UnityWebRequest.downloadHandler.text is empty, eventhough the POST method returns a response

Question

• I am making a POST api call to my server using UnityWebRequest (Unity version that i have is 2017.4.0f1)
• I am sending some data elements in the request body to the server, which inserts into my DB and returns a response body, which is a json string
• I am using UnityWebRequest.downloadhandler.text to read the response message, but it is empty, eventhough the data elements are getting inserted into my DB. request.downloadHandler.data.Length also gives me 0
• Making the same call through Postman returns me the appropriate response (so does using HTTPWebRequest and reading the response via a stream reader)

This is the code snippet that i have for it:

UnityWebRequest request=new UnityWebRequest(endpoint,"POST");
request.SetRequestHeader("Content-Type","application/json");
request.SetRequestHeader("host",host);
request.SetRequestHeader("X-Amz-Date",dateTime);
request.SetRequestHeader("Authorization",authorizationHeader);

request.uploadHandler=(UploadHandler)new 
UploadHandlerRaw(Encoding.UTF8.GetBytes(requestParameter));

request.chunkedTransfer=false;
request.downloadHandler=new DownloadHandlerBuffer();
request.SendWebRequest();
print(request.downloadHandler.text);

Please advise as to what i am doing wrong here.....

Answer 1

As frankhermes says you need wait for the results to be downloaded before you do anything

yield return request.SendWebRequest();

But the above line alone didn't work for me.

public IEnumerator LoadData()
{
    // ......
    // all your code goes here, up to the SendWebRequest line

    var asyncOperation = request.SendWebRequest();

    while (!asyncOperation.isDone)
    {
     // wherever you want to show the progress:

        float progress = request.downloadProgress;
        Debug.Log("Loading " + progress);
        yield return null;
    }

    while (!request.isDone)
       yield return null; // this worked for me

    // after this, you will have a result
    print(request.downloadHandler.text);
}

Answer 2

You need to wait for the results to be downloaded before you can do anything with it. Webrequests are asynchronous!

Typically, you would use a Coroutine to do this, like

public IEnumerator LoadData()
{
    // ......
    // all your code goes here, up to the SendWebRequest line

    // then you yield to wait for the request to return
    yield return request.SendWebRequest();

    // after this, you will have a result
    print(request.downloadHandler.text);
}

Start this coroutine like this:

StartCoroutine(LoadData());

More examples in the answer to this question: Sending http requests in C# with Unity