How to preserve scope data when changing states with ui-router? - angularjs

Question

I'm building a single page web app using AngularJS with ui-router. I have two different states, one parent and one child. In the parent state, 'spots', users can make a selection from an ng-repeat and their selection is shown using the scope.
When a user makes the selection, I have ng-click fire a function which uses $state.go to load the child state 'details'. I would like to load their selection in the child state, but it appears that the scope data is gone?
I've tried using the same controller for each state. ui-sref doesn't work either.
From the parent state HTML template
<div class="card-column mx-0" data-ng-click="makeSelection = true">
<div class="card mx-0 mb-3 ng-scope" data-ng-click="showSpot(spot);" data-ng-repeat="spot in spots | filter:{'game':gameID} | filter:{'walking':distanceID} | filter:{'vehicle':vehicleID} | orderBy:'price' | filter as results">
<div class="row no-gutters">
<div class="col-sm-12 col-md-3 col-lg-3">
<img src="{{ spot.image }}" alt="parking spot"/>
</div>
<div class="col-sm-12 col-md-9 col-lg-9">
<div class="card-body px-4 pt-4">
<h6 class="text-small-extra text-muted font-weight-normal text-uppercase"><span style="letter-spacing: .05rem;">{{ spot.type }}</span></h6>
<h5 class="card-title">{{ spot.address }}</h5>
<h4 class="text-muted float-md-right">${{ spot.price }}<span style="font-size: 1rem; font-weight: 400">/day</span></h4>
</div>
</div>
</div>
</div>
Snippet from the controller
$scope.showDetails = function() {
$state.go('spots.details'); //my route...
}
$scope.showSpot = function(spot) {
$scope.spot = spot;
$scope.showDetails();
}
Snippet from app.js
.config(function($stateProvider, $urlRouterProvider) {
$urlRouterProvider.otherwise("/")
$stateProvider
.state('spots',{
url: '/',
templateUrl: "/parkit/master/spots-available.html",
controller: 'parkitController'
})
.state('details', {
parent: 'spots',
url: '/details',
templateUrl: '/parkit/master/details.html',
})
.state('statetwo', {
url: '/statetwo',
template: '<h1>State Two</h1>',
controller: 'parkitController'
});
})
I expected the user selection to show on the child state after ng-click is fired.

Answer 1

You need to under stand how prototypal inheritance works. When a parent puts a property value on the scope with
$scope.value = 'something';
In a child component if you access $scope.value the inheritance chain will find $scope.value.
If the child sets
$scope.otherValue = 'something';
If follows the inheritance chain, doesn't find a value of otherValue and creates a property on the child scope, not the inherited prototype so the parent component and any other children of the parent do not see it.
You can use what is called the dot rule of prototypal inheritance. If the parent creates an object on the scope called something like data
$scope.data = { value: 'something' };
Now if the child puts a property on the data object
$scope.data.otherValue = 'something';
It looks for the data object, finds it in the inheritence chain and because you are adding a property to an instance of an object it is visible to the parent and any children of the parent.
let parent = {
value: 'some value',
data: { value: 'some value' }
};
let child = Object.create(parent);
console.log(child.value); // Finds value on the prototype chain
child.newValue = 'new value'; // Does not affect the parent
console.log(parent.newValue);
child.data.newValue = 'new value'; // newValue is visible to the parent
console.log(parent.data.newValue);
Short answer is to just never inject $scope and use controllerAs syntax.
To share data between controllers you use a service that is injected to both controllers. You have the spots collection on the service and use a route param to identify which spot the other controller should use or have a place on the service called currentSpot set by the other controller.
Services are a singleton object that you create at the module level and then all controllers that ask for them in their dependency list get the same instance. They are the preferred way to share data between controllers, $scope hierarchies are bound to lead to confusion as the prototypal inheritance nature of them can be confusing. A child $scope is prototypally inherited from it's parent, this seems like you should be sharing data but when a child controller sets a property it is not visible to the parent.
You are learning an outdated way of Angular programming. Injecting $scope is no longer a recommended way. Look at using components. Components are a wrapper for a controller with an isolated scope and using contollerAs syntax. Isolated scopes make it much cleaner to know where data comes from.
Take a look at my answer on this question
Trying to activate a checkbox from a controller that lives in another controller