Use CGFloat instead of float? They don't do it
[I might be misunderstanding this entire topic, as I've grown up with languages that allow the dev to almost entirely ignore processor architecture, like Java, except in some particular cases. Please correct me if I have some of the concepts wrong.]
Reading here it seems that the advice is to use CGFloat instead of, say, float, because it future-proofs my code for different processor architectures (64-bit handles float differently). Assuming that is right, then why does UISlider, for instance, use float directly (for the value)? Wouldn't it be wrong (or something) for me to read their float and convert it to a CGFloat, because in any case my code is not right if the architecture changes anyway?
CGFloat is just a typedef for float. This provides flexibility for CGFloat to be something different down the road. Which is why using it future-proofs your code. Objective-C does this with many types, NSInteger is another example.
Although they can be used interchangeably, I agree that it doesn't appear in the case of UISlider that Apple was dogfooding.
CGFloat is part of Core Graphics, and used for things like pixel values, which has changed greatly over the years (anyone here a TRS-80 lover?). SO, using CGFloat for display-related drawing values is advised.
The value of the slider is not graphics-related. It is simply 0.0 to 1.0, which can be handled precisely by a float, and probably a 16-bit float at that.