The @dynamicmemberlookup and callasfunction features in swift implement the object transparent proxy function

summary

In some cases , We want to hide an internal object , Access all properties of the inner object only through the outer wrapper object .

such as , object A contain name attribute , object P Contains objects A, When we read and write P Of name Attribute , What you actually read and write is A Of name attribute ：

struct A { 
    
	var name: String
}

struct P { 
    
	var a: A
	//  How to implement object attribute proxy ？？？