Swift分组数组值
示例
如果我们有这样的结构
struct Box {
let name: String
let thingsInside: Int
}和一系列Box(es)
let boxes = [
Box(name: "Box 0", thingsInside: 1),
Box(name: "Box 1", thingsInside: 2),
Box(name: "Box 2", thingsInside: 3),
Box(name: "Box 3", thingsInside: 1),
Box(name: "Box 4", thingsInside: 2),
Box(name: "Box 5", thingsInside: 3),
Box(name: "Box 6", thingsInside: 1)
]我们可以按thingsInside属性对这些框进行分组，以获取，Dictionary其中key是事物的数量，而值是盒子的数组。
let grouped = boxes.reduce([Int:[Box]]()) { (res, box) -> [Int:[Box]] in
var res = res
res[box.thingsInside] = (res[box.thingsInside] ?? []) + [box]
return res
}现在分组为一个，[Int:[Box]]并具有以下内容
[
2: [Box(name: "Box 1", thingsInside: 2), Box(name: "Box 4", thingsInside: 2)],
3: [Box(name: "Box 2", thingsInside: 3), Box(name: "Box 5", thingsInside: 3)],
1: [Box(name: "Box 0", thingsInside: 1), Box(name: "Box 3", thingsInside: 1), Box(name: "Box 6", thingsInside: 1)]
]