CODEWITHSUNDEEP
javascriptdependency-injection
razorbeard
razorbeard

Reputation: 2944

How to access unique injected dependency values outside of the function that required them in JavaScript

Here's the scenario:

I want to inject dependencies into a callback function that is executed by a third party library. This is simple enough, as I can wrap the callback in a closure - but the issue stems from the fact that I also want to be able to use any modified properties of that dependency outside of the function that requires it.

I'll give an example. First off, the example use case:

Dynamically constructing app.[verb] calls in Express.js - the [verb] property is manually set by the user like so:

ItemController.js:

exports.create = function(req, res, $scope) {
  $scope.method = 'post';
  $scope.path = 'item/create';

  res.send('Creates a new item');
};

Say I have an injector object, with a process method that returns the function's required dependencies as an array:

injector.process = function(fn) {
  // RegExp constant matching code comments
  var STRIP_COMMENTS = /((\/\/.*$)|(\/\*[\s\S]*?\*\/))/mg,
  // convert the function to a string and strip any comments out
  fnString = fn.toString().replace(STRIP_COMMENTS, ''),
  // find the opening and closing parentheses of the function
  openParenIndex = fnString.indexOf('('),
  closeParenIndex = fnString.indexOf(')'),
  // slice the content between the parens to their own string
  contents = fnString.slice(openParenIndex + 1, closeParenIndex),
  // convert contents to an array, split by comma or whitespace
  args = contents.match(/([^\s,]+)/g);

  // if the function expects no arguments, we need to specify an empty array
  if (args === null) { args = []; }

  // return an array of the expected arguments
  return args;
}

How would I ensure that each method of itemController.js gets it's own unique instance of $scope, and that the app[verb] call is dynamically constructed into something like this?:

app.post('/item/create', function(req, res) {
  res.send('Creates a new item');
});

Upvotes: 1

Views: 169

Answers (1)

clu3Less
clu3Less

Reputation: 1892

Try creating a the functions in an object like this,

var app = {
    post : function() {
        alert('posted');
    },
    get : function() {
        alert('got');       
    }
}

Then you could call a function like this. (Lets say verb has function name)

app[verb](); //if verb = "post" it will alert "posted"

I hope this is what you wanted.

Upvotes: 1

Related Questions