NSFileManager监视目录

Question

您将如何监视目录NSFileManager？

我想在我的应用程序运行时检测何时在我的文档目录中删除/添加了文件。

Answer 1

查看Apple 文档中的“内核队列：文件系统事件的替代方案”。AVPlayerDemo（外观类）中有一个适用于 iOS 的示例DirectoryWatcher。

另外，请查看目录监视器博客文章。

Answer 2

这是我用Swift用GCD代替Mach并用闭包代替委托编写的DirectoryWatcher版本

import Foundation

@objc public class DirectoryWatcher : NSObject {
    override public init() {
        super.init()
    }

    deinit {
        stop()
    }

    public typealias Callback = (_ directoryWatcher: DirectoryWatcher) -> Void

    @objc public convenience init(withPath path: String, callback: @escaping Callback) {
        self.init() // modified for Swift 3+
        if !watch(path: path, callback: callback) {
            assert(false)
        }
    }

    private var dirFD : Int32 = -1 {
        didSet {
            if oldValue != -1 {
                close(oldValue)
            }
        }
    }
    private var dispatchSource : DispatchSourceFileSystemObject?

    @objc public func watch(path: String, callback: @escaping Callback) -> Bool {
        // Open the directory
        dirFD = open(path, O_EVTONLY)
        if dirFD < 0 {
            return false
        }

        // Create and configure a DispatchSource to monitor it
        let dispatchSource = DispatchSource.makeFileSystemObjectSource(fileDescriptor: dirFD, eventMask: .write, queue: DispatchQueue.main)
        dispatchSource.setEventHandler {[unowned self] in
            callback(self)
        }
        dispatchSource.setCancelHandler {[unowned self] in
            self.dirFD = -1
        }
        self.dispatchSource = dispatchSource

        // Start monitoring
        dispatchSource.resume()

        // Success
        return true
    }

    @objc public func stop() {
        // Leave if not monitoring
        guard let dispatchSource = dispatchSource else {
            return
        }

        // Don't listen to more events
        dispatchSource.setEventHandler(handler: nil)

        // Cancel the source (this will also close the directory)
        dispatchSource.cancel()
        self.dispatchSource = nil
    }
}

像苹果公司的DirectoryWatcher示例一样使用它，如下所示：

let directoryWatcher = DirectoryWatcher(withPath: "/path/to/the/folder/you/want/to/monitor/", callback: {
    print("the folder changed")
})

销毁该对象将停止监视，或者您可以显式停止它

directoryWatcher.stop()

它应该以编写（未测试）的方式与Objective C兼容。使用它会像这样：

DirectoryWatcher *directoryWatcher = [DirectoryWatcher.alloc initWithPath: @"/path/to/the/folder/you/want/to/monitor/" callback: ^(DirectoryWatcher *directoryWatcher) {
    NSLog(@"the folder changed")
}];

停止它是相似的

[directoryWatcher stop];