member initialization in definition and c'tor: redundant?

[mzimmers]

Hi all -

Consider the following struct (could just as easily be a class):

struct Pump: Equipment {       
    QString m_fwVersion = QStringLiteral("");
    QString m_address = QStringLiteral("");
    ApplicationType m_application = INVALID_APPLICATION;
    PumpCategory m_pumpCategory = INVALID_CATEGORY;
    int m_primeDuration = INVALID_DURATION;
    int m_primeSpeed = INVALID_SPEED;
    int m_minSpeed = INVALID_SPEED;
    int m_maxSpeed = INVALID_SPEED;
    int m_freezeSpeed = INVALID_SPEED;
    
public:
    Pump(
        QString fwVersion = QStringLiteral(""),
        QString address = QStringLiteral(""),
        ApplicationType application = INVALID_APPLICATION,
        PumpCategory pumpCategory = INVALID_CATEGORY,
        int primeDuration = INVALID_DURATION,
        int primeSpeed = INVALID_SPEED,
        int minSpeed = INVALID_SPEED,
        int maxSpeed = INVALID_SPEED,
        int freezeSpeed = INVALID_SPEED
        );
};

I'm wondering whether it's redundant to initialize the members both in-line, and in the c'tor. It would seem so, as the c'tor will do the initialization whenever a new object is constructed. But, it seems kind of negligent not to initialize all the members inline.

What do the experts do?

Thanks...

[JoeCFD]

@mzimmers said in member initialization in definition and c'tor: redundant?:

Pump(
    QString fwVersion = QStringLiteral(""),
    QString address = QStringLiteral(""),
    ApplicationType application = INVALID_APPLICATION,
    PumpCategory pumpCategory = INVALID_CATEGORY,
    int primeDuration = INVALID_DURATION,
    int primeSpeed = INVALID_SPEED,
    int minSpeed = INVALID_SPEED,
    int maxSpeed = INVALID_SPEED,
    int freezeSpeed = INVALID_SPEED
    );

if you have something following in a class:

   Pump::Pump(
        QString fwVersion = QStringLiteral(""),
        QString address = QStringLiteral(""),
        ApplicationType application = INVALID_APPLICATION,
        PumpCategory pumpCategory = INVALID_CATEGORY,
        int primeDuration = INVALID_DURATION,
        int primeSpeed = INVALID_SPEED,
        int minSpeed = INVALID_SPEED,
        int maxSpeed = INVALID_SPEED,
        int freezeSpeed = INVALID_SPEED
        ):   m_fwVersion{ fwVersion  },
            m_address{ address  }, (...all...)
            m_freezeSpeed{ freezeSpeed }
{
} 

the following initialization is redundant.

    QString m_fwVersion = QStringLiteral("");
    QString m_address = QStringLiteral("");
    ApplicationType m_application = INVALID_APPLICATION;
    PumpCategory m_pumpCategory = INVALID_CATEGORY;
    int m_primeDuration = INVALID_DURATION;
    int m_primeSpeed = INVALID_SPEED;
    int m_minSpeed = INVALID_SPEED;
    int m_maxSpeed = INVALID_SPEED;
    int m_freezeSpeed = INVALID_SPEED;

[mzimmers]

@JoeCFD yeah, that's what I figured. Thanks for the confirmation.

[SimonSchroeder]

@JoeCFD said in member initialization in definition and c'tor: redundant?:

the following initialization is redundant.

And it will eventually get out of sync. This is only true as long as you only have this one constructor (or only copy/move constructors in addition).

If the constructor does nothing else than just initialize the member, you can ditch the constructor all together. This would then even allow (with C++20) to use aggregate initialization: https://en.cppreference.com/w/cpp/language/aggregate_initialization (which would be better than default parameters in a constructor as some members could be skipped and it would be more expressive).