无法从 Swift 中的协议扩展调用泛型初始化程序

Question

我正在尝试调用我从我也制作的协议扩展方法制作的struct：

public struct AdjacentDifferenceArrayGenerator<T: Strideable where T.Stride == T>: GeneratorType {
    private var array: [T]
    public init<U: SequenceType where U.Generator.Element == T>(source: U) {
        self.array = source.adjacentDifference()
    }
    public mutating func next() -> [T]? {
        guard !array.isEmpty else {
            return nil
        }
        defer {
            self.array = self.array.adjacentDifference()
        }
        return self.array
    }
}

public extension SequenceType where Generator.Element: Strideable {
    public func adjacentDifference() -> [Self.Generator.Element.Stride] {
        var result: [Self.Generator.Element.Stride] = []
        var generator = AdjacentDifferenceGenerator(generator: self.generate())
        while let difference = generator.next() {
            result.append(difference)
        }
        return result
    }
}

public extension SequenceType where Generator.Element: Strideable, Generator.Element.Stride: Strideable, Generator.Element.Stride.Stride == Generator.Element.Stride {
    public func pyramidOfAdjacentDifferences() -> [[Self.Generator.Element.Stride]] {
        var result: [[Self.Generator.Element.Stride]] = []
        var array = self.adjacentDifference()
        while !array.isEmpty {
            result.append(array)
            array = array.adjacentDifference()
        }
        //var generator = AdjacentDifferenceArrayGenerator(source: self)
        //while let differences = generator.next() {
            //result.append(differences)
        //}
        return result
    }

最后注释的四行，在替代算法之后，试图使用与第一个扩展中的方法相同的算法。当我取消注释掉这些行中的第一行时，光标在“AdjacentDifferenceArrayGenerator”处等待并说：“无法使用类型为 '(source: Self)' 的参数列表调用类型 'AdjacentDifferenceArrayGenerator<_>' 的初始化程序”最后“Self”在错误消息中大写，尽管它在代码中没有大写。在类型和初始化器参数之间添加显式模板括号没有帮助。有什么想法吗？

Answer 1

我通过第一次迭代解决了这个问题：

public extension SequenceType where Generator.Element: Strideable, Generator.Element.Stride: Strideable, Generator.Element.Stride.Stride == Generator.Element.Stride {
    public func pyramidOfAdjacentDifferences() -> [[Self.Generator.Element.Stride]] {
        var result = [self.adjacentDifference()]
        if result.first!.isEmpty {
            return []
        }

        var generator = AdjacentDifferenceArrayGenerator(source: result.first!)
        while let differences = generator.next() {
            result.append(differences)
        }
        return result
    }
}

我必须测试第一次迭代结果是否合法，因为将其退出循环意味着我失去了自动检查。我不知道使用“self”是问题所在，还是使用通用序列而不是确定数组是问题所在。这里仍然需要帮助....