arrays - 根据变量 Swift 3 中的公共(public)值减少对象数组

Question

我有这门课:

class Post {
    var key: String
    var uid: String
    var minutes: Int
    var name: String
    let ref: FIRDatabaseReference?

init(key: String, uid: String, minutes: Int, name: String){
    self.key = key
    self.uid = uid
    self.minutes = minutes
    self.name = name
    self.ref = nil
}

我使用此类创建了一个对象数组，虽然我可以计算分钟数，但我无法计算只有具有不同 uid 的元素的分钟数。

有人能帮我指明正确的方向吗？

Answer 1

编辑

我原来的回答似乎没有捕获你的问题，这就是你想要的:

let minutes = posts.reduce(([String : Int]())) { accumulator, value in
    var currentData = accumulator
    if accumulator.keys.contains(value.uid) {
        currentData[value.uid] = accumulator[value.uid]! + value.minutes
        return currentData
    } else {
        currentData[value.uid] = value.minutes
        return currentData
    }
}

---

这是仅计算唯一 uid 的分钟数的 playground 代码:

 let posts = [Post(key: "key", uid: "0", minutes: 5, name: "name"), Post(key: "key", uid: "1", minutes: 5, name: "name"), Post(key: "key", uid: "1", minutes: 5, name: "name"), Post(key: "key", uid: "1", minutes: 5, name: "name"), Post(key: "key", uid: "3", minutes: 2, name: "name")]

 let count = posts.reduce((0, [String]())) { accumulator, value in
    if accumulator.1.contains(value.uid) {
        return accumulator
    } else {
        return (accumulator.0 + value.minutes, accumulator.1 + [value.uid])
    }
  }.0

reduce 允许您“迭代”您的帖子数组。您从 0 分钟计数和一个空的 uid 数组开始。如果 uid 在那里，那么您不会在分钟计数中添加任何分钟，并且您将数组保持原样。如果不是，则添加分钟并将字符串添加到 uid 字符串数组。最后，您通过获取元组的第一个元素(因此是 .0)来获取分钟计数

较短的版本是:

   let count = posts.reduce((0, [String]())) {
       return $0.1.contains($1.uid) ? $0 : ($0.0 + $1.minutes, $0.1 + [$1.uid])
   }.0