How to define code for different iOS versions

Question

I am working on an iOS app. I want it to support iOS 7 and 8. It is going pretty nicely, however there are lots of different parts of the app which use Apple APIs. Some of these APIs work in both iOS 8 and 7. However, some of them are deprecated in iOS 8. So I therefore went to the Apple developer site to see what to replace them with (new methods/etc....).

However, I now have the problem that the app will work on iOS 8 fine, but certain parts of it don't work properly on iOS 7 as I'm trying to use an iOS 8 API...... (lol).

So I just wanted to know, what is the best way to implement code which works on iOS 8 and 7. I had a few ideas (below), but I'm not sure which is best:

IDEA 1

Whenever I have code which doesn't work on both OS's, I use an if function (which calls a macro) like so:

if (SYSTEM_VERSION_LESS_THAN(@"8.0")) {
    // iOS 7 device. Use iOS 7 apis.
}

else {
   // iOS 8 (or higher) - use iOS 8 apis.
}

IDEA 2

I was thinking about using ifdef definitions all around the app like so:

#ifdef __IPHONE_8_0
     // iOS 8 code here....
#else
     // iOS 7 code here....
#endif

Which way is better? I would have thought that the second idea is much faster and uses less resources right?

Or are both my ideas rubbish? Is there a much better way about solving this problem?

Thanks for your time, Dan.

Answer 1

I don't suggest checking the Version and writing code based on that. Instead you need to check whether that API is available or not.

For checking a class available or not:

Class checkClass = NSClassFromString(@"CheckingClass");

if (checkClass)
{
   // Available
}
else
{
  // Not Available
}

If you need to check a feature/function available;

if ([checkClass respondsToSelector:@selector(yourMethod:)])
{
   // Feature/ Method Available
}
else
{
   // Feature/ Method Not Available
}

NOTE:

Deprecated API's doesn't mean that you shouldn't use that in current version. It means, it won't work from next version onwards, and only work till current version.