当我在 Swift 中通过分配策略将 CGFloat 值设置为 AssociatedObject 时，为什么会崩溃？

Question

static var testValue = 1
objc_setAssociatedObject(self, &testValue, 10.1, .OBJC_ASSOCIATION_ASSIGN)
objc_getAssociatedObject(self, &testValue)

When I execute the third line of code, it will crash , But when I change the value that I want to set to 10(or 10.0) , it can successfully get the value. Why this happen?

Answer 1

Associated values store pointer sized items (typically eight bytes). When you try to read it, it will read a pointer sized item and overwrite eight bytes of memory. If the variable you are using is four bytes only, then four bytes of random memory are overwritten, with all kinds of consequences.