The fileprivate access control modifier was used in Swift 3 to make important data visible outside the class in which it was declared but within the same file. This is how it all works in the case of extensions:
class Person { fileprivate let name: String fileprivate let age: Int fileprivate let address: String init(name: String, age: Int, address: String) { self.name = name self.age = age self.address = address }}extension Person { func info() -> String { return "\(self.name) \(self.age) \(self.address)" }}let bestFriend = Person(name: "Robert", age: 31)bestFriend.info()
In the preceding code, we created an extension for the Person class and accessed its private properties in the info() method using String interpolation. ...
