QMap 在获取不到 value 时，默认值为 0

 #include <QApplication>

#include <QtCore/QtCore>

#include <QMap>

enum UnitsType{SPS,DPS,SPC,DPC,INS,MV,CMV,SPG,ING,ASG,STG};

int main(int argc, char *argv[])

{

    QApplication app(argc, argv);

    QMap<QString,int> itemTypeMap;

    itemTypeMap["SPS"] = SPS;

    itemTypeMap["DPS"] = DPS;

    itemTypeMap["SPC"] = SPC;

    itemTypeMap["DPC"] = DPC;

    itemTypeMap["INS"] = INS;

    itemTypeMap["MV"] = MV;

    itemTypeMap["CMV"] = CMV;

    itemTypeMap["SPG"] = SPG;

    itemTypeMap["ING"] = ING;

    itemTypeMap["ASG"] = ASG;

    itemTypeMap["STG"] = STG;

    qDebug()<<itemTypeMap.value("SPS");   // 输出：0

    qDebug()<<itemTypeMap.value("aadfa"); //输出：0

    return app.exec();

}