Having difficulty retrieving the scope variable within the $watch function

While working on my AngularJS filter, I encountered an issue with accessing the scope object in a specific area. After making some code changes, the problem was resolved, but I am unsure of what caused it. It seems like my understanding of scope and directives might be incorrect.

Within a directive, I attempted to access an array and use it in a scope watch function, but it wasn't functioning as expected.

The code that worked:

var currentScope = scope.mainList[scope.$index].list;
// This will trigger whenever any scope variable changes
scope.$watch(function() {
  var hasTrue, hasFalse;
  angular.forEach(currentScope, function(v) {
    if (v["isSelected"]) {
      hasTrue = true;
    } else {
      hasFalse = true;
    }
  });
  if (hasTrue && hasFalse) {
    iElement.attr('checked', false);
   // iElement.addClass('greyed');
  } else {
    iElement.attr('checked', hasTrue);
   // iElement.removeClass('greyed');
  }
}, true);

The code that didn't work:

var currentScope = scope.mainList[scope.$index].list;
// This will only trigger when the corresponding scope variable changes
scope.$watch(currentScope, function(newVal) {
  var hasTrue, hasFalse;
  angular.forEach(newVal, function(v) {
    if (v["isSelected"]) {
      hasTrue = true;
    } else {
      hasFalse = true;
    }
  });
  if (hasTrue && hasFalse) {
    iElement.attr('checked', false);
   // iElement.addClass('greyed');
  } else {
    iElement.attr('checked', hasTrue);
   // iElement.removeClass('greyed');
  }
}, true);

I require the second code snippet, but after altering variables, it is not registering the changes and appears as undefined.

Please refer to the following link for more insights: Code

Answer №1

Expanding on the comment by @tobi, I would like to share a suggested approach for writing your watch function:

var currentScope = scope.mainList[scope.$index].list;
scope.$watch(function () { return currentScope; }, function (newVal) {
  var hasTrue = false, hasFalse = false;
  angular.forEach(newVal, function (v) {
    if (v["isSelected"]) {
      hasTrue = true;
    } else {
      hasFalse = true;
    }
  });
  if (hasTrue && hasFalse) {
    iElement.attr('checked', false);
   // iElement.addClass('greyed');
  } else {
    iElement.attr('checked', hasTrue);
   // iElement.removeClass('greyed');
  }
});

Alternatively, you could also write it like this:

scope.currentScope = scope.mainList[scope.$index].list;
scope.$watch('currentScope', function (newVal) {
  var hasTrue = false, hasFalse = false;
  angular.forEach(newVal, function (v) {
    if (v["isSelected"]) {
      hasTrue = true;
    } else {
      hasFalse = true;
    }
  });
  if (hasTrue && hasFalse) {
    iElement.attr('checked', false);
   // iElement.addClass('greyed');
  } else {
    iElement.attr('checked', hasTrue);
   // iElement.removeClass('greyed');
  }
});

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