C++ 如何在 Qt 中使用枚举？
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How to use enum in Qt?
提问by Alex
I have a QObject class Messageand another one named Requestthat inherits the message class. Here's the header file:
我有一个 QObject 类Message和另一个Request继承消息类的类。这是头文件：
#ifndef MESSAGE_H
#define MESSAGE_H
#include <QObject>
class Message : public QObject
{
Q_OBJECT
public:
explicit Message(QObject *parent = 0);
QString Source;
QString Destination;
QString Transaction;
QList<QObject> Content;
signals:
public slots:
};
class Request : public Message
{
Q_OBJECT
Q_ENUMS(RequestTypes)
public:
explicit Request();
enum RequestTypes
{
SetData,
GetData
};
RequestTypes Type;
QString Id;
};
#endif // MESSAGE_H
Now I want to create a Request in my code and set Type to SetData. How can I do that? Here's my current code which gives the error "'Request::RequestTypes' is not a class or namespace". The header file from above is included in my main programs header file, so Requestis known and can be created and I can set the other properties - but not the Type:
现在我想在我的代码中创建一个请求并将类型设置为 SetData。我怎样才能做到这一点？这是我当前的代码，它给出了错误“'Request::RequestTypes' is not a class or namespace”。上面的头文件包含在我的主程序头文件中，所以Request是已知的并且可以创建，我可以设置其他属性 - 但不是Type：
Request *r = new Request();
r->Source = "My Source";
r->Destination = "My Destination";
r->Type = Request::RequestTypes::SetData;
In other words: I could as well had taken a QString for the Typeproperty of a Request, but it would be nice and safer to do this with an enum. Can someone please show me what's wrong here?
换句话说：我也可以为 a 的Type属性使用 QString Request，但使用枚举来做到这一点会更好也更安全。有人可以告诉我这里有什么问题吗？
回答by
You need to declare the enum like so:
您需要像这样声明枚举：
enum class RequestTypes
{
SetData,
GetData
};
in order to use it like you did, but that requires C++11.
为了像您一样使用它，但这需要 C++11。
The normal usage would be (in your case):
r->Type = RequestTypes::SetData;
正常用法是（在您的情况下）：
r->Type = RequestTypes::SetData;
