Swift通过URLSession实现图片上传

1.URLSession 的介绍

URLSession在2013年随着iOS7的发布一起面世，替换了原来的NSURLConnection,URLSession用于管理网络接口的创建、维护、删除等等工作.

2. URLSession的子类介绍

1. URLSessionDataTask:用于简单的数据请求.
2. URLSessionUploadTask:用于上传数据.
3. URLSessionDownloadTask:用于下载数据.
4. URLSessionStreamTask:提供TCP/IP的链接入口,可以用于双向会话.

3.通过URLSession实现上传图片

创建请求:

 var r  = URLRequest(url: URL(string: "https://*******")!)
        r.httpMethod = "POST"
        let boundary = "Boundary-\(UUID().uuidString)"
        r.setValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")
        r.httpBody = createBody(parameters: [:],
                                boundary: boundary,
                                data: image.jpegData(compressionQuality:0.7)!,
                                mimeType: "image/JPG",
                                filename: "hello.JPG")

上述代码中用到的creatBody方法如下:

 func createBody(parameters: [String: String],
                    boundary: String,
                    data: Data,
                    mimeType: String,
                    filename: String) -> Data {
        let body = NSMutableData()
        
        let boundaryPrefix = "--\(boundary)\r\n"
        
        for (key, value) in parameters {
            body.appendString(boundaryPrefix)
            body.appendString("Content-Disposition: form-data; name=\"\(key)\"\r\n\r\n")
            body.appendString("\(value)\r\n")
        }
        
        body.appendString(boundaryPrefix)
        body.appendString("Content-Disposition: form-data; name=\"file\"; filename=\"\(filename)\"\r\n")
        body.appendString("Content-Type: \(mimeType)\r\n\r\n")
        body.append(data)
        body.appendString("\r\n")
        body.appendString("--".appending(boundary.appending("--")))
        
        return body as Data
    }

对NSMutableData方法扩展:

  func appendString(_ string: String) {
        let data = string.data(using: String.Encoding.utf8, allowLossyConversion: false)
        append(data!)
    }

通过URLSession上传图片:

 let session = URLSession.shared.dataTask(with:r) { (data,response, error) in
            if(error != nil) {
                print("Error: \(error)")
            }else
            {
                
                let outputStr  = String(data: data!, encoding: String.Encoding.utf8) as String?
                print(outputStr)
                //send this block to required place
                //  completionBlock(outputStr!);
            }
        }
        session.resume()