Swift 3 access of private properties in a struct from a extension
From the Swift's book:
Private access restricts the use of an entity to the enclosing declaration. Use private access to hide the implementation details of a specific piece of functionality when those details are used only within a single declaration.
So a private variable is only accessible within the set of curly brackets where it's defined. Swift's Access Control has never been like those of C++, Java or C#.
With release of Swift 4 this has been changed if the extension is implemented within the same file. You can refer the doc herePrivate Member in Extension
Example below is from Swift 4
protocol SomeProtocol { func doSomething()}struct SomeStruct { private var privateVariable = 12}extension SomeStruct: SomeProtocol { func doSomething() { print(privateVariable) }}