hardcopy books cannot be consulted online as you'll need to purchase a seperate ebook instead; please contact training@servicenow.com if you'd like to do so.
"The Comprehensive How To" blog focuses on the ControllerAs concept of AngularJS works and also why we apply the controllerAs (ref "var c = this") instead of $scope in the Service Portal widget controller scripts (= client script) on the NOW platform. In order to understand this, if you're not familiar with AngularJS, it's recommended to read through top 2 blogs first.
The widget-data-table widget has different implementation of subscription with force unsubscribe on widget destruction.
I would like to know what is the difference.
var watcher;
function initRecordWatcher(table, filter){
if (watcher)
watcher.unsubscribe();
if (table && filter) {
var watcherChannel = amb.getChannelRW(table, filter);
amb.connect();
watcher = watcherChannel.subscribe(function(message) {
if (!message.data)
return;
switch(message.data.action) {
case "change":
updateRowFromRW(message);
break;
case "exit":
// A record was removed
case "enter":
// A record was added
default:
spUtil.update($scope);
break;
}
});
}
}
$scope.$on('$destroy', function() {
if (watcher)
watcher.unsubscribe();
});
I think you want to use subscribe + unsubscribe when you refresh/change the content of the widget without refreshing the page.
so in the case of the datatable widget, you could change the table on-the fly - you dont refresh the page, the widget just reloads with new data - the initRecordWatch fn then gets called again and unsubscribes from the old listeners. In This case also the table and filter parameters of the record watchers change because its new table
Most of the time you only listen for specific table and filter, so you can use the simple recordWatch
The example is explained in Dan Conroy's community article: https://community.servicenow.com/community?id=community_article&sys_id=29188f2cdb2b57c08e7c2926ca961983. There you can download the XML file.
When inserting a new record, what does gr.initialize() actually do? Inserting seems to work fine without that line, and I've seen OOB scripts that omit it.
