OK, it's rather self-explanatory.
Let's say we've got our cocoa application.
Let's all assume that you've already got some "plugins", packaged as independent loadable bundles.
This is how bundles are currently being loaded (given that the plugin's "principal class" is actually an NSWindowController subclass :
// Load the bundle
NSString* bundlePath = [[NSBundle mainBundle] pathForResource:#"BundlePlugin"
ofType:#"bundle"]
NSBundle* b = [NSBundle bundleWithPath:bundlePath];
NSError* err = nil;
[b loadAndReturnError:&err];
if (!err)
{
// if everything goes fine, initialise the main controller
Class mainWindowControllerClass = [b principalClass];
id mainWindowController = [[mainWindowControllerClass alloc] initWithWindowNibName:#"PluginWindow"];
}
Now, here's the catch :
How do I "publish" some of my main app's objects to the plugin?
How do I make my plugin "know" about my main app's classes?
Is it even possible to actually establish some sort of communication between them, so that e.g. the plugin can interact with my main app? And if so, how?
SIDENOTES :
Could using Protocols eliminate the "unknown selector" errors and the need for extensive use of performSelector:withObject:?
Obviously I can set and get value to-and-from my newly created mainWindowController as long as they're defined as properties. But is this the most Cocoa-friendly way?
I have an app which utilises a set of custom "controls" which are loaded on demand from Xib files using methods similar to the below:
NSArray * topLevelObjects = [[NSBundle mainBundle] loadNibNamed:#"AudioPlayer" owner:self options:nil];
InteractiveMovieView *newAudio = [topLevelObjects objectAtIndex:0];
This approach works great except where there are multiple controls loaded at once (in effect on one "page" of the app).
Loading from the bundle each time is clearly inefficient but I can't find another way of approaching this. I've tried loading the nib into a copy property once and returning it on demand for re-use, but that doesn't work as the copy returned is never a "clean" copy of the blank nib.
I hope that makes sense, and all help is appreciated.
It sounds like you're looking for the UINib class. From the documentation:
Your application should use UINib objects whenever it needs to repeatedly instantiate the same nib data. For example, if your table view uses a nib file to instantiate table view cells, caching the nib in a UINib object can provide a significant performance improvement.
Following Rob's suggestion, you could do the following:
#implmentation InteractiveMovieView (NibFactory)
+(id)movieView
{
static UINib * __nib ;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
__nib = [ UINib nibWithNibName:#"AudioPlayer" bundle:nil ] ;
});
InteractiveMovieView * view = [ __nib instantiateWithOwner:nil options:nil ][0] ;
return view ;
}
#end
REVISED...
The crux of the app is communicating with a database server. Responses from the server to the app are all in XML. There are several screens. Example, screen 1 lists the user's information, screen 2 lists the user's past trades, allows new trades, and so on.
Here is some code from my AppDelegate:
StartViewController *svc = [[StartViewController alloc] init];
TradeViewController *tvc = [[TradeViewController alloc] init];
CashViewController *cvc = [[CashViewController alloc] init];
ComViewController *covc = [[ComViewController alloc] init];
PrefsViewController *pvc = [[PrefsViewController alloc] init];
NSMutableArray *tabBarViewControllers = [[NSMutableArray alloc] initWithCapacity:5];
UITabBarController *tabBarController = [[UITabBarController alloc] init];
UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:svc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:tvc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:cvc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:covc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
navigationController = [[UINavigationController alloc] initWithRootViewController:pvc];
[tabBarViewControllers addObject:navigationController];
navigationController = nil;
[tabBarController setViewControllers:tabBarViewControllers];
[[self window] setRootViewController:tabBarController];
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
Trying to stick with the MVC style, I have a singleton class which does all of the "processing".
Now an example on how I run into a wall… the user can change their email address on screen 5. Enter new email address into text field and click the save button. The button then calls a method from the singleton class which sends the new email address to the server and (via the URL) and receives a XML response confirming the change.
Here are my problems:
1. I start the spinner from the view controller before I make the singleton class method call - but not knowing when the app to server send/receive is finished, how do I make the spinner stop at the right time? I can't of it from the singleton class, I tried that. From what I know, it has to be from within the VC or is there a way to change VC output from my singleton class?
The singleton class NSURLConnection is handling ALL of my communication. Everything from a simple, email change all the way to updating transaction tables. This just seems wrong to me and makes it very difficult to keep track on who is calling what. Again, I am going by my interpretation of MVC. I think it would be much easier to have a NSURLConnection for every VC and do some processing in those classes. However that would not be MVC(ish).
I have close to a 100 variables, arrays, etc… in my singleton class which I use to assign values to all my VC. This also seems wrong to me but I can't think of any other way.
how can I distinguish in the NSURLConnection delegate
(connectionDidFinishLoading) which URL call is being made?
Each of the delegate methods (such as -connectionDidFinishLoading:) has a connection parameter that tells you which connection sent the message. A given connection can only load one URL at a time, so there's a one to one correspondence between URLs and connections.
How can I tell outside of "connectionDidFinishLoading" when the download is completed?
That method tells you when the connection is finished. It's up to you to store that information somewhere where it's useful to your app.
Update: Based on what you've added, your "processing" class is your app's model. The rest of the app shouldn't care that each transaction involves a message to the server -- that's the model's business alone. Also, there's no reason that the model has to be a single object (let alone a singleton) -- it can be a group of objects that work together.
So, you might have a class (let's call it Processor) that represents the application's interface to the model (some might even call this a "model controller"). An instance of Processor might create a local database for storing the current local state of the app.You might also have a Transaction class that represents a single transaction with the server. A transaction could create a request, send it to the server, get the response, update the database, and tell the Processor that the transaction is done. Or, maybe when some other part of the app (like one of your view controllers) asks the Processor to process a new transaction, the Processor passes the requesting object along to the transaction that it creates so that the transaction can update the requestor directly.
It's hard to say what the best plan for your app is without knowing where you're planning on taking it, but the usual guidelines hold:
break your problem into parts that are easier to solve
limit the scope of each class's responsibilities
if something seems to complicated, it probably is
Breaking your model up into several classes will make it easier to test, as well. You can imagine how easy it would be to write a set of unit tests for the Transaction class. The same goes for Processor -- if the server transaction stuff is in a different class, it's easier to test that the Processor is doing the right thing.
If you have multiple NSURLConnections for the same delegate, consider using a global (well, let's say rather an instance variable) NSMutableDictionary instance, in which you store the data depending on which NSURLConnection is being called. You can use, for example, the in-memory address of the connections converted to an NSString (something like
[NSString stringWithFormat:#"%p", connection]
should do the trick).
Also, in the connectionDidFinishLoading: and connection:didFailLoadWithError: methods, remove the keys corresponding to the NSURLConnections. Thus, you can tell it from 'outside' if a connection is finished: just check if it is in the dictionary or not.
If you're downloading any data over a network connection, I would suggest using ASIHttpRequest. This will allow you to download files asynchronously, meaning your interface doesn't freeze during the download process.
If you use ASIHttpRequest, you can also set the didFinishSelector. By doing this, you can control which method is called when a specific URL has finished loading.
Have a look at this:
NSURL *url = [NSURL URLWithString:#"http://allseeing-i.com"];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setDelegate:self];
[request startAsynchronous];
[request setDidFinishSelector:#selector(requestDone:)];
Then:
- (void)requestDone:(ASIHTTPRequest *)request
{
// Use when fetching text data
NSString *responseString = [request responseString];
// Use when fetching binary data
NSData *responseData = [request responseData];
// If you want, you can get the url of the request like this
NSURL *url = [request url];
}
As for the second part of your question, if the requestDone: method has not been called, you know the download has not completed.
If you want to do something more complicated with multiple downloads, ASIHttpRequest offers queue functionality too. Take a look here.
Hope this will help you.
- (void)connectionDidFinishLoading:(NSURLConnection*)connection
{
NSString *urlString = [[[connection originalRequest] URL] absoluteString];
if ([urlString caseInsensitiveCompare:#"http://www.apple.com"] == NSOrderedSame) {
//Do Task#1
}
else if ([urlString caseInsensitiveCompare:#"http://www.google.com"] == NSOrderedSame)
{
//Do Task#2
}
}
I would recommend subclassing NSURLConnection. Simply add two properties: an NSInteger, tag, and a BOOL, isFinished. This way, you can #define tags for each different request and then identify them by tag in your delegate methods. In connectionDidFinishLoading, you can set the isFinished BOOL to YES, and then you can check in other methods if then connection is finished.
Here's my own NSURLConnection subclass, TTURLConnection:
TTURLConnection.h:
#import <Foundation/Foundation.h>
#interface TTURLConnection : NSURLConnection <NSURLConnectionDelegate>
#property (nonatomic) NSInteger tag;
#property (nonatomic) BOOL isLocked;
- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate startImmediately:
(BOOL)startImmediately tag:(NSInteger)tagParam;
#end
TTURLConnection.m:
#import "TTURLConnection.h"
#implementation TTURLConnection
#synthesize tag;
- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate startImmediately:
(BOOL)startImmediately tag:(NSInteger)tagParam {
self = [super initWithRequest:request delegate:delegate
startImmediately:startImmediately];
if(self) {
self.tag = tagParam;
}
return self;
}
#end
I’m trying to make an app in xcode. I have made a class called myApp.m and .h
In my .m I have these lines of code
- (void)loadApp
AlarmItem *item1 = [[[AlarmItem alloc] initWithTitle:#"TEST2"] autorelease];
NSMutableArray *items = [NSMutableArray arrayWithObjects:item1, nil];
RootViewController *rootController = (RootViewController *) [navigationController.viewControllers objectAtIndex:0];
rootController.items = items;
and in my RootViewController I have an this method:
- (IBAction)RefreshMyApp:(id)sender {
MyApp *myApp2 = [[[MyAppalloc] init] autorelease];
[myApp2 loadData];
}
What I’m trying to do is calling the method from the myApp class and displayed in the tableView, but I always get an empty cell.
Any help is appreciated.
Is this meant to get you your UIApplication singleton? (i'm guessing MyAppalloc is a typo and should be MyApp alloc)
MyApp *myApp2 = [[[MyApp alloc] init] autorelease];
if so then you should be doing it like this:
MyApp *myApp2 = (MyApp*)[UIApplication sharedApplication];
If this is not the case you need to make it clearer what MyApp is (your app delegate?)
I guess, your application running in singleton instance, if this is something kind of NSView or a particular control you want to refresh, you could call its particular refresh method like,
[NSTableView reload];
[NSTextField setString];
etc...
I have a view controller that lists some data in an UITableView. To get the data downloaded I use ASIHTTPRequest which methods I have put in another class.
In my view controller I have setup the appropriate delegates to handle the data that is being retrieved from ASIHTTPRequest. So from my view controller in - viewDidLoad I alloc and init my class that holds the ASIHTTPRequest methods like so:
self.officesParser = [[[OfficesParser alloc] init] autorelease]; // retained property
Then in - viewDidAppear: I call [officesParser downloadOffices];
My - downloadOffices method looks like this:
- (void)downloadOffices {
// 1. Downloaded offices.json
NSURL *officesUrl = [NSURL URLWithString:#"http://example.com/example.json"];
ASIHTTPRequest *officesRequest = [ASIHTTPRequest requestWithURL:officesUrl];
// Always ask the server if there is new content available,
// If the request fails, use data from the cache even if it should have expired.
[officesRequest setCachePolicy:ASIAskServerIfModifiedCachePolicy|ASIFallbackToCacheIfLoadFailsCachePolicy];
// Store the cache permanently
[officesRequest setCacheStoragePolicy:ASICachePermanentlyCacheStoragePolicy];
[officesRequest setTag:1];
OfficesViewController *vc = [[OfficesViewController alloc] init];
[officesRequest setDelegate:vc];
[vc release];
[officesRequest startAsynchronous];
}
Everytime after calling the [officesParser downloadOffices] method I get:
*** -[OfficesViewController respondsToSelector:]: message sent to deallocated instance 0x6a2f6c0
What am I doing wrong here?
You want vc to be delegate for officesRequest, however, after you allocate and initialize vc and set it to be the delegate, you immediately release it. Please note that delegate properties are usually assign, not retain. You are then responsible for keeping your delegate object in existence until no longer needed. So, if you plan to send messages to it in a near future, you can't immediately release it.