javascript - 当变量是函数参数时，应用程序抛出变量引用错误

Question

我正在 MEAN 堆栈中构建后端，但遇到了一个问题。该应用程序的要点很简单:上传文件并将其保存到服务器。然而，我偶然发现了一个问题。当我点击“提交”按钮时，代码中断并在控制台中抛出以下错误:

<h1>photo is not defined</h1>
<h2></h2>
<pre>ReferenceError: photo is not defined
    at \routes\index.js:32:3
    at Layer.handle [as handle_request] (\node_modules\express\lib\router\layer.js:95:5)
    at next (\node_modules\express\lib\router\route.js:131:13)
    at \node_modules\express-jwt\lib\index.js:112:9
    at \node_modules\jsonwebtoken\index.js:98:18
    at process._tickCallback (node.js:355:11)</pre>

以下是我的 angularApp.js 文件:

app.factory('photos', ['$http', 'auth', function($http, auth){
  var o = { photos: [] };
  o.create = function(photo) {
    return $http.post('/photos', photo, {
      headers: {Authorization: 'Bearer '+auth.getToken()}
    }).success(function(data){
      o.photos.push(data);
    }).error(function(a) {
      console.log(a);
    });
  };
  return o;
}]);
app.controller('MainCtrl', [
'$scope',
'photos',
'auth',
function($scope, photos, auth){
  $scope.photos = photos.photos;
  $scope.addPhoto = function(){
    photos.create();
  };
}]);

index.ejs代码:

<form ng-submit="addPhoto()">
  <label for="exampleInputFile">File input</label>
  <input type="file" id="exampleInputFile">
  <button type="submit" class="btn btn-primary">Post</button>
</form>

这里是routes\index.js

router.post('/photos', auth, function(req, res, next) {
  var dirname = require('path').dirname(__dirname);
  var filename = req.files.file.name;
  var path = req.files.file.path;
  var type = req.files.file.mimetype;

  var read_stream = fs.createReadStream(dirname + '/' + path);
  var conn = req.conn;
  var Grid = require('gridfs-stream');
  Grid.mongo = mongoose.mongo;
  var gfs = Grid(conn.db);

  var writestream = gfs.createWriteStream({
    filename: filename
  });
  read_stream.pipe(writestream);

  photo.save(function(err, photo){
    if(err){ return next(err); }

    res.json(photo);
  });
});

据我了解，代码会中断运行 o.create 函数，但我不确定为什么它无法找到 photo，因为这是其中之一函数参数。

Answer 1

使用您为 routes/index.js 发布的代码，该行

photo.save(...

正在使用之前未在当前范围或任何父范围中定义的变量photo。