Swift中的动态协议一致性
您好,我正在努力用swift语言解决动态协议一致性问题。请看代码 协议:Swift中的动态协议一致性,swift,swift3,Swift,Swift3,您好,我正在努力用swift语言解决动态协议一致性问题。请看代码 协议: protocol Object { init(by object: [String: Any]) } 具有协议对象一致性的自定义结构: struct Tree: Object { let treeName: String init(by object: [String: Any]) { self.treeName = object["tree"] as? String ??
protocol Object {
init(by object: [String: Any])
}
具有协议对象一致性的自定义结构:
struct Tree: Object {
let treeName: String
init(by object: [String: Any]) {
self.treeName = object["tree"] as? String ?? "Notree"
}
}
struct Plant: Object {
let plantName: String
init(by object: [String : Any]) {
self.plantName = object["tree"] as? String ?? ""
}
}
上面的代码很好,直到对象成为[String:Any]
。我不能像下面那样使用[[String:Any]]
let coconut = ["tree":"Coconut"] // => This fine
let allTrees = [["tree":"Apple"],["tree":"Orange"],["tree":"Jakfruit"]] //=> Here is the problem
let aTree = Tree(by: coconut)
let bTree = Tree(by: ["data":allTrees])
let cTree = Plant(by: ["data":allTrees])
我不能使用对象数组。所以,我习惯于将对象存储在键“data”中。现在我使用了extension:Array
confirm协议对象
extension Array: Object where Element == Object{
init(by object: [String : Any]) {
if let data = object["data"] as? [[String: Any]]{
self = data.map({ (object) -> Object in
// return Plant.init(by: object) // => Works, But I need dynamic confirmance
// return Tree.init(by: object) // => Works, But I need dynamic confirmance
return Object.init(by: object) //=> How can I do?
})
}else{
self = []
}
}
}
返回的对象
显示错误无法实例化协议类型“对象”。我试图解决很多问题,但没能解决
有人能为这个问题提出更好的想法或解决方案吗?提前感谢您…首先,您不应该使用约束
==Object
。你想说不仅[Object]
是对象
,而且[Plant]
和[Tree]
也是对象
,对吗?为此,应该使用:Object
约束。其次,可以使用Element.init
初始化数组的新元素。由于约束元素:Object
,我们知道存在init(by:)
初始化器:
extension Array: Object where Element: Object{
init(by object: [String : Any]) {
if let data = object["data"] as? [[String: Any]]{
self = data.map({ (object) in
return Element.init(by: object)
})
}else{
self = []
}
}
}
用法:
let trees = [Tree](by: ["data": allTrees])
下面是我认为更快捷的代码版本,使用-initialiser,在初始化对象失败时返回nil
:
protocol Object {
init?(by object: [String: Any])
}
struct Tree: Object {
let treeName: String
init?(by object: [String: Any]) {
if let treeName = object["tree"] as? String {
self.treeName = treeName
} else {
return nil
}
}
}
struct Plant: Object {
let plantName: String
init?(by object: [String : Any]) {
if let plantName = object["tree"] as? String {
self.plantName = plantName
} else {
return nil
}
}
}
extension Array: Object where Element: Object{
init?(by object: [String : Any]) {
if let data = object["data"] as? [[String: Any]]{
self = data.compactMap(Element.init)
}else{
return nil
}
}
}
非常感谢你!我花了几个小时才找到这个。