sort SQL data in xcode - ios

Question

I am trying to sort / order SQL data in my iOS app. the database is working fine. i can add data, display in tableview, edit, delete everything is working fine. just can't sort. below is the code i am using.
-(void)sortTable
{
//CHECKING DIRECTORY AND CREATING DATABASE CODE STARTS
NSString *docsDir;
NSArray *dirPaths;
// Get the documents directory
dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsDir = dirPaths [0];
//Build the path to the database file
_databasePath = [[NSString alloc]initWithString:[docsDir stringByAppendingPathComponent:#"events.db"]];
NSFileManager *filemgr = [NSFileManager defaultManager];
if ([filemgr fileExistsAtPath: _databasePath] == NO)
{
const char *dbpath = [_databasePath UTF8String];
if (sqlite3_open(dbpath, &_eventDB) == SQLITE_OK)
{
char *errMsg;
const char *sql_stmt =
"CREATE TABLE IF NOT EXISTS EVENTS (ID INTEGER PRIMARY KEY AUTOINCREMENT, EVENT TEXT, EVENTDATE TEXT)";
//closing database after creating
if (sqlite3_exec(_eventDB, sql_stmt, NULL, NULL, &errMsg) !=SQLITE_OK)
{
// sqlite3_close(_eventDB);
}
}
}
//CHECKING DIRECTORY AND CREATING DATABASE CODE ENDS
//sort sql table
sqlite3_stmt *statement;
const char *dbpath = [_databasePath UTF8String];
if (sqlite3_open(dbpath, &_eventDB) == SQLITE_OK)
{
NSString *sortSQLTable = [NSString stringWithFormat:#"SELECT EVENT FROM EVENTS ORDER BY EVENT"]; // EVENTS is the table name and EVENT is the column.
const char *sort_stmt = [sortSQLTable UTF8String];
sqlite3_prepare_v2(_eventDB, sort_stmt, -1, &statement, NULL);
}
}
I am executing this void statement in viewDidLoad.
I have searched a lot. tried different things. just could not make it work. can someone help please.
UPDATE:
I just found that the ORDER BY query is actually sorting the table, but its not saving the database.
any idea how i can save the database after sorting?

Answer 1

If you are looking to sort data to display on your tableview you could use a NSSortDescriptor.
Here is the documentation from Apple on how to use them.
The gist though is something like ..
//array of People objects with properties of firstName and lastName just for example
NSArray *firstNames = #[ #"Jan", #"Steve", #"Jay", #"Mike" ];
NSArray *lastNames = #[ #"Joker", #"Jones", #"Smith", #"Pham" ];
NSMutableArray *people = [NSMutableArray array];
[firstNames enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
Person *person = [[Person alloc] init];
person.firstName = [firstNames objectAtIndex:idx];
person.lastName = [lastNames objectAtIndex:idx];
[people addObject:person];
}];
//make the descriptor
NSSortDescriptor *firstNameSortDescriptor = [NSSortDescriptor sortDescriptorWithKey:#"firstName"
ascending:YES ];
//sort the array using the descriptor
NSLog(#"By first name: %#", [people sortedArrayUsingDescriptors:#[firstNameSortDescriptor]]);