Alamofire4.x开源代码分析(三)文件上传下载

Alamofire支持下载图片到内存或者磁盘,Alamofire.request开头的请求会把数据加载进内存,适用于小文件,如果文件比较大,可能会造成内存溢出.因此如果文件比较大,应该是Alamofire.download方法,把数据临时的保存在磁盘中,该方法同时还支持后台下载. 例如

1Alamofire.download("https://httpbin.org/image/png").responseData { response in
2    if let data = response.result.value {
3        let image = UIImage(data: data)
4    }
5}

框架提供了DownloadFileDestination,来允许自定义destinationURL,DownloadOptions这两个属性,如果不指定Destination,文件将被下载到temporaryURL.我们来看看这个闭包的结构

1public typealias DownloadFileDestination = (
2    _ temporaryURL: URL,
3    _ response: HTTPURLResponse)
4    -> (destinationURL: URL, options: DownloadOptions)
5    //options包含的枚举
6    .createIntermediateDirectories//根据路径来创建文件夹
7    .removePreviousFile//移除当前路径的旧文件

通过例子来试一下

1  let destination: DownloadRequest.DownloadFileDestination = { _, _ in
2            let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
3            let fileURL = documentsURL.appendingPathComponent("pig.png")
4            
5            return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
6        }
7        
8        Alamofire.download("https://httpbin.org/image/png", to: destination).response { response in
9            print(response)
10            
11            if response.error == nil, let imagePath = response.destinationURL?.path {
12                let image = UIImage(contentsOfFile: imagePath)
13            }
14        }
15    

在制定路径下顺利拿到图片

Alamofire也提供了建议的destination设置

1let destination = DownloadRequest.suggestedDownloadDestination(for: .documentDirectory)
2Alamofire.download("https://httpbin.org/image/png", to: destination)

下载进度

任何Alamofire.download方法都可以通过downloadProgress获取下载进度

1  Alamofire.download("https://cdn.pixabay.com/photo/2017/06/26/12/49/red-wine-2443699_1280.jpg")
2            .downloadProgress { progress in
3                print("Download Progress: \(progress.fractionCompleted)")
4            }
5            .responseData { response in
6                if let data = response.result.value {
7                    let image = UIImage(data: data)
8                }
9        }

downloadProgress支持自定义queue

1let utilityQueue = DispatchQueue.global(qos: .utility)
2
3Alamofire.download("https://httpbin.org/image/png")
4    .downloadProgress(queue: utilityQueue) { progress in
5        print("Download Progress: \(progress.fractionCompleted)")
6    }
7    .responseData { response in
8        if let data = response.result.value {
9            let image = UIImage(data: data)
10        }
11    }

如果DownloadRequest被取消或者被中断,response会包含一个resumeData,可以用来重新发起请求.

1class ImageRequestor {
2    private var resumeData: Data?
3    private var image: UIImage?
4
5    func fetchImage(completion: (UIImage?) -> Void) {
6        guard image == nil else { completion(image) ; return }
7
8        let destination: DownloadRequest.DownloadFileDestination = { _, _ in
9            let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
10            let fileURL = documentsURL.appendingPathComponent("pig.png")
11
12            return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
13        }
14
15        let request: DownloadRequest
16
17        if let resumeData = resumeData {
18            request = Alamofire.download(resumingWith: resumeData)
19        } else {
20            request = Alamofire.download("https://httpbin.org/image/png")
21        }
22
23        request.responseData { response in
24            switch response.result {
25            case .success(let data):
26                self.image = UIImage(data: data)
27            case .failure:
28                self.resumeData = response.resumeData
29            }
30        }
31    }
32}

上传数据

• Alamofire.request//上传小数据(JSON,URL编码参数)
• Alamofire.upload //上传大数据或者数据流(支持后台上传) Alamofire可以通过下列方式上传数据
• Data
• fileURL
• inputStream
• MultipartFormData

Data上传

1let imageData = UIPNGRepresentation(image)!
2
3Alamofire.upload(imageData, to: "https://httpbin.org/post").responseJSON { response in
4    debugPrint(response)
5}

通过路径上传

1let imageData = UIPNGRepresentation(image)!
2        Alamofire.upload(imageData, to: "https://httpbin.org/post").responseJSON { response in
3            debugPrint(response)
4        }

Multipart Form Data

1Alamofire.upload(
2//通过 multipartFormData.append拼接,参数是获取数据的方式和数据名称
3    multipartFormData: { multipartFormData in
4        multipartFormData.append(unicornImageURL, withName: "unicorn")
5        multipartFormData.append(rainbowImageURL, withName: "rainbow")
6    },
7    to: "https://httpbin.org/post",
8    //要上传的数据编码后的回调
9    encodingCompletion: { encodingResult in
10    	switch encodingResult {
11    	case .success(let upload, _, _):
12    	//如果是成功的，那么它会返回一个UploadRequest
13            upload.responseJSON { response in
14                debugPrint(response)
15            }
16    	case .failure(let encodingError):
17    	    print(encodingError)
18    	}
19    }
20)

上传进度

1let fileURL = Bundle.main.url(forResource: "video", withExtension: "mov")
2
3Alamofire.upload(fileURL, to: "https://httpbin.org/post")
4    .uploadProgress { progress in // main queue by default
5        print("Upload Progress: \(progress.fractionCompleted)")
6    }
7    .downloadProgress { progress in // main queue by default
8        print("Download Progress: \(progress.fractionCompleted)")
9    }
10    .responseJSON { response in
11        debugPrint(response)
12    }