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

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

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

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

通过例子来试一下

  let destination: DownloadRequest.DownloadFileDestination = { _, _ in
            let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
            let fileURL = documentsURL.appendingPathComponent("pig.png")
            
            return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
        }
        
        Alamofire.download("https://httpbin.org/image/png", to: destination).response { response in
            print(response)
            
            if response.error == nil, let imagePath = response.destinationURL?.path {
                let image = UIImage(contentsOfFile: imagePath)
            }
        }
    

在制定路径下顺利拿到图片

Alamofire也提供了建议的destination设置

let destination = DownloadRequest.suggestedDownloadDestination(for: .documentDirectory)
Alamofire.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

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

downloadProgress支持自定义queue

let utilityQueue = DispatchQueue.global(qos: .utility)

Alamofire.download("https://httpbin.org/image/png")
    .downloadProgress(queue: utilityQueue) { progress in
        print("Download Progress: \(progress.fractionCompleted)")
    }
    .responseData { response in
        if let data = response.result.value {
            let image = UIImage(data: data)
        }
    }

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.

class ImageRequestor {
    private var resumeData: Data?
    private var image: UIImage?

    func fetchImage(completion: (UIImage?) -> Void) {
        guard image == nil else { completion(image) ; return }

        let destination: DownloadRequest.DownloadFileDestination = { _, _ in
            let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
            let fileURL = documentsURL.appendingPathComponent("pig.png")

            return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
        }

        let request: DownloadRequest

        if let resumeData = resumeData {
            request = Alamofire.download(resumingWith: resumeData)
        } else {
            request = Alamofire.download("https://httpbin.org/image/png")
        }

        request.responseData { response in
            switch response.result {
            case .success(let data):
                self.image = UIImage(data: data)
            case .failure:
                self.resumeData = response.resumeData
            }
        }
    }
}

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

let imageData = UIPNGRepresentation(image)!

Alamofire.upload(imageData, to: "https://httpbin.org/post").responseJSON { response in
    debugPrint(response)
}

通过路径上传

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

Multipart Form Data

Alamofire.upload(
//通过 multipartFormData.append拼接,参数是获取数据的方式和数据名称
    multipartFormData: { multipartFormData in
        multipartFormData.append(unicornImageURL, withName: "unicorn")
        multipartFormData.append(rainbowImageURL, withName: "rainbow")
    },
    to: "https://httpbin.org/post",
    //要上传的数据编码后的回调
    encodingCompletion: { encodingResult in
        switch encodingResult {
        case .success(let upload, _, _):
        //如果是成功的，那么它会返回一个UploadRequest
            upload.responseJSON { response in
                debugPrint(response)
            }
        case .failure(let encodingError):
            print(encodingError)
        }
    }
)

上传进度

let fileURL = Bundle.main.url(forResource: "video", withExtension: "mov")

Alamofire.upload(fileURL, to: "https://httpbin.org/post")
    .uploadProgress { progress in // main queue by default
        print("Upload Progress: \(progress.fractionCompleted)")
    }
    .downloadProgress { progress in // main queue by default
        print("Download Progress: \(progress.fractionCompleted)")
    }
    .responseJSON { response in
        debugPrint(response)
    }