Question

Hopefully you can see a bit from the code what I’m trying to do here, basically I need to check if a record exists in a database, so I call a function to do so, but I’m using the sqlrunner class wherein the result of a query is called as an event response and I don’t know how to get that value out of the resulting function back to the parent.
I feel like I must be doing things backwards or something..

        public function dbmatch(datetime:String, typecode:String):Boolean {
            var q:String = "SELECT DateTime FROM Event WHERE DateTime='"+datetime+"' AND EventTypeCode='"+typecode+"'"
            SQLService.getInstance().execute(q,null,matchresult);
            function matchresult(result:SQLResult):Boolean{
                var match:String = result.data[0];
                if (match == null){return false} else {return true}
            }
            return matchresult();
        }

elsewhere:

var recordexists:Boolean = dbmatch(datetime, "Gb");

if (!recordexists){...}

Answer 1

Basically the problem is that the SQLService class can’t immediatly return a result for your query. That is why it uses a callback listener function (matchresult in your example) to inform your program at a later time that it has finished the search.

A basic way of handling this would be to call the query, then wait for the Query to “callback” to your listening funciton, that can then continue execution.

public function dbmatch(datetime:String, typecode:String, callbackListener:Function):void {
    var q:String = "SELECT DateTime FROM Event WHERE DateTime='"+datetime+"' AND EventTypeCode='"+typecode+"'"
    SQLService.getInstance().execute(q, null, callbackListener);
}

Elsewhere:

    // Start the query, but can't react to it immediatly        
    dbmatch(datetime, "Gb", onSQLQueryResult);

    // Your callback function
    public function onSQLQueryResult(result:SQLResult):void {
        var match:String = result.data[0];
        if (match == null) {
            // Do stuff you were going to do at (!recordexists)
        }
    }