usage of std bind in c++ for functions with an argument (string)

Question

I'm trying to create a vector of std::functions in my logger class. When I try to bind a method to my std::function like that :

NcursesWindow log_win("Logs",LINES-1,COLS/3,0,COLS*2/3);
std::function<void(std::string)> f = std::bind(&NcursesWindow::add_string,&log_win);

the add_string function being defined like :

void add_string(string text);

However, gcc (with the gfilt addon to try to understand the template errors) returns :

BD Software STL Message Decryptor v3.10 for gcc 2/3/4
In file included from ./inc/ncursesui.h:6:0,
from src/ncursesui.cpp:1:
functional: In static member function ‘static void _Function_handler<
    void({basic_string<char>} ...), _Bind<
        _Mem_fn<void (NcursesWindow::*)(basic_string<char>)>(
            NcursesWindow)> 
>::_M_invoke(const _Any_data &, {basic_string<char>} ...)’:
[STL Decryptor: Suppressed 1 more STL standard header message]
src/ncursesui.cpp:32:86:   instantiated from here
functional:1778:2: erreur: no match for call to ‘(
    _Bind<
        _Mem_fn<void (NcursesWindow::*)(basic_string<char>)>(
            NcursesWindow)>) (basic_string<char>)’

STL Decryptor reminders:
Use the /hdr:L option to see all suppressed standard lib headers
Use the /cand:L option to see all suppressed template candidates

Isn't there a placeholder for the string parameter missing in your bind call? In boost you would need bind(&NcursesWindow::add_string,&log_win,_1) — nabulke
– nabulke, Commented Feb 9, 2012 at 14:33
yes, this function prototype is taken from the NcursesWindows .h — Tuxer
– Tuxer, Commented Feb 9, 2012 at 14:36

nabulke · Accepted Answer · 2012-03-05 21:59:24Z

9

Isn't there a placeholder for the string parameter missing in your bind call?

Try this:

bind(&NcursesWindow::add_string,&log_win,std::placeholders::_1);

The member function has two parameters: the hidden this pointer and a std::string. You bind the first to the instance of your class, and the other will stay, therefore the placeholder.

edited Mar 5, 2012 at 21:59

answered Feb 9, 2012 at 14:37

nabulke

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