Ios – Completion block for popViewController

cocoa-touchiosuiviewuiviewanimationuiviewcontroller

When dismissing a modal view controller using dismissViewController, there is the option to provide a completion block. Is there a similar equivalent for popViewController?

The completion argument is quite handy. For instance, I can use it to hold off removing a row from a tableview until the modal is off screen, letting the user see the row animation. When returning from a pushed view controller, I would like the same opportunity.

I have tried placing popViewController in an UIView animation block, where I do have access to a completion block. However, this produces some unwanted side effects on the view being popped to.

If there is no such method available, what are some workarounds?

Best Answer

I know an answer has been accepted over two years ago, however this answer is incomplete.

There is no way to do what you're wanting out-of-the-box

This is technically correct because the UINavigationController API doesn't offer any options for this. However by using the CoreAnimation framework it's possible to add a completion block to the underlying animation:

[CATransaction begin];
[CATransaction setCompletionBlock:^{
    // handle completion here
}];

[self.navigationController popViewControllerAnimated:YES];

[CATransaction commit];

The completion block will be called as soon as the animation used by popViewControllerAnimated: ends. This functionality has been available since iOS 4.

Swift

Install via CocoaPods or Carthage: https://github.com/ashleymills/Reachability.swift

Test reachability via closures

let reachability = Reachability()!

reachability.whenReachable = { reachability in
    if reachability.connection == .wifi {
        print("Reachable via WiFi")
    } else {
        print("Reachable via Cellular")
    }
}

reachability.whenUnreachable = { _ in
    print("Not reachable")
}

do {
    try reachability.startNotifier()
} catch {
    print("Unable to start notifier")
}

Objective-C

Add SystemConfiguration framework to the project but don't worry about including it anywhere
Add Tony Million's version of Reachability.h and Reachability.m to the project (found here: https://github.com/tonymillion/Reachability)

Update the interface section

#import "Reachability.h"

// Add this to the interface in the .m file of your view controller
@interface MyViewController ()
{
    Reachability *internetReachableFoo;
}
@end

Then implement this method in the .m file of your view controller which you can call

// Checks if we have an internet connection or not
- (void)testInternetConnection
{
    internetReachableFoo = [Reachability reachabilityWithHostname:@"www.google.com"];

    // Internet is reachable
    internetReachableFoo.reachableBlock = ^(Reachability*reach)
    {
        // Update the UI on the main thread
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"Yayyy, we have the interwebs!");
        });
    };

    // Internet is not reachable
    internetReachableFoo.unreachableBlock = ^(Reachability*reach)
    {
        // Update the UI on the main thread
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"Someone broke the internet :(");
        });
    };

    [internetReachableFoo startNotifier];
}

Important Note: The Reachability class is one of the most used classes in projects so you might run into naming conflicts with other projects. If this happens, you'll have to rename one of the pairs of Reachability.h and Reachability.m files to something else to resolve the issue.

Note: The domain you use doesn't matter. It's just testing for a gateway to any domain.

Ios – Xcode – How to fix ‘NSUnknownKeyException’, reason: … this class is not key value coding-compliant for the key X” error

You may have a bad connection in your xib.

I've had this error many times. While TechZen's answer is absolutely right in this case, another common cause is when you change the name of a IBOutlet property in your .h/.m which you've already connected up to File's Owner in the nib.

From your nib:

Select the object in IB and go to the 'Connections Inspector'.
Under 'Referencing Outlets' make sure that your object isn't still connected to the old property name... if it is, click the small 'x' to delete the reference and build again.

Another common cause if you are using Storyboard, your UIButton might have more then one assignings (Solution is almost the same as for nib):

Open your storyboard and right click the UIButton
You will see that there is more than one assign/ref to this button. Remove one of the "Main..." greyed windows with the small "x":

Best Answer

Related Solutions

Ios – How to check for an active Internet connection on iOS or macOS

Swift

Objective-C

Ios – Xcode – How to fix ‘NSUnknownKeyException’, reason: … this class is not key value coding-compliant for the key X” error

You may have a bad connection in your xib.

Related Topic