2016 11:49:07 UTC+2, ruben safir wrote:
>>> Why can't the threads library handle object methods that are not static
>>> to the class
>>>
>>>
>>> such as std::thread paint(read_chunk);
>>> paint.detach();
>>>
>>>
>>> where read_chunk is an method of an object of class Images.
>>
>> Again some voodoo trying-out nonsense that we can't even
>> copy-paste and run? :-/ The 'std::thread' *can* use non-static
>> methods. However the caller has to supply arguments (starting
>> from 'this') to it.
>>
>> #include
>> #include
>>
>> struct Reader
>> {
>> void read_chunk()
>> {
>> std::cout << "quod erat demonstrandum" << std::endl;
>> }
>> };
>>
>> int main()
>> {
>> std::thread paint(&Reader::read_chunk, Reader());
>> paint.join();
>> }
>>
>> See? It is easy peasy.
>>
>
> if you call it like that it loses its context of the object that
> instantated it which, especially in this case, it needs in order to do
> its job.
>
You're missing the second parameter to the function. Perhaps if he'd written
Reader foo;
std::thread paint(&reader::read_chunk, &foo);
it would have made more sense to you. You can pass args to the function,
which may include a pointer to an object of the type. I prefer to pass a
pointer to a static member function for the first parameter which takes
a pointer to an object of the class and invokes a corresponding
non-static member.
Andy
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