ios App通过预先请求数据来提高网络性能

Question

I have an application that I'm writing that pulls data from a few network sources: 1) list of blog posts (UITableViewController) 2) list of videos (UIViewController with an embedded UIScrollView) 3) list of images (UIViewController with an embedded UIScrollView)

Right now, there is a home screen with a menu and when you push one of the buttons, a destinationViewController (described above) is what loads the data on demand. I've noticed this is quite slow, especially when on a cellular data connection as opposed to wifi.

I was thinking about creating a class that requests all the data up front and kick it off every time the app is reentered. Does anyone have suggestions that could help me answer the following?

1) are there any classes, frameworks, or existing i code i can use to kick off these requests in a single place? 2) how do my destination view controllers (mentioned above) get the data? 3) how do my destination view controllers get informed that the data is ready if they happen to be invoked before the data is available? 4) is there a better strategy i should employ?

I appreciate the help.

Thanks, jas

Answer 1

1) RestKit is generally regarded as one of the the standard web interaction frameworks http://restkit.org

2) RestKit provides methods such as -[getObjectsAtPath: parameters: success: failure:] or post, which will provide the response in success. Additionally, it can convert the response directly into the respective objects for you with mapping.

3) Generally I would post a notification which is unique to that request, and any controller interested would get notified, with the response located on notification.object within the listener. Additionally most network requests provide for a callback handler where you could update the UI directly.

4) I would advise against preemptive loading since you're using resources for something that you may not actually use. My advice would be to breakdown your calls to the smallest possible level, then as the notifications are posted, that data would be inserted into the UI.

Answer 2

Off the top of my head, I would make the request class you mentioned and start all the request methods in applicationDidFinishLaunching in AppDelegate. I would also probably make custom NSObjects for each type of object you would be fetching and in each of your request class methods, convert the fetched data into said object, then cache each object to disk as they are downloaded. Then in your viewcontrollers, fetch the cached objects as needed.

When you are cacheing, make sure you cache each object with a key that will 100% be unique, because you are going to want to run a check on the current local cache before you start a new download. I would probably string together the file type and file name, and set that string as the key for the cached object.

To run the check on current cache in your request class methods, something that says "if current cache contains object for key: uniqueKey... do nothing. If else, start the download and cache the object when finished."

Also run a check in your view controllers, because you're also going to want to handle the case where your view controller is requesting a cached object, but it hasn't downloaded yet. So something along the lines of "if current cache has object for key:key, great! use it. If else, start the download... cache it... then give me a call back here so i can use it while I display a loading message to the end user."

Im sure there are other scenarios that you are going to have to deal with, but that's the theoretical direction I would head in.

EDIT:

check out this, it will probably help you a lot. I think it also uses Ego Cache (if you dont want to write your own cache methods): https://github.com/Infusion-apps/Download-Manager

EDIT 2: I also agree with @RyanDignards point #4. If possible, avoid fetching data you don't need. However, only you really know your UI/UX and app functionality, and my suggestion is assuming there is a good chance your end user is going to be using your app for the sole purpose of consuming the content you provide. So they are most likely going to be wanting to read the blog posts, watch the videos etc... The call is up to you, if you think there is more of a chance that the user will be viewing all the content than not, I would go the preload route, because nothing pisses off a user like having to wait.