Creating an Angular directive that shares a single scope while displaying multiple behaviors

Question

Creating an Angular directive that shares a single scope while displaying multiple behaviors

I am facing a specific scenario with my directive where the refresh scope needs to be either an object or a function. How can I properly assign this to my directive?

1. Initial scenario

<!--HTML-->
<directive 
  refresh="vm.refresh">
</directive>

//JS
scope:{refresh:"="}

2. Alternative scenario

<directive 
  refresh="vm.refresh(search)">
</directive>

//JS
scope:{refresh:"&"}

3. My current situation

<directive 
  refresh="vm.refresh or vm.refresh(search)">
</directive>

//JS - Unsure what to do, need assistance
scope:{refresh:"=&needHelp"}

However, I require both of these functionalities in my directive. So how can I segregate and differentiate between an object and a function within the link function of the directive?

javascript angularjs angularjs-directive angularjs-scope

Answer 1

Answer №1

This situation can be quite complex. If you encounter this scenario, it is important to examine the type of expression stored in the refresh attribute. To achieve this, manual parsing of the attribute value using the $parse service is necessary.

.directive('customDirective', function($parse) {
  return {
    scope: {
      // other bindings go here - isolated scope
    },
    template: '<button ng-click="runTest()">Run Test</button>',
    link: function(scope, element, attrs) {

      // parse the attribute expression (not yet evaluated)
      var callback = $parse(attrs.refresh);

      scope.query = 'Sample query';

      scope.runTest = function() {

        // when a refresh is needed: evaluate the refresh callback
        var evaluated = callback(scope.$parent, {query: scope.query});
        if (typeof evaluated == 'function') {
          evaluated(scope.query);
        }
      };
    }
  };
})

If the situation involves

refresh="vm.triggerRefresh(query)"

, using

callback(scope.$parent, {query: scope.query})

will work effectively. However, if the evaluation results in a function, indicating a case like refresh="vm.triggerRefresh", the code enters the if block and executes the function with the required parameter.

Check out the live demo: http://example.com

Answer 2

This situation can be quite complex. If you encounter this scenario, it is important to examine the type of expression stored in the refresh attribute. To achieve this, manual parsing of the attribute value using the $parse service is necessary.

.directive('customDirective', function($parse) {
  return {
    scope: {
      // other bindings go here - isolated scope
    },
    template: '<button ng-click="runTest()">Run Test</button>',
    link: function(scope, element, attrs) {

      // parse the attribute expression (not yet evaluated)
      var callback = $parse(attrs.refresh);

      scope.query = 'Sample query';

      scope.runTest = function() {

        // when a refresh is needed: evaluate the refresh callback
        var evaluated = callback(scope.$parent, {query: scope.query});
        if (typeof evaluated == 'function') {
          evaluated(scope.query);
        }
      };
    }
  };
})

If the situation involves

refresh="vm.triggerRefresh(query)"

, using

callback(scope.$parent, {query: scope.query})

will work effectively. However, if the evaluation results in a function, indicating a case like refresh="vm.triggerRefresh", the code enters the if block and executes the function with the required parameter.

Check out the live demo: http://example.com

Answer 3

Answer №2

To assess the scope variable, you can utilize expression binding and inspect the $attrs object to identify its type. Take a look at the example below...

JSFiddle: http://jsfiddle.net/g4bft6rL/

JavaScript

var myApp = angular.module('myApp',[]);

myApp.directive('myDirective', function() {
    return {
        restrict: 'E',
        scope: {
            refresh: '&'
        },
        controller: function ($scope, $attrs) {
            $scope.$watch('refresh', function (prev, curr) {
                $scope.text = 'refresh is a ' + getExpressionType($attrs.refresh);
                $scope.value = $scope.refresh();
            });
        },
        template: "result: {{ text }} = {{ value }}"
    };

    function getExpressionType (expression) {
        // simple logic for illustration
        return expression.slice(-1)[0] === ')' ? 'function' : 'object';
    }
});

function MyCtrl($scope) {
    $scope.refresh = { a: 1 };
    $scope.refreshFn = function what (arg) {
        return {
            value: arg
        };
    };
    $scope.param = 123;
}

HTML

<div ng-controller="MyCtrl">
  <my-directive refresh="refreshFn(param)"></my-directive>
  <my-directive refresh="refresh"></my-directive>
</div>

Answer 4

To assess the scope variable, you can utilize expression binding and inspect the $attrs object to identify its type. Take a look at the example below...

JSFiddle: http://jsfiddle.net/g4bft6rL/

JavaScript

var myApp = angular.module('myApp',[]);

myApp.directive('myDirective', function() {
    return {
        restrict: 'E',
        scope: {
            refresh: '&'
        },
        controller: function ($scope, $attrs) {
            $scope.$watch('refresh', function (prev, curr) {
                $scope.text = 'refresh is a ' + getExpressionType($attrs.refresh);
                $scope.value = $scope.refresh();
            });
        },
        template: "result: {{ text }} = {{ value }}"
    };

    function getExpressionType (expression) {
        // simple logic for illustration
        return expression.slice(-1)[0] === ')' ? 'function' : 'object';
    }
});

function MyCtrl($scope) {
    $scope.refresh = { a: 1 };
    $scope.refreshFn = function what (arg) {
        return {
            value: arg
        };
    };
    $scope.param = 123;
}

HTML

<div ng-controller="MyCtrl">
  <my-directive refresh="refreshFn(param)"></my-directive>
  <my-directive refresh="refresh"></my-directive>
</div>

Answer 5

Answer №3

If you want to experiment with an approach similar to the one below, keep in mind that I have not actually tested this code, but it should give you a general idea.

<directive update="updateFromExternal" filter="externalFilterString">" </directive>

The value of updateFromExternal can either be a string or a function. Within the directive's controller:

 return {
        restrict: 'EA',
        scope: {
            name: '=',
          update:'=',
          filter:'@'
        }, 
        controller:function($scope){
            console.log($scope);
          if(angular.isFunction($scope.show)){
            alert('is Function');
            $scope.update($scope.filter || '');
          }
          else{
            alert($scope.update + 'as string');
          }
        },
        template: '<div>Some template</div>'
    };

Answer 6

If you want to experiment with an approach similar to the one below, keep in mind that I have not actually tested this code, but it should give you a general idea.

<directive update="updateFromExternal" filter="externalFilterString">" </directive>

The value of updateFromExternal can either be a string or a function. Within the directive's controller:

 return {
        restrict: 'EA',
        scope: {
            name: '=',
          update:'=',
          filter:'@'
        }, 
        controller:function($scope){
            console.log($scope);
          if(angular.isFunction($scope.show)){
            alert('is Function');
            $scope.update($scope.filter || '');
          }
          else{
            alert($scope.update + 'as string');
          }
        },
        template: '<div>Some template</div>'
    };

Creating an Angular directive that shares a single scope while displaying multiple behaviors

1. Initial scenario

2. Alternative scenario

3. My current situation

Answer №1

Answer №2

Answer №3

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