I ended up solving this by creating a deferred object that gets or creates the value I need:
function get_or_create_cache(storage, key, service_endpoint) {
return $.Deferred(function(deferred) {
var c = storage.get(key);
if (c === null || c === undefined) {
$.when(jsonp_service_request(service_endpoint)).done(function(json) {
storage.set(key, json);
deferred.resolve(json);
});
}
else {
deferred.resolve(c);
}
}).promise();
}
In this function, storage
refers to a Sammy.Storage instance. jsonp_service_request
is a local function that returns a jsonp response, taking into account the location.hostname
for local development, where I'm pointing to local.json files, or a remote environment, where I'm calling into an actual API. jsonp_service_request
returns an $.ajax
function.
Then in my Sammy route, I can do:
this.get('#/', function(event_context) {
$.when(get_or_create_cache(storage, 'my-cache-key', 'service-endpoint'))
.then(function(json) {
event_context.render('my-template.template', {'value-name': json})
.appendTo('#my-target');
});
});