I have created a project in Xcode using storyboards. I created a segue between two of the view controllers with a button using the click and drag method. However, there are a certain set of conditions that I want to be met in order for the segue to happen. So I already coded the button as an IB action and wrote the conditional code in the implementation file. If the conditions are not met, an alert view pops up, and I don't want the segue to happen. But if the conditions are met then I do want the segue to happen.
Is there any way to programmatically command a segue to happen or not happen inside an IB action function? Or any other way to get the same kind of result?
THANKS! Any help is appreciated!
I found a great solution for this that someone posted... create a segue that originates from from the status bar of the originating view controller, give it an identifier, and then add this code inside the action button:
[self performSegueWithIdentifier:#"identifierName" sender:sender];
Works great!
You can create a custom segue by subclassing UIStoryboardSegue and setting the segue style to "custom" along with your class name in the attributes inspector. Then you can override the perform method in order to see if your conditions are met before you perform the segue. For example
- (void) perform {
if (...) {
[[self sourceViewController] presentModalViewController:[self destinationViewController] animated:YES];
}
}
See also the documentation http://developer.apple.com/library/IOs/#featuredarticles/ViewControllerPGforiPhoneOS/CreatingCustomSegues/CreatingCustomSegues.html
Alternatively, you could disable the button as long as your conditions are not met. Maybe that's the better approach, since then the user has a visual indication that the segue won't happen, instead of getting a negative feedback after pressing the button.
Related
Required:
I want to enable iOS7 swipe to back feature with custom navigation back button item.
Current Implementation:
After researching a lot, I found the following solution to be best:
Set the delegate of the gesture recognizer as follows
self.navigationController.interactivePopGestureRecognizer.delegate = (id<UIGestureRecognizerDelegate>)self;
This, creates a lot of bugs as mentioned in this stackoverflow answer. To avoid that, subclassing the UINavigationController seems to be the only feasible option. I did that as mentioned in this blog by Keighl.
Problem:
Basic swipe to back feature is working, but the strange thing is that, sometimes, the same viewController that is being dismissed, appears again after the pop action is completed.
i.e. suppose the navigation stack looks like A -> B. Popping B will again bring up B. This keeps on happening until eventually the viewController B actually gets dismissed and A appears.
This happens to all views in all viewController objects and not just to a specific one.
Also, I have ensured that the push method is called only once at all places.
I also tried logging the navigation stack at each point, but there is only one instance of each viewController.
Point to note:
I need to disable the swipe feature in certain views. I did this by writing the code to disable and enable the swipe gesture in viewDidAppear and viewDidDisappear respectively.
Please provide your valuable suggestions or a solution to this problem. Thanks!
Short answer: You should add a UIScreenEdgePanGestureRecognizer to your view controller if you want to add a pop gesture where none exists. Modifying the existing interactivePopGestureRecognizer is probably not the right approach. Do this:
[self addGestureRecognizer:({
UIScreenEdgePanGestureRecognizer *gesture =
[[UIScreenEdgePanGestureRecognizer alloc]
initWithTarget:self action:#selector(pop)];
gesture;
})];
and
-(void)pop {
// pop your view controller here
}
Long answer: Forcing the interactivePopGestureRecognizer.delegate is what breaks your code.
If you need to cast self as such:
self.navigationController.interactivePopGestureRecognizer.delegate =
(id<UIGestureRecognizerDelegate>)self;
...it is because self is not a UIGestureRecognizerDelegate. The following should compile, link, build and run or you are setting yourself up for trouble:
self.navigationController.interactivePopGestureRecognizer.delegate = self;
Note that being a UIGestureRecognizerDelegate specifically allows you to tweak a gesture's behavior at runtime, assuming you are implementing one of the following and ensuring that the tweak applies to a gesture you own:
gestureRecognizerShouldBegin:
gestureRecognizer:shouldReceiveTouch:
gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer:
gestureRecognizer:shouldRequireFailureOfGestureRecognizer:
gestureRecognizer:shouldBeRequiredToFailByGestureRecognizer:
By constantly changing the delegate of that interactivePopGestureRecognizer you did not create, all you are doing is preventing the iOS behavior to take place.
From the documentation
UINavigationController -interactivePopGestureRecognizer
The gesture recognizer responsible for popping the top view controller off the navigation stack. (read-only)
In plain English: Use this value is you need to combine that gesture with your own gesture. But you are not supposed to modify its behavior:
...You can use this property to retrieve the gesture recognizer and tie it to the behavior of other gesture recognizers in your user interface...
Playing around with some Objective-C (well, iOS) and have done the following... loaded some UIButtons programmatically into a UIScrollView. That works well. Though I've always just connected UIViewControllers together using control-click and drag. Now I've created buttons programmatically, I have no idea how to go from one view controller to another in a Storyboard because there is nothing to drag from!
I'm not really sure what code to post as such, because I haven't done anything that /nearly/ works or doesn't work as such. I get how to do it with XIBs. But I suppose the question is : 3 UIButtons have been created programmatically and I have 3 UIViewControllers. How do I access those ViewControllers using my UIButtons?
Thanks
In the Interface builder view control click and drag from the viewcontroller icon under the first view controller, to the middle of the second view controller. A segue will be created, selected the appropriate type.
Now select the segue and in the inspector give it a unique identifier (say 'myNewSegue').
Now in your first viewcontroller you can create a method that has the following code:
-(void)myButtonAction:(id)sender {
[self performSegueWithIdentifier:#"myNewSegue" sender:self];
}
And add this method as a target action to your button:
[myButton addTarget:self
action:#selector(myButtonAction:)
forControlEvents:UIControlEventTouchUpInside];]
A segue doesn't have to have a button at the leading end of it; you can instead draw it from an entire view controller to another. You can also give a segue an identifier, a string that's used as a name for that segue. Once you've done that, you can programmatically trigger that segue by calling -performSegueWithIdentifier:sender:.
To actually call -performSegueWithIdentifier:sender:, though, you'll need to connect the button to a target and action. If you've never done that, read the Event Handling Guide for iOS in your documentation.
Is there a simple way to disable a single storyboard scene based on a condition?
I'm using to check if location services are enabled for my app:
[CLLocationManager authorizationStatus] != kCLAuthorizationStatusDenied
If the above is true then I want to disable a scene that I created and the associated segues to get to that scene (I'm using left/right swipe gestures).
** UPDATED: I was confusing multiple storyboards with multiple scenes...my question has been updated to reflect this. I'm wanting to disable a specific scene in my storyboard, not a storyboard.
To do what you want, you should write an action in your view controller that uses the condition(s) you set to choose the scene to segue to (or none at all). Don't just have a button or gesture trigger a push segue -- have it trigger the action in the view controller so that you can select the next scene in your code.
It's all well and good that you can set up segues right in the storyboard file, and it makes a great demo, but when you want to determine the destination scene at runtime you need to do that in code.
I ended up taking a hint from this post: https://stackoverflow.com/questions/8309104/enable-disable-swiper-gesture-or-view-change-in-storyboard
I just created an IBOutlet in the header for a swipe gesture and placed the following code in an if statement that checks if the user has location services enabled or not and wired it up in addition to the segue in IB:
swipe.enable = NO;
Thanks for the assistance all!
I've set up a really simple project using storyboards including two views as shown here: http://i.stack.imgur.com/iRx21.png. The navigation can be done by either selecting a cell in the custom table view or hitting the back button labelled with "<<". Everything works fine except the following:
when I switch between the views, every time an instantiation happens. The profiling shows an increasing number of view objects. I would like to keep only one of each view and instantiation should be happen only once. What am I doing wrong? (I'm using ARC.)
Thanks in advance!
You should not link your back button to the parent view controller. This is what causes the new instantiation.
The way to go is to embed the table view into UINavigationController (in IB, choose Editor -> Imbed In -> Navigation Controller. Then change your segue to a Push segue. You can of course hide the navigation bar etc. to make things look exactly as you like. Then, link the back button to the controller with an IBAction and in the handler do a simple
[self.navigationController popViewControllerAnimated:YES];
This would be the appropriate logic of what you are doing. Of course, you can also push the web view modally and then handle the button click with
[self dismissModalViewControllerAnimated:YES];
The structure of my MainStoryboard is:
->Tab Bar Controller -> Navigation Controller -> View Controller (Search)
The behaviour I want to have is that when the user re-selects the Search tab, the UIScrollView on it scrolls to the top. I am unsure how to get the event from the TabBarController, however.
I've been looking at a lot of stuff about UITabBarDelegate, particularly:
- (void)tabBar:(UITabBar *)tabBar didSelectItem:(UITabBarItem *)item
I have, not quite managed to get this to work properly though. I am very unsure about how to go about setting the delegate (assuming that is the way it's done). I've tried hooking it up in IB, but it wouldn't let me. I also tried to get the UITabBar from the AppDelegate (after looking at some seemingly-related answers).
Any pointers will be greatly appreciated (unless they're null).
UITabBar *aTabBar = [UITabBarItem alloc] init];
....Any other modifications you want to make to aTabBar....
[aTabBar setDelegate:self]
Don't forget to add "<UITabBarDelegate>" to the "#interface" part of whatever object you're trying to designate as the delegate.
For my own code, I usually use some object that isn't the application delegate (as the app delegate is usually meant for application level events like "application is suspending" or "application is coming back into foreground"). If you add "<UITabBarDelegate>" to your Search view controller, make sure that whatever you do with the "didSelectItem" method is applicable only to the Search view controller. Otherwise instantiate some different object if you want to do actions on various view controllers based on which tab bar item is being displayed.