why string, array and dictionary in Swift changed to value type

Question

In Objc string, array and dictionary are all reference types, while in Swift they are all value types.

1. I want to figure out what\'s the reason behind the scenes

Answer 1

In addition to the previous answers, there are also multi-threading issues to consider with sharing a Reference-Based collection type that we don't have to worry as much with sharing an instance of a type that is Value-Based and has Copy-On-Write behavior. Multi-core is becoming more and more proliferant even on iOS devices, so it has become more of an issue for the Swift language developers to consider.