Angularjs using service to pass a parameter to a function - angularjs

Question

I'm fetching a Json with a factory "chapters", so I get the value of the property "json_file" which is another json file that I need to fetch dynamically with the factory "contents". I just need to pass the parameter "json_file" to the second factory, but I get an undefined value.
Maybe I need a service?
This is the first json file:
structure.js
[
{
"title": "Introduction",
"pages": [
{
"title": "Buongiorno",
"type" : "standard",
"json_file" : "cover_1"
},
{
"title": "Introduction",
"type" : "standard",
"json_file" : "cover_1"
}
]
},
{
"title": "Storytelling",
"pages": [
{
"title": "Italian Design & Swiss Watchmaking Expertise",
"type" : "standard",
"json_file" : "cover_1"
},
{
"title": "Interaction",
"type" : "standard",
"json_file" : "cover_1"
}
]
}
]
This is the controller.js
var bControllers = angular.module('bControllers',[]);
bControllers.controller('structureCtrl', function ($scope, $routeParams,chapters,contents){
$scope.indexChapter = 0;
$scope.indexPage = 0;
chapters.list(function(chapters) {
$scope.chapters = chapters;
$scope.pages = [];
$scope.json_file = [];
angular.forEach($scope.chapters, function(chapters,index){
angular.forEach(chapters.pages, function(page,index2){
$scope.pages.push(page);
$scope.json_file.push(page.json_file);
})
});
$scope.currentJson = $scope.chapters[$scope.indexChapter].pages[$scope.indexPage].json_file;
console.log('json-file:'+$scope.currentJson);
return $scope.currentJson;
});
contents.find($scope.currentJson, function(content) {
$scope.content = content;
});
});
And this is the factory.js
var bFactory = angular.module('bFactory',[]);
bFactory.factory('chapters', function($http){
return {
list: function (callback){
$http({
method: 'GET',
url: 'json/structure.json',
cache: true
}).success(callback);
}
}
});
bFactory.factory('contents', function($http){
return{
find:function(json_file, callback){
$http({
method: 'GET',
url: 'json/'+json_file+'.json',
cache: true
}).success(callback);
}
}
})