Hi friends i tried to parse the xml and show in table view .
but without use of appDelegate object how can we .
i have seen in many site that was started from application beginning .
but i want to know if i need to parse and show in different view controller which is not root
view controller and also should not use the application delegate?
please any genius
So it sounds like you have a data model saved as XML somewhere, and when your application loads, you want to parse it and keep the model in memory.
In my experience, the application delegate is actually the place to keep stuff like this. Since it's something that both the application delegate, and the random UIViewController need to know about, the app delegate is a good place to keep it.
Once you've loaded your model using the NSXMLParser or your preferred loader, you can (in your UIViewController) use something like:
MyModel *model = ((MyAppDelegate *)[[UIApplication sharedApplication] delegate]).myModel;
Related
First i was wondering if this is a good idea, essentially i have user class and throughout the application i would have a current user and various views would want to access this users data. would it make sense to store this user in the navigation controller so that each class can access it without having to pass it through the prepareforsegue on every view?
Second if this is ok to do, how do i access a variable in the navigation controller? i have it setup so it has one called _myUser just like i would in the other views but how do i call/set that from a view?
I would recommend saving data to either your application delegate or if it starts to get messy creating a singleton. The application delegate is a better practice and can be shared throughout your app easily. You can access it easily with something like this:
YourAppDelegate * del = (YourAppDelegate *)[[UIApplication sharedApplication] delegate];
NSLog(#"%#", del.yourPropertyToShare);
I looked through a core data tutorial which puts the core data code in the AppDelegate class that is created upon creating a Window project. I was able to successfully save and retrieve data from the premade AppDelegate class.
My question is, if i have a ViewController that saves data, how do i go about saving data from that specific class.
Do i need to redefine the persistent store and managedObjectModel in that class?
If that is the case, what is the programmatic way to do it (since previously it was generated for me) i.e what methods/instancevariables/properties do i need to declare.
Standing by for any clarifications there may be
No need to go through the app delegate or redefine persistent store etc. All you need is a reference to the managedObjectContext. Normally, this is a property (say, of a view controller) that you can set from the outside after creation and easily access from inside the view controller class (much easier than going through the app delegate!). You can pass this on easily to other view controllers, and read from and write to core data with the standard methods.
If you want to save your own objects, yes - you have to create your own managed object model (by modifying the one the template generated for you).
Why not just have a reference to your application delegate in the view controller you wish to save data in? You can then access the managed object context and call its save method as usual.
In the .h file of your view controller have a property of same type as you application delegate. Then in the viewDidLoad method in the .m file set the reference like this:
self.appDelegate = (MyApplicationDelegate*)[[UIApplication sharedApplication] delegate];
Then when you want to save you can access the application delegates managed object context like so:
[self.appDelegate.managedObjectContext save:&error];
Hope that helps, I wrote that off the top of my head so there might be some syntax errors but the compiler will let you know.
Very new to programming for iOS and Cocoa so please take it easy on me as I try to wrap my brain around the following. I'm trying to display a tableview populated from an XML feed as the opening screen of my app. I've tried to consume the XML from inside my AppDelegate using the ApplicationDidFinishLaunching method (and then making my AppDelegate a delegate for the XML parser which I access using a NSUrlConnection and its delegate methods) but I can't figure out how to take the parsed XML file and pass it to a tableviewcontroller which can then use it as the datasource for a tableview. When I do try, I always get a blank tableview.
I've written the code a few times and nothing seems to work.. I'll post what I have here to show what I've got so far but I'm afraid its mostly vanilla AppDelegate with a few parser methods thrown in.. any pointers in the right direction would be super appreciated.
Thank you in advance!
Hmm, probably a bad idea to do the network call in the AppDelegate. Try to put all that code at the view controller level. Here's a brief structure of what I do (Since it's very similar)
View Controller listens to button events
Use ASIHTTPRequest to talk to your web service. Handles network really well, you can skip the NSURLConnection stuff.
Try to load your data source (an array?) with static values and see if they come up on the table view.
Parse the response from ASIHTTPRequest using NSXMLParser, and load the data you want into the static array you were using. More here.
Call [tableView reloadData] once you're done and the changes will reflect.
Did you specify a UITableViewDataSource for your table view and implement the two required methods?
tableView:cellForRowAtIndexPath:
and
tableView:numberOfRowsInSection:
http://developer.apple.com/library/ios/#documentation/uikit/reference/UITableViewDataSource_Protocol/Reference/Reference.html
When I get blank tables, this is what it is; I've forgotten to specify the data source
I have following problem:
I have built a tabbar application with 4 tabs. I want to pass a object/variable from the first tab controller to the third one and initialize this controller with the corresponding object.
I've already done some research. The best way, corresponding to a clean model approach, would be to call some initWithObject: method on the called viewcontroller.
How can I achieve this? How can I call the init method of the receivercontroller within the callercontroller? Can you give me some code example?
Edit:
To pass data between several views/classes etc simply create some Kind of data class which holds the data beeing shared between several classes. For more information follow the link:
Singleton
You need a data model object that stores the data for application.
A data model is a customized, standalone object accessible from anywhere in the application. The data model object knows nothing about any views or view controllers. It just stores data and the logical relationships between that data.
When different parts of the app need to write or read data, they write and read to the data model. In your case, view1 would save its data to the data model when it unloads and then view2 would read that data from the data model when it loads (or vice versa.)
In a properly designed app, no two view controllers should have access to the internal data of another controller. (The only reason a view controllers needs to know of the existence of another controller is if it has to trigger the loading of that other controller.)
The quick and dirty way to create a data model is to add attributes to the app delegate and then call the app delegate from the view controllers using:
YourAppDelegateClass *appDelegate = [[UIApplication sharedApplication] delegate];
myLocalProperty = appDelegate.someDataModelProperty;
This will work for small project but as your data grows complex, you should create a dedicated class for your data model.
Edit:
To clarify for your specific case, you would add the call to the data model when the receiver viewController becomes active.
Placing the data in an init method or a viewDidLoad won't work because in a UITabBar the users can switch back and forth without unloading the view or reinitializing the view controller.
The best place to retrieve changing data is in the viewWillAppear controller method. That way the data will be updated every time the user switches to that tab.
You might want to consider NSNotificationCenter (Reference); you register the one viewcontroller with the application notification center, and send a notification when a selection is made. When the notification is received, the other viewcontroller updates itself accordingly.
I don't think this is best practice (also check syntax) however I have got away with:
in the .h
otherclassref *otherclassname
#property (assign) otherclassname otherclassref;
and in the .m
#synthesize otherclassref;
then I just assign the reference from somewhere convenient e.g. the app delegate or wherever you are instantiating your viewcontrollers.
then the view controller can get a reference to the other view controller.
I add #class secondviewcontroller to the .h file for the firstviewcontroller and put put the #imports "secondviewcontroller.h" in the .m file of the first view controller. These are called forward references and prevent compiler errors resulting from having .h files referencing each other.
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.