Immutable/Mutable Collections in Swift

Question

I was referring to Apple\'s Swift programming guide for understanding creation of Mutable/ immutable objects(Array, Dictionary, Sets, Data) in Swift language. But I could\'t

Answer 1

[Unmodifiable and Immutable]

Swift's array can be muted

[let vs var, Value vs Reference Type]

Immutable collection[About] - is a collection structure of which can not be changed. It means that you can not add, remove, modify after creation

let + struct(like Array, Set, Dictionary) is more suitable to be immutable

There are some classes(e.g. NSArray) which does not provide an interface to change the inner state

but

class A {
    var value = "a"
}

func testMutability() {
    //given
    let a = A()
    
    let immutableArr1 = NSArray(array: [a])
    let immutableArr2 = [a]
    
    //when
    a.value = "aa"
    
    //then
    XCTAssertEqual("aa", (immutableArr1[0] as! A).value)
    XCTAssertEqual("aa", immutableArr2[0].value)
}   

It would rather is unmodifiable array