如何使用 swift 从 iOS 设备上传文件（到 REDCap）

Posted 2023-03-10

【中文标题】如何使用 swift 从 iOS 设备上传文件（到 REDCap）

【英文标题】：How to upload a file (to REDCap) from an iOS device using swift

【发布时间】：2021-12-29 19:18:11

【问题描述】：

我正在尝试将保存到应用程序（使用 ResearchKit 构建）中目录的文件上传到服务器（通过 REDCap API）。 REDCap API Playground 建议使用多种语言编写代码，但不建议使用 Obj-C 或 Swift。对于这种情况，我需要使用 Swift，这对我来说是第一次。以下是我尝试的一种方法，不幸的是它不起作用：

func postFileToRedcap (_ fileUrl: URL) 
    guard let url = URL (string: "https://our_redcap_url.edu/api/") else return
    let token = "ABCDEFGHIJK123456789" // unique to REDCap project
    let record = "1" // can be set elsewhere
    let event = ""
    let field = "file_upload_field" // name of field in REDCap
    
    if !fileUrl.pathComponents.isEmpty 
        let fileName = URL(fileURLWithPath: fileUrl.absoluteString).lastPathComponent
        var request = URLRequest.init(url: url)
        request.httpMethod = "POST"
        // parameters required by REDCap
        request.addValue(token, forHTTPHeaderField: "token")
        request.addValue(fileName, forHTTPHeaderField: "content")
        request.addValue("import", forHTTPHeaderField: "action")
        request.addValue(record, forHTTPHeaderField: "record")
        request.addValue(field, forHTTPHeaderField: "field")
        request.addValue(event, forHTTPHeaderField: "event")
        request.addValue("json", forHTTPHeaderField: "returnFormat")
        
        let task = URLSession.shared.uploadTask(
            with: request,
            fromFile: fileUrl
        )
        task.resume()
    

主要问题似乎是参数设置，但我似乎找不到适用于 REDCap 的解决方案。

所有帮助都慷慨地接受了。 提前致谢！

【问题讨论】：

也许从一个参数更少的更简单的 API 调用开始，比如检索服务器版本。然后按自己的方式使用此功能。这是一些软件包开发人员贡献的API trouble shooting vignette。它从与语言无关的部分开始。

【参考方案1】：

经过太多时间，我意识到关键是要使用

request.addValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")

但正是来自 Postman 的代码 sn-ps 使我能够成功构建参数数组和有效负载。我敢肯定，这是一个可以简化的工作版本。

   import Foundation
     
    guard let url = URL (string: "https://our_redcap_url.edu/api/") else return
    let token = "ABCDEFGHIJK123456789" // unique to REDCap project
    let record : = "1" // set elsewhere
    let event = ""
    let field = "file_upload_field" // name of field in REDCap
    let path = "path_of_file_to_be_uploaded"
    let repeat_instance : Int = 1
     
    let parameters = [
        [
        "key": "token",
        "value": token,
        "type": "text"
        ],
        [
        "key": "content",
        "value": "file",
        "type": "text"
        ],
        [
        "key": "action",
        "value": "import",
        "type": "text"
        ],
        [
        "key": "record",
        "value": record,
        "type": "text"
        ],
        [
        "key": "field",
        "value": field_name,
        "type": "text"
        ],
        [
        "key": "event",
        "value": event,
        "type": "text"
        ],
        [
        "key": "repeat_instance",
        "value": repeat_instance,
        "type": "text"
        ],
        [
        "key": "returnFormat",
        "value": "json",
        "type": "text"
        ],
        [
        "key": "file",
        "src": path,
        "type": "file"
        ]] as [[String : Any]]
     
    // build payload
    let boundary = "Boundary-\(UUID().uuidString)"
    var body = ""
    for param in parameters 
    if param["disabled"] == nil 
        let paramName = param["key"]!
        body += "--\(boundary)\r\n"
        body += "Content-Disposition:form-data; name=\"\(paramName)\""
        if param["contentType"] != nil 
            body += "\r\nContent-Type: \(param["contentType"] as! String)"
        
        let paramType = param["type"] as! String
        if paramType == "text" 
            let paramValue = param["value"] as! String
            body += "\r\n\r\n\(paramValue)\r\n"
         else 
            let paramSrc = param["src"] as! String
            let fileData = try? NSData(contentsOfFile:paramSrc, options:[]) as Data
            let fileContent = String(data: fileData!, encoding: .utf8)!
            body += "; filename=\"\(paramSrc)\"\r\n"
            + "Content-Type: \"content-type header\"\r\n\r\n\(fileContent)\r\n"
            
        
    
    body += "--\(boundary)--\r\n";
    let postData = body.data(using: .utf8)
     
    // create URL request and session
    var request = URLRequest(url: url,timeoutInterval: Double.infinity)
    request.addValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")
     
    request.httpMethod = "POST"
    request.httpBody = postData
     
    let task = URLSession.shared.dataTask(with: request)  data, response, error in
    guard let data = data else 
        print(String(describing: error))
        return
        
        print(String(data: data, encoding: .utf8)!)
    
    task.resume()