Swift 如何使用泛型推断类型?
我将一些响应模型定义为Swift 如何使用泛型推断类型?,swift,generics,Swift,Generics,我将一些响应模型定义为 class UserProfile{ var name:String = "Anish" var age:Int = 20 } class StudentProfile:UserProfile{ var std_id:Int = 1 } 我有一个Web API请求类 class WebCaller{ class func callWebService<T>(responseType:T.Type,completion
class UserProfile{
var name:String = "Anish"
var age:Int = 20
}
class StudentProfile:UserProfile{
var std_id:Int = 1
}
我有一个Web API请求类
class WebCaller{
class func callWebService<T>(responseType:T.Type,completionHandler:(T)->()){
let model = StudentProfile() as! responseType//wont compile here
completionHandler(model)
}
}
现在如果我想打电话给你
WebCaller.callWebService(responseType: StudentProfile.self){ responseModel in
//response model should automatically infer the type
print(responseModel.name)
print(responseModel.age)
print(responseModel.std_id)
}
WebCaller.callWebService(responseType: UserProfile.self){ responseModel in
//this should automaticaly infer the type
print(responseModel.name)
print(responseModel.age)
}
但是,这可以通过使用任意对象类型来实现
class func callWebService<T>(responseType:T.Type,completionHandler:(AnyObject)->())
类func callWebService(响应类型:T.Type,completionHandler:(AnyObject)->())
但是我需要将其强制转换为我的响应类型。我试图实现的是,我的API调用者应该向我发送类型,这样我就不应该在我的
视图模型中强制转换它。类型几乎不可用,您不需要在您的场景中使用任何类型的泛型
class A{
let typeA = "property typeA"
}
class B{
let typeB = "property typeB"
}
class C{}
func f0(object: AnyObject) {
if let a = object as? A {
print(1, a.typeA)
return
}
if let b = object as? B {
print(2, b.typeB)
return
}
print("unknown type")
}
f0(object: A())
f0(object: B())
func f1(object: AnyObject) {
switch object {
case is A:
let a = object as! A // will never fail!!
print(3, a.typeA)
case is B:
let b = object as! B // will never fail!!
print(4, b.typeB)
default:
print("unknown type")
break
}
}
f1(object: A())
f1(object: B())
f0(object: C())
f1(object: C())
它打印
1 property typeA
2 property typeB
3 property typeA
4 property typeB
unknown type
unknown type
1 property typeA
I am printable B
2 property typeB
I am printable C
unknown type
要查看A和A.Type之间的关系,请将我们现在的代码片段与下一个代码片段进行比较,这将给出相同的结果
func f3(object: AnyObject) {
switch type(of: object) {
case is A.Type:
let a = object as! A // will never fail!!
print(5, a.typeA)
case is B.Type:
let b = object as! B // will never fail!!
print(6, b.typeB)
default:
print("unknown type")
break
}
}
使用第一个场景可能更实际,因为在对象中构建了一些公共功能
protocol Printable {
}
extension Printable {
func p(){
print("I am printable", type(of: self))
}
}
class A{
let typeA = "property typeA"
}
class B: Printable{
let typeB = "property typeB"
}
class C: Printable{}
func f0(object: AnyObject) {
if let p = object as? Printable {
p.p()
}
if let a = object as? A {
print(1, a.typeA)
return
}
if let b = object as? B {
print(2, b.typeB)
return
}
print("unknown type")
}
f0(object: A())
f0(object: B())
f0(object: C())
它打印
1 property typeA
2 property typeB
3 property typeA
4 property typeB
unknown type
unknown type
1 property typeA
I am printable B
2 property typeB
I am printable C
unknown type
为什么不将model=StudentProfile()设为!T
解决了你的问题?是的,确实如此……但这就是解决问题的方法吗?对不起,这与整个动机相矛盾……我不想每次都演…@Costello,那你想要什么?很快或者很晚你需要施放结果才能使用它,不是吗?