18-访问控制

2021-08-10  本文已影响0人  SwordDevil

访问控制(Access Control)

在访问权限控制这块,Swift提供了5个不同的访问级别(以下是从高到低排列, 实体指被访问级别修饰的内容)

访问级别的使用准则

一个实体不可以被更低访问级别的实体定义,比如

元组类型

internal struct Dog {}
fileprivate class Person {}

// (Dog, Person)的访问级别是fileprivate
fileprivate var data1: (Dog, Person)
private var data2: (Dog, Person)

泛型类型

internal class Car {}
fileprivate class Dog {}
public class Person<T1, T2> {}

// Person<Car, Dog>的访问级别是fileprivate
fileprivate var p = Person<Car, Dog>()

成员、嵌套类型

public class PublicClass {
    public var p1 = 0 // public
    var p2 = 0 // internal
    fileprivate func f1() {} // fileprivate
    private func f2() {} // private
}
class InternalClass { // internal
    var p = 0 // internal
    fileprivate func f1() {} // fileprivate
    private func f2() {} // private
}
fileprivate class FilePrivateClass { // fileprivate
    func f1() {} // fileprivate
    private func f2() {} // private
}
private class PrivateClass { // private
    func f() {} // private
}

成员的重写

public class Person {
    private var age: Int = 0
}
public class Student : Person {
    override var age: Int {
        set {}
        get {10}
    }
}
public class Person {
    private var age: Int = 0
    public class Student : Person {
        override var age: Int {
            set {}
            get {10}
        }
    }
}

下面代码能否编译通过?

private class Person {}
fileprivate class Student : Person {}
private struct Dog {
    var age: Int = 0
    func run() {}
}
fileprivate struct Person {
    var dog: Dog = Dog()
    mutating func walk() {
        dog.run()
        dog.age = 1
    }
}
private struct Dog {
    private var age: Int = 0
    private func run() {}
}
fileprivate struct Person {
    var dog: Dog = Dog()
    mutating func walk() {
        dog.run()
        dog.age = 1
    }
}

getter、setter

fileprivate(set) public var num = 10
class Person {
    private(set) var age = 0
    fileprivate(set) public var weight: Int {
        set {}
        get { 10 }
    }
    internal(set) public subscript(index: Int) -> Int {
        set {}
        get { index }
    }
}

初始化器

枚举类型的case

协议

public protocol Runnable {
    func run()
}
public class Person : Runnable {
    func run() {}
}

扩展

扩展

public class Person {
    private func run0() {}
    private func eat0() {
        run1()
    }
}
extension Person {
    private func run1() {}
    private func eat1() {
        run0()
    }
}
extension Person {
    private func eat2() {
        run1()
    }
}

将方法赋值给var\let

struct Person {
    var age: Int
    func run(_ v: Int) { print("func run", age, v) }
    static func run(_ v: Int) { print("static func run", v) }
}

let fn1 = Person.run
fn1(10) // static func run 10

let fn2: (Int) -> () = Person.run
fn2(20) // static func run 20

let fn3: (Person) -> ((Int) -> ()) = Person.run
fn3(Person(age: 18))(30) // func run 18 30
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