c ++是否可以将对象类型传递给要进行比较的函数

Question

我有一种情况,我需要找出派生对象是否存储在另一个对象中的向量中,并希望将其功能化.我无法找到一种方法来做我想要的,或确定是否可能.我有一个可行的解决方案,但是如果有直接的方法来实现目标,它会更清晰.

这基本上就是我想做的事情:

class IFruit
{
public:
    virtual ~IFruit(){};
};
class Apple : public IFruit {};
class Banana : public IFruit {};
class Orange : public IFruit {};

class FruitBowl
{
public:
    bool HasFruit( datatype?? FruitType )
    {
        for ( auto iter : m_Fruit )
        {
            if ( typeof( iter ) == typeof( FruitType ) )
            {
                return ( true );
            }
        }
        return ( false );
    }

    vector< IFruit* > m_Fruit;
};

int main()
{
    FruitBowl Snacks;
    Snacks.m_Fruit.push_back( new Banana );
    Snacks.m_Fruit.push_back( new Apple );
    Snacks.m_Fruit.push_back( new Orange );

    if ( Snacks.HasFruit( Orange ) )
    {
        cout << "There is an orange available";
    }

    return ( 0 );
}

这是一个实现目标的解决方法,但它提供了额外的步骤来提供我想要根除的回调:

#include <vector>
#include <iostream>
#include <functional>
using namespace std;

class IFruit
{
public:
    virtual ~IFruit(){};
};
class Apple : public IFruit {};
class Banana : public IFruit {};
class Orange : public IFruit {};

class FruitBowl
{
public:
    bool HasFruit( function< bool( IFruit* ) > fnCompareFruitType )
    {
        for ( auto iter : m_Fruit )
        {
            if ( fnCompareFruitType( iter ) )
            {
                return ( true );
            }
        }
        return ( false );
    }

    vector< IFruit* > m_Fruit;
};

int main()
{
    FruitBowl Snacks;
    Snacks.m_Fruit.push_back( new Banana );
    Snacks.m_Fruit.push_back( new Apple );
    Snacks.m_Fruit.push_back( new Orange );

    if ( Snacks.HasFruit( []( IFruit* TestFruit ){ return ( dynamic_cast< Orange* >( TestFruit ) != nullptr ); } ) )
    {
        cout << "There is an orange available";
    }

    return ( 0 );
}

Answer 1

您不能将类型作为运行时函数参数传递,但可以使用一个作为函数模板的编译时模板参数:

#include <vector>
#include <iostream>
#include <algorithm>

class IFruit
{
public:
    virtual ~IFruit(){};
};
class Apple : public IFruit {};
class Banana : public IFruit {};
class Orange : public IFruit {};

class FruitBowl
{
public:
    template <typename T>
    bool HasFruit()
    {
        return std::any_of(m_Fruit.begin(), m_Fruit.end(),
                          [](IFruit* fruit) {
                              return dynamic_cast<T*>(fruit) != nullptr;
                          });
    }

    std::vector< IFruit* > m_Fruit;
};


int main()
{
    FruitBowl Snacks;
    Snacks.m_Fruit.push_back( new Banana );
    Snacks.m_Fruit.push_back( new Apple );
    Snacks.m_Fruit.push_back( new Orange );

    if ( Snacks.HasFruit<Orange>() )
    {
        std::cout << "There is an orange available";
    }
}