how to add column in a sqlite table in SWIFT

问题:

I try to add a column in a table with swift.

my code :

  connect_db();
  adddbfield("mynewfield","mytable");

.

func connect_db() -> Bool {
    let sDBPath=<is correctly set>;
    if sqlite3_open(sDBPath, &db) != SQLITE_OK {
        println("Failed to open db")
        return false;
    }else{
        return true;
    }
}

.

func adddbfield(sFieldName:String, sTable:String) -> Bool {
    var bReturn:Bool=false;
    var sSQL="ALTER TABLE " + sTable + " ADD COLUMN " + sFieldName + " INTEGER DEFAULT -1";
    var statement:COpaquePointer = nil
    if sqlite3_prepare_v2(db, sSQL, -1, &statement, nil) != SQLITE_OK {
        println("Failed to prepare statement")
    }else{
        println("field " + sFieldName + " added  to  " + sTable);
        bReturn=true;
    }
    return bReturn;
}

With this Code no field is added and no error occurs. Any help ? (I would like to use the native access to sqlite and no additional library)

回答1:

You are only preparing the statement, not executing it. You need to call sqlite3_step() and sqlite3_finalize() methods for completing the process.

func adddbfield(sFieldName:String, sTable:String) -> Bool
{
    var bReturn:Bool = false;
    var sSQL="ALTER TABLE " + sTable + " ADD COLUMN " + sFieldName + " INTEGER DEFAULT -1";
    var statement:COpaquePointer = nil
    if sqlite3_prepare_v2(db, sSQL, -1, &statement, nil) != SQLITE_OK
    {
        println("Failed to prepare statement")
    }
    else
    {
        if sqlite3_step(statement) == SQLITE_DONE
        {
           println("field " + sFieldName + " added  to  " + sTable);
        }
        sqlite3_finalize(statement);
        bReturn=true;
    }
    return bReturn;
}