Question

我一直在尝试使用TComponent方法在TMemoryStream对象上编写一个从writecomponent派生的任意类的对象，并使用{{}再次检索此对象1}}方法。虽然我认为这是一项简单的任务，但我无法使其正常工作。实际上没有编译错误，但没有正确加载对象的属性。请帮我找到我做错了什么。这是我的代码段。

readcomponent

Answer 1

它不起作用，因为

您的Woman类没有任何__published读/写属性。 WriteComponent()和ReadComponent()方法是DFM流系统的一部分，DFM依靠已发布属性的RTTI来完成其工作。
DFM无法构造您的类的实例，因为它不是兼容的构造函数，您使用的是DFM无法调用的自定义构造函数。

您需要相应地更新课程，例如：

class Woman : public TComponent
{
private:
    int fAge;
    UnicodeString fName;

public:
    __fastcall Woman(TComponent* Owner)
        : TComponent(Owner)
    {
    }

    __fastcall Woman(TComponent* Owner, int InAge, const UnicodeString &InName)
        : TComponent(Owner)
    {
        fAge = InAge;
        fName = InName;
    }

__published:
    __property int Age = {read=fAge, write=fAge};
    __property UnicodeString Name = {read=fName, write=fName};
};

然后你可以这样做：

int _tmain(int argc, _TCHAR* argv[])
{
    auto_ptr<Woman> FirstWoman(new Woman(NULL, 25, L"Anjelina"));

    auto_ptr<TMemoryStream> MStr(new TMemoryStream);
    auto_ptr<TStringStream> SStr(new TStringStream(L""));

    MStr->WriteComponent(FirstWoman.get());
    MStr->Position = 0;
    ObjectBinaryToText(MStr.get(), SStr.get());
    SStr->Position = 0;
    UnicodeString as = SStr->DataString;

    auto_ptr<TStringStream> pss(new TStringStream(as));
    auto_ptr<TMemoryStream> pms(new TMemoryStream);

    ObjectTextToBinary(pss.get(), pms.get());
    pms->Position = 0;

    auto_ptr<TComponent> pc(pms->ReadComponent(NULL));
    Woman* AWoman = static_cast<Woman*>(pc.get());

    cout << AWoman->Age << endl;
    cout << AWoman->Name.c_str() << endl;

    FirstWoman.reset();
    pc.reset();

    getch();
    return 0;
}

或者这个：

int _tmain(int argc, _TCHAR* argv[])
{
    auto_ptr<Woman> FirstWoman(new Woman(NULL, 25, L"Anjelina"));

    auto_ptr<TMemoryStream> MStr(new TMemoryStream);
    auto_ptr<TStringStream> SStr(new TStringStream(L""));

    MStr->WriteComponent(FirstWoman.get());
    MStr->Position = 0;
    ObjectBinaryToText(MStr.get(), SStr.get());
    SStr->Position = 0;
    UnicodeString as = SStr->DataString;

    auto_ptr<TStringStream> pss(new TStringStream(as));
    auto_ptr<TMemoryStream> pms(new TMemoryStream);

    ObjectTextToBinary(pss.get(), pms.get());
    pms->Position = 0;

    auto_ptr<Woman> SecondWoman(new Woman(NULL));
    pms->ReadComponent(SecondWoman.get());

    cout << SecondWoman->Age << endl;
    cout << SecondWoman->Name.c_str() << endl;

    FirstWoman.reset();
    SecondWoman.reset();

    getch();
    return 0;
}

如何使用TMemoryStrream编写和读取组件

1 个答案: