<p>Modal view controller's delegate is (null) with attempting to restore it </p>
The method is not being called...
+ (UIViewController *)viewControllerWithRestorationIdentifierPath:(NSArray *)identifierComponents
after defining a restorationClass
AppDelegate.m is not using
-(UIViewController *)application:(UIApplication *)application viewControllerWithRestorationIdentifierPath:(NSArray *)identifierComponents coder:(NSCoder *)coder
If I got your question right, try to encode your delegate and decode it when restoring a view controller. Restoring only your view controller won't help. You have to restore all data and delegates to be able to function the app properly.
Related
I am new in Backbone.js and I keep failing to understand how the model and the view are connected.
I played with Angular where things are pretty clear there, how model, view and controller are connected.
I know Angular and Backbone are different and the latter is MV*.
In Backbone I can understand how model and view are created and work, but how are they connected? Seems to me they are seperated.
Please take a minute to explain or point me to a tutorial.
Thanks in advance
EDIT
OK, here is an example. It happens that I read the book that trolle suggests. This is a code from the book's github
I start reading. I understand the Todo model. I understand the TodoList collection. Then I get to the TodoView
creates a new li
uses Underscore template to compile html
defines some functions that imlements later in the same view
defines an initialize function
inside that function
what is this? this.model.bind('change', this.render, this);
how he can magically bind the action change to a model? How the code knows about the model? When he defined the model and how? Just because is there, the code knows that model = Todo model?
How does he do that bind? What am I missing.
This confuses me, so reading AppView view does not help me much
Thanks again
In backbone.js views are used for displaying models in browser.
For example you can have a model object, whose JSON representation resembles the following: {'firstName': 'foo', 'lastName': 'bar' }
And you use view object to map this model to browser DOM.
As a rule, you use view object along with certain template engine.
Templates allows for creating html chunks filled with model's data.
If you are using underscore template function, your template may look something like this:
<div>
<div>First Name: <%= firstName %></div>
<div>Last Name: <%= lastName%></div>
</div>
After merging template with model's data it would be:
<div>
<div>First Name: foo</div>
<div>Last Name: bar</div>
</div>
You can reuse this view object and its template to display another model object, for example {'firstName':'another foo', 'lastName':'another bar'}, so that the result html would be:
<div>
<div>First Name: another foo</div>
<div>Last Name: another bar</div>
</div>
That is one thing about connection between model and view.
Also view object can listen to changes in your model object to render immediately last updates. For example (inside view object):
initialize: function() {this.listenTo(this.model, 'change', this.render);}
In short, views are the logic behind the presentation of the model's data to the user. So in its simplest form, you bind a model to a view through the models change events, so you can update the presentation instantly whenever your data changes. So a simple view would take in a model, create HTML elements based on that models data, insert that html into the DOM and update that HTML whenever the data changes.
You can find a great book full of helpful examples here (free): http://addyosmani.github.io/backbone-fundamentals/
EDIT:
With regards to your updated question about how the view knows about the model, this.model is a reference to the actual model object. You can set the reference to the model when you create the view. That is, when you call your view-constructor to instantiate a view, you could pass in a model. You need to go all the way into the AppView object in the code example to see where this happens, in the addOne method:
addOne: function(todo) {
var view = new TodoView({model: todo});
this.$("#todo-list").append(view.render().el);
}
The function gets a model as a parameter, and when the view is instantiated that model is referenced. So now you have a view that knows about the model, and when the view.render method is called, the view can render it's template with the model data. When you change the data in the model, for instance by using the set method, myModel.set({title: "March 20", content: "In his eyes she eclipses..."});, you trigger the change event for that model. You can see all the built in events for backbone here: http://backbonejs.org/#Events-catalog. The view is listening for that event, just like it could listen for a click event or any other event. In the code in your example the view listenes for a change event from the model. If it hears it it knows that the object behind this.model has changed, and it can then update the DOM with the new data or do something else. In the case of the example it calls this.render, which updates the DOM with the new model data.
I think you want to know about Backbone.Events (http://backbonejs.org/#Events), both Models and Views make use of this module and that's how the view learns about changes in the Model, if you want to learn how this is implemented you can always read the annotated source (http://backbonejs.org/docs/backbone.html#section-19), but more important I think you want to learn about the observer pattern: http://addyosmani.com/resources/essentialjsdesignpatterns/book/#observerpatternjavascript.
I found one weird issue while working in angular js
I am getting data using ajax call. I am binding data to $scope object but view is not getting updated after data bind
following is my code
$scope.getPlanDetail = function (){
$rootScope.planBody.checkUpdate= false;
$http.post('http://MyServerURL',JSON.stringify($rootScope.planBody)).
success(function(response){
$scope.dataVal = response;//Able to view data in console;
console.log($scope.dataVal)//data json shown in log window
localStorage.setItem("tempDataVal", JSON.stringify(response));//able to set data in localStorage;
}
}
getPlanDetail() function is getting called on btn click using ng-click
Same functionality I have done in other case(using get method.) where code is working properly. The only diff I found is that current AJAX call is taking to much of time because of too much of server side processing and its post method I am not sure whether this(using post method) is causing issue in binding
On same view(.html) I added dummy button ng-click event. After ajax success call I click on button and view is loaded because of data use from localStorage variable.
$scope.dummyClick= function(){
console.log($scope.dataVal);//giving Undefined
$scope.dataVal = JSON.parse(localStorage.getItem("tempDataVal"));// this time view binded properly.
}
I didn't understand why data is not bind to view in success method. Does the $scope time out after some time if server takes too much time to respond?
Thanks in Advance.
If you are changing the model inside an ajax call then you need to notify the angular js that you have some changes.
$scope.$apply(); after the below line will fix your issue. This line will update the scope.
$scope.dataVal = response;
Thanks,
Santyy
I'm quite confused with backbone's view rendering. I need your help regarding this.
For example, I've a Album view. It's render method renders each Track view. All the track specific events are binding in the Track view.
Now, Track view is listening to it's model. For example:
this.model.on('destroy', this.destroy, this);
destroy: function(model){
this.close();
},
so when a track is destroyed, the view is removed from UI which is fine. But problem is with sync. The view is removed from the UI not from server. If sync is successful, nothing to do with the view.
However, if the sync is not successful, I want to undo this view change (restore the track markup where it was before I destroyed it).
Can anyone please tell how can I do this?
FYI,
earlier I've altered the UI after getting success from server. But in more than 98% cases we get success, we decided to change the UI immediately and restore when there is an error.
There's a great plugin for dealing with this: https://github.com/derickbailey/backbone.memento
I call view.remove() in the success callback of model.destroy, I think its easier to read the code and understand what happens that way.
But if you really want to restore the view on sync.error I guess you could call a restore method in an error callback from your destroy call. But it feels like more work to restore it than to wait for the ack.
I have been getting memory warnings in my app which is what brought this to my attention. I have a navigation controller and its root view controller. From this root view controller I push another view controller onto the navigation stack via calling:
[self performSegueWithIdentifier:sender:]
The segue is from the root view controller to the new view controller and of mode PUSH.
I then remove this view controller and pop back to the root view controller by calling
[self.navigationController popViewControllerAnimated:YES];
The problem is that if I push and pop the view controller around 20 times I start to get memory warnings.
didRecieveMemoryWarning is called approx 20 times on the view controller in a single frame signifying that that every popped view controller is still hanging about.
The app then eventually crashes.
I have no stored references to the pushed view controller anywhere.
I'm using ios6 so I know the viewDidUnload() will not get called.
I am removing all cached images when I get the memory warnings but ideally destroying the old popped view controllers is the way forward but I do not know how to do this using storyboards.
If I was manually calling pushViewController from code I could maintain a single object reference to re-use each time so I do not keep creating new view controllers to push but that's going back a step away from storyboards.
Any help in this matter is much appreciated.
Thanks,
Stewart.
I've got a backbonejs application with two view. It kind of looks like this:
<body>
<header></header>
<div id="content"></div>
</body>
Every time a view is loaded the app overwrites the current view by completely overwriting the contents of #content.
// Like this...
$('#content').html( new primaryView().render() );
// ...and this.
$('#content').html( new secondaryView().render() );
The application has a global collection.
App.Collection();
The secondary view modifies itself depending on the global collection. Therefor it binds a function to the 'add' event' on App.Collection in the views initialize function;
App.Collection.bind('add', function(){
console.log('Item added');
});
Which result in my problem. Every time the secondary view is loaded a new function is binded to App.Collection's add event. If I go from the primary view to the secondary view three times, the function will fire three times everytime an item is added to App.Collection.
What am I doing wrong?
I can see how I would do it if there was an uninitialize function on views.
I can see how I could do it if I never removed a view once it was loaded.
I can see how I would do it if I could namespace events like in Jquery. (by unbinding before binding).
You can generalize your problem quite a bit. Basically, you are writing an event-driven app, and in such app events should be taken care of.
Check out this post to see a recommended way to work with event handlers in backbone.
Depending on the situation, you can use initialize and render methods to handle different aspects of creating a view. For instance, you can put your binding inside the initialize
initialize: function() {
App.Collection.bind('add', function(){
this.view.render()
});
}
which only fires when the view is created. This binds your render method to the add event. Then in your render method you can actually create the html.
This prevents the binding from happening every time you need to re-render.