在Eloquent模型中更新事件并不火

Question

我已经创建了一个更新EMI的贷款金额的功能。在此功能中，贷款金额在创建和删除EMI期间成功更新，但不会更新EMI。

EMI模型

    <?php namespace App;

       use Illuminate\Database\Eloquent\Model;

      class Emi extends Model {

    //
    protected  $table = 'emi';

    protected $fillable = ['loan_id', 'amount', 'description', 'date'];



    public function loan()
    {
        return $this->belongsTo('App\Loan');
    }

    public static function boot()
    {
        parent::boot();

        static::deleted(function($emi){
            $loan=\App\Loan::find($emi->loan_id);
            $loan->paid -= $emi->amount;
            $loan->balance += $emi->amount;
            $loan->save();
        });

        static::saved(function($emi){
            $loan=\App\Loan::find($emi->loan_id);

            $loan->paid += $emi->amount;
            $loan->balance -= $emi->amount;
            $loan->save();
        });

        static::updating(function($emi){

            $loan=\App\Loan::find($emi->loan_id);

            $loan->paid -= $emi->amount;
            $loan->balance += $emi->amount;
            return $loan->save();
        });


    }
  }

Emi Controller

      <?php

       namespace App\Http\Controllers\Auth;

       use Illuminate\Http\Request as Request;

        use App\Http\Requests;
       use App\Http\Controllers\Controller;
      use Validator;
      use Response;

     use App\Account;
     use App\Loan;
     use App\Emi;

     class EmiController extends Controller
     { 

          /**
 * New data validation
 * @param array $data
 * @return \Illuminate\Validation\Validator
 */
protected function validator(array $data)
{
    return Validator::make($data,[
        'loan_id'     =>'required|numeric',
        'amount'      =>'required|numeric|max:999999999999999999',
        'description' =>'required|alpha_text|max:250',
        'date'        =>'required|date',
    ]);
}

/**
 * Display a listing of the Emi resource.
 * If loan id is not given, then returns all Emi resource.
 * @param Request $request
 * @return \Illuminate\Database\Eloquent\Collection|static[]
 */

public function index(Request $request)
{
    $loan_id = $request->get('loan_id');

    //All Emi recipets for loan
    if($loan_id !==NULL)
        return Loan::find($loan_id)->emi;
    else
        return Emi::with('loan')->get();
}

/**
 * Show the form for creating a new resource.
 *
 * @return Response
 */
public function create()
{
    //
}

/**
 * Store a newly created resource in storage.
 * @param Request $request
 * @return Response
 */
public function store(Request $request)
{

    $validator = $this->validator($request->all());

    if($validator->fails()){
        return Response::json( $validator->errors()
            ,400);
    }

    $emi = new Emi($request->all());

    //TODO Loan balance update

    if($emi->save()){
        return $emi;
    }

    return Response::json( ['error' => 'Server is down']
        ,500);
}

/**
 * Display the specified resource.
 *
 * @param  int  $id
 * @return Response
 */
public function show($id)
{
    //
    return Emi::find($id);
}

/**
 * Show the form for editing the specified resource.
 *
 * @param  int  $id
 * @return Response
 */
public function edit($id)
{
    //
}

/**
 * Update the specified resource in storage.
 * @param $id
 * @param Request $request
 * @return \Illuminate\Http\JsonResponse
 */
public function update($id,Request $request)
{
    $validator = $this->validator($request->all());

    if($validator->fails()){
        return Response::json($validator->errors()
            ,400);
    }

    //TODO Update loan  balance
    $emi = Emi::find($id);
    //$emi->fill($request->all());

    if($emi->update($request->all())){
        return $emi;
    }

    return Response::json( ['error' => 'Server is down']
        ,500);
}


/**
 * Remove the specified resource from storage.
 *
 * @param  int  $id
 * @return Response
 */
public function destroy($id)
{
    //TODO delete emi balance change in loan
    if(Emi::destroy($id))
        return Response::json(array('msg'=>'Emi deleted'));
    else
        return Response::json(array('error'=>'Records not found'),400);
   }
 }