public static async Task SetFromApi <TViewModel, TApiResult>(
this Bindable <TViewModel> @this,
Expression <Func <TViewModel, TApiResult> > viewModelProperty,
string apiUrl,
AsyncEvent <RevisitingEventArgs> pageRevisiting = null)
{
var binding = new Bindable <TViewModel> .ViewModelMemberBinding <TApiResult>(@this, viewModelProperty);
var cacheAvailable = false;
async Task refresh()
{
var fresh = await BaseApi.Get <TApiResult>(apiUrl, cacheChoice : ApiResponseCache.PreferThenUpdate, refresher : binding.Update);
if (!cacheAvailable && fresh != null)
{
binding.Update(fresh);
}
}
// If there is a cached result already available, set it immediately
var result = await BaseApi.Get <TApiResult>(apiUrl, cacheChoice : ApiResponseCache.CacheOrNull);
if (result != null)
{
cacheAvailable = true;
await binding.Update(result);
}
// Otherwise send a fresh request and apply the value.
refresh().RunInParallel();
// When gone back to the page, also refresh.
if (pageRevisiting != null)
{
pageRevisiting.Handle(x => refresh());
}
}