ruby on rails - 406 when uploading image from RestKit to RoR backend -

i'm having serious problem , searched many hours without finding solution.

i have backend server using ruby of rails , paperclip image saving.

the image upload works fine browser, posting /pictures

but when try upload /pictures.json using multipart request restkit (ios), 406.

when image (picture object) created server-side, reward (reward object) associated it. reward object i'm expecting json response.

here objective-c code:

nsmutableurlrequest* uploadrequest = [self.objectmanager multipartformrequestwithobject:nil method:rkrequestmethodpost  path:@"/pictures.json"  parameters:nil  constructingbodywithblock:^(id<afmultipartformdata> formdata) {         [formdata           appendpartwithfiledata:uiimagepngrepresentation(socialreward.image)          name:@"picture[pict]"           filename:imagename           mimetype:@"image/png"];  }]; 

here controller:

@picture = picture.create( params[:picture] )  respond_to |format|     format.html {         redirect_to @picture.reward     }     format.js {         render :json => @picture.reward.to_json(:include => :picture)     } end 

the csrf check disabled.

when comparing requests browser , ios using wireshark, extremely similar.

thanks in advance help.

the problem ror, in respond_to should using format.json, not format.js.