sequenceDiagram
    participant ClientCode as "Client Code"
    participant Constructor as "RoleCombineModel(...)"
    participant RCM_Instance as "RoleCombineModel Instance"
    participant CreateRN_Method as "RCM_Instance.createRoleNames()"
    participant RoleNames_Method as "RCM_Instance.roleNames()"

    Note over ClientCode, RoleNames_Method: Illustrates refactoring of role name generation and access in RoleCombineModel

    ClientCode ->> Constructor: new RoleCombineModel(major, minor)
    activate Constructor
        Constructor ->> CreateRN_Method: Call to generate and combine role names
        activate CreateRN_Method
            Note right of CreateRN_Method: Internally fetches role names from sourceModel and m_minor
            CreateRN_Method -->> Constructor: combined_role_names
        deactivate CreateRN_Method
        Constructor ->> RCM_Instance: m_roleNames = combined_role_names (Cache populated)
        Note over Constructor, RCM_Instance: m_minorRolesMap is then populated using m_roleNames.key() (cached)
    deactivate Constructor

    ClientCode ->> RoleNames_Method: getRoleNames()
    activate RoleNames_Method
        RoleNames_Method ->> RCM_Instance: Access m_roleNames
        RCM_Instance -->> RoleNames_Method: Returns cached m_roleNames
    deactivate RoleNames_Method
    RoleNames_Method -->> ClientCode: cached_role_names

classDiagram
  class RoleCombineModel {
    +RoleCombineModel(QAbstractItemModel* major, QAbstractItemModel* minor, QObject *parent) // Logic modified for caching
    +roleNames() const : QHash<int, QByteArray> // Now returns cached m_roleNames
    -createRoleNames() const : QHash<int, QByteArray> // New: Encapsulates role name generation
    -m_roleNames: QHash<int, QByteArray> // New: Cache for role names
    -m_minor: QAbstractItemModel* // Existing relevant member
    -m_minorRolesMap: QHash<int, int> // Existing relevant member, population logic changed
  }
  RoleCombineModel --|> QAbstractProxyModel

classDiagram
  class RoleGroupModel {
    +rowCount(const QModelIndex &parent) const : int // Logic modified: Added null check for sourceModel()
    +setSourceModel(QAbstractItemModel *model) // Existing method, provides context
  }
  RoleGroupModel --|> QAbstractProxyModel