Xcode 12 - 当有另一个 Swift 包作为依赖项时，SwiftUI 预览在 Swift 包上不起作用 - 'previewInstances' 消息给代理

Question

当我的代码从其他 swift 包中导入控件或值时，我在位于 Swift 包中的视图中的 SwiftUI 预览上遇到问题。

import Foundation
import SwiftUI
import Common

struct AppointmentListItem: View {
    var appointment: Appointment
    var body: some View {
        VStack{
            HStack(spacing: 10){
               //Client Info
                Image(self.appointment.client.profilePicture)
                   .resizable()
                   .aspectRatio(contentMode: .fill)
                   .frame(width: 35, height: 35)
                   .clipShape(Circle())
                   .shadow(radius: 10)
                   .overlay(Circle().stroke(Color.white, lineWidth: 1.5))
                Text(self.appointment.client.fullName)
                   .font(.system(size: 18))
                   .bold()
                   .frame(maxWidth: .infinity, alignment: .leading)
                Text(self.appointment.getHourAndMinutes()).bold()
               //Detail info
               Button(action: {
                   withAnimation{
                       print("Go to details")
                   }
               }){
                   Image(systemName: "ellipsis")
                       .font(.system(size: 18))
                       .frame(width: 20, height: 20)
                    .rotationEffect(Angle.init(degrees: 90))
               }
            }
            .padding()
        }
        .foregroundColor(Color.white)
        .background(RoundedRectangle(cornerRadius: 20)
                        .fill(Color.hippoPrimary)// <- this color is part of Common package
        )
    }
}

如果我删除或更改.fill(Color.hippoPrimary)预览可用。

Xcode 提供的错误如下：

RemoteHumanReadableError: Failed to update preview.

The preview process appears to have crashed.

Error encountered when sending 'previewInstances' message to agent.

==================================

|  RemoteHumanReadableError: The operation couldn’t be completed. (BSServiceConnectionErrorDomain error 3.)
|  
|  BSServiceConnectionErrorDomain (3):
|  ==BSErrorCodeDescription: OperationFailed

这是我的 Package.swift 文件：

// swift-tools-version:5.3
// The swift-tools-version declares the minimum version of Swift required to build this package.

import PackageDescription

let package = Package(
    name: "TodayAppointments",
    platforms: [
        .iOS(.v13)
    ],
    products: [
        // Products define the executables and libraries a package produces, and make them visible to other packages.
        .library(
            name: "TodayAppointments",
            targets: ["TodayAppointments"]),
    ],
    dependencies: [
        // Dependencies declare other packages that this package depends on.
        // .package(url: /* package url */, from: "1.0.0"),
        .package(path: "../Common")
    ],
    targets: [
        // Targets are the basic building blocks of a package. A target can define a module or a test suite.
        // Targets can depend on other targets in this package, and on products in packages this package depends on.
        .target(
            name: "TodayAppointments",
            dependencies: ["Common"]),
        .testTarget(
            name: "TodayAppointmentsTests",
            dependencies: ["TodayAppointments"]),
    ]
)

在 Common Package 中，颜色是这样定义的：

public extension Color {
    static let hippoPrimary = Color("Primary", bundle: .module)
    static let progressBarBackground = Color("ProgressBarBackground", bundle: .module)
    static let textBackground = Color("TextBackground", bundle: .module)
    static let textColor = Color("TextColor", bundle: .module)
    static let appleSignInBackground = Color("AppleSignInBackground", bundle: .module)
    static let buttonActionText = Color("Text", bundle: .module)
}

构建没有错误，所以我知道依赖关系没问题，听起来像一个 IDE。

提前致谢。

Answer 1

适用于 iOS 和 macOS 的解决方法（未使用 Catalyst 测试）

public let imageBundle = Bundle.myModule

private class CurrentBundleFinder {}

extension Foundation.Bundle {

    static var myModule: Bundle = {

        /* The name of your local package, prepended by "LocalPackages_" for iOS and "PackageName_" for macOS. You may have same PackageName and TargetName*/



        let bundleNameIOS = "LocalPackages_TargetName"

        let bundleNameMacOs = "PackageName_TargetName"

        let candidates = [

            /* Bundle should be present here when the package is linked into an App. */

            Bundle.main.resourceURL,

            /* Bundle should be present here when the package is linked into a framework. */

            Bundle(for: CurrentBundleFinder.self).resourceURL,

            /* For command-line tools. */

            Bundle.main.bundleURL,

            /* Bundle should be present here when running previews from a different package (this is the path to "…/Debug-iphonesimulator/"). */

            Bundle(for: CurrentBundleFinder.self).resourceURL?.deletingLastPathComponent().deletingLastPathComponent().deletingLastPathComponent(),

            Bundle(for: CurrentBundleFinder.self).resourceURL?.deletingLastPathComponent().deletingLastPathComponent(),

        ]

        

        for candidate in candidates {

            let bundlePathiOS = candidate?.appendingPathComponent(bundleNameIOS + ".bundle")

            let bundlePathMacOS = candidate?.appendingPathComponent(bundleNameMacOs + ".bundle")

            if let bundle = bundlePathiOS.flatMap(Bundle.init(url:)) {

                return bundle

            } else if let bundle = bundlePathMacOS.flatMap(Bundle.init(url:)) {

                return bundle

            }

        }

        fatalError("unable to find bundle")

    }()

}

Answer 2

更新1：

抱歉，我的上一篇文章不准确。这是 Xcode 中的一个错误，无法解决。刚刚向 Apple 提交了一份错误报告 ( FB8880328 )。另外，在此处发布了带有示例代码和重现步骤的详细信息。直接链接到 GitHub 项目：https://github.com/ryanholden8/SwiftUI-Preview-Failing-Test-Project

旧帖子：

做同样的事情时遇到了这个确切的错误，将颜色放入单独的包中。这篇文章帮助我了解了真相。我删除了颜色包中生成的默认类。但是，我没有删除基于该默认类的单元测试。

简而言之：删除包中自动生成的单元测试Common。或者确保所有单元测试都通过。