Getting SQLite Misuse error

Question

I am attempting to set up a button that will save the given fields into a SQLite DB. I was able to create the table, but the insert statement on the button click is giving me a SQLite_MISUSE error instead of giving me SQLite_OK. I am unable to figure out what the issue is in my code, please let me know if you have any clue as to why this is happening.

- (IBAction)SignUp:(id)sender {
    sqlite3_stmt *statement;
    const char *dbPath = [_databasePath UTF8String];

    if(sqlite3_open(dbPath, &_DB) == SQLITE_OK) {
        NSString *insertSQL = [NSString stringWithFormat:@"INSERT INTO users(username, email, password) values(\"%@\", \"%@\", \"%@\")", _Username.text, _Email.text, _Password1.text];

        const char *insert_statement = [insertSQL UTF8String];
        sqlite3_prepare_v2(_DB, insert_statement, -1, &statement, NULL);


        if(sqlite3_step(statement) == SQLITE_DONE) {
            //below creates a popup success message upon adding user to the db
            UIAlertController * alert = [UIAlertController
                                         alertControllerWithTitle:@"Congrats!"
                                         message:@"You are now a member"
                                         preferredStyle:UIAlertControllerStyleAlert];

            UIAlertAction* okButton = [UIAlertAction
                                        actionWithTitle:@"Ok"
                                        style:UIAlertActionStyleDefault
                                        handler:^(UIAlertAction * action) {
                                        //
                                        }];

            [alert addAction:okButton];
            [self presentViewController:alert animated:YES completion:nil];

            //returns the text fields back to original empty state
            _Username.text = @"";
            _Email.text = @"";
            _Password1.text = @"";
            _Password2.text = @"";
        }
        else {
            //some other error
            UIAlertController * alert=   [UIAlertController
                                          alertControllerWithTitle:@"Some"
                                          message:@"Other Error"
                                          preferredStyle:UIAlertControllerStyleAlert];
            UIAlertAction* ok = [UIAlertAction
                                 actionWithTitle:@"OK"
                                 style:UIAlertActionStyleDefault
                                 handler:^(UIAlertAction * action)
                                 {
                                     [alert dismissViewControllerAnimated:YES completion:nil];
                                 }];
            [alert addAction:ok];
            [self presentViewController:alert animated:YES completion:nil];
        }
        sqlite3_close(_DB);
    }
}

Answer 1

You have several issues with the posted code.

1. You never finalize the prepared statement.
2. You don't do any error checking on the call to sqlite3_prepare_v2.
3. Never build a query with stringWithFormat:. Properly bind values into the query using the appropriate sqlite3_bind_xxx functions.

See https://stackoverflow.com/a/39001417/1226963 for an example that fixes these issues.