Class

NSStackView

A view that arranges an array of views horizontally or vertically and updates their placement and sizing when the window size changes.

Declaration

class NSStackView : NSView

Overview

A stack view employs Auto Layout (the system’s constraint-based layout feature) to arrange and align an array of views according to your specification. To use a stack view effectively, you need to understand the basics of Auto Layout constraints as described in Auto Layout Guide.

Basic Features of Stack Views

A stack view supports vertical and horizontal layouts and interacts dynamically with window resizing and Cocoa animations. You can easily reconfigure the contents of a stack view at runtime. That is, after you create and configure a stack view in Interface Builder, you can add or remove views dynamically without explicitly working with layout constraints. For example, if you configure a stack view with three checkboxes and dynamically add a fourth, the stack view automatically adds constraints as needed, according to the stack view’s configuration. The new checkbox gains dynamic layout configuration from the stack view.

Stack views are nestable: a stack view is a valid element in the views array of another stack view.

For more information on NSStackView, see Organize Your User Interface with a Stack View.

Layout Direction and Gravity Areas

A stack view has three so-called gravity areas that each identify a section of the stack view’s layout. A horizontal stack view, which is the default type, has a leading, a center, and a trailing gravity area. The ordering of these areas depends on the value of the stack view’s userInterfaceLayoutDirection property (inherited from the NSView class). In a left to right language, the leading gravity area in a horizontal stack view is on the left. To enforce a left to right layout independently of language, explicitly set the layout direction by calling the inherited userInterfaceLayoutDirection method on your stack view instance.

To specify vertical layout, use the orientation property and the NSUserInterfaceLayoutOrientation.vertical constant from the NSUserInterfaceLayoutOrientation enumeration. In a vertical stack view, the gravity areas always are top, center, and bottom.

View Detachment and Hiding

A stack view can automatically detach and reattach its views in response to layout changes, such as window resizing performed by the user, or resizing/repositioning of another view in the same view hierarchy. A view in a detached state is not present in the stack view’s view hierarchy, but it still consumes memory. A view that is hidden, but not detached, remains part of the view hierarchy and continues to participate in Auto Layout, but it is not visible and doesn't receive input events.

To allow views to detach, set the so-called clipping resistance for a stack view to a value lower than its default of required. See the setClippingResistancePriority(_:for:) method.

You can influence which views detach first (and reattach last). Do this by setting the so-called visibility priority for each view whose detachment order you want to specify. A view with a lower visibility priority detaches before one with a higher priority, and reattaches after it. See the NSStackView.VisibilityPriority enumeration and the setVisibilityPriority(_:for:) method.

To explicitly detach a view from a stack view, call the setVisibilityPriority(_:for:) method with a value of NSStackViewVisibilityPriorityNotVisible. To explicitly reattach a view to a stack view, call the same method with a value of NSStackViewVisibilityPriorityMustHold. If you hide a view that belongs to a stack view (by setting the view's isHidden property to true), the view detaches from the stack view by default. Use the detachesHiddenViews property to change the default behavior.

The system calls a stack view delegate method when a view is about to be detached and when a view has been reattached, giving you the opportunity to run code at those times. See NSStackViewDelegate.

Topics

Creating a Stack View

init(views: [NSView])

Creates and returns a stack view with a specified array of views.

Responding to Stack-Related Changes

var delegate: NSStackViewDelegate?

The delegate object for the stack view.

protocol NSStackViewDelegate

A set of methods you use to respond to a stack view detaching and reattaching views.

Managing Views in Gravity Areas

func addView(NSView, in: NSStackView.Gravity)

Adds a view to the end of the stack view gravity area.

func insertView(NSView, at: Int, in: NSStackView.Gravity)

Adds a view to a stack view gravity area at a specified index position.

func setViews([NSView], in: NSStackView.Gravity)

Specifies an array of views for a specified gravity area in the stack view, replacing any previous views in that area.

func removeView(NSView)

Removes a specified view from the stack view.

enum NSStackView.Gravity

The gravity areas available in a stack view.

Managing the Arranged Subviews

func addArrangedSubview(NSView)

Adds the specified view to the end of the arranged subviews list.

func insertArrangedSubview(NSView, at: Int)

Adds the provided view to the array of arranged subviews at the specified index.

func removeArrangedSubview(NSView)

Removes the provided view from the stack’s array of arranged subviews.

var arrangedSubviews: [NSView]

The array of views arranged by the stack view.

Inspecting a Stack View

var views: [NSView]

The array of views owned by the stack view.

func views(in: NSStackView.Gravity) -> [NSView]

Returns the array of views in the specified gravity area in the stack view.

var detachedViews: [NSView]

An array that contains the detached views from all the stack view’s gravity areas.

func clippingResistancePriority(for: NSLayoutConstraint.Orientation) -> NSLayoutConstraint.Priority

Returns the Auto Layout priority for resisting clipping of views in the stack view when Auto Layout attempts to reduce the stack view’s size.

func huggingPriority(for: NSLayoutConstraint.Orientation) -> NSLayoutConstraint.Priority

Returns the Auto Layout priority for the stack view to minimize its size to fit its contained views as closely as possible, for a specified user interface axis.

Configuring the Stack View Layout

var orientation: NSUserInterfaceLayoutOrientation

The horizontal or vertical layout direction of the stack view.

enum NSUserInterfaceLayoutOrientation

The stack view layout directions, and user interface axes for hugging priority and clipping resistance.

var alignment: NSLayoutConstraint.Attribute

The view alignment within the stack view.

var spacing: CGFloat

The minimum spacing, in points, between adjacent views in the stack view.

var edgeInsets: NSEdgeInsets

The geometric padding, in points, inside the stack view, surrounding its views.

var hasEqualSpacing: Bool

A Boolean value that indicates whether the spacing between adjacent views should be equal to each other.

Deprecated

Configuring Views in a Stack View

func customSpacing(after: NSView) -> CGFloat

Returns the custom spacing, in points, between a specified view in the stack view and the view that follows it.

func setCustomSpacing(CGFloat, after: NSView)

Specifies the custom spacing, in points, between a specified view and the view that follows it in the stack view.

func visibilityPriority(for: NSView) -> NSStackView.VisibilityPriority

Returns the visibility priority for a specified view in the stack view.

func setVisibilityPriority(NSStackView.VisibilityPriority, for: NSView)

Sets the Auto Layout priority for a view to remain attached to the stack view when Auto Layout reduces the stack view’s size.

struct NSStackView.VisibilityPriority

The various Auto Layout priorities for a view in the stack view to remain attached.

Configuring Dynamic Behavior for a Stack View

var detachesHiddenViews: Bool

A Boolean value that indicates whether the stack view removes hidden views from its view hierarchy.

func setClippingResistancePriority(NSLayoutConstraint.Priority, for: NSLayoutConstraint.Orientation)

Sets the Auto Layout priority for resisting clipping of views in the stack view when Auto Layout attempts to reduce the stack view’s size.

func setHuggingPriority(NSLayoutConstraint.Priority, for: NSLayoutConstraint.Orientation)

Sets the Auto Layout priority for the stack view to minimize its size, for a specified user interface axis.