Messaging between ViewControllers Using Delegates

I'm trying to send an array from one viewController to another using protocols and delegates. I declared the delegate on viewcontroller B and used the following code in viewcontroller A to send the message from A to B. The protocol's method is didReceiveMessage. Unfortunately, the message never arrives.

Attached is the code from viewController A

- (IBAction) graphPressed:(UIButton *)sender {

 GraphingViewController *gvc=[[GraphingViewController alloc] initWithNibName:nil bundle:nil];
 [self presentModalViewController:gvc animated:YES];
 [gvc release];

 [delegate didReceiveMessage:brain.internalExpression];

}

and the code from viewcontrollerB

- (IBAction) ViewdidLoad {
 CalculatorViewController *cvc =[[CalculatorViewController 开发者_开发百科alloc] init];
 cvc.delegate=self;
 [cvc release];  
}

- (void) didReceiveMessage:(NSMutableArray *)expression {

 NSLog(@"message received from CalculatorAppDelegate");
}

Any suggestions would be greatly appreciated.

---

I'm not sure what are you doing in second sample? You created an object, assign its delegate property and then released it. Why?

---

If that is code from your application it could probably be from releasing cvc at the end of your ViewDidLoad method.

init would give it a retain count of 1, and the release would take it back to 0.

Also the code seems sort of backwards, if you wanted to set view A as the delegate for view B, you would do so in view A.

Unless there is a more complex reason to use a delegate that I'm not seeing from the code, I would just keep a pointer around to the child if you really need to send it messages.

---

Like others have posted, you are just getting rid of the Calculator VC after creating it. I would recommend adding an @property to the second VC and using it to store a pointer to the Calculator. It should be a retain property. Then set the delegate of that property to self.

Also, you make sure to use an assign property for the delegate value, and try to use the property syntax (self.delegate) whenever possible.

There could absolutely be more going on here, so if this doesn't actually solve the problem try and post up more of your code (header files, what connections are made in IB, etc.)

Edit: For the record, the method is -(void)viewDidLoad, not -(void)ViewDidLoad, so that could be contributing to the problem.

---

As you said you are trying to pass an array from one view controller to another.Well i use in this way.Here is the code

- (IBAction) graphPressed:(UIButton *)sender {

 GraphingViewController *gvc=[[GraphingViewController alloc] initWithNibName:nil bundle:nil];
 gvc.myArray=infoArray;
 [self presentModalViewController:gvc animated:YES];
 [gvc release];
}

Where myArray is array in your GraphingViewController,You just need to make property of this array with retain attribute,simply as

@property(nonatomic,retain)NSMutableArray *myArray;

And you need to Synthesize it as well.