Check iOS version at runtime?

Question

This is sort of a follow on from my last question. I am using beginAnimations:context: to setup an animation block to animate some UITextLabels. However I noticed in the docs that is says: "Use of this method is discouraged in iOS 4.0 and later. You should use the block-based animation methods instead."

My question is I would love to use animateWithDuration:animations: (available in iOS 4.0 and later) but do not want to exclude folks using iOS 3.0. Is there a way to check to iOS version of a device at runtime so that I can make a decision as to which statement to use?

Answer 1

to conform to version specified in system defines

//#define __IPHONE_2_0 20000
//#define __IPHONE_2_1 20100
//#define __IPHONE_2_2 20200
//#define __IPHONE_3_0 30000
//#define __IPHONE_3_1 30100
//#define __IPHONE_3_2 30200
//#define __IPHONE_4_0 40000
You can write function like this ( you should probably store this version somewhere rather than calculate it each time ):

+ (NSInteger) getSystemVersionAsAnInteger{
    int index = 0;
    NSInteger version = 0;

    NSArray* digits = [[UIDevice currentDevice].systemVersion componentsSeparatedByString:@"."];
    NSEnumerator* enumer = [digits objectEnumerator];
    NSString* number;
    while (number = [enumer nextObject]) {
        if (index>2) {
            break;
        }
        NSInteger multipler = powf(100, 2-index);
        version += [number intValue]*multipler;
        index++;
    }
return version;
}

Then you can use this as follows:

if([Toolbox getSystemVersionAsAnInteger] >= __IPHONE_4_0)
{
  //blocks
} else 
{
  //oldstyle
}

Answer 2

You must not check iOS version, instead of that you must check in runtime if a particular method is present or not. In your case you can do the following:

if ([[UIView class] respondsToSelector:@selector(animateWithDuration:animations:)]){
// animate using blocks
}
else {
// animate the "old way"
}

Answer 3

Discouraged is not the same as deprecated.

If you need to support earlier versions of iOS that do not have the block based methods, there is nothing wrong with using the older methods (as long as they haven't been removed, of course).