我们如何将Objective-C常量导入为Swift类型？

I want to declare constant in Swift 3. For example if we have following constant in Objective-C :

我想在Swift 3中声明常量。例如，如果我们在Objective-C中有以下常量：

HK_EXTERN NSString * const HKQuantityTypeIdentifierHeight;
HK_EXTERN NSString * const HKQuantityTypeIdentifierBodyMass;

3 个解决方案

#1

Add New Swift file : Constant.swift

添加新的Swift文件：Constant.swift

import Foundation
import HealthKit

let HK_EXTERN_Height : NSString = HKQuantityTypeIdentifierHeight
let HK_EXTERN_BodyMass : NSString = HKQuantityTypeIdentifierBodyMass

Use in ViewController.swift

在ViewController.swift中使用

print(HK_EXTERN_Height)
print(HK_EXTERN_BodyMass)

Hope this help you....

希望这能帮到你....

#2

Adding constants into a separate file is also possible in Swift.

在Swift中也可以将常量添加到单独的文件中。

For using constants, it is even smarter, if you use structs, because huge number of constants can be messy:

对于使用常量，如果你使用结构，它甚至更聪明，因为大量的常量可能很乱：

import HealthKit

struct Constants {

    struct Health {

        struct Quantities {
            let height : NSString = HKQuantityTypeIdentifierHeight
            let bodyMass : NSString = HKQuantityTypeIdentifierBodyMass
            static let minWeight: Double = 30.0
        }  
        ...          
    } 
    ...
}

Usage:

用法：

print(Constants.Health.Quantities.minWeight)

or

要么

let healthNumbers = Constants.Health.Quantities
print(healthNumbers.minWeight)

#3

I believe in the Swift language you can declare using let key word.

我相信您可以使用let关键字声明Swift语言。