何时应该在Play框架中返回一个Promise而不是实际的结果？(When should a method return a Promise instead of actual result in Play Framework?)

 应用程序切片目前无法正常工作，直至另行通知。 目前，减少应用规模的唯一方法是减少.ipa中包含的资产数量。 
 
 如果它们对您的应用有意义，您可以尝试使用On Demand Resources 。 

Searching app thining, bit code and on demand app resource from yesterday, Now I debug all these things and sharing my knowledge that I got from beautiful apple documentation with help of my sample project.
 
App thinning concept covers bit code and on-demand resource. I will discuss on-demand resource in detail below:-
 
On-Demand Resources in iOS:- It is accessing the images/videos/.h/.m/swift file whenever needed (Yes, on-demand resouring include source code files also).
 
 
 
Goto Resource tags setting in your target. 
 
 
Create a new Tag. It will appear under Download Only On demand.
 
 
You can add .h, .m, .xassest, .png etc under various tags. You can also assign tag by selecting individual file like this in file inspector.
 
 
Now comes the coding part (my favourite site):-
 
NSBundleResourceRequest *resourceRequest;


#pragma mark - On demand resource
-(void)getOnDemandResource{
    NSSet *setOfTag = [NSSet setWithObjects:@"chair", nil];
    resourceRequest = [[NSBundleResourceRequest alloc]initWithTags:setOfTag];

    [resourceRequest conditionallyBeginAccessingResourcesWithCompletionHandler:^(BOOL resourcesAvailable) {
        if (!resourcesAvailable) {
//            resourceRequest.loadingPriority = 1;//set the downloading priority (0 - 1) , NSBundleResourceRequestLoadingPriorityUrgent

            [resourceRequest beginAccessingResourcesWithCompletionHandler:^(NSError * _Nullable error) {
                if (error) {
                    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"Error" message:error.debugDescription preferredStyle:UIAlertControllerStyleAlert];
                    [self presentViewController:alert animated:YES completion:nil];
                }else{
                    //// The associated resources are loaded
                }
            }];
        }else{
            // The associated resources are available
        }
    }];
}
 
End accessing the on demand resource when not in use(generally when game level changes)
 
#pragma mark - Remove access to on demand
-(void)endAccessToOnDemandResource{
    [resourceRequest endAccessingResources];
}
 
NOTE:- Don't forgot to enable On_Demand_Resources in build setting.
 
EXAMPLE PROJECT:- I create a sample project and uploaded here:- [http://www.dropbox.com/s/edi5zj68a4wuguh/WebOnTab.zip?dl=0][6]
 
Please don't bother about autolayout in this project. My main focus is on demand resourcing/App thing.
 
SUMMARY:- Thus we can achieve app thinning by on-demand resourcing using above technique. Please also have a look at official documentation which also describes about tracking progress, priorities of resourceRequests(NSBundleResourceRequest).