我正在使用Stroustrup的包装器模板类:

template<class T, class Pref, class Suf>
class Wrap {
protected:
    T* p;
    int* owned;
    void incr_owned() { if (owned) ++*owned; }
    void decr_owned() { if (owned && --*owned == 0) { delete p; delete owned; } }

    Pref prefix;
    Suf suffix;
public:
    Wrap(T& x, Pref pr, Suf su)
        :p(&x), owned(0), prefix(pr), suffix(su) { }

    Wrap(T* pp, Pref pr, Suf su)
        :p(pp), owned(new int(1)), prefix(pr), suffix(su) { }

    Wrap(const Wrap& a)
        :p(a.p), owned(a.owned), prefix(a.prefix), suffix(a.suffix)
        { incr_owned(); }


我将其子类化以创建线程安全对象:

template<class DSP> class DspWrap : public Wrap<DSP, void(*)(), void(*)()> {
protected:
    CriticalSection* criticalSection;

public:
    DspWrap(DSP& x) : Wrap<DSP, void(*)(), void(*)()>(x, &DspWrap::prefix, &DspWrap::suffix) {
    }

    DspWrap(DSP* pp) : Wrap<DSP, void(*)(), void(*)()>(pp, &DspWrap::prefix, &DspWrap::suffix) { //compiler error here
    }


但是在创建对象DspWrap<PpmDsp> wrap = DspWrap<PpmDsp>(new PpmDsp());的行中时,出现以下错误error C2664: 'Wrap<T,Pref,Suf>::Wrap(T &,Pref,Suf)' : cannot convert parameter 1 from 'PpmDsp *' to 'PpmDsp &'

但是,为什么调用了错误的构造函数?实际上,有一个PpmDsp*的构造函数,那么为什么要尝试调用PpmDsp&

提前致谢

最佳答案

我不确定您要对成员进行初始化方面要做什么,但是您需要基类的适当构造参数,而基类成员*本身*并不是这样做的方法。

一旦我为prefixsuffix声明了两个实函数,其余的就起作用了,并且基本构造函数正确初始化了。由于我没有您对CriticalSectionDSP的定义,因此我不得不假冒该示例,但是....

#include <iostream>

typedef int CriticalSection;

template<class T, class Pref, class Suf>
class Wrap {
protected:
    T* p;
    int* owned;
    void incr_owned() { if (owned) ++*owned; }
    void decr_owned() { if (owned && --*owned == 0) { delete p; delete owned; } }

    Pref prefix;
    Suf suffix;
public:
    Wrap(T& x, Pref pr, Suf su)
        :p(&x), owned(0), prefix(pr), suffix(su) { }

    Wrap(T* pp, Pref pr, Suf su)
        :p(pp), owned(new int(1)), prefix(pr), suffix(su) { }
};

template<class DSP> class DspWrap : public Wrap<DSP, void(*)(), void(*)()> {
protected:
    CriticalSection* criticalSection;

    // implemenations of these
    static void prefix_fn() {};
    static void suffix_fn() {};

public:
    DspWrap(DSP& x)
        : Wrap<DSP, void(*)(), void(*)()>(x, &prefix_fn, &suffix_fn)
        , criticalSection(new CriticalSection)
    {
        std::cout << __PRETTY_FUNCTION__ << std::endl;
    }

    DspWrap(DSP* pp)
        : Wrap<DSP, void(*)(), void(*)()>(pp, &prefix_fn, &suffix_fn)
        , criticalSection(new CriticalSection)
    {
        std::cout << __PRETTY_FUNCTION__ << std::endl;
    }
};

struct MyDSP { };

int main()
{
    MyDSP dsp;
    DspWrap<MyDSP> wrap1(dsp);

    MyDSP *dsp2 = new MyDSP;
    DspWrap<MyDSP> wrap2(dsp2);
    return 0;
}


输出量

DspWrap<MyDSP>::DspWrap(DSP &) [DSP = MyDSP]
DspWrap<MyDSP>::DspWrap(DSP *) [DSP = MyDSP]

10-08 19:58