CRUD model with nested model

I'm currently building a CRUD for my app admin. I'm using AngularJS with a RESTfull API. I can sucessfully save a simple model. But when I have Many-to-many relationship I'm a bit lost when it comes to set the update/create form. I have build a Plunker to showcase the attempt: http://plnkr.co/edit/okeNuYBJ5f33gtu6WBoW

EDIT:

Now using checkbox instead of dropdown as Jason suggested:
http://plnkr.co/edit/okeNuYBJ5f33gtu6WBoW
But my problem #3 is still not fixed. How can I save those updated/created relationships?

So I have that User model that has a Many-to-Many relationship with a Role model. I am able to display/list the model with its relationship. When editing a User I load all Roles so UI can build a dropdown of Roles to be selected. I want to have as many dropdown as there is a relationship. So I nested my dropdown in a repeat="userRole in user.role".

When doing an update

First problem: if a user has many roles it display as many dropdown as there is but the selected role for each one is the first relationship.

Second problem: I have a button to add a new role to the loaded user. I'm not sure I made it right since when saving I don't see any trace of the new attached role.

Third problem: when saving I loose the connection from my roles. Only the user is updated. My form is wrong but where is the problem?

When doing a create

I'm not able to link a role to a new user. When I clic on "Add a new role" the first role of the Roles list is pushed to the user. But user is not yet created. So I get an error. Once again my form is wrong. What is the error? When saving a new user how can I also POST the related roles?

Here is some code in case the Plunker doesn't work:

index.html

<!DOCTYPE html>
<html lang="en" xmlns:ng="http://angularjs.org" data-ng-app="CRUD">
    <head>
         <meta charset="UTF-8" />
         <link rel="stylesheet" href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.1.1/css/bootstrap.no-icons.min.css" />
         <link rel="stylesheet" href="http://netdna.bootstrapcdn.com/font-awesome/2.0/css/font-awesome.css" />
    </head>
    <body>
        <div class="span6" ng-view></div>
        <script src="http://code.angularjs.org/1.1.0/angular.min.js"></script>
        <script src="http://code.angularjs.org/1.1.0/angular-resource.js"></script>
        <script src="/crud.js"></script>
    </body>
</html>

crud.js My AngularJS specific code

var users = [
    {'id':1,'name':'User 1', 'role':[{'id':1,'name':'Role 1'},{'id':2,'name':'Role 2'}]},
    {'id':2,'name':'User 2', 'role':[{'id':2,'name':'Role 2'}]},
    {'id':3,'name':'User 3', 'role':[{'id':1,'name':'Role 1'}]},
    {'id':4,'name':'User 4', 'role':[{'id':3,'name':'Role 3'},{'id':2,'name':'Role 2'}]}
];
var roles = [
    {'id':1,'name':'Role 1'},
    {'id':2,'name':'Role 2'},
    {'id':3,'name':'Role 3'}
];
/* Route */
angular.module('CRUD', []).
    config(['$routeProvider', function ($routeProvider) {
        $routeProvider.
            when('/create', {templateUrl: 'create.html',controller: ctrlCreate}).
            when('/read', {templateUrl: 'read.html',controller: ctrlRead}).
            when('/update/:userId', {templateUrl: 'update.html', controller: ctrlUpdate}).
            otherwise({redirectTo: 'read'});
    }]);


/* Controller CREATE */
function ctrlCreate($scope, $http, $location) {

    // dirty hack to find the user to update (in real life it would be loaded via REST)
    $scope.user = null;
    $scope.roles = roles;

    $scope.save = function() {
        // dirty hack to change the user (in real life it would be trigger a POST request to the server with updated model)
        users.push($scope.user);

        //if a scope digestion is already going on then it will get picked up and you won't have to call the $scope.$apply() method
        if(!$scope.$$phase) { //this is used to prevent an overlap of scope digestion
            $scope.$apply(); //this will kickstart angular to recognize the change
        }
        $location.path('/');
    };

    $scope.addRole = function(){
        $scope.user.role.push(roles[0]);
    };
}
ctrlCreate.$inject = ['$scope','$http','$location'];

/* Controller READ */
function ctrlRead($scope, $http, $location) {
    // dirty hack to find the user to update (in real life it would be loaded via REST)
    $scope.users = users;
    $scope.roles = roles;
}
ctrlRead.$inject = ['$scope','$http','$location'];

/* Controller UPDATE */
function ctrlUpdate($scope, $http, $location, $routeParams) {
    $scope.user = null;
    $scope.roles = roles;
    var id=$routeParams.userId;
    // dirty hack to find the user to update (in real life it would be loaded via REST)
    for (var i = 0; i < users.length; i++) {
        if (users[i].id==id) {
            $scope.user=users[i];
            console.debug($scope.user.role);
        }
    }

    $scope.save = function() {
        // dirty hack to change the user (in real life it would be trigger a PUT request to the server with updated model)
        for (var i = 0; i < users.length; i++) {
            if (users[i].id==id) {
                users[i] = $scope.user;
            }
        }
        //if a scope digestion is already going on then it will get picked up and you won't have to call the $scope.$apply() method
        if(!$scope.$$phase) { //this is used to prevent an overlap of scope digestion
            $scope.$apply(); //this will kickstart angular to recognize the change
        }
        $location.path('/');
    };

    $scope.addRole = function(){
        $scope.user.role.push(roles);
        console.debug($scope.user.role);
    };
}
ctrlUpdate.$inject = ['$scope','$http','$location', '$routeParams'];

Now my templates:

create.html

<form>
    <div class="control-group">
        <label class="control-label">Name</label>
         <input type="text" ng-model="user.name" placeholder="Enter a name here">
    </div>
    <div ng-repeat="userRole in user.role">
        <div class="control-group">
        <label class="control-label">Role</label>
        <select ng-selected="userRole.id">
            <option ng-repeat="role in roles" value="{{role.id}}">{{role.name}}</option>
        </select>
        </div>
    </div>
    <button ng-click="addRole()">Attach another role</button>
    <br />
    <br />
    <input type="submit" value="Submit" ng-click="save()" class="btn btn-primary">
    <a href="#/" class="btn">Cancel</a>
</form>

read.html

<br />
<table class="table table-bordered table-striped table-centred table-condensed table-hover">
    <thead>
        <tr>
            <th>User Name</th>
            <th>Role Name</th>
            <th>Action</th>
        </tr>
        </thead>
    <tbody>
        <tr ng-repeat="user in users">
            <td>{{user.name}}</td>
            <td>
                <span ng-repeat="role in user.role">{{role.name}}</span>
            </td>
            <td>
                <a title="edit" href="#/update/{{user.id}}"><i class="icon-edit"></i></a>
            </td>
        </tr>
    </tbody>
</table>
<br />
<a href="#/create" class="btn btn-primary"><i class="icon-plus"></i>&nbsp;Create a new user</a>

update.html

<form>
    <div class="control-group">
        <label class="control-label">Name</label>
         <input type="text" ng-model="user.name" placeholder="Enter a name here">
    </div>
    <div ng-repeat="userRole in user.role">
        <div class="control-group">
        <label class="control-label">Role</label>
        <select ng-selected="userRole.id">
            <option ng-repeat="role in roles" value="{{role.id}}">{{role.name}}</option>
        </select>
        </div>
    </div>
    <button ng-click="addRole()">Attach another role</button>
    <br />
    <br />
    <input type="submit" value="Submit" ng-click="save()" class="btn btn-primary">
    <a href="#/" class="btn">Cancel</a>
</form>

Please made advice if you see some bad coding or wrong architecture (I think I could do some directive for instance when it comes to add a new role maybe?). I hope this is clear enough. Thanks!

You can solve the first 2 problems you are having by redesigning your UI. Instead of using dropdowns use a checkbox field. Example plnkr: http://plnkr.co/edit/hgq2hmbRty7B9oryQnkm

Once you have less moving parts on your page, hopefully it will be easy to debug the 3rd problem.