Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
import SwiftUI
// T.Type -> AlignmentID.Type -> Any.Type -> UInt
extension HorizontalAlignment {
enum TestH: AlignmentID {
static func defaultValue(in context: ViewDimensions) -> CGFloat {
0
}
}
static let testH = HorizontalAlignment(TestH.self)
}
extension VerticalAlignment {
enum TestV: AlignmentID {
static func defaultValue(in context: ViewDimensions) -> CGFloat {
0
}
}
static let testV = VerticalAlignment(TestV.self)
}
var testType = HorizontalAlignment.TestH.self
var alignmentIDType: AlignmentID.Type = testType
let anyType: Any.Type = alignmentIDType
MemoryLayout<HorizontalAlignment.TestH.Type>.size // 0
MemoryLayout<AlignmentID.Type>.size // 16
MemoryLayout<Any.Type>.size // 8
let ob_1 = ObjectIdentifier(testType)
let ob_2 = ObjectIdentifier(alignmentIDType)
let ob_3 = ObjectIdentifier(anyType)
let testH = HorizontalAlignment.testH
dump(testH)
// Obtain `bits: UInt` from `AlignmentKey` type.
let key = Mirror(reflecting: testH).children.first!.value
let bits = Mirror(reflecting: key).children.first!.value as! UInt
print(String(bits, radix: 16))
let i_1 = UInt(bitPattern: ob_1)
let i_2 = UInt(bitPattern: ob_2)
let i_3 = UInt(bitPattern: ob_3)
let i_4 = unsafeBitCast(anyType, to: UInt.self)
i_1 == i_2 && i_2 == i_3 && i_3 == i_4 // true
print(String(i_1, radix: 16))
// UInt -> Any.Type -> AlignmentID.Type
let e_1 = unsafeBitCast(i_1, to: Any.Type.self)
let e_2 = unsafeBitCast(bits, to: Any.Type.self)
anyType == e_1
anyType == e_2
let a_1 = e_1 as! AlignmentID.Type
a_1 == testType // true
a_1 == alignmentIDType // true
let a_2 = e_2 as! AlignmentID.Type
a_2 == testType // true
a_2 == alignmentIDType // true
func extract(_ guide: HorizontalAlignment) -> AlignmentID.Type {
let key = Mirror(reflecting: guide).children.first!.value
let bits = Mirror(reflecting: key).children.first!.value as! UInt
let existential = unsafeBitCast(bits, to: Any.Type.self)
return existential as! AlignmentID.Type
}
func extract(_ guide: VerticalAlignment) -> AlignmentID.Type {
let key = Mirror(reflecting: guide).children.first!.value
var bits = Mirror(reflecting: key).children.first!.value as! UInt
// align the value as VerticalAlignment key is intentionally misaligned
bits -= 1
let existential = unsafeBitCast(bits, to: Any.Type.self)
return existential as! AlignmentID.Type
}
print(extract(.leading)) // Leading
print(extract(HorizontalAlignment.center)) // Center
print(extract(.trailing)) // Trailing
print(extract(HorizontalAlignment.testH)) // TestH
print(extract(.top)) // Top
print(extract(VerticalAlignment.center)) // Center
print(extract(.bottom)) // Bottom
print(extract(VerticalAlignment.testV)) // TestV
print(extract(.firstTextBaseline)) // FirstTextBaseline
print(extract(.lastTextBaseline)) // LastTextBaseline
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment