AlamofireImage磁盘缓存不工作

Question

我希望使用AlamofireImage从url下载图像，然后将其缓存在设备磁盘空间中。我阅读了有关这方面的几篇文章，发现AlamofireImage在ImageDownloader类的帮助下支持这一点。最有趣的信息是给在这个答案中的

因此，我尝试为NSURLCache设置一个自定义ImageDownloader，这样它就可以直接将图像缓存到磁盘上。为此，我将内存容量设置为0。然后我使用这个定制的ImageDownloader下载一个图像。我为磁盘路径指定的文件夹是在磁盘上创建的，但不幸的是，它仍然是空的，映像没有以任何方式被缓存。

**编辑：**注意缓存的响应不是保存在缓存目录的文件夹中，而是保存在文件夹旁边的数据库文件中。

有人能告诉我我在这里做错了什么吗？非常感谢你的阅读！

func diskImageDownloader(diskSpaceMB: Int = 100) -> ImageDownloader {

    let diskCapacity = diskSpaceMB * 1024 * 1024
    let diskCache = NSURLCache(memoryCapacity: 0, diskCapacity: diskCapacity, diskPath: "alamofireimage_disk_cache")
    let configuration = NSURLSessionConfiguration.defaultSessionConfiguration()
    configuration.URLCache = diskCache
    let downloader = ImageDownloader(configuration: configuration)
    UIImageView.af_sharedImageDownloader = downloader

    return downloader
}

func getProfileImage(atURL url: String, onComplete: SRServiceResponse<UIImage> -> Void) {
    guard let imageURL = NSURL(string: url) else
    {
        // TODO: Fail here
        return
    }

    let request = NSURLRequest(URL: imageURL)

    let imageDownloader = self.diskImageDownloader()

    imageDownloader.downloadImage(URLRequest: request) { (response) in
        switch response.result
        {
        case .Success(let image):
            // Do something
        case .Failure(let error):
            // Do something
        }
    }
}

Answer 1

为了达到您的目标，您可以使用NSURLCache作为diskCache来为存储的图像设置您自己的过期日期：

class DiskCache: NSURLCache {
    private let constSecondsToKeepOnDisk = 30*24*60*60 // 30 days

    override func storeCachedResponse(cachedResponse: NSCachedURLResponse, forRequest request: NSURLRequest) {
        var customCachedResponse = cachedResponse
        // Set custom Cache-Control for Image-Response
        if let response = cachedResponse.response as? NSHTTPURLResponse,
            let contentType = response.allHeaderFields["Content-Type"] as? String,
            var newHeaders = response.allHeaderFields as? [String: String] where contentType.containsString("image") {
            newHeaders["Cache-Control"] = "public, max-age=\(constSecondsToKeepOnDisk)"
            if let url = response.URL, newResponse = NSHTTPURLResponse(URL: url, statusCode: response.statusCode, HTTPVersion: "HTTP/1.1", headerFields: newHeaders) {
                customCachedResponse = NSCachedURLResponse(response: newResponse, data: cachedResponse.data, userInfo: cachedResponse.userInfo, storagePolicy: cachedResponse.storagePolicy)
            }
        }
        super.storeCachedResponse(customCachedResponse, forRequest: request)
    }
}

而不是每次您可以重用共享实例来调用downloadImage方法：UIImageView.af_sharedImageDownloader.downloadImage(URLRequest: request)时创建一个新的UIImageView.af_sharedImageDownloader.downloadImage(URLRequest: request)

Answer 2

我这么做不是为了代表。只是为了节省编译器的时间。

在SWIFT3.0中

class DiskCache: URLCache {


  private let constSecondsToKeepOnDisk = numDaysToKeep*24*60*60 // numDaysToKeep is your own constant or hard-coded value

  override func storeCachedResponse(_ cachedResponse: CachedURLResponse, for request: URLRequest) {

    var customCachedResponse = cachedResponse
    // Set custom Cache-Control for Image-Response
    let response = cachedResponse.response as! HTTPURLResponse

    if let contentType = response.allHeaderFields["Content-Type"] as? String,
        var newHeaders = response.allHeaderFields as? [String: String], contentType.contains("image") {
        newHeaders["Cache-Control"] = "public, max-age=\(constSecondsToKeepOnDisk)"
        if let url = response.url, let newResponse = HTTPURLResponse(url: url, statusCode: response.statusCode, httpVersion: "HTTP/1.1", headerFields: newHeaders) {
            customCachedResponse = CachedURLResponse(response: newResponse, data: cachedResponse.data, userInfo: cachedResponse.userInfo, storagePolicy: cachedResponse.storagePolicy)
        }
    }
    super.storeCachedResponse(customCachedResponse, for: request)
  }
}