带有JSON响应的Alamofire错误

Question

I have been struggling with Alamofire issue for days and I'm not sure if it's from the backend or the way I structure my code.

Here is the issue:

when I text my API with Postman I get the correct response if I hit the params button and add the parameters Notice the lower body is empty but the upper one is filled with parameters

However, when I use the lower parameters with the same info I get an error with no JSON. Also same error appears in Xcode when I try to call the API with the same link

this is Xcode Alamofire error

FAILURE: responseSerializationFailed(Alamofire.AFError.ResponseSerializationFailureReason.jsonSerializationFailed(Error Domain=NSCocoaErrorDomain Code=3840 "Invalid value around character 0." UserInfo={NSDebugDescription=Invalid value around character 0.}))

and here is Postman error

and finally this is my code to call API:

    let urlStr = "api/client/meal_add"
    let url = URL(string: urlStr)
    let para = ["meal_id": "31",
                "user_id": "2",
                "qty":"2"]

    let headers: HTTPHeaders = [
        "Auth": "Auth" // Edited for security
    ]

    Alamofire.request(url!, method: .post, parameters: para,encoding: URLEncoding.default, headers: headers).responseJSON { response in
        print(response)
        print(response.result.debugDescription)
        if let value : AnyObject = response.result.value as AnyObject {

it used to work perfectly 5 days ago but I have no idea why it stoped. Also In other View Controllers I do HTTP calls to the same API and the responses have no issues, only this one.

Answer 1

First, I want to talk about the difference between HTTP get and post request. Get request is putting parameters in url. They are appended to the url in this format

URL?key1=value1&key2=value2

The RESTful hanlder for that URL will then parse the key value pair and use them. When you click on the param button in your postman, it actuall doing this append param to url thing. However this get into problem when you have lots of param. Usually, an url will have some problem if it exceeds length 8000. So a post request is actually nesting the parameters inside the request, not on the url. So normally in a post request, you will only see the URL, not the ?key1=value1&key2=value2 part.

Back to your problem , I have no idea how your server side handles this post request with parameters in url but since an empty post request with param in url works, in your swift code, you can simply append the param in your url and do a post request with no parameters.

let urlStr = "api/client/meal_add?meal_id=31&user_id=2&qty=2"
let url = URL(string: urlStr)

Alamofire.request(url!, method: .post, parameters: [],encoding: URLEncoding.default, headers: headers).responseJSON { response in

Moving forward, I strongly recommand you to have a look at your server side to make sure your post request is written in the correct way