Difference between revisions of "Intermediate C++ Game Programming Tutorial 25"

#include <iostream>
#include <memory>
#include <unordered_map>
#include <string>

struct CaseFunction
{
    virtual void operator()() const = 0;
};
struct SixtyNine : public CaseFunction
{
    void operator()() const override;
    {
         std::cout << "The S number\n";
    }
};

int main()
{
    std::unordered_map<std::string,std::unique_ptr<CaseFunction>> sw;
    sw["sixty-nine"] = std::make_unique<SixtyNine>();
    (*sw["sixty-nine"])();
    return 0;
}

int Double( int x )
{
    return x * 2;
}

int main()
{
    int ( *pFunc )(int);
    pFunc = &Double;
    // Note: the 'Address Of' operator & is optional, [ pFunc = Double; ] also works
    std::cout << pFunc( 2 ) << std::endl;
}

void SixtyNine()
{
    std::cout << "The S number\n";
}

int main()
{
    std::unordered_map<std::string,void(*)()> sw;
    sw["s9"] = SixtyNine;
    sw["s9"]();
}

...
#include <functional>

int main()
{
    std::unordered_map<std::string,std::function<void()>> sw;
    sw["sixty-nine"] = []()
    {
        std::cout << "The S value";
    }
    sw["sixty-nine"]();
}

#pragma once
#include <functional>
#include <unordered_map>
#include <string>
#include <iostream>

class StringSwitch
{
public:
    std::function<void()>& Case(const std::string& str)
    {
        return map[str];
    }
    std::function<void()>& Default()
    {
         return def;
    }
    void operator[](const std::string& str) const
    {
        auto it = map.find(str);
        if (it == map.end())
        {
            def();
        }
        else
        {
            it->second();
        }
    }
private:
	std::unordered_map<std::string, std::function<void()>> map;
	std::function<void()> def = [](){};
};

#include <functional>

int Thing(int x, int y)
{
    return 2*x + y;
}

int main()
{
    std::function<int(int)> f;
    f = std::bind( Thing, std::placeholders::_1 , 5 );
    f(10); // returns: 25
}

std::function<int(Foo&,int)> f = &Foo::DoublePlus;

auto f = std::mem_fn( &Foo::DoublePlus );

    auto g = [](int x) { return Thing(x,5); };
    g(10); // returns 25

    std::function<void()> f;
    f = [&myfoo](){myfoo.DoublePlus(69);};
    f();

    int(*pStaticFunc)(int) = &Foo::DoStatic; // & is optional here
    std::cout << pStaticFunc(2); // same as:
    std::cout << (*pStaticFunc)(2);

// Remove dying boxes
boxPtrs.erase(
    std::remove_if( boxPtrs.begin(),boxPtrs.end(),std::mem_fn(&Box::HasToDie) ),
    boxPtrs.end();
);

// Remove dying boxes
boxPtrs.erase(
    std::remove_if( boxPtrs.begin(),boxPtrs.end(),[](auto& b){return b->HasToDie();}),
    boxPtrs.end();
);

// Use std::bind to swap the order of the parameters of a function
// (f is of type std::function<void(T,T)>)
std::bind(f,std::placeholder::_2,std::placeholder::_1);

[](const T& a,const T& b) {f(b,a);};   [[CHECK are these const refs? !!]]