在Angular 4调用的CodeIgniter API中，input-> post和$ _POST是空的，在angular 4中发出post请求的正确方法是什么

Question

This is the first time I'm making a post method request from Angular to CodeIgniter rest API.

postUsertask(Userid,TaskName)
  {
    let body ={
      userid:Userid, taskname:TaskName
    };  
    console.log(body);
    return this.http.post("http://localhost/ci-abc/api/add_task",JSON.stringify(body) )
    .map(res => res.json());
  }

API method in codeigniter:

function add_task_post()
{
    $obj=json_decode(file_get_contents('php://input'));
    $taskname = $obj->taskname;
    $userid = $obj->userid;
    if (!$taskname || !$userid) {
        $this->response("Enter taskname and userid to add", 400);
    } else

        $result = $this->todo_model->add_task($taskname, $userid);

    if ($result === 0) {
        $this->response("Task could not be added. Try again.", 404);
    } else {
        $this->response("success", 200);
    }
}

Had to include to access the data

$obj=json_decode(file_get_contents('php://input'));

Because the $this->input->post and $_POST were empty and the data recieved from angular was an object so had to be accessed with -> notation. I am curious that this is not the right and ethical way to do this. Also when I didn't put JSON.stringify it gave me Cross Origin Request blocked error so that's why I put it. How should I make POST and PUT request in angular4 to rest API in CodeIgniter?

How do I get rid of CORS error which doesn't let me call the API method, if I can get rid of CORS error then I could also remove JSON.stringify which will send the data as it is and I believe the data should be accessed via input->post or $_POST.

EDIT 2: These sort of errors while making POST PUT and DELETE API call.

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost/ci-abc/api/del_task?taskid=34. (Reason: CORS preflight channel did not succeed)

Answer 1

EDIT (Perfect Solution):

Found out that the formdata object approach was deprecated so I just included a header in options and included in the API call http.post method which works fine and is much better solution.

constructor(public http:Http) { 
let headers = new Headers();
    headers.append('Content-Type', 'application/json');
    let options = new RequestOptions({ headers: headers });}

createUser(userName)
  {
    let body = { username:userName};
    return this.http.post("http://localhost/ci-abc/api/create_user",body,this.options)
    .map(res => res.json());
  }

Deprecated approach (Works but deprecated/not usual practice):

Took few hours but found the solution, I created body as a new formdata object, appended parameters to it as key and their values and it worked fine now I am retrieving through $this->input->post.

  let body = new FormData;
    body.append('userid', Userid);
    body.append('taskname', TaskName);
    console.log(body);
    return this.http.post("http://localhost/ci-abc/api/add_task",body)
    .map(res => res.json());

Using these headers in the constructor of my codeigniters API controller

header("Access-Control-Allow-Origin: *");
header('Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Access-Control-Allow-Origin');
header('Access-Control-Allow-Methods: POST, GET, OPTIONS, PUT, DELETE');

API method:

 function add_task_post()
    {
        $userid = $this->input->post('userid');
        $taskname = $this->input->post('taskname');

        if (!$taskname || !$userid) {
            $this->response("Enter taskname and userid to add", 400);
        } else
            $result = $this->todo_model->add_task($taskname, $userid);
        if ($result === 0) {
            $this->response("Task could not be added. Try again.", 404);
        } else {
            $this->response("success", 200);
        }
    }