How to use Swift struct in Objective-C

Sad to say, you can not expose struct, nor global variables to Objective-C. see the documentation, which states in part:

Use Classes When You Need Objective-C Interoperability

If you use an Objective-C API that needs to process your data, or you need to fit your data model into an existing class hierarchy defined in an Objective-C framework, you might need to use classes and class inheritance to model your data. For example, many Objective-C frameworks expose classes that you are expected to subclass.

As of now, IMHO, the best way is something like this:

let ParseApplicationId = "xxx"let ParseClientKey = "xxx"let AppGreenColor = UIColor(red: 0.2, green: 0.7, blue: 0.3 alpha: 1.0)@objc class Constant: NSObject {    private init() {}    class func parseApplicationId() -> String { return ParseApplicationId }    class func parseClientKey() -> String { return ParseClientKey }    class func appGreenColor() -> UIColor { return AppGreenColor }}

In Objective-C, you can use them like this:

NSString *appklicationId = [Constant parseApplicationId];NSString *clientKey = [Constant parseClientKey];UIColor *greenColor = [Constant appGreenColor];

Why not create a file with both a struct and an @objc class, something like this:

import UIKitextension UIColor {    convenience init(hex: Int) {        let components = (            R: CGFloat((hex >> 16) & 0xff) / 255,            G: CGFloat((hex >> 08) & 0xff) / 255,            B: CGFloat((hex >> 00) & 0xff) / 255        )        self.init(red: components.R, green: components.G, blue: components.B, alpha: 1)    }}extension CGColor {    class func colorWithHex(hex: Int) -> CGColorRef {        return UIColor(hex: hex).CGColor    }}struct Constant {    static let kParseApplicationId = "5678"    static let kParseClientKey = "1234"    static var kAppGreenColor: UIColor { return UIColor(hex:0x67B632) }    static var kTextBlackColor: UIColor { return UIColor(hex:0x000000) }    static var kSomeBgBlueColor: UIColor { return UIColor(hex:0x0000FF) }    static var kLineGrayCGColor: CGColor { return CGColor.colorWithHex(0xCCCCCC) }    static var kLineRedCGColor: CGColor { return CGColor.colorWithHex(0xFF0000) }}@objc class Constants: NSObject {    private override init() {}    class func parseApplicationId() -> String { return Constant.kParseApplicationId }    class func parseClientKey() -> String { return Constant.kParseClientKey }    class func appGreenColor() -> UIColor { return Constant.kAppGreenColor }    class func textBlackColor() -> UIColor { return Constant.kTextBlackColor }    class func someBgBlueColor() -> UIColor { return Constant.kSomeBgBlueColor }    class func lineGrayCGColor() -> CGColor { return Constant.kLineGrayCGColor }    class func lineRedCGColor() -> CGColor { return Constant.kLineRedCGColor }}

For use in Objective-C files add this when you need to use constants:

#import "ProjectModuleName-Swift.h"

Swift usage:

self.view.backgroundColor = Constant.kAppGreenColor

Objective-C usage:

self.view.backgroundColor = [Constants appGreenColor];

This way you can update colors, default text, web service urls for whole app in one place.

Though this might be late or redundant, I could make it work with the following code :

@objcMembers class Flags: NSObject {    static let abcEnabled = false    static let pqrEnabled = false    .    .    .}

Obviously, to use in objc c code, you have to do #import "ProjectModuleName-Swift.h"