AutoLayout - Visual Format Language not working iOS8

Question

I'm trying to learn how to use autolayout and write constraints using the visual format language. for a simple test I have a test view and want it to expand the full size. So top, bottom, trailing, leading to superview would all be zero.

If I run in iOS 7, it seems to mostly work, but get black bars on the top and bottom of iPhone 5 simulator with no ambiguous layout errors.

In iOS 8, I get ambiguous layout errors. Can anyone show me where my problem is?

Here's my code:

- (void)viewDidLoad {
    [super viewDidLoad];

    testView = [UIView new];
    testView.backgroundColor = [UIColor blueColor];
    testView.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:testView];

    [self.view needsUpdateConstraints];
}
- (void)updateViewConstraints
{
    [super updateViewConstraints];
    [self.view removeConstraints:self.view.constraints];

    NSDictionary *viewsDictionary =
    NSDictionaryOfVariableBindings(testView);
    NSArray *constraints = [NSLayoutConstraint
                            constraintsWithVisualFormat:@"|[testView]|"
                            options:0
                            metrics:nil
                            views:viewsDictionary];
    [self.view addConstraints:constraints];

    constraints = [NSLayoutConstraint
                   constraintsWithVisualFormat:@"V:|[testView]|"
                   options:0
                   metrics:nil
                   views:viewsDictionary];
    [self.view addConstraints:constraints];
}

Thanks!

-- Update - the issue seems to be with [self.view removeConstraints:self.view.constraints]; If I comment that out, it works fine. Not sure why though.

Answer 1

Try calling [self.view setNeedsUpdateConstraints]. You are calling [self.view needsUpdateConstraints], which just asks whether setNeedsUpdateConstraints has been called.