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NSLayoutAnchor

UIView does not provide anchor properties for the layout margin attributes. Instead, the layoutMarginsGuide property provides a UILayoutGuide object that represents these margins. Use the guide’s anchor properties to create your constraints.

These are the available layout anchors for UIView:

  • widthAnchor

  • heightAnchor

  • topAnchor

  • bottomAnchor

  • leadingAnchor

  • trailingAnchor

  • leftAnchor

  • rightAnchor

  • centerXAnchor

  • centerYAnchor

  • firstBaselineAnchor

  • lastBaselineAnchor

    // Creating constraints using NSLayoutConstraint

NSLayoutConstraint(item: subview, attribute: .Leading, relatedBy: .Equal, toItem: view, attribute: .LeadingMargin, multiplier: 1.0, constant: 0.0).active = true

NSLayoutConstraint(item: subview, attribute: .Trailing, relatedBy: .Equal, toItem: view, attribute: .TrailingMargin, multiplier: 1.0, constant: 0.0).active = true

// Creating the same constraints using Layout Anchors let margins = view.layoutMarginsGuide

subview.leadingAnchor.constraintEqualToAnchor(margins.leadingAnchor).active = true subview.trailingAnchor.constraintEqualToAnchor(margins.trailingAnchor).active = true

// Create & Add Layout Constraint let leadingConstraint = subview.leadingAnchor.constraintEqualToAnchor(superview.leadingAnchor, constant: 8.0)

// Activate Layout Constraint leadingConstraint.active = true

centerXAnchor.constraint(equalTo: (superview?.centerXAnchor)!, constant: 0).isActive = true

centerYAnchor.constraint(equalTo: (superview?.centerYAnchor)!, constant: 0).isActive = true



Reference: https://developer.apple.com/reference/uikit/nslayoutanchor