起初使用runtime添加属性的时候照着OC习惯

objc_setAssociatedObject(self, "sharedInstance","sharedInstance",.OBJC_ASSOCIATION_RETAIN_NONATOMIC)

print(objc_getAssociatedObject(self, "sharedInstance"))

结果无论如何都添加不成功,
后来参照此文

let key: UnsafeRawPointer! = UnsafeRawPointer.init(bitPattern: "sharedInstance".hashValue)

objc_setAssociatedObject(self,key, "sharedInstance", .OBJC_ASSOCIATION_RETAIN_NONATOMIC)

print(objc_getAssociatedObject(self, key))

成功,mark一下