/// <summary>
/// Hilfsmethode, die aus einem durch eine Query zurückgelieferten Statement ein Objekt des Typs Kanal extrahiert.
/// Je nach Typ des Kanals werden zusätzliche Informationen aus Subklassen-Tabellen abgefragt und ein Objekt
/// der Subklasse extrahiert.
/// </summary>
/// <param name="conn">Eine aktive Connection zur Datenbank, um Informationen aus Subklassen-Tabellen abfragen zu können.</param>
/// <param name="stmt">Das Statement, aus dem die Informationen extrahiert werden sollen.</param>
/// <returns>Ein Objekt vom Typ Channel.</returns>
private Channel retrieveChannelObjectFromStatement(SQLiteConnection conn, ISQLiteStatement stmt)
{
// Channel Objekt.
Channel channel = null;
try
{
// Initialisierung der Variablen.
int id;
string name, description, term, location, dates, contact, website, startDate, endDate, lecturer,
assistant, cost, organizer, participants;
bool deleted;
ChannelType type;
Faculty faculty;
NotificationSetting announcementNotificationSetting;
DateTimeOffset creationDate, modificationDate;
// Frage Kanal-Werte ab.
id = Convert.ToInt32(stmt["Id"]);
name = (string)stmt["Name"];
description = (string)stmt["Description"];
type = (ChannelType)Enum.ToObject(typeof(ChannelType), stmt["Type"]);
creationDate = DatabaseManager.DateTimeFromSQLite(stmt["CreationDate"].ToString());
modificationDate = DatabaseManager.DateTimeFromSQLite(stmt["ModificationDate"].ToString());
term = (string)stmt["Term"];
location = (string)stmt["Location"];
dates = (string)stmt["Dates"];
contact = (string)stmt["Contact"];
website = (string)stmt["Website"];
deleted = ((long)stmt["Deleted"] == 1) ? true : false;
announcementNotificationSetting = (NotificationSetting)Enum.ToObject(typeof(NotificationSetting), stmt["NotificationSettings_NotifierId"]);
// Falls notwendig, hole Daten aus Tabelle der Subklasse.
switch (type)
{
case ChannelType.LECTURE:
using (var getLectureStmt = conn.Prepare("SELECT * FROM Lecture WHERE Channel_Id=?;"))
{
getLectureStmt.Bind(1, id);
// Hole Ergebnis der Query.
if (getLectureStmt.Step() == SQLiteResult.ROW)
{
faculty = (Faculty)Enum.ToObject(typeof(Faculty), getLectureStmt["Faculty"]);
startDate = (string)getLectureStmt["StartDate"];
endDate = (string)getLectureStmt["EndDate"];
lecturer = (string)getLectureStmt["Lecturer"];
assistant = (string)getLectureStmt["Assistant"];
// Erstelle Lecture Objekt und füge es der Liste hinzu.
Lecture lecture = new Lecture(id, name, description, type, creationDate, modificationDate, term, location,
dates, contact, website, deleted, faculty, startDate, endDate, lecturer, assistant);
channel = lecture;
}
}
break;
case ChannelType.EVENT:
using (var getEventStmt = conn.Prepare("SELECT * FROM Event WHERE Channel_Id=?;"))
{
getEventStmt.Bind(1, id);
// Hole Ergebnis der Query.
if (getEventStmt.Step() == SQLiteResult.ROW)
{
cost = (string)getEventStmt["Cost"];
organizer = (string)getEventStmt["Organizer"];
// Erstelle Event Objekt und füge es der Liste hinzu.
Event eventObj = new Event(id, name, description, type, creationDate, modificationDate, term, location,
dates, contact, website, deleted, cost, organizer);
channel = eventObj;
}
}
break;
case ChannelType.SPORTS:
using (var getSportsStmt = conn.Prepare("SELECT * FROM Sports WHERE Channel_Id=?;"))
{
getSportsStmt.Bind(1, id);
// Hole Ergebnis der Query.
if (getSportsStmt.Step() == SQLiteResult.ROW)
{
cost = (string)getSportsStmt["Cost"];
participants = (string)getSportsStmt["NumberOfParticipants"];
// Erstelle Sports Objekt und füge es der Liste hinzu.
Sports sportsObj = new Sports(id, name, description, type, creationDate, modificationDate, term, location,
dates, contact, website, deleted, cost, participants);
channel = sportsObj;
}
}
break;
default:
// Keine Subklasse, also erzeuge Kanal Objekt.
channel = new Channel(id, name, description, type, creationDate, modificationDate, term, location,
dates, contact, website, deleted);
break;
}
// Füge announcementNotificationSetting Einstellung noch dem Objekt hinzu.
channel.AnnouncementNotificationSetting = announcementNotificationSetting;
}
catch(SQLiteException sqlEx){
Debug.WriteLine("SQLiteException has occurred in retrieveChannelObjectFromStatement. The message is: {0}.", sqlEx.Message);
throw new DatabaseException("Retrieve channel has failed.");
}
catch(Exception ex)
{
Debug.WriteLine("Exception has occurred in retrieveChannelObjectFromStatement. The message is: {0}, " +
"and the stack trace: {1}.", ex.Message, ex.StackTrace);
throw new DatabaseException("Retrieve channel has failed.");
}
return channel;
}
/// <summary>
/// Hilfsmethode, welche aus den eingegebenen Daten ein Objekt
/// vom Typ Channel erstellt. Eventuelle Subklassen-Attribute
/// werden ebenfalls gesetzt.
/// </summary>
/// <returns>Ein Objekt der Klasse Channel, welches die vom Nutzer eingegebenen Daten enthält.</returns>
private Channel createChannelObjectFromEnteredData()
{
// Setze den String für das Semester zusammen.
string termString = string.Empty;
if (TermYear != null)
{
if (IsSummerTermSelected)
{
termString += "S" + TermYear;
}
else if (IsWinterTermSelected)
{
termString += "W" + TermYear;
}
}
// Erzeuge Instanz aus den eingegebenen Daten.
Channel newChannel = null;
switch (SelectedChannelType)
{
case ChannelType.LECTURE:
Lecture lecture = new Lecture()
{
Name = ChannelName,
Description = ChannelDescription,
Type = SelectedChannelType,
Term = termString,
Locations = this.Locations,
Dates = this.Dates,
Contacts = this.Contacts,
Website = this.Website,
Faculty = SelectedFaculty,
StartDate = LectureStartDate,
EndDate = LectureEndDate,
Lecturer = this.Lecturer,
Assistant = this.Assistant
};
newChannel = lecture;
break;
case ChannelType.EVENT:
Event eventObj = new Event()
{
Name = ChannelName,
Description = ChannelDescription,
Type = SelectedChannelType,
Term = termString,
Locations = this.Locations,
Dates = this.Dates,
Contacts = this.Contacts,
Website = this.Website,
Cost = EventCost,
Organizer = EventOrganizer
};
newChannel = eventObj;
break;
case ChannelType.SPORTS:
Sports sportsObj = new Sports()
{
Name = ChannelName,
Description = ChannelDescription,
Type = SelectedChannelType,
Term = termString,
Locations = this.Locations,
Dates = this.Dates,
Contacts = this.Contacts,
Website = this.Website,
Cost = SportsCost,
NumberOfParticipants = AmountOfParticipants
};
newChannel = sportsObj;
break;
default:
newChannel = new Channel()
{
Name = ChannelName,
Description = ChannelDescription,
Type = SelectedChannelType,
Term = termString,
Locations = this.Locations,
Dates = this.Dates,
Contacts = this.Contacts,
Website = this.Website
};
break;
}
return newChannel;
}
/// <summary>
/// Bereitet ein Objekt vom Typ Channel vor, welches alle Properties enthält, die sich geändert haben.
/// Die Methode bekommt eine alte Version eines Channel Objekts und eine neue Version und ermittelt
/// dann die Properties, die eine Aktualisierung erhalten haben und schreibt diese in eine neue Channel
/// Instanz. Die von der Methode zurückgelieferte Channel Instanz kann dann direkt für die Aktualisierung auf
/// dem Server verwendet werden. Achtung: Hat sich überhaupt keine Property geändert, so gibt die Methode null zurück.
/// </summary>
/// <param name="oldChannel">Das Channel Objekt vor der Aktualisierung.</param>
/// <param name="newChannel">Das Channel Objekt mit den aktuellen Werten.</param>
/// <returns>Ein Objekt der Klasse Channel, bei dem die Properties, die sich geändert haben, mit den
/// aktualisierten Werten gefüllt sind.</returns>
private Channel prepareUpdatableChannelInstance(Channel oldChannel, Channel newChannel)
{
bool hasChanged = false;
Channel updatedChannel = new Channel();
// Vergleiche zunächst Properties der allgemeinen Channel Klasse.
if (oldChannel.Name != newChannel.Name)
{
hasChanged = true;
updatedChannel.Name = newChannel.Name;
}
if (oldChannel.Description != newChannel.Description)
{
hasChanged = true;
updatedChannel.Description = newChannel.Description;
}
if (oldChannel.Term != newChannel.Term)
{
hasChanged = true;
updatedChannel.Term = newChannel.Term;
}
if (oldChannel.Locations != newChannel.Locations)
{
hasChanged = true;
updatedChannel.Locations = newChannel.Locations;
}
if (oldChannel.Dates != newChannel.Dates)
{
hasChanged = true;
updatedChannel.Dates = newChannel.Dates;
}
if (oldChannel.Contacts != newChannel.Contacts)
{
hasChanged = true;
updatedChannel.Contacts = newChannel.Contacts;
}
if (oldChannel.Website != newChannel.Website)
{
hasChanged = true;
updatedChannel.Website = newChannel.Website;
}
// Vergleiche, ob kanalspezifische Felder sich geändert haben bei den Kanälen eines Typs mit solchen Feldern.
if (oldChannel.Type == newChannel.Type)
{
switch (oldChannel.Type)
{
case ChannelType.LECTURE:
Lecture updatedLecture = new Lecture()
{
Name = updatedChannel.Name,
Description = updatedChannel.Description,
Type = ChannelType.LECTURE,
Term = updatedChannel.Term,
Locations = updatedChannel.Locations,
Dates = updatedChannel.Dates,
Contacts = updatedChannel.Contacts,
Website = updatedChannel.Website
};
Lecture oldLecture = oldChannel as Lecture;
Lecture newLecture = newChannel as Lecture;
if (oldLecture.Lecturer != newLecture.Lecturer)
{
hasChanged = true;
updatedLecture.Lecturer = newLecture.Lecturer;
}
if (oldLecture.Assistant != newLecture.Assistant)
{
hasChanged = true;
updatedLecture.Assistant = newLecture.Assistant;
}
if (oldLecture.Faculty != newLecture.Faculty)
{
hasChanged = true;
updatedLecture.Faculty = newLecture.Faculty;
}
if (oldLecture.StartDate != newLecture.StartDate)
{
hasChanged = true;
updatedLecture.StartDate = newLecture.StartDate;
}
if (oldLecture.EndDate != newLecture.EndDate)
{
hasChanged = true;
updatedLecture.EndDate = newLecture.EndDate;
}
// Setze updatedChannel neu.
updatedChannel = updatedLecture;
break;
case ChannelType.EVENT:
Event updatedEvent = new Event()
{
Name = updatedChannel.Name,
Description = updatedChannel.Description,
Type = ChannelType.EVENT,
Term = updatedChannel.Term,
Locations = updatedChannel.Locations,
Dates = updatedChannel.Dates,
Contacts = updatedChannel.Contacts,
Website = updatedChannel.Website
};
Event oldEvent = oldChannel as Event;
Event newEvent = newChannel as Event;
if (oldEvent.Cost != newEvent.Cost)
{
hasChanged = true;
updatedEvent.Cost = newEvent.Cost;
}
if (oldEvent.Organizer != newEvent.Organizer)
{
hasChanged = true;
updatedEvent.Organizer = newEvent.Organizer;
}
// Setze updatedChannel neu.
updatedChannel = updatedEvent;
break;
case ChannelType.SPORTS:
Sports updatedSport = new Sports()
{
Name = updatedChannel.Name,
Description = updatedChannel.Description,
Type = ChannelType.SPORTS,
Term = updatedChannel.Term,
Locations = updatedChannel.Locations,
Dates = updatedChannel.Dates,
Contacts = updatedChannel.Contacts,
Website = updatedChannel.Website
};
Sports oldSport = oldChannel as Sports;
Sports newSport = newChannel as Sports;
if (oldSport.Cost != newSport.Cost)
{
hasChanged = true;
updatedSport.Cost = newSport.Cost;
}
if (oldSport.NumberOfParticipants != newSport.NumberOfParticipants)
{
hasChanged = true;
updatedSport.NumberOfParticipants = newSport.NumberOfParticipants;
}
// Setze updatedChannel neu.
updatedChannel = updatedSport;
break;
case ChannelType.OTHER:
updatedChannel.Type = ChannelType.OTHER;
break;
case ChannelType.STUDENT_GROUP:
updatedChannel.Type = ChannelType.STUDENT_GROUP;
break;
}
}
// Prüfe, ob sich überhaupt eine Property geändert hat.
if (!hasChanged)
{
Debug.WriteLine("No Property of channel has been updated. Method will return null.");
updatedChannel = null;
}
return updatedChannel;
}