Change constraints based on text length - ios

Question

I have two labels, that are ordered like this:
H:[label1]-10-[label2]
I want to change their order, based on the first label's length. So, if its text won't fit on one line, I want to change the constraints to look like this:
V:[label1]-2.5-[label2]
Here are my constraints right now:
[self.containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[_carLabel]-2.5-[_statusLabel]|" options:0 metrics:nil views:views]];
[self.containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[_carLabel]|" options:0 metrics:nil views:views]];
[self.containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[_statusLabel]|" options:0 metrics:nil views:views]];
And this is how I want them to look, when _carLabel won't fit in one line:
[self.containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"H:|[_carLabel]-10-[_statusLabel]|" options:0 metrics:nil views:views]];
[self.containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[_carLabel]|" options:0 metrics:nil views:views]];
[self.containerView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[_statusLabel]|" options:0 metrics:nil views:views]];
How would I do this?

Answer 1

I think your best bet would be to conditionally apply constraints based on the size of the label. I don't believe there's a way to add both constraints and have this work how you described. (Though if it is possible it will likely have to do with setting the priority of each constraint #"[label1]-10#99-[label2]" and #"V:[label1]-2.5#98-[label2] but I was unable to get that to work. The code below however seems to do what you're looking for.
UILabel *label1 = [[UILabel alloc] init];
label1.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:label1];
[label1 setText:#"Small text"];
// [label1 setText:#"Some really long text to test the other scenario also works"];
UILabel *label2 = [[UILabel alloc] init];
label2.translatesAutoresizingMaskIntoConstraints = NO;
[self.view addSubview:label2];
[label2 setText:#"Small text 2"];
[label1 sizeToFit];
if (label1.frame.size.width + kPadding + label2.frame.size.width < self.view.frame.size.width) {
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"|[label1]-padding#100-[label2]"
options:0
metrics:#{#"padding": #(kPadding)}
views:NSDictionaryOfVariableBindings(label1, label2)]];
} else {
[self.view addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:#"V:|[label1]-2.5#100-[label2]"
options:0
metrics:nil
views:NSDictionaryOfVariableBindings(label1, label2)]];
}