Switch View Controller and Pass Button Info

[DenVog]

I have ViewController A with two buttons. After pressing a button on View Controller A, I need to launch ViewController B and make it aware which of the two buttons was pressed. This is not a navigation controller.

Launching the second view controller is no sweat. I'm guessing button tag is the attribute to distinguish between the buttons. I can never get the button value to recognize in ViewController B though.

ViewControllerA.m:

- (IBAction)buttonOnePressed:(id)sender {
setButton.tag = 1;
BViewController *bViewController = [[BViewController alloc] init];
[bViewController.buttonPressedTag = setButton.tag]; // always warning or error
[bViewController setModalPresentationStyle:UIModalPresentationFormSheet];
[self presentModalViewController:bViewController animated:YES];
[bViewController release], bViewController = nil;
}

ViewControllerB.h:

@interface BViewController : UIViewController {
	int buttonPressedTag;
}
@property (nonatomic) int buttonPressedTag;

ViewControllerB.m:

@synthesize buttonPressedTag;

- (void)viewDidLoad {
if (self.buttonPressedTag == 1)
   {
   NSLog(@"It was button One. Do something specific to button one.");
   }
else if (self.buttonPressedTag == 2)
   {
   NSLog(@"It was button Two. Do something specific to button two.");
   }
[super viewDidLoad];
}

Suggestions appreciated.

[SoulRed12]

Two things.

First, what is the warning or error you receive on the line you marked in the first bit of code? That could be a separate issue in and of itself.

Second, I'm 99% sure that ViewControllerB's viewDidLoad will actually occur BEFORE ViewControllerA makes it to the line where it sets ViewControllerB's buttonPressedTag property. Instead, you're going to want to put the code in ViewControllerB's viewWillAppear method.

[BrianSlick]

The tag should probably be defined before you get to this method. As written, there is no reason to use the tag.

You may want to avoid naming things starting with set. set implies a setter, which doesn't seem to be the case.

[DenVog]

Thanks for your reply.

Originally Posted by SoulRed12

First, what is the warning or error you receive on the line you marked in the first bit of code? That could be a separate issue in and of itself.

The Error I get with what's posted above is "Expected ':' before ']' token. I've tried some other implementations at that line, but they all warn or error. For example using setValue warns "invalid receiver type 'int'.

Originally Posted by SoulRed12

Second, I'm 99% sure that ViewControllerB's viewDidLoad will actually occur BEFORE ViewControllerA makes it to the line where it sets ViewControllerB's buttonPressedTag property. Instead, you're going to want to put the code in ViewControllerB's viewWillAppear method.

Thanks for that suggestion. It's not fixed this particular issue, but it did address another area I was working around by setting a delay in viewDidLoad.

[DenVog]

Originally Posted by BrianSlick

The tag should probably be defined before you get to this method. As written, there is no reason to use the tag.

Hi Brian. Can you please clarify? I've been doing quite a bit of searching on this topic, and found several examples that use myButton.tag or setTag within the IBAction to identify the button. Maybe they are bad examples?

Originally Posted by BrianSlick

You may want to avoid naming things starting with set. set implies a setter, which doesn't seem to be the case.

Good suggestion. I could see how this would be confusing. Thanks.

[BrianSlick]

Yes, in terms of a conditional. if (tag == whatever). So the tag already has a value. You are assigning the value in the IBAction. The tag would be assigned in IB, or perhaps viewDidLoad.

[SoulRed12]

Originally Posted by DenVog

Thanks for your reply.

The Error I get with what's posted above is "Expected ':' before ']' token. I've tried some other implementations at that line, but they all warn or error. For example using setValue warns "invalid receiver type 'int'.

Just noticed it:

[bViewController.buttonPressedTag = setButton.tag]; // always warning or error

This line shouldn't have square brackets around it. You only need them when you're sending a message to an instance.

Thanks for that suggestion. It's not fixed this particular issue, but it did address another area I was working around by setting a delay in viewDidLoad.

In what way did it not fix the issue? Was the main issue the error on the above line? Or that the bViewController didn't seem to be getting the value of the button's tag?

If it's the latter, then try this. Create a custom init method on the BViewController class, like this:

-(id)initWithButtonTag:(int)tag {
   if (self = [super init]) {
      self.buttonPressedTag = tag;
   }
   return self; //Must always return self on init methods
}

And be sure to add the method signature to the .h file:

-(id)initWithButtonTag:(int)tag;

Then instead of calling alloc/init, call [[BViewController alloc] initWithButtonTag:setButton.tag];

That will DEFINITELY assign to the variable before the bViewController checks for it.

But as others are saying, you shouldn't have a variable or pointer prefixed with "set", for the reasons BrianSlick mentioned.

[DenVog]

Originally Posted by SoulRed12

Just noticed it:

[bViewController.buttonPressedTag = setButton.tag]; // always warning or error

This line shouldn't have square brackets around it. You only need them when you're sending a message to an instance.

Doh! That got rid of the error. I seem to have tried everything else, don't know why that did not occur to me.

Originally Posted by SoulRed12

If it's the latter, then try this. Create a custom init method on the BViewController class, like this:

-(id)initWithButtonTag:(int)tag {
   if (self = [super init]) {
      self.buttonPressedTag = tag;
   }
   return self; //Must always return self on init methods
}

And be sure to add the method signature to the .h file:

-(id)initWithButtonTag:(int)tag;

Then instead of calling alloc/init, call [[BViewController alloc] initWithButtonTag:setButton.tag];

That will DEFINITELY assign to the variable before the bViewController checks for it.

Hmm. I quickly threw this in there, but the BViewController is still not getting the message. I need to look at it in more detail this afternoon to make sure I've not done something else silly. Thanks for your replies.

[DenVog]

Originally Posted by SoulRed12

In what way did it not fix the issue? Was the main issue the error on the above line? Or that the bViewController didn't seem to be getting the value of the button's tag?

I found the issue. After removing the brackets, it is in fact working. Even without the additional init method. The problem was I was watching for which button tag was pushed via NSLog in the viewDidAppear method of ViewControllerB. I guess you can not log in viewDidAppear?! Once I moved that check after viewDidLoad, I now see which button was pressed.

Arrgggh. That was frustrating!

Thanks for your help.

[BrianSlick]

You can log anywhere. If the log wasn't appearing, the method isn't being called.

[DenVog]

Originally Posted by BrianSlick

You can log anywhere. If the log wasn't appearing, the method isn't being called.

Hmm. Well I thought you should be able to as well. However, I'm using the following, and I never see it in the log:

- (void)viewDidAppear:(BOOL)animated {
	NSLog(@"View did appear.");
	[super viewDidAppear:animated];
}

I don't know what would prevent that method from getting called.

[BrianSlick]

You're usually using addSubview: and it doesn't get called very often doing that.