mixinsホストクラス（最終的にはミックスインに渡される）で渡されたタプルをアンパックする方法

Question

私は "BaseSensor"ホストクラスのさまざまなミックスインに様々なstd::tuplesを転送するのにうまく動作する次のコードを持っています。

#include <iostream> // std::cout std::endl 
#include <string> // std::string 
#include <map> // std::map 
#include <tuple> // std::map 

using namespace std; 

struct BaseSensorData 
{ 
    BaseSensorData(const string & _sensorName) 
     : sensorName(_sensorName) 
    {} 

    const string sensorName; 
}; 

class TrendSensor //mixin for BaseSensor 
{ 
    public: 
     TrendSensor(BaseSensorData * bsd , std::tuple<size_t , double > && tp) 
     { 
      cout << "TrendSensor: " << std::get<0>(tp) << " " << bsd->sensorName << " " << std::get<1>(tp) << endl; 
     } 
}; 

typedef struct{ double trough; double peak; } Edges; 
class EdgeSensor //mixin for BaseSensor 
{ 
    public: 
     EdgeSensor(BaseSensorData * bsd , std::tuple<size_t , double > && tp) 
     { 
      cout << "EdgeSensor: " << std::get<0>(tp) << " " << bsd->sensorName << " " << std::get<1>(tp) << endl; 
     } 
}; 

class CO2Threshold// : public ThresholdData 
{ 
    std::map<std::string , double>thresholds; 

    public: 
     CO2Threshold(const double & _toxicThres , const double & _zeroThres , const double &) 
     { 
      thresholds["toxic"] = _toxicThres; 
      thresholds["zero"] = _zeroThres; 
      cout << "CO2Threshold: " << _toxicThres << " " << thresholds["zero"] << endl; 
     } 
}; 
class O2Threshold// : public ThresholdData 
{ 
    std::map<std::string , double>thresholds; 

    public: 
     O2Threshold(const double & _toxicThres , const double & _lowThres , const double & _elecChemThres) 
     { 
      thresholds["toxic"] = _toxicThres; 
      thresholds["low"] = _lowThres; 
      thresholds["elecchem"] = _elecChemThres; 
      cout << "O2Threshold: " << _toxicThres << " " << thresholds["low"] << " " << thresholds["elecchem"] << endl; 
     } 
}; 

template<typename ThresholdMixin> //CO2Threshold , O2Threshold , or others ... 
class ThresholdSensor : public ThresholdMixin //mixin for BaseSensor 
{ 
    public: 
     ThresholdSensor (BaseSensorData * bsd 
         , std::tuple<size_t , double , double , double , double> && tp) 
      : ThresholdMixin 
       (std::get<2>(tp) 
       , std::get<3>(tp) 
       , std::get<4>(tp) 
       ) 
     { 
      cout << "ThresholdSensor: " << std::get<0>(tp) << " " << bsd->sensorName << " " 
       << std::get<1>(tp) << " " << std::get<2>(tp) << " " << std::get<3>(tp) << " " << std::get<4>(tp) 
       << endl; 
     } 

}; 

template<typename ... SensorType> 
class BaseSensor : public BaseSensorData , public SensorType ... //to my BaseSensor class 
{ 
    size_t windowSize; 
    public: 
     template<typename ... Args> 
     BaseSensor(const string& _sensorName , Args && ... args) 
      : BaseSensorData(_sensorName) 
      , SensorType(this , std::forward<Args>(args))... 
      , windowSize(0U) 
     { 
      std::tuple<Args...> arr[sizeof...(SensorType)] = { args ... }; //line A 
      /*for (size_t i = 0; i < sizeof...(SensorType); ++i) 
      { 
       for (size_t i = 0; i < sizeof...(Args); ++i) 
       { 
        // do stuff 
       } 
      }*/ 
      cout << "BaseSensor: " << /*_windowSize << " " << */sensorName << " " << endl; 
     } 

}; 

int main() { 
    BaseSensor<ThresholdSensor<O2Threshold> , TrendSensor, EdgeSensor>bs 
    { 
     string("testSensor") 
     , std::make_tuple<size_t , double , double , double , double>(54U , 2.5f , 10000.3f , 400.5f , 200.3f) 
     , std::make_tuple<size_t , double >(53U , 6.5f) 
     , std::make_tuple<size_t , double >(52U , 3.5f) 
    }; 

    /*BaseSensor<ThresholdSensor<CO2Threshold> , TrendSensor, EdgeSensor>bs5 
    { 
     string("testSensor") 
     , std::make_tuple<size_t , double , double , double , double>(54U , 2.5f , 10000.3f , 400.5f , 200.3f) 
     , std::make_tuple<size_t , double >(53U , 6.5f) 
     , std::make_tuple<size_t , double >(52U , 3.5f) 
    };*/ 
    //BaseSensor<ThresholdSensor<CO2Threshold> > bs2{string("test"),11U , 12.5f}; 
    //BaseSensor<TrendSensor> bs3{string("test"), 8U , 10.5f}; 
    //BaseSensor<EdgeSensor> bs4{string("test"), 6U , 18.5f}; 

} 

だから、「BaseSensor」内のすべてのミックスイン（すなわち「SensorTypes ...」）のタプルは「Argsの...」パラメータパックを介して転送されます。これはうまく動作しますが、私はBaseSensor::BaseSensor()本体でこれらのタプルにアクセスする必要があります。しかし、それを行うための構文は私を逃す。

私は同時にどのように拡大することができますSensorType ...とArgs ...とタプルに従って "args"を分類しますか？上記のコードでは は、私がg ++ v4.7.1およびC++ 11が有効で、次を得る：

varcon.cpp:104:64: error: could not convert ‘args#0’ from ‘std::tuple<long unsigned int, double, double, double, double>’ to ‘std::tuple<std::tuple<long unsigned int, double, double, double, double>, std::tuple<long unsigned int, double>, std::tuple<long unsigned int, double> >’ 
varcon.cpp:104:64: error: could not convert ‘args#1’ from ‘std::tuple<long unsigned int, double>’ to ‘std::tuple<std::tuple<long unsigned int, double, double, double, double>, std::tuple<long unsigned int, double>, std::tuple<long unsigned int, double> >’ 
varcon.cpp:104:64: error: could not convert ‘args#2’ from ‘std::tuple<long unsigned int, double>’ to ‘std::tuple<std::tuple<long unsigned int, double, double, double, double>, std::tuple<long unsigned int, double>, std::tuple<long unsigned int, double> >’ 
varcon.cpp:108:59: error: incomplete type ‘std::tuple_size<std::tuple<std::tuple<long unsigned int, double, double, double, double>, std::tuple<long unsigned int, double>, std::tuple<long unsigned int, double> >&>’ used in nested name specifier 

Answer 1

次の命令を取得したいですか？

std::tuple<Args...> arr[sizeof...(SensorType)] = { args ... }; 

Args...

パックは貴様std::tupleタイプのパスです。あなたのarrはタプルのタプルの配列です。そのため、タプルの一連のタプルをフィードに追加する必要があります。しかし、args...はタプルのパックであり、タプルのタプルではありません。

だから私はあなたが単一の要素にアクセスしたい場合は、あなたの次の配列の一部を捨ててarr

として

std::tuple<Args...> arr { args ... }; 

を定義することができたと++

tmp_002-11,14,gcc,clang.cpp:93:64: error: no viable conversion from 
     'tuple<unsigned long, double, double, double, double>' to 
     'tuple<std::tuple<unsigned long, double, double, double, double>, 
     std::tuple<unsigned long, double>, std::tuple<unsigned long, double>, 
     (no argument), (no argument)>' 

私の打ち鳴らすからのエラー何かを書くことができる

std::get<0>(std::get<1>(arr)); 

ここで最初のタプル（args...の1つ）とタプルの要素（size_tまたはdouble）への2番目のstd::get（より外部の）アクセスへのアクセスは、（内部のもの）です。