objective-c - Objective C - 在属性上声明可选字段

Question

在 objective-c 中是否可以将 Bool 和 float 类型设置为 Optional 我找不到任何解决方法？

 @property (nonatomic, assign) float percentageOfCases;
    @property (nonatomic, assign) float inspectionPercentageOfCases;
    @property (nonatomic, assign) NSString<Optional> *inspectionStatus;
@property (nonatomic, assign) BOOL sendNotification;

Answer 1

swift 的 Optional对应于Objective-C中的可空性，而在Objective-C中，只有指针类型可以为空。所以你必须将你的属性更改为指针类型，在本例中这意味着 NSNumber *对于 float属性和 NSNumber *或 CFBooleanRef对于 BOOL属性(property)。

但是，更改类型将使 Swift 将属性导入为 NSNumber和 CFBoolean而不是 Float和 Bool .所以你可能还想申请 NS_REFINED_FOR_SWIFT每个属性，以及一个 Swift extension定义 Float 类型的属性和 Bool .这是它的样子:

// In your Objective-C header:

@interface MyObject : NSObject
@property (nonatomic, assign, nullable) NSNumber *percentageOfCases NS_REFINED_FOR_SWIFT;
@property (nonatomic, assign, nullable) NSNumber *inspectionPercentageOfCases NS_REFINED_FOR_SWIFT;
@property (nonatomic, assign, nullable) NSString *inspectionStatus;
@property (nonatomic, assign, nullable) CFBooleanRef sendNotification NS_REFINED_FOR_SWIFT;
@end

extension MyObject {
    var percentageOfCases: Float? {
        get { __percentageOfCases?.floatValue }
        set { __percentageOfCases = newValue as NSNumber? }
    }

    var inspectionPercentageOfCases: Float? {
        get { __inspectionPercentageOfCases?.floatValue }
        set { __inspectionPercentageOfCases = newValue as NSNumber? }
    }

    var sendNotification: Bool? {
        get { (__sendNotification as NSNumber?)?.boolValue }
        set { __sendNotification = newValue as NSNumber? }
    }
}

请注意，Xcode 不会为双下划线标识符(如 __percentageOfCases )提供代码完成。