Method pointer with boost::bind and map

Question

Is there a nicer way of doing this

auto commodityOneLeg = boost::bind(&VegaFactory::load_commodity_one_leg,this,conn,_1);
std::map<std::string,decltype(commodityOneLeg)> methods;
methods.insert(std::make_pair("COMMODITYONELEG",commodityOneLeg));
methods.insert(std::make_pair("FXOPTION",boost::bind(&VegaFactory::load_fx_index,this,conn,_1)));
methods.insert(std::make_pair("FXBARROPT",boost::bind(&VegaFactory::load_fx_bar_opt,this,conn,_1)));

methods.insert(std::make_pair("COMMODITYINDEX",boost::bind(&VegaFactory::load_fx_index,this,conn,_1)));
auto f = methods.find(trade_table);

if(f != methods.end()) {
    fx_opt = (f->second)(t_id);
}

Is there a way of declaring the type of std:map<> without having to declare a mapping first on the previous line? I guess I mean aesthetically - Code should look neat right?

Is there a cleaner/simpler way to do this c++ string switch statement overall when the input is a 'trade type' string.

Edit

To clarify further. I can manually write out the type of the boost:bind type but that seems excessive. And this is probably a really good example of where auto and decltype can be used to simplify the code. However having to declare one entry in the map one way and the others in a different way just looks wrong; so that's what I want to address

Maybe you could use boost signals?

bennofs
– bennofs

2013-07-03 17:54:17 +00:00
Commented Jul 3, 2013 at 17:54 — bennofs
– bennofs, Commented Jul 3, 2013 at 17:54

megabyte1024 · Accepted Answer · 2013-07-03 18:10:07Z

IMHO using Boost.Signals2 is a more clear way. There is also the Boost.Signals library but it is deprecated starting from Boost 1.54. The following code demonstrates it. I think something similar is possible to implement using the Boost.Function library too.

#include <boost/signals2.hpp>
#include <map>
#include <string>

typedef boost::signals2::signal<bool (int)> CSignal;
typedef CSignal::slot_type CSignalSlotType;
typedef std::map<std::string, CSignalSlotType> CMethodMap;

bool Func1(int a, int b) {
    return a == b;
}

bool Func2(int a, int b) {
    return a < b;
}

int main(int, char *[]) {
    CMethodMap methods;
    methods.insert(std::make_pair("Func1", boost::bind(&Func1, 1, _1)));
    methods.insert(std::make_pair("Func2", boost::bind(&Func2, 2, _1)));

    auto it = methods.find("Func1");
    if(it != methods.end()) {
        CSignal signal;
        signal.connect(it->second);
        auto rt = signal(2);
        if (rt) {
            const bool result = *rt;
        }
    }
    return 0;
}

Here is a sample code using the Boost.Function. It looks even simpler but I used to use the Signals2 library.

#include <map>
#include <string>
#include <boost/function.hpp>
#include <boost/bind.hpp>

typedef boost::function<bool (int)> CFunction;
typedef std::map<std::string, CFunction> CMethodMap;

bool Func1(int a, int b) {
    return a == b;
}

bool Func2(int a, int b) {
    return a < b;
}

int main(int, char *[]) {
    CMethodMap methods;
    methods.insert(std::make_pair("Func1", boost::bind(&Func1, 1, _1)));
    methods.insert(std::make_pair("Func2", boost::bind(&Func2, 2, _1)));

    auto it = methods.find("Func1");
    if(it != methods.end()) {
        auto &f = it->second;
        const bool result = f(2);
    }
    return 0;
}

Now thats clean. I'll have a browse through Signals2 as I didn't know about that

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