A small extension for PreviewDevice to avoid enter the values in the SwiftUI previews manually

PreviewDevice+ListOfPads.swift

/**
*  PreviewDevice+ListOfPads.swift
*  Copyright (c) Thiago Holanda 2020
*  https://twitter.com/tholanda
*
*  MIT license
*/

import SwiftUI

extension PreviewDevice {
    private enum Devices: String {
        case iPadMini4           = "iPad mini 4"
        case iPadAir2            = "iPad Air 2"
        case iPadPro_9_7         = "iPad Pro (9.7-inch)"
        case iPadPro_12_9        = "iPad Pro (12.9-inch)"
        case iPad5thGen          = "iPad (5th generation)"
        case iPadPro_12_9_2ndGen = "iPad Pro (12.9-inch) (2nd generation)"
        case iPadPro_10_5        = "iPad Pro (10.5-inch)"
        case iPad6thGen          = "iPad (6th generation)"
        case iPadPro_11          = "iPad Pro (11-inch)"
        case iPadPro_12_9_3rdGen = "iPad Pro (12.9-inch) (3rd generation)"
        case iPadMini5thGen      = "iPad mini (5th generation)"
        case iPadAir3rdGen       = "iPad Air (3rd generation)"
    }
    
    private enum Orientation {
        case portrait
        case landscape
    }
    
    /// iPad mini 4
    static var iPadMini4 = PreviewDevice(rawValue: Devices.iPadMini4.rawValue)
    
    /// iPad Air 2
    static var iPadAir2 = PreviewDevice(rawValue: Devices.iPadAir2.rawValue)
    
    /// iPad Pro (9.7-inch)
    static var iPadPro_9_7 = PreviewDevice(rawValue: Devices.iPadPro_9_7.rawValue)
    
    /// iPad Pro (12.9-inch)
    static var iPadPro_12_9 = PreviewDevice(rawValue: Devices.iPadPro_12_9.rawValue)
    
    /// iPad (5th generation)
    static var iPad5thGen = PreviewDevice(rawValue: Devices.iPad5thGen.rawValue)
    
    /// iPad Pro (12.9-inch) (2nd generation)
    static var iPadPro_12_9_2ndGen = PreviewDevice(rawValue: Devices.iPadPro_12_9_2ndGen.rawValue)
    
    /// iPad Pro (10.5-inch)
    static var iPadPro_10_5 = PreviewDevice(rawValue: Devices.iPadPro_10_5.rawValue)
    
    /// iPad (6th generation)
    static var iPad6thGen = PreviewDevice(rawValue: Devices.iPad6thGen.rawValue)
    
    /// iPad Pro (11-inch)
    static var iPadPro_11 = PreviewDevice(rawValue: Devices.iPadPro_11.rawValue)
    
    /// iPad Pro (12.9-inch) (3rd generation)
    static var iPadPro_12_9_3rdGen = PreviewDevice(rawValue: Devices.iPadPro_12_9_3rdGen.rawValue)
    
    /// iPad mini (5th generation)
    static var iPadMini5thGen = PreviewDevice(rawValue: Devices.iPadMini5thGen.rawValue)
    
    /// iPad Air (3rd generation)
    static var iPadAir3rdGen = PreviewDevice(rawValue: Devices.iPadAir3rdGen.rawValue)


    /// Syntax sugar for the property `rawvalue`
    var displayName: String {
        rawValue
    }
    
    var landscapeLayout: PreviewLayout {
        screenSize(orientation: .landscape)
    }
    
    var portraitLayout: PreviewLayout {
        screenSize(orientation: .landscape)
    }
    
    private func screenSize(orientation: Orientation) -> PreviewLayout {
        guard let device = Devices(rawValue: rawValue) else {
            return .sizeThatFits
        }
        
        switch device {
            case .iPadMini4,
                 .iPadMini5thGen:
                return orientation == .portrait ?
                    .fixed(width: 1536, height: 2048)
                    : .fixed(width: 2048, height: 1536)
            
            case .iPadAir2,
                 .iPadAir3rdGen:
                return orientation == .portrait ?
                    .fixed(width: 1536, height: 2048)
                    : .fixed(width: 2048, height: 1536)
            
            case .iPadPro_9_7,
                 .iPad5thGen,
                 .iPad6thGen:
                return orientation == .portrait ?
                    .fixed(width: 1536, height: 2048)
                    : .fixed(width: 2048, height: 1536)
            
            case .iPadPro_10_5:
                return orientation == .portrait ?
                    .fixed(width: 1668, height: 2224)
                    : .fixed(width: 2224, height: 1668)
            
            case .iPadPro_11:
                return orientation == .portrait ?
                    .fixed(width: 1536, height: 2048)
                    : .fixed(width: 2048, height: 1536)
            
            case .iPadPro_12_9,
                 .iPadPro_12_9_2ndGen,
                 .iPadPro_12_9_3rdGen:
                return orientation == .portrait ?
                    .fixed(width: 2048, height: 2732)
                    : .fixed(width: 2732, height: 2048)
        }
    }
}

Usage.swift

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        let device = PreviewDevice.iPadMini4
        
        return ContentView()
            .previewLayout(device.landscapeLayout)
            .previewDisplayName(device.displayName)
    }
}