Using iOS Face ID (and Touch ID) with Qt5

biometrics.cpp

#include "biometrics.h"

#ifdef Q_OS_IOS
#include "localAuth-c-interface.h"
#endif

#include <QDebug>

Biometrics::Biometrics(QObject *parent) : QObject(parent)
{

}

void Biometrics::invokeBiometrics(){
#ifdef Q_OS_IOS
    qDebug() << "Local Auth:" << localAuth();
#endif
}

biometrics.h

#ifndef BIOMETRICS_H
#define BIOMETRICS_H

#include <QObject>

class Biometrics : public QObject
{
    Q_OBJECT
public:
    explicit Biometrics(QObject *parent = nullptr);

public slots:
    void invokeBiometrics();

signals:

};

#endif // BIOMETRICS_H

localAuth-c-interface.h

#ifndef LOCALAUTHCINTERFACE_H
#define LOCALAUTHCINTERFACE_H

bool localAuth();

#endif // LOCALAUTHCINTERFACE_H

localAuth.h

BOOL localAuth();

localAuth.mm

#import <LocalAuthentication/LocalAuthentication.h>

BOOL localAuth() {
    LAContext *laContext=[[LAContext alloc] init];
 
    NSError *authError=nil;
    NSString *localisedReasonString=@"App would like to make logging in easier.";
    __block BOOL result=false;

    dispatch_semaphore_t sema=dispatch_semaphore_create(0);

    if ([laContext canEvaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics error:&authError]){
        [laContext evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics localizedReason:localisedReasonString reply:^(BOOL success, NSError *error){
            result=success;
            dispatch_semaphore_signal(sema);
        }];
    } else return false;

    if(![NSThread isMainThread]){
        dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
    } else {
        while(dispatch_semaphore_wait(sema, DISPATCH_TIME_NOW)){
            [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate dateWithTimeIntervalSinceNow:0]];
        }
    }

    return result;
}

QtProjectWithFaceID.pro

...
ios {
    OBJECTIVE_HEADERS += localAuth.h
    OBJECTIVE_SOURCES += localAuth.mm
    HEADERS += localAuth-c-interface.h
    LIBS += -framework LocalAuthentication
}