Swift protocols mutability [duplicate] - swift

Question

This question already has answers here:
Read-only properties of protocols in Swift
(3 answers)
Why am I allowed to set a read only property of a protocol using a struct that inherits said protocol?
(3 answers)
Closed 2 years ago.
I'm currently a bit confused about gettable properties in protocols. Consider this example:
protocol Person {
var name: String { get }
}
I expected the name property to be read-only, but I found that you could change the value without compiler complaints:
struct Driver: Person {
var name: String
}
var driver = Driver(name: "Ryan")
driver.name = "Changed!"
If we define driver with let keyword, then compiler raises the error, but if I understand correctly, it has nothing to do with protocols, as constant structs are immutable by design in Swift.
Method interactions behave as I would've expected:
extension Person {
mutating func changeName(_ newName: String) {
self.name = newName // Error: 'name' is a get-only property
}
}
I'm new to Swift, and the nuance mentioned may not have any practical use, but this behavior made me ask myself if I lack some basic understanding of how structs work.

Answer 1

The protocol requirement is
a variable name which can be read
which doesn't mean that the variable in a struct adopting this protocol is necessarily read-only.
In the code you are changing the variable directly in the Driver type, the protocol is not involved.
On the other hand if you annotate the protocol type you get the expected error
var driver : Person = Driver(name: "Ryan")
driver.name = "Changed!" // Cannot assign to property: 'name' is a get-only property

Answer 2

A protocol only declares the required interface, but not the full interface of conforming types. Your conforming types can add extra properties/methods that aren't required by the protocol.
The same is true for getters and setter. If a protocol property requirement is get, that means the conformant type must have a getter for the property, but doesn't mean it cannot have a setter for it as well.
However, the same doesn't work the other way around. If a protocol declares a property as { get set }, that property must have a setter (be mutable).

Answer 3

The apple documentation explains this very well.
The getter and setter requirements can be satisfied by a conforming type in a variety of ways. If a property declaration includes both the get and set keywords, a conforming type can implement it with a stored variable property or a computed property that is both readable and writeable (that is, one that implements both a getter and a setter). However, that property declaration can’t be implemented as a constant property or a read-only computed property. If a property declaration includes only the get keyword, it can be implemented as any kind of property.