Charles Map Local not working for JSON data?

Question

I am trying to simulate (mocking it) a server using Charles. I found out that Charles has something called "Map Local..." which allows me to reply to a client using files I have stored locally.

The files I am pointing to have been stored by right clicking in the Charles Sequence list and choosing "Save Response...".

However when testing this with my iOS app I get the following error message:

Failed to get areas: Error Domain=AFNetworkingErrorDomain Code=-1016 "Expected content type {(
    "text/json",
    "application/json",
    "text/javascript"
)}, got text/plain" 

So somehow I am not sending the response with the correct header information for Content type. Is there a way of telling Charles that the response is JSON? A possible problem is that the files stored only contains the JSON data and not any header.

Answer 1

You need to add a rewrite rule in Charles to change the Content-Type header back to application/json.

Map Local will only give a text/plain Content-Type.

To do this, go to Tools > Rewrite... > Add.

Add all the locations that you are mapping locally and then for the rules, add one that looks like the following:

I would never recommend adjusting your code just for Charles as this defeats the point of testing your web services if you can't replicate them exactly.

Answer 2

I know you are asking how to tell Charles to treat response as JSON but on the other hand there is also another solution.

I can see you are using AFNetworking. Your request is expecting to receive "text/json", "application/json", "text/javascript" but your files are text/plain so we need to change this. While building AFHTTPRequestOperation you can set acceptableContentTypes with this line of code operation.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"text/plain"];

So whole code can look like this

AFHTTPRequestOperation* operation = [manager HTTPRequestOperationWithRequest:req success:^(AFHTTPRequestOperation *operation, id responseObject) {

   //success

} failure:^(AFHTTPRequestOperation *operation, NSError *error) {

  //failure
 }];

operation.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"text/plain"];
[operation start];