Knowing device type — Retina/non-Retina [duplicate]

Answer 1

You can check the scale property on [UIScreen mainScreen] if it is 2.0 you are running on retina, if it is 1.0 you are not. You can also get the scale from the current CoreGraphics Context.

Answer 2

if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]
    && [[UIScreen mainScreen] scale] >= 2.0) {
    // Retina
} else {
    // Not Retina
}

Answer 3

I don't think you can determine that directly. You'll have to infer it from the model information you can get back from sysctlbyname (see the iOS man pages). For example:

sysctlbyname("hw.machine", NULL, &size, NULL, 0);
char *machine = malloc(size);
sysctlbyname("hw.machine", machine, &size, NULL, 0);

will give you back a string like "iPhone3,1" which has a retina display, or "iPhone 2,1" which hasn't.