How to "cancel" a UIStoryBoardSegue

Question

Does anyone know how to "stop" a segue transition conditionally:

My table view cells represent products which can be viewed in a drill-down "detail" view... or cannot! (It depends on a couple of things)

Now my App considers all products "unlocked":

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    NSIndexPath *selectedRowIndex = [self.tableView indexPathForSelectedRow];
    ListaProdottiController *prodottiViewController = [segue destinationViewController];
    prodottiViewController.blocco = [self.fetchedResultsController objectAtIndexPath:selectedRowIndex];
}

How can I cancel the row selection => drilldown, at this point?

Solution 1

If you are targeting iOS 6 or greater, then my knowledge of the cleanest way to do this is the following:

-(BOOL)shouldPerformSegueWithIdentifier:(NSString *)identifier sender:(id)sender
{
    if([identifier isEqualToString:@"show"])
    {
        NSIndexPath *selectedRowIndex = [self.tableView indexPathForSelectedRow];
        Blocco *blocco = [self.fetchedResultsController objectAtIndexPath:selectedRowIndex];
        return [blocco meetRequiredConditions];
    }
    return YES;
}

Where there is a method

-(BOOL) meetsRequiredConditions;

Defined on your Blocco class returns YES if the "couple of things" which permit a drill-down are valid.

Solution 2

I don't know if it is the right way to do it but I discovered a workaround.

From the storyboard I associate(control+click) a segue from the status bar in the view controller. Give the segue an ID (for example: switchSegue).

Now, from an action in your code (in my code I use a button), I call:

 [self performSegueWithIdentifier:@"switchSegue" sender:sender];

That way you can control if your segue is performed or not. Try tutorials that helped me from here and here

Hope this helps.

Solution 3

I am using an much easier and tidy approach.

Storyboard

1. Create two identical cell with different identifiers. Eg: "cellWithSegue" and "cellWithoutSegue".
2. Connect the first cell ("cellWithSegue") with the segue you want to display.
3. Do not connect the second cell with any segue.

Table View

1. On cellForRowAtIndexPath, implement a logic to determine if the cell should be linked a segue or not.
2. For cells that should be linked with the segue use the "cellWithSegue" identifier, for the rest the "cellWithoutSegue".

This way looks a lot easier to implement and also does not alter the way segues are supposed to work.

Solution 4

I may be wrong here, but after struggling myself with this, I just disabled the cell's user interaction on the cells where I didn't want the seque triggered (in cellForRowAtIndexPath:). Seems to work perfectly, and it's only 1 line of code!

cell.userInteractionEnabled = NO;

Solution 5

The easiest solution is to create manual segue in story board and use that as seen below.

[self performSegueWithIdentifier:@"loginSuccessSegue" sender:self];

---

Or

---

@Fabio: I was trying to get a solution for same kind of use-cases and I almost found a solution.

Use-cases 1. Stop segue transition conditionally 2. Change destination viewController conditionally

Solution:

Use "Custom" segue. Follow below steps to create Custom segue 1. Create a subclass of UIStoryboardSegue "MyCustomSegue.h"

@interface MyCustomSegue : UIStoryboardSegue
@end

"MyCustomSegue.m"

Override initWithIdentifier for implementing use-case 1 and 2 If you return nil, segue will be cancelled/no action will be taken You instantiate your ViewController and set that as a destination. You can set destination as your old xib file also.. that code is commented, but I ensured that will work.

@implementation MyCustomSegue
- (id)initWithIdentifier:(NSString *)identifier source:(UIViewController *)source destination:(UIViewController *)destination{

    UIStoryboard *storyBoard= [UIStoryboard storyboardWithName:@"MainStoryboard_iPhone" bundle:nil];

    UIViewController *viewController = [storyBoard instantiateViewControllerWithIdentifier:@"testIdentifier"];

    // MyViewController* viewController= [[MyViewController alloc]initWithNibName:@"MyViewController" bundle:nil];
    return [super initWithIdentifier:identifier source:source destination:viewController];
}

2. You must override "perform".

You can implement use-case 1 here also..

- (void)perform {
    // if either source or destination is nil, stop
    if (nil == self.sourceViewController || nil == self.destinationViewController) return;
    // return; //No Action. Segue will be cancelled
    UINavigationController *ctrl = [self.sourceViewController navigationController];
    [ctrl
     pushViewController:self.destinationViewController
     animated:YES];
}

Hope this helps. Plz write if you are not clear.

View more solutions

Comments

[Joshcodes]

If you are using iOS 6 or greater, see my answer below for a proper way to handle this.

[Dan Waterbly]

This seems to be a lot of extra work than what is needed. Wouldn't it be easier to choose which seque you wanted to invoke (or not) based on what table cell is selected? You would not have create a custom segue and your view controller would lose its dependency on other view controllers. You can request that a seque be perfomed in code by using: [self performSegueWithIdentifier:@"SegueIdentiferName" sender:self];.

[JordanC]

Agreed this is not needed. Just manually call performSegueWithIdentifier and you will not need to override UIStoryboardSegue

[Leonardo]

in my opinion it is not a lot of code, it is just one class than you can reuse for other segue and controllers by use of categories and protocols for example. I found it much better than writing lot of it-then-else case for deciding which button or cell has been pressed in the xib.

[Senad Uka]

It's the simplest way I have found :) Cool! Thank you!

[Dave]

Great tip! Perfect solution in my case.

[Phil Hale]

It's my preferred solution as well. Thanks!

[Patrick]

This is by far the most robust solution and still very easy. Much thanks. I would up vote it again if I could.

[lhunath]

Probably the most generically applicable solution.

[mcrute]

This just doesn't work at all. You can't dismiss the view controller because you're running before the segue happens.

[mcrute]

A better approach would be connect the thing that triggers the segue to an IBAction that determines if the segue should occur and triggers [self performSegueWithIdentifier:@"Whatever" sender:self]

[Hank Brekke]

For some reason it still works when the segue is presented modally though, even though it doesn't seem like it would. It worked in my application that I discontinued. It may not work now that 5.0.1 and 5.1 are released. There is a shouldPerformSegueWithIdentifier:sender: method in iOS 6 but nothing more can be explained because of NDA.

[Amandir]

A simple and fast fixed, good explanation and sources - I wish every answer would be this great

[jweyrich]

Although this will not work as expected if you still want the cell to be selected without performing the segue.

[JK Laiho]

jweyrich: True. Programmatically doing the cell selection in willSelectRow... (perhaps with a timed unselection) is still possible I think, and in any case, you'd want to give the user some type of indication of why the cell tap isn't doing what they expect.

[jweyrich]

Imagine a picker, but on its own screen. The user taps an item on the table, it calls a delegate passing the selected item, which then handles it and pops the controller. This required me to extend UITableViewController, add a property inSelectionMode and conditionally change accessoryType from Disclosure to Mark. Consequently I wanted the cell to be visually selected, without performing the segue. Both seem to require didSelectRowAtIndexPath to be called. The easiest solution I found was to link the segue directly to the controller and call performSegueWithIdentifier conditionally.

[Sten Petrov]

wow, this is the most tedious way around - now you have to maintain the looks of two cell types, the code that determines which one to show them instead of if (this) doSegue() kind of thing.

[devios1]

-1 This is a horrible solution. "Create two identical cells" is a direct violation of the DRY principle.

[AlanObject]

Looking at the Apple reference it seems this is how it is intended to be used. In my case if the segue is blocked I would like to do a dialog box. One thing at a time though.

[Radu Simionescu]

and what makes you think this is "tidy"?

[zirinisp]

I don't any more. I was not aware of the accepted solution at the time.

[Cœur]

Note that this solution is OK for cellForRowAtIndexPath: but is not enough when used in a different method, for instance when attempting to prevent double-triggering in prepareForSegue:sender:, as the cell may be recreated without user interaction disabled.