How to differentiate between iphone4 and iphone 3

Question

Hi All,

I am trying to build a game for the iphone using cocos2d engine. I wanted to know how can I tell a difference whether the user is using iphone 4 or iphone 3 as I wanted to load hi-resolution graphics for the iphone4 and low-resolution for iphone 3. I know if I use @2x.png at the end of the image file name UIImage loads the hi-resolution image by itself if I am using an iphone 4 but for the game I am using cocos2d engine's CCSprite class to load the graphics.

I would really appreciate the reply.

Regards, Ankur

Answer 1

You could check the scale of the screen.

if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)] && [[UIScreen mainScreen] scale] == 2){
    //iPhone 4
}

Answer 2

I'd Love to use

if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)] && [[UIScreen mainScreen] scale] == 2){
        //iPhone 4
}

But it won't compile on 3.1.3

I've tried something like

    if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {
        // Knowledge about scale (retina display)
        // Now see if we can get the scale value without a compile error on 3.1.3.

        NSMethodSignature *scaleMethodSig = [[UIScreen mainScreen] methodSignatureForSelector:@selector(scale)];
        NSInvocation *scaleInvocation = [NSInvocation invocationWithMethodSignature:(NSMethodSignature *)scaleMethodSig];
        NSUInteger length = [scaleMethodSig methodReturnLength];

        float usedScale;
        [scaleInvocation getReturnValue:&usedScale];

But failed..... Anybody know of a way to read the scale float which compiles on 3.1.3?

Answer 3

Despite what Apple's docs say, the UIScreen's scale property isn't just available in iOS4, it's also available in 3.2 on the iPad. This means it's probably an unreliable way to check which device you're on.

Instead, you should check if contentScaleFactor is available on your main window(or any UIView), and then check the scale value.