CODEWITHSUNDEEP
javascriptcordovajquery-callback
galgo
galgo

Reputation: 764

Handling javascript db.transaction callback

I'm stuck with the following and I'm sure it's do to my lack of experience dealing with callbacks, I want to query a db as follows:

db.transaction(queryFoodDBAll, errorCB);

function errorCB(tx, err) {
    alert("Error processing SQL: "+err);
}

function queryFoodDBAll(tx) {
    tx.executeSql('SELECT * FROM Food', [], displayAllFood, errorCB);
}

function displayAllFood(tx, results) {
    var len = results.rows.length;
    var items = new Array();
    for (var i=0; i<len; i++){
        items[i] = results.rows.item(i).data
    }
    printdata('settings-food',items, 'Food');
}

function printData(type,data,title) {
    switch(type)
    {
        case 'settings-food':
            alert("Data: "+data);
            var content = '<div data-role="collapsible" data-theme="c"><h3>'+title+'</h3>';
            for (var i=0;i<data.length;i++) {
                content += '<p>'+data[i]+'</p>';
            }
            content += '</div>';
            $("#settings-food").append(content);
            break;
}

Now, when I run it, all the information is retrieved successfully until I run the printData function, which gives me the the errorCB displaying "Error processing SQL: undefined".

Any ideas on this?

Upvotes: 3

Views: 2437

Answers (1)

Ryan
Ryan

Reputation: 5682

Your issue is the return stack:

When you get to printData your call stack looks like this:

----queryFoodDAll
----executeSQL
----disiplayAllFood (jump to printData)
----errorCB
----printData

Javascript will return up that call stack; so while you skipped errorCB on your way down, on the way back up it hits that function, no matter what you do; because it's part of the callback stack.

What you want to do is not have your errorCB as a call back function.

Instead check in your displayAllFood() for valid SQL. If its valid continue down the call list (meaning continue onto printData) but if its not valid then call errorCB.

Upvotes: 2

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