Decreasing loading time

[harrytheshark]

In an app I'm working on, I'm creating custom/XML files from the users iPod (Artists, Albums, Genres, Songs, Playlists).

I'm wanting to do this on start up, so the user only has to wait once, rather than waiting each time these files are needed.

At the moment, I'm just using brute force and a "for" loop to get what I want:

NSArray * songs = [[NSArray alloc] initWithArray:[[MPMediaQuery songsQuery] collections]];
NSMutableString * fullData = [[NSMutableString alloc] init];

for (MPMediaItemCollection * item in songs){
   //Add to a NSMutableString with formatting I want
}

[songs release];

[fullData writeToFile:...];
[fullData release];

The above is run in a background thread, so that the UI doesn't hang.
On the device I'm testing with, I have just over 1000 songs, and this takes about 40 seconds to do on a iPhone 3G.

I've then got to write similar files for Artists, Albums, etc.
So in total it could take a few minutes.

I've tried running them all at the same time in different threads, and running them one after the other. There doesn't seem to be a massive difference in times.

Basically I'm wondering if there is a way I'm unaware of that would allow me to decrease the loading time, or am I already using the 'best' way?

Thanks,
Tom

[smithdale87]

I think "lazy loading" is the best technique in general. You don't need to load those things until you absolutely have to. If possible split it up. Even though you may want the user to have instantaneous satisfaction after your app has fully loaded, waiting for minutes at a time is not good either.

I think a user is more likely to wait 5-10 secs here and there, rather than 30-40 secs all at once.

[harrytheshark]

Thanks for the reply.

Would you mind explaining lazy loading in a little more detail. I think I've got the basic gist that it's loading when needed, and in smaller chunks, but I'm unsure of how I can implement it for what I'm doing here, as one file can take 40 seconds on it's own.

Thanks again,
Tom

[smithdale87]

Originally Posted by harrytheshark

Thanks for the reply.

Would you mind explaining lazy loading in a little more detail. I think I've got the basic gist that it's loading when needed, and in smaller chunks, but I'm unsure of how I can implement it for what I'm doing here, as one file can take 40 seconds on it's own.

Thanks again,
Tom

I'm not exactly what you're trying to do with these xml files, so it's hard to say for sure.

[harrytheshark]

They're used as a response by a webserver. Eg, a device connects to "192.168.1.2:7654", and the file is returned. Which is why I need them created when the app/webserver starts.