Swift数组实例方法drop(at:Int)

注意:我会使用 remove(at:) ,但我使用的数组是一个常量。

extension Array {
    func drop(at:Int) -> [Element] {
        var temp = self
        temp.remove(at: at)
        return temp
    }
}
let numbers = [1, 2, 3, 4, 5]
print(numbers.drop(at: 2)) // [1, 2, 4, 5]

你可以扩展 RangeReplaceableCollection Array

extension RangeReplaceableCollection {
    func drop(at offset: Int) -> SubSequence {
        let index = self.index(startIndex, offsetBy: offset, limitedBy: endIndex) ?? endIndex
        let next = self.index(index, offsetBy: 1, limitedBy: endIndex) ?? endIndex
        return self[..<index] + self[next...]
    }
}

var str = "Hello, playground"
str.drop(at: 5)  // "Hello playground"

let numbers = [1, 2, 3, 4, 5]
print(numbers.drop(at: 2))  // "[1, 2, 4, 5]\n"

如果你也愿意接受字符串.索引在你的方法中:

extension RangeReplaceableCollection {
    func drop(at index: Index) -> SubSequence {
        let index = self.index(startIndex, offsetBy: distance(from: startIndex, to: index), limitedBy: endIndex) ?? endIndex
        let next = self.index(index, offsetBy: 1, limitedBy: endIndex) ?? endIndex
        return self[..<index] + self[next...]
    }
}

var str = "Hello, playground"
str.drop(at: 0)               // "ello, playground"
str.drop(at: str.startIndex)  // "ello, playground"

我唯一要添加到您的实现中的是一个带有有用错误消息的guard语句:

extension Array {
    func drop(at index: Int) -> ArraySlice<Element> {
        guard indices.contains(index) else {
            fatalError("Index out of range")
        }
        return self[0..<index] + self[(index+1)..<endIndex]
    }

    func drop(range: CountableRange<Int>) -> ArraySlice<Element> {
        guard (indices.lowerBound, range.upperBound) <= (range.lowerBound, indices.upperBound) else {
            fatalError("Range is out of the indices bounds")
        }
        return self[0..<range.lowerBound] + self[range.upperBound..<endIndex]
    }
}

let a = [1,2,3]
a.drop(at: 3)          //Fatal error: Index out of range
let b = [0,1,2,3,4,5]
b.drop(range: 1..<5)   //[0, 5]

return self[0..<index] + self[index+1..<endIndex]

丑陋。为什么不使用你得到的工具?

extension Array {
    func drop(at:Int) -> ArraySlice<Element> {
        return prefix(upTo: at) + suffix(from: at+1)
    }
}
let arr = [1,2,3,4,5]
let slice = arr.drop(at:2) // [1,2,4,5]

编辑

return self[..<at] + self[(at+1)...]

但就我个人而言,我觉得这更难看,毕竟我建议的方法并没有遭到反对。

Swift extension drop(at:) Array

extension Array {
  func drop(at index: Int) -> ArraySlice<Element> {
    precondition(indices.contains(index), "Index out of range")
    return self[..<index] + self[(index+1)...]
  }
}

它返回原始数组的一个片段,该片段不包含指定索引处的元素。

let numbers = [1, 2, 3, 4, 5]
print(numbers.drop(at: 2))
// Prints "[1, 2, 4, 5]"

注意:您可能还需要添加 下降(在:) 到 ArraySlice