roop

class MyClass {
    var value: Int
    init(value v: Int) { value = v }
}

var instanceOfMyClass = MyClass(value: 42)
var assignedInstance2 = instanceOfMyClass
assignedInstance2.value = 2 // Change the copied instance
instanceOfMyClass.value     // 2: Original is also changed

roop

struct MyStruct {
    var value: Int = 0
}

var instanceOfMyStruct = MyStruct(value: 42)
var assignedInstance1 = instanceOfMyStruct
assignedInstance1.value = 2 // Change the copied instance
instanceOfMyStruct.value    // 42: Original is unchanged