如何使用Alamofire 4以字节为单位获得下载进度？

Question

我目前正在开发一个iOS项目,需要我一次下载10个不同的文件.我知道文件大小和所有文件的大小相结合,但我很难找到一种方法来计算所有下载任务的进度.

progress.totalUnitCount = object.size // The size of all the files combined
    for file in files {
        let destination: DownloadRequest.DownloadFileDestination = { _, _ in
            let path = NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.applicationSupportDirectory,
                                                           FileManager.SearchPathDomainMask.userDomainMask, true)
            let documentDirectoryPath: String = path[0]
            let destinationURLForFile = URL(fileURLWithPath: documentDirectoryPath)
            return (destinationURLForFile, [.removePreviousFile, .createIntermediateDirectories])
        }

        Alamofire.download(file.urlOnServer, to: destination)
            .downloadProgress(queue: .main, closure: { progress in

            })
            .response { response in
                if let error = response.error {
                    print(error)
                }
        }
    }

大多数代码仅用于上下文.

我发现,直到Alamofire 3才有这样的电话:

 .progress { bytesRead, totalBytesRead, totalBytesExpectedToRead in
    print("Bytes: \(bytesRead), Total Bytes: \(totalBytesRead), Total Bytes Expected: \(totalBytesExpectedToRead)")
}

这不再存在了,我想知道如何才能获得相同的功能.

先感谢您!

Answer 1

在Alamofire 4中,Progress API发生了变化.所有更改都在Alamofire 4.0迁移指南中进行了解释.

总结最重要的更改,这会影响您的用例:

// Alamofire 3
Alamofire.request(.GET, urlString, parameters: parameters, encoding: .JSON)
.progress { bytesRead, totalBytesRead, totalBytesExpectedToRead in
    print("Bytes: \(bytesRead), Total Bytes: \(totalBytesRead), Total Bytes Expected: \(totalBytesExpectedToRead)")
}

可以实现

// Alamofire 4
Alamofire.request(urlString, method: .get, parameters: parameters, encoding: JSONEncoding.default)
.downloadProgress { progress in
    print("Progress: \(progress.fractionCompleted)")
}

返回的progress对象属于ProgressApple的Foundation框架类型,因此您可以访问该fractionCompleted属性.

有关更改的详细说明,请参阅Alamofire 4.0迁移指南的" 请求子类"部分.Alamofire GitHub仓库中的拉取请求1455引入了新的Progress API,也可能有所帮助.