Swift: 正确初始化 SIMD3 并从结构中调用它

Question

我正在尝试调用已定义的结构，以便在按下按钮时能够更改其值。我在结构内调用 SIMD3 时遇到问题。目前我有，

struct CaptureData {
    var vertices: [SIMD3<Float>]

    var mode: Mode = .one
    mutating func nextCase() {
     mode = mode.next()
    }
    var verticesFormatted : String {

    let v = "<" + vertices.map{ "\([=11=].x):\([=11=].y):\([=11=].z)" }.joined(separator: "~") + "method: \(mode.next().rawValue)"
            return "\(v)"
        }
}

我之前从@Joshua 那里得到帮助的扩展

enum Mode: String, CaseIterable {
    case one, two, three
}
extension CaseIterable where Self: Equatable {
    var allCases: AllCases { Self.allCases }
    var nextCase: Self {
        let index = allCases.index(after: allCases.firstIndex(of: self)!)
        guard index != allCases.endIndex else { return allCases.first! }
        return allCases[index]
    }
    @discardableResult
    func next() -> Self {
        return self.nextCase
    }
}

我正在尝试初始化 var instance = CaptureData(vertices: [SIMD3<Float>])，但出现错误：Cannot convert value of type '[SIMD3<Float>].Type' to expected argument type '[SIMD3<Float>]'

@Jousha 还建议我使用以下内容：

 typealias XYZVar = (x: Float, y: Float, z: Float) 

struct CaptureData { 
var vertices:[XYZVar] 
.... other variables 
}

但是，我也用 var instance = CaptureData(vertices: [XYZVar]) 尝试过，但它也不起作用：Cannot convert value of type '[XYZVar].Type' (aka 'Array<(x: Float, y: Float, z: Float)>.Type') to expected argument type '[XYZVar]' (aka 'Array<(x: Float, y: Float, z: Float)>')

我的问题是，如何正确调用 SIMD3 并修复来自 var instance = CaptureData(vertices: [SIMD3<Float>]) 的上述错误？

非常感谢。

Answer 1

嗯，我从哪里开始？

您正在将类型 [SIMD3<Float>] 和 [XYZVar] 传递给需要值作为参数的 function/initializer。这就是编译器抱怨的原因。

让我解释一下。

在 swift 中，当你写 var vertices: [SIMD3<Float>] 时，你是在说："vertices" 是 SIMD3<Float> 的数组。现在，如果你想给 "vertices" 赋值，你可以写 vertices = [] 或 vertices = [SIMD3<Float>]() 它们是等价的。

我对您的代码做了一些修改。看看：


    import simd

    enum Mode: String, CaseIterable {
        case one, two, three
    }

    extension CaseIterable where Self: Equatable {

        var allCases: AllCases { Self.allCases }

        var nextCase: Self {
            let index = allCases.index(after: allCases.firstIndex(of: self)!)
            guard index != allCases.endIndex else { return allCases.first! }
            return allCases[index]
        }

        @discardableResult
        func next() -> Self {
            return self.nextCase
        }
    }

    struct CaptureData {
        var vertices: [SIMD3<Float>]

        var mode: Mode = .one

        mutating func nextCase() {
            mode = mode.next()
        }

        var verticesFormatted : String {

            let verticesDescribed = vertices
                .map({ "\([=10=].x):\([=10=].y):\([=10=].z)" })
                .joined(separator: "~")

            let v = "< \(verticesDescribed) method: \(mode.next().rawValue)"

            return v
        }
    }

    let data = CaptureData(vertices: [
        SIMD3<Float>(x: 0, y: 0, z: 0),
        SIMD3<Float>(x: 0.5, y: 1, z: 0),
        SIMD3<Float>(x: 1, y: 0, z: 0)
    ])

    print(data.verticesFormatted) 
    // prints: < 0.0:0.0:0.0~0.5:1.0:0.0~1.0:0.0:0.0 method: two

Swift: 正确初始化 SIMD3 并从结构中调用它

Swift: Properly initialize SIMD3 and call it from struct

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