Question

I found the following code:

UIButton * cancelButton = [UIButton buttonWithType:101];

What is that magic number 101?

Answer 1

It is a hidden (private to Apple) value that someone took the time to figure out. There is no constant or enumeration in the UIKit for creating a button with that ‘type’. The only “official” button type enums exposed by Apple are (from UIButton.h):

typedef enum {
    UIButtonTypeCustom = 0,           // no button type
    UIButtonTypeRoundedRect,          // rounded rect, flat white button, like in address card

    UIButtonTypeDetailDisclosure,
    UIButtonTypeInfoLight,
    UIButtonTypeInfoDark,
    UIButtonTypeContactAdd,
} UIButtonType;

As you can see, at this time, it only covers 0 – 5.