This is an interesting question, and I started thinking about how I would implement something like this.
I came up with this (fiddle);
Basically, instead of trying to call a directive from a controller, I created a module to house all the popdown logic:
var PopdownModule = angular.module('Popdown', []);
I put two things in the module, a factory for the API which can be injected anywhere, and the directive for defining the behavior of the actual popdown element:
The factory just defines a couple of functions success and error and keeps track of a couple of variables:
PopdownModule.factory('PopdownAPI', function() {
return {
status: null,
message: null,
success: function(msg) {
this.status = 'success';
this.message = msg;
},
error: function(msg) {
this.status = 'error';
this.message = msg;
},
clear: function() {
this.status = null;
this.message = null;
}
}
});
The directive gets the API injected into its controller, and watches the api for changes (I'm using bootstrap css for convenience):
PopdownModule.directive('popdown', function() {
return {
restrict: 'E',
scope: {},
replace: true,
controller: function($scope, PopdownAPI) {
$scope.show = false;
$scope.api = PopdownAPI;
$scope.$watch('api.status', toggledisplay)
$scope.$watch('api.message', toggledisplay)
$scope.hide = function() {
$scope.show = false;
$scope.api.clear();
};
function toggledisplay() {
$scope.show = !!($scope.api.status && $scope.api.message);
}
},
template: '<div class="alert alert-{{api.status}}" ng-show="show">' +
' <button type="button" class="close" ng-click="hide()">×</button>' +
' {{api.message}}' +
'</div>'
}
})
Then I define an app module that depends on Popdown:
var app = angular.module('app', ['Popdown']);
app.controller('main', function($scope, PopdownAPI) {
$scope.success = function(msg) { PopdownAPI.success(msg); }
$scope.error = function(msg) { PopdownAPI.error(msg); }
});
And the HTML looks like:
<html ng-app="app">
<body ng-controller="main">
<popdown></popdown>
<a class="btn" ng-click="success('I am a success!')">Succeed</a>
<a class="btn" ng-click="error('Alas, I am a failure!')">Fail</a>
</body>
</html>
I'm not sure if it's completely ideal, but it seemed like a reasonable way to set up communication with a global-ish popdown directive.
Again, for reference, the fiddle.