ios - reorder items in uitableview and apply changes to sqlite database - ios

Question

i'm trying to reorder a table view - have set up the canMoveRowAtIndexPath and moveRowAtIndexPath so that I can drag the cells around when i'm in editing mode, but I need to basically mirror these changes in an sqlite database that I have. i have a column called "orderid" which i'm using to keep track of the order of the cells. My approach has been to basically set the cell being moved to orderid=9999, then add or subtract 1 from from the orderid of the rest of the affected cells, then set the new cell to its destination orderid. i think it's likely to be an sql error but i can't figure it out. if anyone has any advice it would be much appreciated.
these are my methods:
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath {
return YES;
}
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath{
long source = (long)sourceIndexPath.row;
long dest = (long)destinationIndexPath.row;
source++;
dest++;
//reorder in db
NSString *sql;
if (source>dest) {
sql = [NSString stringWithFormat:#"UPDATE entries SET orderid=9999 where orderid=%ld; update entries set orderid = orderid + 1 where orderid<%ld AND orderid>=%ld update entries set orderid=%ld where orderid=9999", source, source,dest, dest];
} else if (source<dest){
sql = [NSString stringWithFormat:#"UPDATE entries SET orderid=9999 where orderid=%ld; update entries set orderid = orderid - 1 where orderid BETWEEN orderid>%ld AND orderid<=%ld; update entries set orderid=%ld where orderid=9999", source, source, dest, dest];
}
NSLog(#"%#", sql);
char *err;
if (sqlite3_exec(db, [sql UTF8String], NULL, NULL, &err) !=SQLITE_OK) {
sqlite3_close(db);
NSLog(#"could not reorder");
} else {
NSLog(#"rows reordered");
}
}

Answer 1

I am using pageOrder to create an order in my pages table. This is table :
.s pages
CREATE TABLE pages (
uuid INTEGER PRIMARY KEY,
name TEXT,
pageOrder INTEGER DEFAULT 0
);
Here is the code :
int fromRow = [sourceIndexPath row];
int toRow = [destinationIndexPath row];
if (toRow != fromRow) {
FMDatabase* db = [FMDatabase databaseWithPath:[appDelegate dbPath]];
[db open];
[db executeUpdate:#"UPDATE pages SET pageOrder = -? WHERE pageOrder = ?",
[NSNumber numberWithInt:toRow + 1],
[NSNumber numberWithInt:fromRow + 1]];
if (toRow < fromRow) {
[db executeUpdate:#"UPDATE pages SET pageOrder = pageOrder + 1 WHERE pageOrder > ? AND pageOrder <= ?",
[NSNumber numberWithInt:toRow],
[NSNumber numberWithInt:fromRow]];
} else {
[db executeUpdate:#"UPDATE pages SET pageOrder = pageOrder - 1 WHERE pageOrder > ? AND pageOrder <= ?",
[NSNumber numberWithInt:fromRow],
[NSNumber numberWithInt:toRow + 1]];
}
[db executeUpdate:#"UPDATE pages SET pageOrder = abs(pageOrder) WHERE pageOrder < 0"];
[db close];
}
Should be working,
Cheers,
Eddy

Answer 2

One possibility may be if the numberOfRows in your tableView does not match the number of entries in your database, for example: if you have an ‘Add new row...’ cell on the bottom of the tableView, then you may run into trouble, like I have in the past. My trouble was that the tableView:moveRowAtIndexPath:toIndexPath was returning the wrong sourceIndexPath. Two solutions both solved the problem. First solution: Call [tableview reloadData] in the tableView:moveRowAtIndexPath:toIndexPath:, you may lose the row animation but you will keep the functionality and sourceIndexPath/destinationIndexPath will be updated. Second solution: Don’t use an ‘Add new row...’ cell on the bottom and find alternate solution to add. Good luck!

Answer 3

I would suggest using float order_id. And when user reorders item, get order_id of previous and next item, get their mean (float) and save to DB. This way, you need to update only reordered item.

Answer 4

This Works fine with me!
- (void) tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)targetIndexPath{
// Define las variables a utilizar: IDorigen hace referencia al ID que tiene la fila antes de moverse e IDDestino hace referencia al ID que va a tener la fila luego de moverse
int IDorigen = (int)[sourceIndexPath row]+1;
int IDdestino = (int)[targetIndexPath row]+1;
int diferencia;
// Define la variable de consulta sobre la base de datos
NSString *consulta;
// Si el IDorigen es menor al IDdestino (es decir, mueve una fila hacia abajo)
if (IDorigen < IDdestino)
{
// Obtiene la diferencia para saber cuantas filas hay entre IDdestino e IDOrigen
diferencia = IDdestino - IDorigen;
// Hace un FOR desde cero hasta diferencia, y a cada fila que encuentra le pone el ID=9000+i. Esto se hace para mandar las filas invoulucradas en el movimientohacia abajo de todo y evitar conflictos de ID
for (int i=0;i<diferencia;i++){
// Define la consulta
consulta = [NSString stringWithFormat:#"update homeTabla set ID=%d where ID=%d", 9000+i,IDorigen+1+i];
// Ejecuta la consulta
[self.dbTouchMeCIS executeQuery:consulta];
}
// Cuando finaliza el FOR, le asigna a la fila que se está moviendo, el IDdestino deseado definiendo la consulta
consulta = [NSString stringWithFormat:#"update homeTabla set ID=%d where ID=%d", IDdestino,IDorigen];
// Ejecuta la consulta
[self.dbTouchMeCIS executeQuery:consulta];
// Hace un FOR para asignarle el valor que corresponde a aquellas filas que se le asigno el ID=9000+i
for (int i=0;i<diferencia;i++){
// Define la consulta
consulta = [NSString stringWithFormat:#"update homeTabla set ID=%d where ID=%d",IDorigen+i,9000+i];
// Ejecuta la consulta
[self.dbTouchMeCIS executeQuery:consulta];
}
// Si el IDorigen es mayor al IDdestino (es decir, mueve una fila hacia arriba)
}else if (IDorigen > IDdestino){
// Obtiene la diferencia para saber cuantas filas hay entre IDdestino e IDOrigen
diferencia = IDorigen - IDdestino;
// Hace un FOR desde cero hasta diferencia, y a cada fila que encuentra le pone el ID=9000+i. Esto se hace para mandar las filas involucradas en el movimiento hacia abajo de todo y evitar conflictos de ID
for (int i=0;i<diferencia;i++){
// Define la consulta
consulta = [NSString stringWithFormat:#"update homeTabla set ID=%d where ID=%d", 9000+i,IDdestino+i];
// Ejecuta la consulta
[self.dbTouchMeCIS executeQuery:consulta];
}
// Cuando finaliza el FOR, le asigna a la fila que se está moviendo, el IDdestino deseado definiendo la consulta
consulta = [NSString stringWithFormat:#"update homeTabla set ID=%d where ID=%d", IDdestino,IDorigen];
// Ejecuta la consulta
[self.dbTouchMeCIS executeQuery:consulta];
// Hace un FOR para asignarle el valor que corresponde a aquellas filas que se le asigno el ID=9000+i
for (int i=0;i<diferencia;i++){
// Define la consulta
consulta = [NSString stringWithFormat:#"update homeTabla set ID=%d where ID=%d",IDdestino+1+i,9000+i];
// Ejecuta la consulta
[self.dbTouchMeCIS executeQuery:consulta];
}
}
// Recarga la base de datos en la tabla una vez finalizado el movimiento
[self recargarDatos];
}