CODEWITHSUNDEEP
ios5ios4backwards-compatibility
shajem
shajem

Reputation: 2121

iOS 4 and iOS 5 backward compatibility

I have a question regarding iOS 4 and 5. I am really confused and hope someone will clear it out for me.

I am using iOS 5 SDK in my application. If i use the iOS 5 Twitter integration which is provided by apple, will it run on an iPhone that has iOS 4 installed ?

Does backward compatibility work ?

I have used Twitter as an example, but does backward compatibility really work with iOS 5 ?

Upvotes: 2

Views: 1600

Answers (4)

Elliot
Elliot

Reputation: 6136

If you set up your app properly, so that it can be run on devices running iOS 4 without crashing, then: yes, it will run on an iPhone that has iOS 4 installed.

Your app should implement logic such that the Twitter API is used when the app is being run on an iOS 5 device. When the app is running on an iOS 4 device, you can conditionally choose not to use the Twitter API.

Instead, you can use a different Twitter library (like MGTwitterEngine, or your own) - or just exclude Twitter functionality for those users.

To check whether the TWRequest Class exists, use NSClassFromString.

Class twRequestClass = NSClassFromString(@"TWRequest");
if (twRequestClass == nil) {
    // TWRequest does not exist on this device (running iOS version < 5.0)
    // ... do something appropriate ...
} else {
    TWRequest *twRequest = [[twRequestClass alloc] init];
    // ^ I didn't look up the proper initializer, so you should change that line if necessary
    // ...
}

Upvotes: 10

Saurabh Passolia
Saurabh Passolia

Reputation: 8109

No, if you use the Twitter APIs available in iOS5, they will not be able to run on iOS4.

The reason being that when app will run on iOS4, the system will not be having the APIs availability.

if you check the documentation, you can see the iOS version from where this Class/API is available. enter image description here

I hope this helps..

Upvotes: 1

allaire
allaire

Reputation: 6045

You would have to create ifs dependently of the iOS version the user is using. Exemple, in iOS 5 there is an Appearance API to modify most of the UI, but not in iOS 4, so you have to create a little if like that:

// not supported on iOS4
UINavigationBar *navBar = [myNavController navigationBar];
if ([navBar respondsToSelector:@selector(setBackgroundImage:forBarMetrics:)])
{
    [navBar setBackgroundImage:[UIImage imageNamed:@"bg.jpg"] forBarMetrics:UIBarMetricsDefault];
}

Upvotes: 4

Amit Shah
Amit Shah

Reputation: 4164

If you set up your app properly, so that it can be run on devices running iOS 4, it will crash. This is because you're trying to access methods/features that arn't available. The way to get around this is to check if a feature is available using

if(NSClassFromString(@"UIPopoverController")) {
// Do something
}

(Popover controller is just an example)

You could also check the version using 

float version = [[[UIDevice currentDevice] systemVersion] floatValue];

And then depending on the version run a specific piece of code (i.e. if iOS 5, preform twitter stuff,else do something different)

Upvotes: 3

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