我正在尝试在 Swift 中创建一个 Matrix 类,但在 self.data[row * columns..<(row + 1) * columns] = data
上收到错误我的线 setRow()
功能。错误是“无法将类型“[Double]”的值分配给类型“ArraySlice””
struct Matrix: CustomStringConvertible {
let rows:Int
let columns:Int
var data:[Double]
// Description
public var description: String {
var description = ""
for r in 0..<rows {
description += data[r * columns..<(r + 1) * columns].description + "\n"
}
return description
}
// Initialisation
init(rows: Int, columns: Int) {
self.rows = rows
self.columns = columns
self.data = Array(repeating: 0.0, count: rows * columns)
}
init(rows: Int, columns: Int, data:[Double]) {
assert(data.count == (rows * columns),"Number of elements must equal rows * columns")
self.rows = rows
self.columns = columns
self.data = data
}
// Validity
func validRow(row: Int) -> Bool {
return row > 0 && row < rows
}
func validColumn(column: Int) -> Bool {
return column > 0 && column < columns
}
func validIndex(row: Int, column: Int) -> Bool {
return validRow(row: row) && validColumn(column: column)
}
// Setters and getters
func get(row: Int, column: Int) -> Double {
assert(validIndex(row: row,column: column), "Index out of range")
return data[(row * columns) + column]
}
mutating func set(row: Int, column: Int, value: Double) {
assert(validIndex(row: row,column: column), "Index out of range")
data[(row * columns) + column] = value
}
func getRow(row: Int) -> [Double] {
assert(validRow(row: row), "Index out of range")
return Array(data[row * columns..<(row + 1) * columns])
}
mutating func setRow(row: Int, data:[Double]) {
assert(validRow(row: row), "Index out of range")
assert(data.count == columns, "Data must be same length ans the number of columns")
self.data[row * columns..<(row + 1) * columns] = data
}
// Swapping
mutating func swapRow(row1: Int, row2: Int) {
assert(validRow(row: row1) && validRow(row: row2), "Index out of range")
let holder = getRow(row: row2)
setRow(row: row2, data: getRow(row: row1))
setRow(row: row1, data: holder)
}
}
最佳答案
正如错误所述,Array
的范围下标处理 ArraySlice
,而不是数组
。
一个解决方案,如 @vacawama says ,就是创建整个输入数组的一个切片。这可以通过使用数组的 indices
下标来完成:
mutating func setRow(row: Int, data newData: [Double]) {
assert(validRow(row: row), "Index out of range")
assert(data.count == columns, "Data must be same length ans the number of columns")
data[row * columns ..< (row + 1) * columns] = newData[newData.indices]
}
或者在 Swift 4 中,您可以利用 the ...
'operator' ,它执行完全相同的操作:
data[row * columns ..< (row + 1) * columns] = newData[...]
但在我看来,一个更好的工具是 replaceSubrange(_:with:)
:
mutating func replaceSubrange<C>(_ subrange: Range<Int>, with newElements: C)
where Element == C.Element, C : Collection
因为它允许您处理新元素的任意Collection
,这意味着您还可以使setRow
通用:
mutating func setRow<C : Collection>(row: Int, data newData: C)
where C.Iterator.Element == Double { // <- in Swift 4, remove ".Iterator"
assert(validRow(row: row), "Index out of range")
assert(data.count == columns, "Data must be same length ans the number of columns")
data.replaceSubrange(row * columns ..< (row + 1) * columns, with: newData)
}
关于arrays - Swift:改变结构中的数组,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45102527/