Snapkit LayoutConstraints Unable to simultaneously satisfy constraints

Question

I have simple UITableView and custom UITablViewCell in my project, which created programmatically and use SnapKit for auto layout its. When I run app, everything work fine and get some LayoutConstraints error in debug console.

UITableViewCell

import UIKit
import SnapKit
class TestTableViewCell: UITableViewCell {
    
    ...
    private lazy var containerView: UIView = {
        let view = UIView()
        return view
    }()
    
    private lazy var centerStackView: UIStackView = {
        let stackView = UIStackView(arrangedSubviews: [titleLabel, disclosureImageView])
        stackView.axis = .horizontal
        stackView.distribution = .fill
        stackView.spacing = 5.0
        return stackView
    }()
    
    private lazy var titleLabel: UILabel = {
        let label = UILabel()
        label.font = UIFont.systemFont(ofSize: 17, weight: .semibold)
        return label
    }()
    
    private lazy var disclosureImageView: UIImageView = {
        let imageView = UIImageView()
        imageView.contentMode = .scaleAspectFit
        imageView.image = UIImage(named: "disclosure")
        return imageView
    }()
    
   ..
    
    private func setupUI() {
        selectionStyle = .none
        backgroundColor = .background
        contentView.addSubview(containerView)
        containerView.backgroundColor = .white
        containerView.layer.cornerRadius = 12
        containerView.clipsToBounds = true
        containerView.addSubview(centerStackView)
        setNeedsUpdateConstraints()
    }
    
    // MARK: - Update Constraints
    override func updateConstraints() {
        containerView.snp.updateConstraints { make in
            make.top.bottom.equalToSuperview().inset(8)
            make.leading.trailing.equalToSuperview().inset(16)
            make.height.equalTo(100)
        }
        
        centerStackView.snp.updateConstraints { make in
            make.center.equalToSuperview()
        }
        
        super.updateConstraints()
    }
}

How I can fix this constraint error ?

Sweeper · Accepted Answer · 2022-07-20 17:47:08Z

1

There are actually two conflicts for each table view cell. You can copy-paste the sets of constraints are in conflict into https://www.wtfautolayout.com and see exactly why they are conflicting. As a result, we get this and this.

We can see that the first conflict is caused by your container view having a height constraint, but the table view itself also adds a height constraint to the cell to enforce its cells' sizes,

"<NSLayoutConstraint:0x7b1400031920 'UIView-Encapsulated-Layout-Height' UITableViewCellContentView:0x7b4c00003640.height == 116.5   (active)>"

For some reason, the constant here is 116.5, not 116 as you would expect from the 100 points of height of the container view + the 16 points of inset.

You can either change it to

make.height.greaterThanOrEqualTo(100)

Or remove the height constraint completely:

// make.height.equalTo(100)

and use the delegate method heightForRowAt to control the cell height instead:

override func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    116
}

As for the second conflict, it is caused by a constraint constraining the stack view's width to 0, being in conflict with the fact that there must be some spacing between the image and label.

"<NSLayoutConstraint:0x7b1400031b50 'UIView-Encapsulated-Layout-Width' UIStackView:0x7b4c000039c0.width == 0   (active)>"

If you move the following code from updateConstraints into setupUI, the conflict is resolved:

containerView.snp.updateConstraints { make in
    make.top.bottom.equalToSuperview().inset(8)
    make.leading.trailing.equalToSuperview().inset(16)
    make.height.greaterThanOrEqualTo(100)
}

centerStackView.snp.updateConstraints { make in
    make.center.equalToSuperview()
}

answered Jul 20, 2022 at 17:47

Sweeper

292k23 gold badges260 silver badges438 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

user3544668 Over a year ago

Thanks for the detailed answer. Can you tell me, I override function updateConstraints() for customization UITableVIewCell and UICollectionViewCell instead makeConstraints(), is it incorrect way to setup constraints ?

Sweeper Over a year ago

@user3544668 I have never overridden updateConstraints for adding constraints for adding constraints to my views. As its name and the discussion in its documentation suggests, it's for updating existing constraints, not for setting things up, so I don't think this is correct... I've always just called makeConstraints and I've never encountered any problems regarding this.

Collectives™ on Stack Overflow

Snapkit LayoutConstraints Unable to simultaneously satisfy constraints

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related