angular $emit发送 后退时$on多次接收

angular 并列作用域，作用域不存在上下级关系，$scope.$emit发送时 后退时$rootScope.$on会出现接收多个消息的情况

$rootScope.$on(‘saveDraft‘, function() {
            $scope.saveDraft();
        });
        $rootScope.$on(‘previewPosition‘, function() {
            $scope.previewPosition();
        });
        $rootScope.$on(‘publishJob‘, function() {
            $scope.publishJob();
        });

    $scope.previewPosition = function() {
        $scope.$emit(‘previewPosition‘);
    };
    $scope.saveDraft = function() {
        $scope.$emit(‘saveDraft‘);
    };
    $scope.publishJob = function() {
        $scope.$emit(‘publishJob‘);
    };

正确方式

$scope.$on(‘saveDraft‘, function() {
            $scope.saveDraft();
        });
        $scope.$on(‘previewPosition‘, function() {
            $scope.previewPosition();
        });
        $scope.$on(‘publishJob‘, function() {
            $scope.publishJob();
        });

    $scope.previewPosition = function() {
        $rootScope.$broadcast(‘previewPosition‘);
    };
    $scope.saveDraft = function() {
        $rootScope.$broadcast(‘saveDraft‘);
    };
    $scope.publishJob = function() {
        $rootScope.$broadcast(‘publishJob‘);
    };