Swift：按名称（字符串）的字母顺序将对象数组映射到新数组中的独立字母集合中 [英] Swift: Map Array of Objects Alphabetically by Name(String) into Separate Letter Collections within a new Array

问题描述

我创建了一个名为Contact的结构，该结构代表了一个人的接触，当前在数组中有一些接触。它们已经按字母顺序排序，但是我想通过name属性按字母顺序对它们进行排序，但这是一个字符串，但我不只是希望将它们按顺序排列在单个数组中，我想将对象分成不同的集合，由他们名字的首字母对应。例如。 A包含2个对象，其中联系人名称以A开头， B表示Bobby，Brad等名称，依此类推等等。

I have created a struct called Contact which represents a human contact where there are currently a few in an Array. They are already sorted alphabetically however I would like to sort them alphabetically by the name property which is a String BUT I don't just want to have them in order in a single array, I would like to split the objects out into different collections which is corresponded by the first letter of their name. eg. "A" contains 2 objects where a Contacts name begins with A, "B" for names like Bobby, Brad etc.. and so on and so forth.

let contactData:[Contact] = [
  Contact(id: 1, available: true, name: "Adam"),
  Contact(id: 2, available: true, name: "Adrian"),
  Contact(id: 3, available: true, name: "Balthazar"),
  Contact(id: 4, available: true, name: "Bobby")
]

I想要创建类似

let sectionTitles = ["A", "B"]
let sortedContactData = [
  [
    Contact(name: "Adam"),
    Contact(name: "Adrian")
  ],
  [
     Contact(name:"Balthazar")
     Contact(name:"Bobby")
  ]         
]

或类似的东西...

最终结果是我想将它们显示在UITableView中，并将Sections中的字母和Objects放入indexPath。行非常类似于iPhone本身的联系人应用程序如何执行。我实际上不确定这是否是实现此结果的最理想方法，所以我欢迎对此问题提出任何挑战！

The end result is that I would like to display them into a UITableView with the letters in Sections and the Objects into indexPath.rows much like how the Contacts app native to the iPhone does it. I am actually not sure whether this is the most ideal way to achieve this result so I welcome any challenges to this question!

推荐答案

let sortedContacts = contactData.sorted(by: { $0.name < $1.name }) // sort the Array first.
print(sortedContacts)

let groupedContacts = sortedContacts.reduce([[Contact]]()) {
    guard var last = $0.last else { return [[$1]] }
    var collection = $0
    if last.first!.name.characters.first == $1.name.characters.first {
        last += [$1]
        collection[collection.count - 1] = last
    } else {
        collection += [[$1]]
    }
    return collection
}
print(groupedContacts)

1. 对列表进行排序。 O（nlogn），其中n是数组（contactData）中的项目数。


2. 使用 reduce 迭代每个联系人
   ，然后将其添加到新组或最后一个组中。 O（n），其中n是数组中的项目数（sortedContacts）。

1. sort the list. O(nlogn) , where n is the number of items in the Array(contactData).
2. use reduce to iterate each contact in the list, then either add it to new group, or the last one. O(n), where n is the number of items in the Array(sortedContacts).

如果需要打印效果更好信息，最好使Contact符合协议 CustomStringConvertible

If you need to have a better printed information, you better make Contact conforms to protocol CustomStringConvertible

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