ProgressManager 是一个类，旨在使处理 Progress 及其子任务变得更直接和容易。为什么要使用它？它允许对多步操作的细节进行细粒度但易于访问的控制，同时自动将其状态反映在诸如 ProgressView、UIProgressView 和 NSProgressIndicator 等视图中。

private enum ProgressSteps: ChildProgressTask {
    case importantStep, smallStep, aMultiUnitStep
    
    var childUnits: Int64 {
        switch self {
        // 1 unit of this task must be completed for it to be considered "complete" by the parent
        case .importantStep: 1
        // 1 unit of this task must be completed for it to be considered "complete" by the parent
        case .smallStep: 1
        // 6 units of this task must be completed for it to be considered "complete" by the parent
        case .aMultiUnitStep: 6
        }
    }
    
    var parentUnits: Int64 {
        switch self {
        // Once all units of this child task have been completed (1 unit),
        // it counts as 5 units in the context of the parent progress
        case .importantStep: 5
        // Once all units of this child task have been completed (1 unit),
        // it counts as 1 unit in the context of the parent progress
        case .smallStep: 1
        // Once all units of this child task have been completed (6 units),
        // it counts as 1 unit in the context of the parent progress
        case .aMultiUnitStep: 1
        }
    }
}

let progress = ProgressManager(
    // can be ommitted if type can be inferred
    ProgressSteps.self,
    // a Set of unique child tasks
    childTasks: [.importantStemp, .smallStep, .aMultiUnitStep]
)

// Perform `.importantStep`.
progress.setCompletedUnitCount(1, forChildTask: .importantStep)

// Perform `.smallStemp`.
progress.setCompletedUnitCount(1, forChildTask: .smallStemp)

// Perform `.aMultiUnitStep`.
for i in 0..<6 {
    progress.addToCompletedUnitCount(i, forChildTask: .aMultiUnitStep)
}

就是这样！如果您需要更细粒度的控制，您可以通过 childTasks 属性或者直接通过下标（progress[.aMultiUnitStep]）访问子任务。

ProgressManager

如何使用 ProgressManager