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    <p><strong>answer completely edited</strong></p> <p>Your question leads to multiple solutions and strategies.</p> <h3>First: general posibilities to implement bidirectional data-transfer between two classes.</h3> <p>via multiple protocols: loose cupling but leads to import-loops which are annoying. I know ho to solve import loops for class-definitions (@class) but I dont know how to solve this for protocols</p> <p>A.h:</p> <pre><code>#import "B.h" @protocol ADelegate -(void) adelegate:(NSString*)data; @end @interface A : NSObject&lt;BDelegate&gt; { id&lt;ADelegate&gt; delegate; } @end </code></pre> <p>B.h:</p> <pre><code>#import "A.h" @protocol BDelegate -(void) bdelegate:(NSString*)data; @end @interface B : NSObject&lt;ADelegate&gt; { id&lt;BDelegate&gt; delegate; } @end </code></pre> <p>via a single protocol: dense cupling :( but no import-loop (this is a working ugly style)</p> <p>A.h:</p> <pre><code>//no import here needed @protocol ADelegate -(void) adelegate:(NSString*)data; @end @interface A : NSObject&lt;BDelegate&gt; { id&lt;ADelegate&gt; delegate; } @end </code></pre> <p>B.h:</p> <pre><code>#import "A.h" @interface B : NSObject&lt;ADelegate&gt; { A* delegate; } @end </code></pre> <p>via pipe/stream: bidirectional data-transfer should by done using a pipe (unbuffered) or stream (buffered) here I show you a small and simple delegate-pipe but there also exists a NSPipe/NSStream</p> <p>DelegatePipe.h</p> <pre><code>@protocol DelegatePipeDelegate - dataArrived:(NSString*)data; @end @interface DelegatePipe : NSObject { NSMutableArray *delegates; } -(void)open:(id&lt;DelegatePipeDelegate&gt;)d; -(void)close:(id&lt;DelegatePipeDelegate&gt;)d; -(void)send:(NSString*)data; @end </code></pre> <p>DelegatePipe.m</p> <pre><code>@implementation DelegatePipe -(id)init { if(self = [super init]) { delegates = [NSMutableArray array]; } return self; } -(void) dealloc { [delegates release]; delegates = nil; } -(void) open:(id &lt;DelegatePipeDelegate&gt;)d { @synchronized(self) { if([delegates containsObject:d]) return; //if([delegates count]&gt;=2) //Pipe contains originally only 2 delegates. but a broadcaster is also nice ;) // return; [delegates addObject:d]; } } -(void) close:(id &lt;DelegatePipeDelegate&gt;)d { @synchronized(self) { [delegates removeObject:d]; } } -(void) send:(NSString *)data { @synchronized(self) { for(id&lt;DelegatePipeDelegate&gt; d in delegates) [d dataArrived:data]; } } @end </code></pre> <h3>Second: KVO</h3> <p>KVO is often used in a ModelViewController (MVC) Pattern. eg: visualize data in a view. The network-connection-state in your case is part of data and your loginipad is a view (<em>and a controller</em>)</p> <p>Authentificator.h</p> <pre><code>typedef enum eAuthState { NOT_CONNECTED = 0, LOGIN_FAILED, CONNECING, CONNECTED } AuthState; @interface Authentificator : NSObject { AuthState state; } @property (nonatomic, assign) AuthState state; @end </code></pre> <p>Authentificator.m</p> <pre><code>... -(void) doAuthWithUsername:(NSString*)name password:(NSString*)pw { self.state = CONNECING; //do network-stuff } //delegate from network. here NSURLConnection -(void) connectionDidFinishLoading:(NSURLConnection *)connection { //parse network-answer BOOL success = YES; if(success) self.state = CONNECTED; else self.state = LOGIN_FAILED; } </code></pre> <p>loginipad.h</p> <pre><code>@interface loginipad : UIViewController { Authentificator *auth; } @property (nonatomic, retain) Authentificator *auth; @end </code></pre> <p>loginipad.m</p> <pre><code>@implementation loginipad @synthesize auth; //override setter for more comfortable use (add/removeObserver) -(void) setAuth:(Authentificator *)a { @synchronized(auth) { [auth removeObserver:self forKeyPath:@"state"]; [auth release]; auth = a; [auth retain]; [auth addObserver:self forKeyPath:@"state" options:0 context:nil]; } } -(IBAction) buttonClicked:(id)aSender { self.auth = [Authentificator sharedAuthentificator]; } -(void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if(![object isKindOfClass:Authentificator.class]) return; AuthState state = ((Authentificator*)object).state; NSLog(@"curState: %i",state); //do sth with state } - (void)dealloc { self.auth = nil; [super dealloc]; } </code></pre>
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    1. COHi Thoomas, thanks for reply, i use this code for call loginipad from mainviewcontroller loginipad on my updated question.
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    2. COso you create an instance, present it and release it. My naive approach would be to store the instance of loginipad: @interface MainViewController : UIViewController { loginipad *loginVC }. As a result you also have to send from loginipad back to MainViewController that the modal view is not longer visible if the user closes that view
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    3. COhemm.., i'm not close the view for waiting data from mainView to modal view, i'm just parsing data to mainView and proccess it, by send user and password to server, if the user/password correct the modalview will be dismiss, this is work, but i want while the process authetication i want show message on modal view ex, loading, connected, auntentcated and successed..
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