Question

I am new in iOS. I want to use CAEmitterLayer, which is only support by iOS 5, but my app should support iOS 4 and above. I am using [UIDevice currentDevice].systemVersion
to check the version, but it crashes.

Here is the code:

@class CAEmitterLayer;

@interface FireView : UIView

@property (strong) CAEmitterLayer *fireEmitter;
@property (strong) CAEmitterLayer *smokeEmitter;

- (void) setFireAmount:(float)zeroToOne;
@end

// create the FireView if iOS>=5.0

if ([[UIDevice currentDevice].systemVersion doubleValue] >=5.0) {
            FireView *fireView = [[[FireView alloc] initWithFrame:CGRectMake(0, 95, 100, 280)] autorelease];
            [self.view addSubview:fireView];
}

The problem is it crash before I create the FireView.

error:dyld: Symbol not found: _OBJC_CLASS_$_CAEmitterCell

even I don’t include the FireView.h file, still crashes.
Should I create both iOS4 and iOS5 version?

Can you give me some advice?
Please help. Thank you very much.

Answer 1

You can check to see if CAEmitterLayer class is available on current device’s iOS version by:

if (NSClassFromString(@"CAEmitterLayer"))
{
// available
}