67 lines
2.9 KiB
Swift
67 lines
2.9 KiB
Swift
/// Result builder for composing ``View`` hierarchies.
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@resultBuilder public enum ViewBuilder {
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/// Wraps a single ``View`` in an ``AnyView``.
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public static func buildExpression<V: View>(_ v: V) -> [AnyView] { [AnyView(v)] }
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/// Keeps one contribution per source statement while flattening its array.
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public static func buildBlock(_ parts: [AnyView]...) -> [AnyView] { parts.flatMap { $0 } }
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/// Records the optional branch as one stable conditional slot.
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public static func buildOptional(_ part: [AnyView]?) -> [AnyView] {
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[AnyView.conditional(.taken(index: part == nil ? nil : 0, content: part ?? []))]
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}
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/// Records the first branch as one stable conditional slot.
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public static func buildEither(first: [AnyView]) -> [AnyView] {
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[AnyView.conditional(.taken(index: 0, content: first))]
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}
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/// Records the second branch as one stable conditional slot.
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public static func buildEither(second: [AnyView]) -> [AnyView] {
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[AnyView.conditional(.taken(index: 1, content: second))]
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}
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/// Records loop rows as one positional list slot.
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public static func buildArray(_ parts: [[AnyView]]) -> [AnyView] { [AnyView.list(parts)] }
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/// Treats availability branches as one positional list slot.
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public static func buildLimitedAvailability(_ part: [AnyView]) -> [AnyView] {
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[AnyView.list([part])]
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}
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}
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/// Result builder for a slot that must receive exactly one ``View``.
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@resultBuilder public enum SingleViewBuilder {
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/// Wraps a single ``View`` in an ``AnyView``.
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public static func buildExpression<V: View>(_ v: V) -> AnyView { AnyView(v) }
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/// Preserves the terminal ``Never`` body witness.
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public static func buildExpression(_ content: Never) -> Never { content }
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/// Passes through the block's single view.
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public static func buildBlock(_ view: AnyView) -> AnyView { view }
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/// Preserves a terminal ``Never`` body witness in a block.
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public static func buildBlock(_ content: Never) -> Never { content }
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/// Records the first branch as a conditional slot.
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public static func buildEither(first: AnyView) -> AnyView {
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AnyView.conditional(.taken(index: 0, content: [first]))
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}
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/// Records the second branch as a conditional slot.
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public static func buildEither(second: AnyView) -> AnyView {
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AnyView.conditional(.taken(index: 1, content: [second]))
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}
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/// Produces a stable conditional node for an absent or present optional body.
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public static func buildOptional(_ part: AnyView?) -> AnyView {
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AnyView.conditional(.taken(index: part == nil ? nil : 0, content: part.map { [$0] } ?? []))
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}
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/// Passes through an availability-guarded branch unchanged.
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public static func buildLimitedAvailability(_ part: AnyView) -> AnyView { part }
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/// Preserves a terminal ``Never`` body witness in an availability branch.
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public static func buildLimitedAvailability(_ content: Never) -> Never { content }
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}
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