如何检查是否已使用Swift反射设置属性？

我的一些模型具有可选属性.我正在尝试编写一种可以评估它们是否已设置的方法.

下面是一个尝试,但我无法弄清楚如何从Any对象确定一个nil值[编辑:(子变量的类型为Any)].它不编译.

func allPropertiesHaveValues(obj: AnyObject) -> Bool {
    let mirror = Mirror(reflecting: obj)
    for child in mirror.children {
       let value = child.value
       if let optionalValue = value as? AnyObject? { //Does not compile
          if optionalValue == nil {
             return false 
          }
       }
    }
    return true
}

编辑：

我忘了澄清上面示例中的子值始终是Any类型. Any类型很难,因为它无法与nil进行比较,并且对AnyObject的强制转换总是失败.我试图在下面的操场上说明它.

var anyArray = [Any]();

var optionalStringWithValue: String? = "foo";
anyArray.append(optionalStringWithValue);

var nilOptional: String?
anyArray.append(nilOptional)

print(anyArray[0]);   // "Optional("foo")\n"
print(anyArray[1]);   // "nil\n"

if let optionalString = anyArray[0] as? AnyObject {
    //will always fail
    print("success")
}

//if anyArray[1] == nil {  //  will not compile

//}

过时：

您只需检查可选值是否为零：

func allPropertiesHaveValues(obj: AnyObject) -> Bool {
   let mirror = Mirror(reflecting: obj)
   for child in mirror.children {
     //child.value being an optional
     if child.value == nil {
       return false
     }
    }
   return true
}

编辑：

要检查Any对象是否是可选的并且是否包含使用反射的值：

let optionalString : String? = "optional string"
let any : Any = optionalString

//First you will need to create a mirror of the any object
let mirror = Mirror(reflecting : any)

//Then you can check the display style to see if it's an optional
if mirror.displayStyle == .Optional {
    //If it is,check the count of its children to see if there is a value or not
    if mirror.children.count == 0 {
        print("I don't have a value")
    }
    else {
        print("I have a value")
    }
}

这是一个游乐场示例(基于您的)：

var anyArray = [Any]()

var optionalStringWithValue: String? = "foo"
anyArray.append(optionalStringWithValue)

var nilOptional: String?
anyArray.append(nilOptional)

let string = "string not optional"
anyArray.append(string)

print(anyArray[0])   // "Optional("foo")\n"
print(anyArray[1])   // "nil\n"
print(anyArray[2])   // "string not optional\n"

let mirrorOptionalWithValue = Mirror(reflecting: anyArray[0])

if mirrorOptionalWithValue.displayStyle == .Optional
    && mirrorOptionalWithValue.children.count == 1 {
    print("Is an optional and contains a value")
}

let mirrorOptionalWithoutValue = Mirror(reflecting: anyArray[1])

if mirrorOptionalWithoutValue.displayStyle == .Optional &&
    mirrorOptionalWithoutValue.children.count == 0 {
    print("Is an optional but is nil")
}

let mirrorNotAnOptional = Mirror(reflecting: anyArray[2])

if mirrorNotAnOptional.displayStyle != .Optional {
    print("Is not an optional")
}

原文链接：/swift/319602.html

如何检查是否已使用Swift反射设置属性？

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