Setting dynamic scope variables in AngularJs - sco

Question

I have a string I have gotten from a routeParam or a directive attribute or whatever, and I want to create a variable on the scope based on this. So:

$scope.<the_string> = "something".

However, if the string contains one or more dots I want to split it and actually "drill down" into the scope. So 'foo.bar' should become $scope.foo.bar. This means that the simple version won't work!

// This will not work as assigning variables like this will not "drill down"
// It will assign to a variables named the exact string, dots and all.
var the_string = 'life.meaning';
$scope[the_string] = 42;
console.log($scope.life.meaning);  // <-- Nope! This is undefined.
console.log($scope['life.meaning']);  // <-- It is in here instead!

When reading a variable based on a string you can get this behavior by doing $scope.$eval(the_string), but how to do it when assigning a value?

Answer 1

Using Erik's answer, as a starting point. I found a simpler solution that worked for me.

In my ng-click function I have:

var the_string = 'lifeMeaning';
if ($scope[the_string] === undefined) {
   //Valid in my application for first usage
   $scope[the_string] = true;
} else {
   $scope[the_string] = !$scope[the_string];
}
//$scope.$apply

I've tested it with and without $scope.$apply. Works correctly without it!

Answer 2

The solution I have found is to use $parse.

"Converts Angular expression into a function."

If anyone has a better one please add a new answer to the question!

Here is the example:

var the_string = 'life.meaning';

// Get the model
var model = $parse(the_string);

// Assigns a value to it
model.assign($scope, 42);

// Apply it to the scope
// $scope.$apply(); <- According to comments, this is no longer needed

console.log($scope.life.meaning);  // logs 42

Answer 3

Please keep in mind: this is just a JavaScript thing and has nothing to do with Angular JS. So don't be confused about the magical '$' sign ;)

The main problem is that this is an hierarchical structure.

console.log($scope.life.meaning);  // <-- Nope! This is undefined.
=> a.b.c

This is undefined because "$scope.life" is not existing but the term above want to solve "meaning".

A solution should be

var the_string = 'lifeMeaning';
$scope[the_string] = 42;
console.log($scope.lifeMeaning);
console.log($scope['lifeMeaning']);

or with a little more efford.

var the_string_level_one = 'life';
var the_string_level_two = the_string_level_one + '.meaning';
$scope[the_string_level_two ] = 42;
console.log($scope.life.meaning);
console.log($scope['the_string_level_two ']);

Since you can access a structural objecte with

var a = {};
a.b = "ab";
console.log(a.b === a['b']);

There are several good tutorials about this which guide you well through the fun with JavaScript.

There is something about the

$scope.$apply();
do...somthing...bla...bla

Go and search the web for 'angular $apply' and you will find information about the $apply function. And you should use is wisely more this way (if you are not alreay with a $apply phase).

$scope.$apply(function (){
    do...somthing...bla...bla
})

Answer 4

If you are using Lodash library below is the way to set a dynamic variable in the angular scope.

To set the value in the angular scope.

_.set($scope, the_string, 'life.meaning')

To get the value from the angular scope.

_.get($scope, 'life.meaning')

Answer 5

Create Dynamic angular variables from results

angular.forEach(results, function (value, key) {          
  if (key != null) {                       
    $parse(key).assign($scope, value);                                
  }          
});

ps. don't forget to pass in the $parse attribute into your controller's function

Answer 6

Just to add into alread given answers, the following worked for me:

HTML:

<div id="div{{$index+1}}" data-ng-show="val{{$index}}">

Where $index is the loop index.

Javascript (where value is the passed parameter to the function and it will be the value of $index, current loop index):

var variable = "val"+value;
if ($scope[variable] === undefined)
{
    $scope[variable] = true;
}else {
    $scope[variable] = !$scope[variable];
}