I have an application in which
i want to do pushing and poping of my view controllers to the
navigation controller while a webservice call is on
.Now when i am doing it i make all the buttons inactive untill the request finished.But i need to remove this.I need to go back and forth while calling the service.Can anybody help me on this regard
From what I get out of your question, solution could be as follow:
You need to implement delegation for this purpose. You have to define a protocol in the class from which your web service is getting invoked. And then implement that protocol into the class to which you want to navigate to. By doing this you will be able to handle the response/error to the navigated ViewController class.
Again, When you want to move back and forth, you again need to implement delegation to the main ViewController, from which your web service is getting called. (Just to handle response/error, in case if you are in the same class while response is returned)
Hope this clears the point.
P.S. My answer is as par the understanding of your question. For detailed answer please elaborate your question accordingly. Thanks.
Just a wild guess.. how about creating a singleton object which handles all you network related stuff. So instead of calling the web service and implementing its delegate methods in your view controller you assign this object the responsibility of handling the network interaction. This way your view controllers will remain clean (less code) and you can reuse this object anywhere throughout the application... any other thoughts on this are welcome.
Related
I have a general working knowledge of object-oriented programming and I'm currently trying to create an interactive novel program in Objective C using Xcode 4.2 with storyboarding.
I have a storyController class that instantiates the page objects and a viewController class that needs to display the pages. My fundamental question is the best approach for my storyController to tell the viewController to update it's text to display that of the new page object. My instinct tells me that my storyController needs to call a method on the viewController and pass it a page object. However, I'm not sure how to reference the view controller since it seems to be automatically created and linked by the storyboard (I don't see the viewController instantiated in the appDelegate).
I've read this post: http://www.iphonedevsdk.com/forum/iphone-sdk-development/54859-sharing-data-between-view-controllers-other-objects.html and it seems to address the issue. I could make a shared object on my appDelegate and use KVN or NSNotification to tell the view controller to check it.
I've also been reading about delegates and protocols as possible solutions.
So considering these potentially different approaches, which would be best to tell my viewController to update itself and pass it an object that contains the updates?
I would suggest looking at the UIPageViewController class, which probably will do a lot of the heavy lifting work for you, depending on the specifics of your app. This class is essentially a controller class that contains multiple viewControllers. Each managed viewController becomes essentially a "page" in your book.
Here is a tutorial using UIPageViewController.
If this approach won't work for your app, I'd still suggest using a separate viewController instance for each "page" of your book and handle the transition between the pages with segues.
Firstly, I studied apple's sample codes : SeismicXML and TopSongs but both of them and other tutorials generally calls NSURLConnection in app delegate.
In my ugly project, I have to call NSURLConnection after user reach some viewcontroller in uinavigationcontroller.
So, I'm asking this design issue, Should I still keep NSURLConnection methods in app delegate, and calling from my internet aware vc or completely move this NSURLConnection methods and delegates to my internet aware vc ?
Also, there is another design issues which mess my head since I'm not even starter :)
I have to keep the number of view uitableview which is constructed from xml, and its
detailed view. Therefore, I think that I must two request to my web service. One to getting xml file and the other one must be made in detailed view to increase view count of related data in web service.
But, I think that it's not a good solution, Is there any library or any other approach to keep this list and its detailed view counts and notify my server?
The way I do it is make a separate class that I use only for connection calls and methods, instantiate it from the delegate, set that instance from the delegate as a property (or manually create its setters and getters) and use in in any class/controller I want to.
This way you modularize your application and the classes don't get tangled up and it's easier to debug/follow the flow of the application.
I'm new to Objective-C and not a full time programmer. I'm beginning to understand the Model-View-Controller design pattern for differentiating the UI from the model. So the user takes an action and the view controller sends a message to the delegate (model). But I'm not sure what the best way to send actions from the delegate back to the view controller.
For example, the user pushes a button, the VC messages the Delegate. That part I understand. Then the delegate takes action, and following that the delegate wants to update the VC (e.g., update a label).
So what I missed (or have forgotten) is how this gets done, while maintaining separation between the UI and the model. I suppose I can use the notification center. Or I think I can just have the view controller pass a callback to the delegate. Or maybe there's another choice I don't know of. Can someone give me a recommendation, please?
I think you're slightly misunderstanding the MVC paradigm. Models should never be delegates of views, since models should have no dependencies or knowledge of any view classes. Typically, a view sends a message to its delegate or target (if you're using target/action), which is usually a controller (often a subclass of UIViewController on iOS). The controller then accesses data from the model and can update any views that need updating. I'd recommend reading the MVC fundamentals guide for a more complete explanation.
Basically you're right, you could do all the notification-related things yourself (i.e. with NotificationCenter) but since we're talking about UI-Stuff here I would greatly recommend you to use IBAction-Methods and IBOutlet-Properties in your code which you can easily connect to UI-Elements respectively their Callbacks in Interface Builder.
A very basic introduction to this topic can be found here:
iPhone SDK Interface Builder basic training
i hope that it is not too basic tough, and that I could lead you on the right track.
First of all delegate is NOT a Model.
Model is something passive that only holds the data (DB, plist, array, dictionary etc.).
While delegate is some set of functions that exist in order to react to some events.
Delegate is more likely to be a view controller in your case.
The view controller should react to user's action.
If the button tap should display some data from your model in some label then view controller should do all the work (receive user's action, take the necessary data from the model and display it on the view...).
I am developing an app which requires interaction with a SOAP web service, to retreive and display data. Now in the application, multiple view controllers have the possibility of calling different methods, of the web service to retreive some data.
I tried to write a common class to handle all the web service related stuff, but was unsuccessfull. The problem I am facing is as mentioned below:
I call the common class method, which has web service handling methods, from a view controller with required parameters. The common class hits the web service, parses the data and returns me the result. I receive the result and use it in my view controller. The problem here is that view controller's execution doesn't wait for the completion of execution of common class's all the delegate methods. That is my view would for exapmle navigate, without waiting for the result from the common class.
Anyone solved this problem??Hoping to get a reply soon. Thanks.
Create a protocol for your view controllers to conform to, for callbacks when the data is retrieved. The view controller implementation will refresh display as appropriate. You can present a spinner while waiting; it is best to use the status bar activity indicator to show that this is network activity.
considering good design, is it better for each view controller to manager their own connection / networking / loading, or to centralize it in the app delegate, or a separate object?
Context:
I have a multi-tab app, each with a navigation controller, and a number of view controller below. Each view controller is doing networking loading XML and images. Currently, i have it setup that it calls to the app delegate to get the xml asynchronously, processing it, and then calling back the top view controller to display the info, and then launching a separate process of loading the images into an array, and sending callbacks for when each is loaded.
From an architectural view-point, is it better to have more networking code in each of the view controllers or calling back to the app delegate?
Ideas / opinions?
TIA.
It's going to make much more sense to have this in each View Controller, I think. The way you've got it set up now sounds a bit weird - you must either be using delegation so that the App Delegate can speak to each view controller, or you have a ton of references to your View Controllers in your app delegate which you probably don't need. I'd imagine your app delegate is cluttered, and I'm curious as to how you're handling things like if the user decides to stop looking at a particular view before the XML related to that view has been sent back to your app and parsed.
If you're worried about having code duplication in your View Controllers, you can probably mitigate that by using Categories.
In the end though I think it's probably best for domain objects to handle this, and not the View Controllers. For example, in viewWillAppear you get or create an instance of a domain object and kick off a getData method which has the view controller as a delegate. All of the requesting/parsing is done in your domain object and when it's completed, it sends your view controller a getDataDidFinish message or something like that.
When I have a situation like this I tend to create an object that handles all the networking stuff for me. That way I end up being able to write code like:
[netObj getXML:somePlace];
The main reason I like this approach is because it keeps my code base tidy and minimizes duplicated code.