Superview not increasing in height based on the subviews constraint - ios

Question

I have a scrollview and a separate UIView where I placed a series of textFields and labels with constraints which fully occupies the top and bottom. I'm trying to adjust the UIView's height based on its subview constraints but it won't. What is happening is that the view keeps its height and force other textfields to collapse or shrink thus breaking the constraints.
Details
Each subview priority values :
compression = 750
hugging = 250
UIView priority values:
compression = 249
hugging = 749 Set to be lower than the rest.
Most of the textfields has aspect ratio constraint. This causes the field to adjust.
Each subview has vertical/top/bottom spacing between each other. The top and bottom elements has top and bottom constraints to the view as well.
What's on my code:
-(void)viewDidLayoutSubviews{
[super viewDidLayoutSubviews];
/* I had to adjust the UIView's width to fill the entire self.view.*/
if(![contentView isDescendantOfView:detailsScrollView]){
CGRect r = contentView.frame;
r.size.width = self.view.frame.size.width;
contentView.frame = r;
[detailsScrollView addSubview:contentView];
}
}
Screenshots
The view
This is what currently happens. In this instance it forces the email field to shrink. If I place a height value on it, it does not shrink but the layout engine finds another element to break
Edit:
Solved
Maybe I just needed some break to freshen up a bit. I did tried using constraints before but got no luck. However thanks to the suggestion I went back setting the constraints instead of setting the frame on this one and got it finally working.
Solution:
-(void)viewDidLoad{
[detailsScrollView addSubview:contentView];
[contentView setTranslatesAutoresizingMaskIntoConstraints:NO];
[detailsScrollView setTranslatesAutoresizingMaskIntoConstraints:NO];
NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings(contentView,detailsScrollView);
NSArray *horizontalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:#"H:|-0-[contentView]-0-|"
options:NSLayoutFormatDirectionLeadingToTrailing metrics:nil
views:viewsDictionary];
NSArray *verticalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:#"V:|-0-[contentView]-0-|"
options:NSLayoutFormatDirectionLeadingToTrailing
metrics:nil
views:viewsDictionary];
NSArray *widthConstraints = [NSLayoutConstraint constraintsWithVisualFormat:#"H:|-0-[contentView(==detailsScrollView)]-0-|" options:0 metrics:nil views:viewsDictionary];
}

Answer 1

When you use interface builder to deal with the UIScrollView and its child UIView. usually a top, bottom, left and equal width constraints are set between the UIScrollView and its child which is the contentView in your case.
Without those constraints the other option is to set the content size of the UIScrollView. which was the way of using the UIScrollView before introducing constraints.
So, 1. you should add those constraints programmatically.
By using the constraints, the views frame is no longer needed to resize the views.
So, 2. remove frame setting for your content view.
I am not so happy with the way you set the frame in the viewDidLayoutMethod. if I am going to do that here I would take the frame setting out of the if statement.
The code would be as follow with no if statement:
[detailsScrollView addSubview:contentView];
// then set the constraints here after adding the subview.
Put this code anywhere but not inside your viewDidLayoutSubviews method. it will be a bigger problem than setting the frame in there inside if statement.
Note: Originally, if you are going to set frame in the viewDidLayoutSubviews
method. you should do it for all cases. for example for the if case
and the else case. because, next time this method is going to be
called the views will respond to the constraint. and lose its frame.
Another observation: if you want the view to response to its subviews constraint why you need to set the frame for it? right?
After adding the constraint you may need to call the method constraintNeedsUpdate or another related method.