Enum value to QString

ODБOï

Hi,
In one of my classes i have an enum defined like this :

 Q_PROPERTY(CurrentState state READ state WRITE setState NOTIFY stateChanged)
 enum CurrentState {
        Buzy, StandBy, Error
    };
Q_ENUM(CurrentState)
    CurrentState state()const{
        return m_state;
    }
    void setState(const CurrentState &st){
        if(m_state!=st){
            m_state=st;
            emit stateChanged(m_state);
        }
    }
private:
CurrentState m_state;

i have a function that will handle the stateChanged signal

in that function i can do this :

qDebug()<<"State changed : " << m_state;
// output will be states changed : ClassName::Buzy // or StandBy or Error

QString stateMessage = QString("states changed : %1").arg(m_state);
// here output is : state changed : 0 // or 1 or 2 (so the index of the m_state )

How to assigne the enum value rather than index to my QString stateMessage ?

raven-worx

@LeLev

QMetaEnum::fromType<ClassName::MyEnum>().valueToKey(value) // MyEnum needs to be declared with Q_ENUM macro

ODБOï

@raven-worx Thank you very much.

ODБOï

@raven-worx hi,

I have changed

enum CurrentState {
        Buzy, StandBy, Error
    };

to,

enum class CurrentState : qint32{
        Buzy, StandBy, Error
    };
...
 qRegisterMetaType<ClassName::CurrentState>();
...
Q_DECLARE_METATYPE(ClassName::CurrentState)

to be able to use the enum from QML

Button{
  visible : !ClassName.CurrentState.Busy
}

Now i need to adapt the statement you gave me :

QString message = QMetaEnum::fromType<ClassName::CurrentState>().valueToKey(m_state)

output : cannot initialize a parameter of type 'int' with an lvalue of type 'ClassName::CurrentState'

is there still a possibility to do this 'simply' or i will have to use a switch and manually assign values?

switch(m_state){
case  CalassName::Busy : message = "Busy";break; ...
}

Thank you

raven-worx

@LeLev

did you add the Q_ENUM as i said?
try QMetaEnum::fromType<ClassName::CurrentState>().valueToKey( int(m_state) )

ODБOï

@raven-worx
as you can see in my first code the Q_ENUM is there from the beginnig thank you :)

QMetaEnum::fromType<ClassName::CurrentState>().valueToKey( int(m_state) )

this worked, now i can create a QString with my state name and get it from QML .

but i have one more thing to solve : i can reach the enum from my QML code :

 Connections{
        target: machine
        onStateChanged:{
            if(machine.state === Machine.CurrentState.Buzy){
                  console.log("machine buzy...")
            }
        }
    }

But if i assign the state name to a QML Text i get the index

Text{
    text:machine.state
  // text : Machine.CurrentState.Buzy  ? "Buzy" : ...   ?
}

Thank you

J.Hilk

@LeLev of course, qml still handles this an integer, internaly

you''ll need someting like

QINVOKABLE QString stateToString(CurrentState state ){return QMetaEnum::fromTypeClassName::CurrentState().valueToKey( int(m_state) );}

Text{
    text: Machine.stateToString(machine.state)
}

as a JS-expression, the text will update when state changes.

raven-worx

@LeLev said in Enum value to QString:

But if i assign the state name to a QML Text i get the index

QML (better said the QML engine) doesn't have this capabilities AFAIK.
You can however create an INVOKABLE C++ method with does the translation for you, following the same principle.

Edit: yes, just like @J-Hilk showed :)

ODБOï

Thank you @raven-worx and @J-Hilk

Just to be exact if someone reads this in the future

Text{
    text: machine.stateToString(machine.state)
}

Here machine is instance of class Machine so i use lowercase letter
setContextProperty("machine",&machine);
I belive @J-Hilk just did a missclick.

@J.Hilk said in Enum value to QString:

as a JS-expression, the text will update when state changes.

Since this is a Q_INVOKABLE i have to call it every time no ?

this is not refreshing the text :

 Text {
            id: machineState
            text: machine.stateToString()

        }

I can do like this :

  Connections{
        target: machine
        onStateChanged:{
           machineState.text = machine.stateToString()
        }
    }

Correct me if im wrong please. Maybe there is a trick with that Capital Machine.stateToString(machine.state) that i don't know yet.

raven-worx

@LeLev said in Enum value to QString:

Since this is a Q_INVOKABLE i have to call it every time no ?

if the call contains another property (machine.state in your case) the rules for property binding kick in.
So no you do not need to call it every time.

works automagically: machine.stateToString(machine.state)
doesnt work (needs manual execution): machine.stateToString() -> if you want to use this way, you can create a Q_PROPERTY stateStr for example which returns the string representation of the current state value. Note in order to take advantage property binding, the property needs to needs to declare a NOTIFY signal and call it whenever the value has changed (whenever the state property of your machine class has changed)

Maybe there is a trick with that Capital Machine.stateToString(machine.state) that i don't know yet.

this would work if the class has been registered as singleton type.

ODБOï

@raven-worx said in Enum value to QString:

if you want to use this way, you can create a Q_PROPERTY stateStr for example which returns the string representation of the current state value. Note in order to take advantage property binding, the property needs to needs to declare a NOTIFY signal and call it whenever the value has changed (whenever the state property of your machine class has changed)

This is what i do generally.

@raven-worx said in Enum value to QString:

if the call contains another property (machine.state in your case) the rules for property binding kick in.

@raven-worx said in Enum value to QString:

this would work if the class has been registered as singleton type.

awsome ! Thank you very much !

This is definitely solved!

osirisgothra

@raven-worx awesome, this pointed me in the right direction. In my case I needed the keyboard combo and key name in string form, so QMetaEnum::fromType was the call I was trying to find, thanks for that.