Katakanlah saya memiliki kode ini:

class Stat {
   var statEvents : [StatEvents] = []
}

struct StatEvents {
   var name: String
   var date: String
   var hours: Int
}


var currentStat = Stat()

currentStat.statEvents = [
   StatEvents(name: "lunch", date: "01-01-2015", hours: 1),
   StatEvents(name: "dinner", date: "01-01-2015", hours: 1),
   StatEvents(name: "dinner", date: "01-01-2015", hours: 1),
   StatEvents(name: "lunch", date: "01-01-2015", hours: 1),
   StatEvents(name: "dinner", date: "01-01-2015", hours: 1)
]

var filteredArray1 : [StatEvents] = []
var filteredArray2 : [StatEvents] = []

Saya bisa memanggil sebanyak mungkin fungsi berikutnya secara manual agar memiliki 2 array yang dikelompokkan dengan "nama yang sama".

filteredArray1 = currentStat.statEvents.filter({$0.name == "dinner"})
filteredArray2 = currentStat.statEvents.filter({$0.name == "lunch"})

Masalahnya adalah saya tidak akan tahu nilai variabelnya, dalam hal ini "makan malam" dan "makan siang", jadi saya ingin mengelompokkan array statEvents ini secara otomatis berdasarkan nama, jadi saya mendapatkan array sebanyak namanya berbeda.

Bagaimana saya bisa melakukan itu?

Cepat 4:

Sejak Swift 4, fungsionalitas ini telah ditambahkan ke pustaka standar . Anda dapat menggunakannya seperti ini:

Dictionary(grouping: statEvents, by: { $0.name })
[
  "dinner": [
    StatEvents(name: "dinner", date: "01-01-2015", hours: 1),
    StatEvents(name: "dinner", date: "01-01-2015", hours: 1),
    StatEvents(name: "dinner", date: "01-01-2015", hours: 1)
  ],
  "lunch": [
    StatEvents(name: "lunch", date: "01-01-2015", hours: 1),
    StatEvents(name: "lunch", date: "01-01-2015", hours: 1)
]

Cepat 3:

public extension Sequence {
    func group<U: Hashable>(by key: (Iterator.Element) -> U) -> [U:[Iterator.Element]] {
        var categories: [U: [Iterator.Element]] = [:]
        for element in self {
            let key = key(element)
            if case nil = categories[key]?.append(element) {
                categories[key] = [element]
            }
        }
        return categories
    }
}

Sayangnya, appendfungsi di atas menyalin larik yang mendasarinya, alih-alih memutasinya di tempatnya, yang lebih disukai. Ini menyebabkan perlambatan yang cukup besar . Anda bisa mengatasi masalah ini dengan menggunakan pembungkus tipe referensi:

class Box<A> {
  var value: A
  init(_ val: A) {
    self.value = val
  }
}

public extension Sequence {
  func group<U: Hashable>(by key: (Iterator.Element) -> U) -> [U:[Iterator.Element]] {
    var categories: [U: Box<[Iterator.Element]>] = [:]
    for element in self {
      let key = key(element)
      if case nil = categories[key]?.value.append(element) {
        categories[key] = Box([element])
      }
    }
    var result: [U: [Iterator.Element]] = Dictionary(minimumCapacity: categories.count)
    for (key,val) in categories {
      result[key] = val.value
    }
    return result
  }
}

Meskipun Anda melintasi kamus terakhir dua kali, versi ini masih lebih cepat daripada aslinya dalam banyak kasus.

Cepat 2:

public extension SequenceType {

  /// Categorises elements of self into a dictionary, with the keys given by keyFunc

  func categorise<U : Hashable>(@noescape keyFunc: Generator.Element -> U) -> [U:[Generator.Element]] {
    var dict: [U:[Generator.Element]] = [:]
    for el in self {
      let key = keyFunc(el)
      if case nil = dict[key]?.append(el) { dict[key] = [el] }
    }
    return dict
  }
}

Dalam kasus Anda, Anda dapat memiliki "kunci" yang dikembalikan dengan keyFuncnama:

currentStat.statEvents.categorise { $0.name }
[  
  dinner: [
    StatEvents(name: "dinner", date: "01-01-2015", hours: 1),
    StatEvents(name: "dinner", date: "01-01-2015", hours: 1),
    StatEvents(name: "dinner", date: "01-01-2015", hours: 1)
  ], lunch: [
    StatEvents(name: "lunch", date: "01-01-2015", hours: 1),
    StatEvents(name: "lunch", date: "01-01-2015", hours: 1)
  ]
]

Jadi Anda akan mendapatkan kamus, di mana setiap kunci adalah nama, dan setiap nilai adalah larik StatEvents dengan nama itu.

Cepat 1

func categorise<S : SequenceType, U : Hashable>(seq: S, @noescape keyFunc: S.Generator.Element -> U) -> [U:[S.Generator.Element]] {
  var dict: [U:[S.Generator.Element]] = [:]
  for el in seq {
    let key = keyFunc(el)
    dict[key] = (dict[key] ?? []) + [el]
  }
  return dict
}

categorise(currentStat.statEvents) { $0.name }

Yang memberikan output:

extension StatEvents : Printable {
  var description: String {
    return "\(self.name): \(self.date)"
  }
}
print(categorise(currentStat.statEvents) { $0.name })
[
  dinner: [
    dinner: 01-01-2015,
    dinner: 01-01-2015,
    dinner: 01-01-2015
  ], lunch: [
    lunch: 01-01-2015,
    lunch: 01-01-2015
  ]
]

(Swiftstub ada di sini )

Dengan Swift 5, Dictionarymemiliki metode penginisialisasi yang disebut init(grouping:by:). init(grouping:by:)memiliki deklarasi berikut:

init<S>(grouping values: S, by keyForValue: (S.Element) throws -> Key) rethrows where Value == [S.Element], S : Sequence

Membuat kamus baru di mana kuncinya adalah pengelompokan yang dikembalikan oleh closure yang diberikan dan nilainya adalah array dari elemen yang mengembalikan setiap kunci tertentu.

Kode Playground berikut menunjukkan cara menggunakan init(grouping:by:)untuk memecahkan masalah Anda:

struct StatEvents: CustomStringConvertible {
    
    let name: String
    let date: String
    let hours: Int
    
    var description: String {
        return "Event: \(name) - \(date) - \(hours)"
    }
    
}

let statEvents = [
    StatEvents(name: "lunch", date: "01-01-2015", hours: 1),
    StatEvents(name: "dinner", date: "01-01-2015", hours: 1),
    StatEvents(name: "lunch", date: "01-01-2015", hours: 1),
    StatEvents(name: "dinner", date: "01-01-2015", hours: 1)
]

let dictionary = Dictionary(grouping: statEvents, by: { (element: StatEvents) in
    return element.name
})
//let dictionary = Dictionary(grouping: statEvents) { $0.name } // also works  
//let dictionary = Dictionary(grouping: statEvents, by: \.name) // also works

print(dictionary)
/*
prints:
[
    "dinner": [Event: dinner - 01-01-2015 - 1, Event: dinner - 01-01-2015 - 1],
    "lunch": [Event: lunch - 01-01-2015 - 1, Event: lunch - 01-01-2015 - 1]
]
*/

Swift 4: Anda dapat menggunakan init (pengelompokan: menurut :) dari situs pengembang apple

Contoh :

let students = ["Kofi", "Abena", "Efua", "Kweku", "Akosua"]
let studentsByLetter = Dictionary(grouping: students, by: { $0.first! })
// ["E": ["Efua"], "K": ["Kofi", "Kweku"], "A": ["Abena", "Akosua"]]

Jadi dalam kasus Anda

   let dictionary = Dictionary(grouping: currentStat.statEvents, by:  { $0.name! })

Untuk Swift 3:

public extension Sequence {
    func categorise<U : Hashable>(_ key: (Iterator.Element) -> U) -> [U:[Iterator.Element]] {
        var dict: [U:[Iterator.Element]] = [:]
        for el in self {
            let key = key(el)
            if case nil = dict[key]?.append(el) { dict[key] = [el] }
        }
        return dict
    }
}

Pemakaian:

currentStat.statEvents.categorise { $0.name }
[  
  dinner: [
    StatEvents(name: "dinner", date: "01-01-2015", hours: 1),
    StatEvents(name: "dinner", date: "01-01-2015", hours: 1),
    StatEvents(name: "dinner", date: "01-01-2015", hours: 1)
  ], lunch: [
    StatEvents(name: "lunch", date: "01-01-2015", hours: 1),
    StatEvents(name: "lunch", date: "01-01-2015", hours: 1)
  ]
]

Di Swift 4, ekstensi ini memiliki kinerja terbaik dan membantu menghubungkan operator Anda

extension Sequence {
    func group<U: Hashable>(by key: (Iterator.Element) -> U) -> [U:[Iterator.Element]] {
        return Dictionary.init(grouping: self, by: key)
    }
}

Contoh:

struct Asset {
    let coin: String
    let amount: Int
}

let assets = [
    Asset(coin: "BTC", amount: 12),
    Asset(coin: "ETH", amount: 15),
    Asset(coin: "BTC", amount: 30),
]
let grouped = assets.group(by: { $0.coin })

menciptakan:

[
    "ETH": [
        Asset(coin: "ETH", amount: 15)
    ],
    "BTC": [
        Asset(coin: "BTC", amount: 12),
        Asset(coin: "BTC", amount: 30)
    ]
]

Anda juga dapat mengelompokkan menurut KeyPath, seperti ini:

public extension Sequence {
    func group<Key>(by keyPath: KeyPath<Element, Key>) -> [Key: [Element]] where Key: Hashable {
        return Dictionary(grouping: self, by: {
            $0[keyPath: keyPath]
        })
    }
}

Menggunakan contoh kripto @ duan:

struct Asset {
    let coin: String
    let amount: Int
}

let assets = [
    Asset(coin: "BTC", amount: 12),
    Asset(coin: "ETH", amount: 15),
    Asset(coin: "BTC", amount: 30),
]

Kemudian penggunaannya terlihat seperti ini:

let grouped = assets.group(by: \.coin)

Menghasilkan hasil yang sama:

[
    "ETH": [
        Asset(coin: "ETH", amount: 15)
    ],
    "BTC": [
        Asset(coin: "BTC", amount: 12),
        Asset(coin: "BTC", amount: 30)
    ]
]

Cepat 4

struct Foo {
  let fizz: String
  let buzz: Int
}

let foos: [Foo] = [Foo(fizz: "a", buzz: 1), 
                   Foo(fizz: "b", buzz: 2), 
                   Foo(fizz: "a", buzz: 3),
                  ]
// use foos.lazy.map instead of foos.map to avoid allocating an
// intermediate Array. We assume the Dictionary simply needs the
// mapped values and not an actual Array
let foosByFizz: [String: Foo] = 
    Dictionary(foos.lazy.map({ ($0.fizz, $0)}, 
               uniquingKeysWith: { (lhs: Foo, rhs: Foo) in
                   // Arbitrary business logic to pick a Foo from
                   // two that have duplicate fizz-es
                   return lhs.buzz > rhs.buzz ? lhs : rhs
               })
// We don't need a uniquing closure for buzz because we know our buzzes are unique
let foosByBuzz: [String: Foo] = 
    Dictionary(uniqueKeysWithValues: foos.lazy.map({ ($0.buzz, $0)})

Memperluas jawaban yang diterima untuk memungkinkan pengelompokan yang teratur :

extension Sequence {
    func group<GroupingType: Hashable>(by key: (Iterator.Element) -> GroupingType) -> [[Iterator.Element]] {
        var groups: [GroupingType: [Iterator.Element]] = [:]
        var groupsOrder: [GroupingType] = []
        forEach { element in
            let key = key(element)
            if case nil = groups[key]?.append(element) {
                groups[key] = [element]
                groupsOrder.append(key)
            }
        }
        return groupsOrder.map { groups[$0]! }
    }
}

Kemudian ini akan berfungsi pada tupel apa pun :

let a = [(grouping: 10, content: "a"),
         (grouping: 20, content: "b"),
         (grouping: 10, content: "c")]
print(a.group { $0.grouping })

Serta setiap struct atau kelas :

struct GroupInt {
    var grouping: Int
    var content: String
}
let b = [GroupInt(grouping: 10, content: "a"),
         GroupInt(grouping: 20, content: "b"),
         GroupInt(grouping: 10, content: "c")]
print(b.group { $0.grouping })

Berikut adalah pendekatan berbasis tupel saya untuk menjaga ketertiban saat menggunakan Swift 4 KeyPath sebagai pembanding grup:

extension Sequence{

    func group<T:Comparable>(by:KeyPath<Element,T>) -> [(key:T,values:[Element])]{

        return self.reduce([]){(accumulator, element) in

            var accumulator = accumulator
            var result :(key:T,values:[Element]) = accumulator.first(where:{ $0.key == element[keyPath:by]}) ?? (key: element[keyPath:by], values:[])
            result.values.append(element)
            if let index = accumulator.index(where: { $0.key == element[keyPath: by]}){
                accumulator.remove(at: index)
            }
            accumulator.append(result)

            return accumulator
        }
    }
}

Contoh cara menggunakannya:

struct Company{
    let name : String
    let type : String
}

struct Employee{
    let name : String
    let surname : String
    let company: Company
}

let employees : [Employee] = [...]
let companies : [Company] = [...]

employees.group(by: \Employee.company.type) // or
employees.group(by: \Employee.surname) // or
companies.group(by: \Company.type)

Hai jika Anda perlu menjaga ketertiban saat mengelompokkan elemen, bukan kamus hash, saya telah menggunakan tupel dan menjaga urutan daftar saat mengelompokkan.

extension Sequence
{
   func zmGroup<U : Hashable>(by: (Element) -> U) -> [(U,[Element])]
   {
       var groupCategorized: [(U,[Element])] = []
       for item in self {
           let groupKey = by(item)
           guard let index = groupCategorized.index(where: { $0.0 == groupKey }) else { groupCategorized.append((groupKey, [item])); continue }
           groupCategorized[index].1.append(item)
       }
       return groupCategorized
   }
}

Kamus Thr (pengelompokan: arr) sangat mudah!

 func groupArr(arr: [PendingCamera]) {

    let groupDic = Dictionary(grouping: arr) { (pendingCamera) -> DateComponents in
        print("group arr: \(String(describing: pendingCamera.date))")

        let date = Calendar.current.dateComponents([.day, .year, .month], from: (pendingCamera.date)!)

        return date
    }

    var cams = [[PendingCamera]]()

    groupDic.keys.forEach { (key) in
        print(key)
        let values = groupDic[key]
        print(values ?? "")

        cams.append(values ?? [])
    }
    print(" cams are \(cams)")

    self.groupdArr = cams
}

Mengambil contoh dari "oisdk" . Memperluas solusi untuk mengelompokkan objek berdasarkan nama kelas Tautan Demo & Kode Sumber .

Potongan kode untuk pengelompokan berdasarkan Nama Kelas:

 func categorise<S : SequenceType>(seq: S) -> [String:[S.Generator.Element]] {
    var dict: [String:[S.Generator.Element]] = [:]
    for el in seq {
        //Assigning Class Name as Key
        let key = String(el).componentsSeparatedByString(".").last!
        //Generating a dictionary based on key-- Class Names
        dict[key] = (dict[key] ?? []) + [el]
    }
    return dict
}
//Grouping the Objects in Array using categorise
let categorised = categorise(currentStat)
print("Grouped Array :: \(categorised)")

//Key from the Array i.e, 0 here is Statt class type
let key_Statt:String = String(currentStat.objectAtIndex(0)).componentsSeparatedByString(".").last!
print("Search Key :: \(key_Statt)")

//Accessing Grouped Object using above class type key
let arr_Statt = categorised[key_Statt]
print("Array Retrieved:: ",arr_Statt)
print("Full Dump of Array::")
dump(arr_Statt)