How to tell if current running Apple Watch size/dimension is 38mm or 42mm?

Question

We know that there are two screen sizes for Apple Watch: 38mm and 42mm. The WKInterfaceDevice class provides a readable property named screenBounds. I wrote an extension for WKInterfaceDevice, trying to add a method to detect current device type.

import WatchKit

enum WatchResolution {

    case Watch38mm, Watch42mm
}

extension WKInterfaceDevice {

    class func currentResolution() -> WatchResolution {

        let watch38mmRect = CGRectMake(0.0, 0.0, 136.0, 170.0)
        let watch42mmRect = CGRectMake(0.0, 0.0, 156.0, 195.0)

        let currentBounds = WKInterfaceDevice.currentDevice().screenBounds

        if CGRectEqualToRect(currentBounds, watch38mmRect) {

            return WatchResolution.Watch38mm
        } else {

            return WatchResolution.Watch42mm
        }
    }
}

Is that the correct method to detect Apple Watch size? Is there another method I am missing in the Apple docs?

Answer 1

Your code looks good, but has a few minor issues:

• You don't have a case for an "unknown" screen size (possibly released in the future)
• You're using CGRectMake but in Swift you should use a CGRect initializer
• You're using CGRectEqualToRect but in Swift you can just use == or switch
• You're explicitly returning WatchResolution enums, but you don't need to be explicit - Swift will figure it out from your method signature
• You're declaring watch42mmRect but not using it for anything

I would rewrite it like this:

enum WatchResolution {
    case Watch38mm, Watch42mm, Unknown
}

extension WKInterfaceDevice {
    class func currentResolution() -> WatchResolution {
        let watch38mmRect = CGRect(x: 0, y: 0, width: 136, height: 170)
        let watch42mmRect = CGRect(x: 0, y: 0, width: 156, height: 195)

        let currentBounds = WKInterfaceDevice.currentDevice().screenBounds

        switch currentBounds {
        case watch38mmRect:
            return .Watch38mm
        case watch42mmRect:
            return .Watch42mm
        default:
            return .Unknown
        }
    }
}

Answer 2

Update Swift 4:

It includes new launch of Watch resolutions:

enum WatchResolution {
    case Watch38mm, Watch40mm,Watch42mm,Watch44mm, Unknown  
}

extension WKInterfaceDevice {
class func currentResolution() -> WatchResolution {
    let watch38mmRect = CGRect(x: 0, y: 0, width: 136, height: 170)
    let watch40mmRect = CGRect(x: 0, y: 0, width: 162, height: 197)
    let watch42mmRect = CGRect(x: 0, y: 0, width: 156, height: 195)
    let watch44mmRect = CGRect(x: 0, y: 0, width: 184, height: 224)

    let currentBounds = WKInterfaceDevice.current().screenBounds

    switch currentBounds {
    case watch38mmRect:
        return .Watch38mm
    case watch40mmRect:
        return .Watch40mm
    case watch42mmRect:
        return .Watch42mm
    case watch44mmRect:
        return .Watch44mm
    default:
        return .Unknown
    }
  } 
}

Usage

let resol = WKInterfaceDevice.currentResolution()
    switch resol {
    case .Watch38mm, .Watch42mm:
        // Do Something
    case .Watch40mm, .Watch44mm:
        // Do Something
    default:
        // Do Something
    }

Reference Link: Apple Developer Watch Interface Link

Hope that helps....

Thanks