I have setup and successfully logged in via xAuth using an extended class of MGTwitterEngine, my question is if I want to pass this to another view controller, how can I change the delegate class, as it is some sort of weak reference
#interface MGTwitterEngine : NSObject <MGTwitterParserDelegate> {
__weak NSObject <MGTwitterEngineDelegate> *_delegate;
Am I best wrap this up into a singleton class and pass around that way, seems overkill to login in each time, or have I missed a painstakingly obvious way of sharing this object around
At the moment I have added a setDelegate method to the MGTwitterEngine but feel as though I am fighting the framework unnecessarily
If you're sharing the engine across multiple objects then you would want to have some other object/singleton wrap the engine and act as its sole delegate. If you've done database programming then think of it like a database connection -- you probably wouldn't have each view controller create its own database connection. Instead you'd create some sort of data manager object that is shared by the views and possibly abstracts away some of the DB internals.
If different view controllers handle different tasks -- like login, looking up users, querying messages, etc. then the delegate methods in your wrapper should be able to pass the responses along to the appropriate view controller.
If you have different view controllers calling the same methods (and if so, why?), you could still route responses back to the corresponding view controllers. As the MGTwitterEngine docs say, "Each Twitter API method returns an NSString which is a unique identifier for that connection." You would just need to pass an object (your view controller) or a block as an extra parameter to each of your wrapped methods. You can cache the twitter id string and this object/block in a mutable dictionary when your wrapper sends the response, then look up the connection id in the cache when it's time to handle the response.
actually, you can.
The delegate, is nothing but a variable in the MGTwitterEngine. Just add a instance of it in the next view controller adding the proper header and inplementation calls.
after instatiating the new view controller set:
nextViewController._mgTwitterEngine = self.mgTwitterEngine;
nextViewController.mgTwitterEngine.delegate=nextViewController;
then call the nextViewController.
Do not forget to set the delegate back to the original view controller when you return to it (either on viewDidAppear or viewWillAppear)
Hope that helps...
Best Of luck!
Use NSNotifications in the delegate.
Make the view controller where you wish the delegate to be add an observer. Have the delegate method for MGTwitterEngine post the notification.
Related
I have a fairly complex application at this point, and feel as though the way I am handling data is not up to scratch.
So I have started taking some steps towards making my app more MVC friendly.
The first of which, I have gone from having inline parser methods in all of my ViewControllers to creating a dedicated parser class.
Its not hard to call I just set up the class then call the initializer method I have made which I pass the data to for my request.. everything in my object class works sweet I get a whole bunch of return data from the server that I am parsing.. but then this is where I get abit lost.
How do I get that data back to the ViewController that called it? I have worked a little with protocols and delegates.. but I dont know how that would fit into this.
Here is an graphical example of what I am trying to achieve.
So as above View controller calls the initalization method of the object class which connects to the DB downloads the data, and then parses that data. The issue I am having is how do I then get that data to ViewController2..
what is the most appropriate and future proof way of doing this?
A custom -init method does wonders. For instance, I needed to instantiate and push a picker preloaded with the array from the previous screen, so I defined -(id)initWithArray:(NSArray*)array in the second view, then just called secondView = [[SecondView alloc]initWithArray:_population]; then pushed it. Remember to get ownership of any object you pass before it is deallocated and destroyed!
If you want to broadcast data from your object to all view controllers the good way to do this will be by notifications (NSNotificationCenter). You could also write a methods with completion blocks inside your parser object.
Try to send a local notification using NSNotificationCenter. Register your ViewController2 as a listener, then upon receiving the notification, call your data model (singleton!?) for the data.
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 have a view controller which gets an NSObject conforming to a protocol and then displays a view with the object's properties.
The question : How can my controller know that a property of this object has been modified and then refresh the view ?
Thanks a lot
Thierry
There are three ways of doing this:
Have the object call a method in the controller in response to an event e.g. a user clicking the button. This is usually done using an IBAction.
Set the controller to be the delegate of object e.g. a UIWebView sends a message to its delegate when it finishes loading a page.
Use a notification. The object generates the notification and then one or more objects (including the controller) registers to listen for the notification. This is usually not used with interface elements although it can be.
I can't tell you more without more detail about the specifics of your project.
Your viewcontroller should conform to your .
In your model, all your set methods should trigger appropriate functions you define in your modelchangedprotocol.
This OO design pattern is also known as "Observer" design pattern.
I have an NavigationController based app where the data model is stored in the appDelegate after being fetched using CoreData. The views that display the data all have a pointer to appDelegate so that they can query the model for the required data. They then call methods in the appDelegate in response to user selections.
My question is, doesn't the MVC pattern optimally hide the data from the view? Would it be best practice for the appDelegate (in this case serving as model and controller) to supply the data to the view, and for the view to simply send a notification when there is user input? That would eliminate the need for the view to maintain a pointer to the appDelegate.
You're correct to worry about AppDelegate taking on this role. AppDelegate is an easy place to dump stuff, and it quickly becomes overwhelmed with roles. As you note, it's playing data model, data controller and application delegate. If you're getting to the AppDelegate using [[[UIApplication sharedApplication] delegate], it's especially a problem because it makes it very hard to reuse the view in other programs. It's less of a problem if your view has a delegate ivar that just happens to point to the AppDelegate, but could easily point to some other object.
The view often should have a delegate that it passes UI events to. See UITextField and UITextFieldDelegate for a good example pattern. Views generally don't post NSNotification for this kind of stuff. Conversely, model classes typically work best without delegates in my experience.
I am a huge believer in NSNotification. My programs use them for almost all data that moves up from the model layer. But for actions that move down from the view layer, delegation and direct method calls typically work best.
Its not your view that accesses the data. The controller should be the link between the data and the view. If by view you mean the controller, then that's perfectly fine and basically what MVC is all about.
I am developing an iPhone app for some sweet undergrad research I've been working on. Sadly, my school doesn't offer software engineering / design classes so when it comes to questions of best practices in OO Design, I do a lot of reading.
My Dilemma:
My application loads a view (v1) where, upon user's button click, v1's controller class executes an action method. This action method should fill an array with objects. After that, the user will either execute the action again or click a different tab to load another view. Other views in the application will use the array that v1 populated.
So, where should this shared array be declared? Right now, it's in the AppDelegate class from when I was testing features without a GUI. Should I grab the AppDelegate singleton and add items to it in the v1ViewController? Should it be declared as static?
Thanks for the help!
^Buffalo
EDIT:
Follow-up Question: When interacting with a singleton, which is the better way to talk to it:
[[MyAwesomeSingleton sharedInstance] gimmeSomePizza];
or
MySingleton *s = [MySingleton sharedInstance];
[s gimmeSomePizza];
I guess what I'm wondering is, do you make the sharedInstance method call every time or do you define a pointer to the sharedInstance and then reference the pointer?
Using the app delegate to store data that's shared between views and view controllers is reasonable and appropriate.
In my apps, I view the app delegate as the controller part of MVC, with UIViews and view controllers all being part of the "view". I prefer to use a variant of MVC called Passive View that keeps the model and view parts of my app strictly segregated with only the controller connecting them.
I'm assuming that the array of objects you're storing is your app's model, so storing them on your app delegate makes sense. As Daniel D said, there's no need to make it static.
The app delegate is really the heart of your program. You create and initialize your model and views in your -applicationDidFinishLaunching: method and save your model data and view state in -applicationWillTerminate:. When your view controllers receive events that changes your model, you can call methods on your app delegate to make those changes.
You could store it in an ivar in the app delegate. You don't need to make it static since the app delegate is a singleton anyways (there's never more than 1 instance).
If the app delegate is getting a bit complicated, you can factor out the data storage into a separate model object or perhaps use Core Data.