Byte Buffers NSData

Question

I'm just confused about when to use NSData. I'm about to get some data stored in the server (I'm just using dropbox here instead for some practice.) What I did so far is

• Made some p-list storing 2 arrays, one stores string object , and the other stores string objects of the public URL for the audio data.

• When I created the NSString from the plist , I didn't use NSData object

• When I created the NSAudio Player with data stored in the same project folder, I didn't use NSData object
• When I created the NSAudio Player with data stored in a server, I used the NSData

I just don't understand when to use NSData object properly. I checked the app document, but it says "Data objects let simple allocated buffers" What is the allocated buffers here? Thanks,

Answer 1

NSData is just a wrapper for a byte array. Anywhere that you specifically need a byte array you can either use a byte array and do all manipulations manually (accessing and manipulating the data) or you can wrap it in an NSData (or NSMutableData if you need to modify the bytes) and use Apple provided functions to easily access or modify the data.

The allocated buffer is the byte array stored inside the NSData wrapper. Say you have an audio object on disk that you want to modify one byte in the middle of. You could load that data from disk into an audio element, but then you can't modify it. If you load it's byte values from disk into an NSMutableData you can have access to the bytes directly, modify whatever you would like using simple methods provided to the NSMutableData class, then same the audio element back to disk (or load that data directly into your audio element).

The best use of an NSData object is only when you need it, just like any other class. If you specifically need the functionality to run your app, then use it. Otherwise it is likely just an added step that is not required (ex data-on-disk -> audio-element vs data-on-disk -> NSData -> audio-element).