我想使用另一个数组创建一个带有reduce()
的数组或字典。通常我会使用:
class Foo {
var number: Int
init(number: Int) {
self.number = number
}
}
let array1 = [Foo(number: 1), Foo(number: 1), Foo(number: 2)]
let array2: [Int] = array1.reduce([]) { $0 + [$1.number] }
println(array2)
[1, 1, 1]
但是如果我想操纵初始值,我首先必须将它分配给一个新数组,操纵它并返回该数组:
let array2: [Int: [Int]] = array1.reduce([:]) {
var results = $0
results[$1.number] = (results[$1.number] ?? []) + [$1.number]
return results
}
println(array2)
[2: [2], 1: [1, 1]]
有没有办法避免必须创建一个新数组并返回它并直接使用初始值?
答案 0 :(得分:0)
您可以在reduce()闭包中创建参数变量:
let array2: [Int: [Int]] = array1.reduce([:]) {
(var results, i) in
results[i.number] = (results[i.number] ?? []) + [i.number]
return results
}