Conditionally adjust visible columns in Rally Cardboard UI - rally

Question

So I want to allow the user to conditionally turn columns on/off in a Cardboard app I built. I have two problems.
I tried using the 'columns' attribute in the config but I can't seem to find a default value for it that would allow ALL columns to display(All check boxes checked) based on the attribute, ie. the default behavior if I don't include 'columns' in the config object at all (tried null, [] but that displays NO columns).
So that gets to my second problem, if there is no default value is there a simple way to only change that value in the config object or do I have to encapsulate the entire variable in 'if-else' statements?
Finally if I have to manually build the string I need to parse the values of an existing custom attribute (a drop list) we have on the portfolio object. I can't seem to get the rally.forEach loop syntax right. Does someone have a simple example?
Thanks
Dax - Autodesk
I found a example in the online SDK from Rally that I could modify to answer the second part (This assumes a custom attribute on Portfolio item called "ADSK Kanban State" and will output values to console) :
var showAttributeValues = function(results) {
for (var property in results) {
for (var i=0 ; i < results[property].length ; i++) {
console.log("Attribute Value : " + results[property][i]);
}
}
};
var queryConfig = [];
queryConfig[0] = {
type: 'Portfolio Item',
key : 'eKanbanState',
attribute: 'ADSK Kanban State'
};
rallyDataSource.findAll(queryConfig, showAttributeValues);

Answer 1

rally.forEach loops over each key in the first argument and will execute the function passed as the second argument each time.
It will work with either objects or arrays.
For an array:
var array = [1];
rally.forEach(array, function(value, i) {
//value = 1
//i = 0
});
For an object:
var obj = {
foo: 'bar'
};
rally.forEach(obj, function(value, key) {
//value = 'bar'
//key = 'foo'
});

Answer 2

I think that the code to dynamically build a config using the "results" collection created by your query above and passed to your sample showAttributeValues callback, is going to look a lot like the example of dynamically building a set of Table columns as shown in:
Rally App SDK: Is there a way to have variable columns for table?
I'm envisioning something like the following:
// Dynamically build column config array for cardboard config
var columnsArray = new Array();
for (var property in results) {
for (var i=0 ; i < results[property].length ; i++) {
columnsArray.push("'" + results[property][i] + "'");
}
}
var cardboardConfig = {
{
attribute: 'eKanbanState',
columns: columnsArray,
// .. rest of config here
}
// .. (re)-construct cardboard...

Answer 3

Sounds like you're building a neat board. You'll have to provide the board with the list of columns to show each time (destroying the old board and creating a new one).
Example config:
{
attribute: 'ScheduleState'
columns: [
'In-Progress',
'Completed'
]
}