StructClass.swift

class SomeClass {
  var a, b: Int
  init(a: Int, b: Int) {
    (self.a, self.b) = (a, b)
  }
}
struct SomeStruct {
  var a, b: Int
}

var cla = SomeClass (a: 1, b: 1)
var str = SomeStruct(a: 1, b: 1)

var ar1 = [cla]
var ar2 = [str]

cla.b = 2
str.b = 2

ar1 // [{a 1, b 2}]
ar2 // [{a 1, b 1}]