This comes down to the difference between reference types and value types.
In Swift, when you have a variable that is a value type (link Ints, Strings, etc), then the variable holds that value. When you have a variable that is a reference type (e.g. a Class), then it holds a reference to that object in memory.
This means that when you pass a value type variable around, you're passing around the actual data that the variable holds. But when you pass around a reference type variable, you're passing around a reference to that object.
Take the following code snippet, you can see that when you make a copy of a value type, you get an actual copy of it. When you make a copy of a reference type, you just get another reference to the same object in memory, which means any changes are reflected in the other variable, because they all reference the same object.
// Structs are a VALUE type struct myStruct { var value: Int init(x: Int) { self.value = x } } // Classes are a REFERENCE type class myClass { var value: Int init(x: Int) { self.value = x } } var a = myStruct(x: 5) var originalA = a // This has made a copy of a, and stores it in originalA a.value = 100 print(originalA.value) print(a.value) var b = myClass(x: 5) var originalB = b // This is still referencing the same object as the variable b. b.value = 100 print(originalB.value) print(b.value)
Now as for your specific example, I am confused as to why it doesn't work, because from what I can see CGRect is a struct, which is a value type, so making a copy the way you have should work fine. In fact, I just added the code you have to the end of a method in one of my apps, and it worked exactly as you would expect:
let x = textView.frame textView.transform = CGAffineTransform.identity.translatedBy(x: 0, y: +5) print(x) // Prints (16.0, *83.0*, 343.0, 564.0) print(textView.frame) // Prints (16.0, *88.0*, 343.0, 564.0)
Hope this helps, Jacob.
