[英]Swift sort array of dictionaries by key where value is optional AnyObject
I'm pulling an array of dictionaries straight from Parse and displaying them in a table. 我正在直接从Parse中提取一系列字典并将它们显示在表格中。 So I'd really like to work with the data structure I'm handed (the oddly structured dictionaries below). 所以我真的很想处理我所掌握的数据结构(下面奇怪的结构化词典)。
A PFObject
is [String : AnyObject?]
and I want to be able to sort by any key so I don't know the object type AND the key might be missing from some of the dictionaries. PFObject
是[String : AnyObject?]
,我希望能够按任意键排序,所以我不知道对象类型,并且某些字典可能缺少密钥。 Because in Parse, if you don't give a property a value, it is simply nonexistent. 因为在Parse中,如果不给属性赋值,则它根本就不存在。 For example: 例如:
[
{
"ObjectId" : "1",
"Name" : "Frank",
"Age" : 32
},
{
"ObjectId" : "2",
"Name" : "Bill"
},
{
"ObjectId" : "3",
"Age" : 18
}
{
"ObjectId" : "4",
"Name" : "Susan",
"Age" : 47
}
] ]
I want the dictionaries with missing keys to always be ordered after the sorted dictionaries. 我希望在排序的词典之后始终对缺少键的词典进行排序。 An example: 一个例子:
Original Table: 原表:
ObjectId Name Age
1 Frank 32
2 Bill
3 18
4 Susan 47
Ordered By Name: 按名称排序:
ObjectId Name Age
2 Bill
1 Frank 32
4 Susan 47
3 18
As I don't have a lot of control over the data model, and it's usage is limited throughout the application, I'd prefer to focus on an algorithmic solution rather than structural. 由于我对数据模型没有太多控制权,并且它的使用在整个应用程序中受到限制,我更倾向于关注算法解决方案而不是结构化解决方案。
I came up with a way to do this but it just seems inefficient and slow, I'm certain there's someone who can do this better. 我想出了一个方法来做到这一点,但它似乎效率低而且速度慢,我确信有人可以做得更好。
//dataModel is an array of dictionary objects used as my table source
//sort mode is NSComparisonResult ascending or descending
//propertyName is the dictionary key
//first filter out any objects that dont have this key
let filteredFirstHalf = dataModel.filter({ $0[propertyName] != nil })
let filteredSecondHalf = dataModel.filter({ $0[propertyName] == nil })
//sort the dictionaries that have the key
let sortedAndFiltered = filteredFirstHalf { some1, some2 in
if let one = some1[propertyName] as? NSDate, two = some2[propertyName] as? NSDate {
return one.compare(two) == sortMode
} else if let one = some1[propertyName] as? String, two = some2[propertyName] as? String {
return one.compare(two) == sortMode
} else if let one = some1[propertyName] as? NSNumber, two = some2[propertyName] as? NSNumber {
return one.compare(two) == sortMode
} else {
fatalError("filteredFirstHalf shouldn't be here")
}
}
//this will always put the blanks behind the sorted
dataModel = sortedAndFiltered + filteredSecondHalf
Thanks! 谢谢!
Swift can't compare any two objects. Swift无法比较任何两个对象。 You have to cast them to a specific type first: 您必须先将它们转换为特定类型:
let arr: [[String: Any]] = [
["Name" : "Frank", "Age" : 32],
["Name" : "Bill"],
["Age" : 18],
["Name" : "Susan", "Age" : 47]
]
let key = "Name" // The key you want to sort by
let result = arr.sort {
switch ($0[key], $1[key]) {
case (nil, nil), (_, nil):
return true
case (nil, _):
return false
case let (lhs as String, rhs as String):
return lhs < rhs
case let (lhs as Int, rhs as Int):
return lhs < rhs
// Add more for Double, Date, etc.
default:
return true
}
}
print(result)
If there are multiple dictionaries that have no value for the specified key
, they will be placed at the end of the result
array but their relative orders are uncertain. 如果有多个字典没有指定key
值,它们将被放置在result
数组的末尾,但它们的相对顺序是不确定的。
So you have an array of dictionaries. 所以你有一系列词典。
let dictionaries: [[String:AnyObject?]] = [
["Name" : "Frank", "Age" : 32],
["Name" : "Bill"],
["Age" : 18],
["Name" : "Susan", "Age" : 47]
]
You want to sort the array: 您想要对数组进行排序:
Name
value ascending Name
值升序 Name
String
should be at the end 没有Name
String
字典应该在最后 Here's the code ( in functional programming style ) 这是代码( 在函数式编程风格中 )
let sorted = dictionaries.sort { left, right -> Bool in
guard let rightKey = right["Name"] as? String else { return true }
guard let leftKey = left["Name"] as? String else { return false }
return leftKey < rightKey
}
print(sorted)
[
["Name": Optional(Bill)],
["Name": Optional(Frank), "Age": Optional(32)],
["Name": Optional(Susan), "Age": Optional(47)],
["Age": Optional(18)]
]
Make a datatype to represent your data: 创建一个数据类型来表示您的数据:
struct Person
{
let identifier: String
let name: String?
let age: Int?
}
Make an extraction routine: 提取程序:
func unpack(objects: [[String : Any]]) -> [Person]
{
return objects.flatMap { object in
guard let identifier = object["ObjectID"] as? String else {
// Invalid object
return nil
}
let name = object["Name"] as? String
let age = object["Age"] as? Int
return Person(identifier: identifier, name: name, age: age)
}
}
Your datatype can be sorted by its fields, because they have real types. 您的数据类型可以按其字段排序,因为它们具有实际类型。
let objects: [[String : Any]] =
[["ObjectID" : "1", "Name" : "Frank", "Age" : 32],
["ObjectID" : "2", "Name" : "Bill"],
["ObjectID" : "3", "Age" : 18],
["ObjectID" : "4", "Name" : "Susan", "Age" : 47]]
let persons = unpack(objects)
let byName = persons.sort { $0.name < $1.name }
nil
s compare as "before" any other value; nil
s比较“之前”任何其他值; you can write your own comparator if you'd like to change that. 你可以编写自己的比较器,如果你想改变它。
Here is what I would do. 这就是我要做的。 If you are able to, I would make the struct more specific by giving it a Name and Age other than just key and value. 如果你能够,我会通过给它一个名称和年龄而不仅仅是键和值来使结构更具体。 This should give you an outline for how to achieve that though! 这应该为您提供如何实现这一目标的大纲!
struct PersonInfo {
var key: String!
var value: AnyObject?
init(key key: String, value: AnyObject?) {
self.key = key
self.value = value
}
}
class ViewController: UIViewController {
var possibleKeys: [String] = ["Name", "Age", "ObjectId"]
var personInfos: [PersonInfo] = []
override func viewDidLoad() {
super.viewDidLoad()
for infos in json {
for key in possibleKeys {
if let value = infos[key] {
personInfos.append(PersonInfo(key: key, value: value))
}
}
}
personInfos.sortInPlace({$0.value as? Int > $1.value as? Int})
}
}
to make it easier, here: 为了方便起见,这里:
struct PersonInfo {
var key: String!
var objectId: Int!
var name: String?
var age: Int?
init(key key: String, objectId: Int, name: String?, age: Int?) {
self.key = key
self.objectId = objectId
self.name = name
self.age = age
}
}
class ViewController: UIViewController {
var possibleKeys: [String] = ["Name", "Age", "ObjectId"]
var personInfos: [PersonInfo] = []
override func viewDidLoad() {
super.viewDidLoad()
for infos in json {
var objectId: String!
var name: String? = nil
var age: Int? = nil
for key in possibleKeys {
if let value = infos[key] {
if key == "ObjectId" {
objectId = value as? String
}
if key == "Name" {
name = value as? String
}
if key == "Age" {
age = value as? Int
}
}
}
personInfos.append(PersonInfo(key: key, objectId: objectId, name: String?, age: Int?))
}
//by objectId
personInfos.sortInPlace({$0.objectId? > $1.objectId?})
//by age
personInfos.sortInPlace({$0.age? > $1.age?})
//byName
personInfos.sortInPlace({$0.name?.compare($1.name?) == NSComparisonResult.OrderedAscending})
}
}
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