How to use QString in Enum

[dan1973]

I want to have an Enum of QStrings: like "ON", "OFF", "IDLE"

how to do it in Qt?

[VRonin]

JonB is mostly correct but Qt has some extra magic: QMetaEnum

class StringEnums
{
Q_GADGET
public:
enum MachineState{
ON,OFF,IDLE
};
Q_ENUM(MachineState)
};

Now you can use it:

const auto statesMetaEnum = QMetaEnum::fromType<StringEnums::MachineState>();
QStringList allStates;
for (int i = 0; i < statesMetaEnum.keyCount(); ++i) 
allStates.append(statesMetaEnum.key(i));
qDebug() << allStates;

[JonB]

@dan1973
You can't have "an Enum of QStrings" since C++ enum only allows integer values for the explicitly-named enumerators. Do you mean you want an integral enum for which code can produce string "names", when requested, like "ON" for an enum value whose definition has an ON constant in its enumerators? Or maybe you don't really want an "enum" but just, say, some named constants for specific QString values wrapped into their own class? Depends what for/how you intend to use these symbols.

[VRonin]

JonB is mostly correct but Qt has some extra magic: QMetaEnum

class StringEnums
{
Q_GADGET
public:
enum MachineState{
ON,OFF,IDLE
};
Q_ENUM(MachineState)
};

Now you can use it:

const auto statesMetaEnum = QMetaEnum::fromType<StringEnums::MachineState>();
QStringList allStates;
for (int i = 0; i < statesMetaEnum.keyCount(); ++i) 
allStates.append(statesMetaEnum.key(i));
qDebug() << allStates;

[JonB]

@VRonin said in How to use QString in Enum:

JonB is mostly correct but Qt has some extra magic: QMetaEnum

As I said and your code shows the enum must be integral constants. I said OP can add "code can produce string "names", when requested" and that is what the call QMetaEnum::fromType<StringEnums::MachineState>() does. I was waiting to hear how the OP wishes to use these strings.

It also does not affect the fact that OP cannot use these strings in the same way as the actual underlying integral enum, for example in a switch-case statement. Which is why I asked how the OP actually wishes to use the strings for the enumerators.

[dan1973]

@JonB Thank you. You were right. I gave 3 values as example. in actuals, i will be using many more enum values.
Thanks again.

[dan1973]

@VRonin thank you. Your example was helpful to me. good thinking and solution.

[Redman]

// Only works with Q_ENUMS
template <typename T>
T
keyToEnumValue(const QString& key) {
   QString tmp = key;
   return static_cast<T>(
       QMetaEnum::fromType<T>().keyToValue(tmp.toLocal8Bit()));
}

// Only works with Q_ENUMS
template <typename T>
QString
valueToEnumKey(const T& val) {
   QMetaEnum mEnum = QMetaEnum::fromType<T>();
   return mEnum.valueToKey(val);
}

[allisons]

@dan1973 locksmith said in How to use QString in Enum:

I want to have an Enum of QStrings: like "ON", "OFF", "IDLE"

how to do it in Qt?
In Qt, you can create an enum of QStrings by using a Q_ENUMS macro in combination with a QMap or QStringList to map enum values to QStrings. Here’s a simple example using QMap:

#include <QMap>
#include <QString>

enum State {
ON,
OFF,
IDLE
};

QMap<State, QString> stateToString = {
{ON, "ON"},
{OFF, "OFF"},
{IDLE, "IDLE"}
};

// Usage example
QString stateString = stateToString[ON];
This approach allows you to map enum values to corresponding QStrings and use them as needed.

[janam]

@allisons said in How to use QString in Enum:

@dan1973 ehall login said in How to use QString in Enum:

I want to have an Enum of QStrings: like "ON", "OFF", "IDLE"

how to do it in Qt?
In Qt, you can create an enum of QStrings by using a Q_ENUMS macro in combination with a QMap or QStringList to map enum values to QStrings. Here’s a simple example using QMap:

#include <QMap>
#include <QString>

enum State {
ON,
OFF,
IDLE
};

QMap<State, QString> stateToString = {
{ON, "ON"},
{OFF, "OFF"},
{IDLE, "IDLE"}
};

// Usage example
QString stateString = stateToString[ON];
This approach allows you to map enum values to corresponding QStrings and use them as needed.

Thanks! your code worked in enum. I try many time but failed. Now I try with your code. It worked.