Any与AnyObject,AnyClass

2019-01-31

Any

在Swift中Any是什么？在Swift中是这样定义的：public typealias Any = protocol<> 。是一个空协议集合的别名，它表示没有实现任何协议，因此可以是任何类型，包括函数，枚举，结构体，保持类型的原生状态(不会隐式转换)，可以存储swift的类型或者Object-C类型。所有类型都隐式遵守了这个协议。官方文档是这样解释的/// The protocol to which all types implicitly conform.

看看具体内容

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class MediaItem {
    var name: String
    init(name: String) {
        self.name = name
    }
}
class Movie: MediaItem {
    var director: String
    init(name: String, director: String) {
        self.director = director
        super.init(name: name)
    }
}
var things = [Any]()
things.append(9)
things.append(9.0)
things.append("hello")
typealias closureType2 = @convention(block)(String) -> String
let closureGreet2: closureType = {
    (name: String) -> String in
    return "Hello, \(name)"
}
things.append(closureGreet2)
things.append({(name: String) -> String in "Hello, \(name)"})
things.append(Movie(name: "Ghostbusters", director: "Ivan Reitman"))
let optionalNumber: Int? = 3
things.append(optionalNumber as Any)
let OCArray: NSArray = ["a","b"];
things.append(OCArray)
let number = 4 as NSNumber
things.append(number)
print(things)
for object in things {
    print(type(of: object))
}

看看显示结果

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[9, 9.0, "hello", (Function), (Function), __lldb_expr_30.Movie, Optional(3), <__NSArrayI 0x600003275b40>(
a,
b
)
, 4]
Int
Double
String
@convention(block) (String) -> String
(String) -> String
Movie
Optional<Int>
__NSArrayI
__NSCFNumber

类型保持了原生状态，包括OC中的数据类型，注意@convertion(block)类型，待会对比。

AnyObject

苹果官方文档是这样定义的：@objc public protocol AnyObject { } ，可以表示任何class类型的实例，来替代OC中的id类型，也就是swift转OC的桥梁。所有的类都隐式遵循了这个协议，官方文档the protocol to which all classes implicitly conform.

我们来看看使用AnyObject会发生什么情况

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class MediaItem {
    var name: String
    init(name: String) {
        self.name = name
    }
}
class Movie: MediaItem {
    var director: String
    init(name: String, director: String) {
        self.director = director
        super.init(name: name)
    }
}
var objects: [AnyObject] = [AnyObject]()
// 元祖类型不是一个类的实例
objects.append((3.0,5.0) as AnyObject)
//字面量不是 一个类的实例
objects.append(0 as AnyObject)
objects.append("hello" as AnyObject)
struct Person {
    var name: String
    init(name: String) {
        self.name = name
    }
}
let jack = Person(name: "jack")
objects.append(jack as AnyObject)
let alpha = ["a","b"]
objects.append(alpha as AnyObject)
objects.append(Movie(name: "Ghostbusters", director: "Ivan Reitman"))
// 函数 不是一个实例
typealias closureType = @convention(block)(String) -> String
let closureGreet: closureType = {
    (name: String) -> String in
    return "Hello, \(name)"
}

objects.append(closureGreet as AnyObject)
objects.append({(name: String) -> String in "Hello, \(name)"} as AnyObject )
let optionalNum: Int? = 3
objects.append(optionalNum as AnyObject)
let ocArray: NSArray = ["c","d"]//OC 中 的 NSArray类型
objects.append(ocArray)

for object in objects {
    if let obj = object as? (String)->String {
        print(obj("World!\(obj)"))
    }
    print(type(of: object))
}
print(objects)

输出结果显示

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_SwiftValue
__NSCFNumber
NSTaggedPointerString
_SwiftValue
_SwiftDeferredNSArray
Movie
__NSMallocBlock__
Hello, World!(Function)
_SwiftValue
__NSCFNumber
__NSArrayI
[(3.0, 5.0), 0, hello, __lldb_expr_36.Person(name: "jack"), <Swift._SwiftDeferredNSArray 0x60000398e7a0>(
a,
b
)
, __lldb_expr_36.Movie, <__NSMallocBlock__: 0x60000378dda0>, (Function), 3, <__NSArrayI 0x600003984f60>(
c,
d
)
]

可以看出AnyObject隐式转换了类型，对于Tuple、struct类型，OC并不存在或者定义不一样，所以保持swift的值类型，对于使用了@conversion(block)修饰一个闭包，被转换成了__NSMallocBlock__，真正转换成OC中的block块，如果把@conversion(block)去掉，会转换成一个(Function)，仅仅被当成普通函数。可以看使用Any的时候对比下。

AnyClass

AnyClass 表示任意类的元类型，苹果官方文档：public typealias AnyClass = AnyObject.Type , 解释道：/// The protocol to which all class types implicitly conform.任意类的类型都隐式遵守这个协议.其中 .Type就是获得元类型的。注意如果某个变量或者常量的类型是AnyClass，你需要显示的转换成具体类型，然后再调用init()方法实例对象。参考：swift根据类型（AnyClass）创建对象

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