Protocol

AlignmentID

Types used to identify alignment guides.

---

Declaration

protocol AlignmentID

---

Overview

Use this protocol to create custom alignment guides. Custom alignment guides are needed to align views which are not in the same container.

To conform to this protocol, there is only one requirement: defaultValue(in:).

The most convenient way to create a custom alignment is with an extension.

A custom vertical alignment:

extension VerticalAlignment {
    enum CustomAlignment: AlignmentID {
       static func defaultVAlue(in d: ViewDimensions) -> CGFloat {
            d[VerticalAlignment.center]
        }
    }
    static let custom = VerticalAlignment(CustomAlignment.self)
}

To create a custom alignment for a ZStack, extend both VerticalAlignment and HorizontalAlignment:

extension VerticalAlignment {
    enum CustomAlignment: AlignmentID {
       static func defaultVAlue(in d: ViewDimensions) -> CGFloat {
            d[.top]
        }
    }
    static let vertical = VerticalAlignment(CustomAlignment.self)
}

extension HorizontalAlignment {
    enum CustomAlignment: AlignmentID {
       static func defaultVAlue(in d: ViewDimensions) -> CGFloat {
            d[.leading]
        }
    }
    static let horizontal = HorizontalAlignment(CustomAlignment.self)
}

extension Alignment {
    static let custom = Alignment(horizontal: .horizontal, vertical: .vertical)
}

For more on creating your own alignments, check out this article.

Availability

iOS 13.0+

macOS 10.15+

tvOS 13.0+

watchOS 6.0+

Topics

---

Type Method

defaultValue(in:) The value of the corresponding guide in the given context when not otherwise set in that context.