CakePHP REST API multipart file with json in one request - php

Question

I have problem with CakePHP request handling…
I wrote an REST API to post some data and files and use multipart/form-data when want to send data.
When sending POST request(Multipart/form-data and send data as json),need to convert $this->request->data from json string to Array:
I wrote below code to convert json data to Array in beforeFilter of my controller:
$parser = function ($data) {
return json_decode($this->request->data,true);
};
$this->RequestHandler->addInputType("file", array($parser));
This is work fine and when I get $this->request->data in controller, JSON data successfully converted to Array,
But If I send request with file, this error happen:
Argument 1 passed to Hash::insert() must be of the type array, string given, called in /home/besepari/public_html/android/lib/Cake/Network/CakeRequest.php on line 401 and defined …
After research on codes,I find the problem but I couldn’t find a way to fix that.I think the error was generated because conversion of $data from json to array(in beforeFilter) happens after of this event so json string passed to Hash::insert() and make the error.need a way to convert json string of $data before of Hash::insert() execution.
Finally I found a way to fix this,but my approach maybe isn't good solution.Because I changed the core of cakephp class.
For fix the bug, replace cakeRequest.php _processFileData() method with this:
protected function _processFileData($path, $data, $field) {
//Fix bug of hash::insert string given(because in json multipart,$this->data is string and made a bug)
//check if string is json,parse it and save it to $this->data
if(!is_array($this->data)){
$parsedData=json_decode($this->data,true);
if (json_last_error() === JSON_ERROR_NONE) {
// JSON is valid
$this->data=$parsedData;
}
}
foreach ($data as $key => $fields) {
$newPath = $key;
if (strlen($path) > 0) {
$newPath = $path . '.' . $key;
}
if (is_array($fields)) {
$this->_processFileData($newPath, $fields, $field);
} else {
$newPath .= '.' . $field;
$this->data = Hash::insert($this->data, $newPath, $fields);
}
}
}
Thanks,
I use cakephp 2
sorry for bad English.