KeyPathKit

Build Status platforms pod Carthage compatible Swift Package Manager compatible

上下文

Swift 4 引入了一种名为 KeyPath 的新类型，它允许使用非常简洁的语法访问对象的属性。例如

let string = "Foo"
let keyPathForCount = \String.count

let count = string[keyPath: keyPathForCount] // count == 3

最棒的是，这种语法可以非常简洁，因为它支持类型推断和属性链。

KeyPathKit 的目的

因此，我认为利用这个新概念来构建一个 API 会很好，该 API 允许以非常声明式的方式执行数据操作。

SQL 是一种非常适合此类操作的语言，因此我从中汲取灵感，并使用 KeyPath 在 Swift 4 中实现了它的大部分标准运算符。

但真正使 KeyPathKit 从竞争中脱颖而出的是其巧妙的语法，它允许以非常无缝的方式表达查询。例如

contacts.filter(where: \.lastName == "Webb" && \.age < 40)

安装

CocoaPods

将以下内容添加到您的 Podfile 中

pod "KeyPathKit"

Carthage

将以下内容添加到您的 Cartfile 中

github "vincent-pradeilles/KeyPathKit"

Swift Package Manager

创建一个文件 Package.swift

// swift-tools-version:4.0

import PackageDescription

let package = Package(
    name: "YourProject",
    dependencies: [
        .package(url: "https://github.com/vincent-pradeilles/KeyPathKit.git", "1.0.0" ..< "2.0.0")
    ],
    targets: [
        .target(name: "YourProject", dependencies: ["KeyPathKit"])
    ]
)

运算符

运算符详情

为了演示运算符的用法，定义了以下模拟数据

struct Person {
    let firstName: String
    let lastName: String
    let age: Int
    let hasDriverLicense: Bool
    let isAmerican: Bool
}

let contacts = [
    Person(firstName: "Charlie", lastName: "Webb", age: 10, hasDriverLicense: false, isAmerican: true),
    Person(firstName: "Alex", lastName: "Elexson", age: 22, hasDriverLicense: false, isAmerican: true),
    Person(firstName: "Charles", lastName: "Webb", age: 45, hasDriverLicense: true, isAmerican: true),
    Person(firstName: "Alex", lastName: "Zunino", age: 34, hasDriverLicense: true, isAmerican: true),
    Person(firstName: "Alex", lastName: "Alexson", age: 8, hasDriverLicense: false, isAmerican: true),
    Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true),
    Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true)
]

and

对 Bool 类型的属性执行布尔 AND 运算。

contacts.and(\.hasDriverLicense)
contacts.and(\.isAmerican)
false
true

average

计算数值属性的平均值。

contacts.average(of: \.age).rounded()
25

between

过滤掉属性值不在范围内的元素。

contacts.between(\.age, range: 20...30)
// or
contacts.filter(where: 20...30 ~= \.age)
[Person(firstName: "Alex", lastName: "Elexson", age: 22, hasDriverLicense: false, isAmerican: true),
 Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true)]

contains

返回序列是否包含一个元素，该元素的指定布尔属性或谓词为真。

contacts.contains(where: \.hasDriverLicense)
contacts.contains(where: \.lastName.count > 10)
true
false

distinct

返回属性的所有不同值。

contacts.distinct(\.lastName)
["Webb", "Elexson", "Zunino", "Alexson"]

drop

通过跳过元素（当 Bool 类型的属性或谓词评估为 true 时）并返回剩余元素，返回一个子序列。

contacts.drop(while: \.age < 40)
[Person(firstName: "Charles", lastName: "Webb", age: 45, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Zunino", age: 34, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Alexson", age: 8, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true)]

filter

过滤掉一个（或多个）布尔属性值为 false 的元素。

contacts.filter(where: \.hasDriverLicense)
[Person(firstName: "Charles", lastName: "Webb", age: 45, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Zunino", age: 34, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true)]

Filter 也适用于谓词

contacts.filter(where: \.firstName == "Webb")
[Person(firstName: "Charlie", lastName: "Webb", age: 10, hasDriverLicense: false, isAmerican: true),
 Person(firstName: "Charles", lastName: "Webb", age: 45, hasDriverLicense: true, isAmerican: true),
 Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true)]

filterIn

过滤掉 Equatable 属性的值不在给定 Sequence 中的元素。

contacts.filter(where: \.firstName, in: ["Alex", "John"])
[Person(firstName: "Alex", lastName: "Elexson", age: 22, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Zunino", age: 34, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Alexson", age: 8, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true)]

filterLess

过滤掉 Comparable 属性的值大于常量的元素。

contacts.filter(where: \.age, lessThan: 30)
// or
contacts.filter(where: \.age < 30)
[Person(firstName: "Charlie", lastName: "Webb", age: 10, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Elexson", age: 22, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Alexson", age: 8, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true)]

contacts.filter(where: \.age, lessOrEqual: 30)
// or
contacts.filter(where: \.age <= 30)
[Person(firstName: "Charlie", lastName: "Webb", age: 10, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Elexson", age: 22, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Alexson", age: 8, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true)]

filterLike

过滤掉字符串属性的值与正则表达式不匹配的元素。

contacts.filter(where: \.lastName, like: "^[A-Za-z]*son$")
[Person(firstName: "Alex", lastName: "Elexson", age: 22, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Alexson", age: 8, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true)]

filterMore

过滤掉 Comparable 属性的值小于常量的元素。

contacts.filter(where: \.age, moreThan: 30)
// or
contacts.filter(where: \.age > 30)
[Person(firstName: "Charles", lastName: "Webb", age: 45, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Zunino", age: 34, hasDriverLicense: true, isAmerican: true)]

contacts.filter(where: \.age, moreOrEqual: 30)
// or
contacts.filter(where: \.age >= 30)
[Person(firstName: "Charles", lastName: "Webb", age: 45, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Zunino", age: 34, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true)]

first

返回第一个匹配谓词的元素。

contacts.first(where: \.lastName == "Webb")
Optional(Person(firstName: "Charlie", lastName: "Webb", age: 10, hasDriverLicense: false, isAmerican: true))

groupBy

按属性的相等性对值进行分组。

contacts.groupBy(\.lastName)
["Alexson": [Person(firstName: "Alex", lastName: "Alexson", age: 8, hasDriverLicense: false, isAmerican: true)], 
 "Webb": [Person(firstName: "Charlie", lastName: "Webb", age: 10, hasDriverLicense: false, isAmerican: true), Person(firstName: "Charles", lastName: "Webb", age: 45, hasDriverLicense: true, isAmerican: true), Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true)], 
 "Elexson": [Person(firstName: "Alex", lastName: "Elexson", age: 22, hasDriverLicense: false, isAmerican: true), Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true)], 
 "Zunino": [Person(firstName: "Alex", lastName: "Zunino", age: 34, hasDriverLicense: true, isAmerican: true)]]

join

通过各自属性的相等性，将两个序列的值在元组中连接起来。

contacts.join(\.firstName, with: contacts, on: \.lastName)
// or
contacts.join(with: contacts, where: \.firstName == \.lastName)
[(Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true), Person(firstName: "Charlie", lastName: "Webb", age: 10, hasDriverLicense: false, isAmerican: true)), 
 (Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true), Person(firstName: "Charles", lastName: "Webb", age: 45, hasDriverLicense: true, isAmerican: true)), 
 (Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true), Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true))]

也支持在多个属性上连接

contacts.join(with: contacts, .where(\.firstName, equals: \.lastName), .where(\.hasDriverLicense, equals: \.isAmerican))
// or
contacts.join(with: contacts, where: \.firstName == \.lastName, \.hasDriverLicense == \.isAmerican)

map

将元素映射到其属性的值。

contacts.map(\.lastName)
["Webb", "Elexson", "Webb", "Zunino", "Alexson", "Webb", "Elexson"]

mapTo

将属性序列映射到一个函数。例如，这对于将属性子集提取到结构化类型中非常有用。

struct ContactCellModel {
    let firstName: String
    let lastName: String
}

contacts.map(\.lastName, \.firstName, to: ContactCellModel.init)
[ContactCellModel(firstName: "Webb", lastName: "Charlie"), 
 ContactCellModel(firstName: "Elexson", lastName: "Alex"), 
 ContactCellModel(firstName: "Webb", lastName: "Charles"), 
 ContactCellModel(firstName: "Zunino", lastName: "Alex"), 
 ContactCellModel(firstName: "Alexson", lastName: "Alex"), 
 ContactCellModel(firstName: "Webb", lastName: "John"), 
 ContactCellModel(firstName: "Elexson", lastName: "Webb")]

max

返回 Comparable 属性值最大的元素。

contacts.max(by: \.age)
contacts.max(\.age)
Optional(Person(firstName: "Charles", lastName: "Webb", age: 45, hasDriverLicense: true, isAmerican: true))
Optional(45)

min

返回 Comparable 属性值最小的元素。

contacts.min(by: \.age)
contacts.min(\.age)
Optional(Person(firstName: "Alex", lastName: "Alexson", age: 8, hasDriverLicense: false, isAmerican: true))
Optional(8)

or

对 Bool 类型的属性执行布尔 OR 运算。

contacts.or(\.hasDriverLicense)
true

patternMatching

允许在 switch 语句中使用谓词

switch person {
case \.firstName == "Charlie":
    print("I'm Charlie!")
    fallthrough
case \.age < 18:
    print("I'm not an adult...")
    fallthrough
default:
    break
}

prefix

返回一个子序列，其中包含初始的、连续的元素，这些元素的 Bool 类型属性或谓词评估为 true。

contacts.prefix(while: \.age < 40)
[Person(firstName: "Charlie", lastName: "Webb", age: 10, hasDriverLicense: false, isAmerican: true),
 Person(firstName: "Alex", lastName: "Elexson", age: 22, hasDriverLicense: false, isAmerican: true)]

sum

计算数值属性的值的总和。

contacts.sum(of: \.age)
177

sort

根据 Comparable 属性对元素进行排序。

contacts.sorted(by: \.age)
[Person(firstName: "Alex", lastName: "Alexson", age: 8, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Charlie", lastName: "Webb", age: 10, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Elexson", age: 22, hasDriverLicense: false, isAmerican: true), Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Zunino", age: 34, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Charles", lastName: "Webb", age: 45, hasDriverLicense: true, isAmerican: true)]

也可以指定排序顺序，按多个条件排序，或两者都做。

contacts.sorted(by: .ascending(\.lastName), .descending(\.age))
[Person(firstName: "Alex", lastName: "Alexson", age: 8, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Webb", lastName: "Elexson", age: 30, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Elexson", age: 22, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Charles", lastName: "Webb", age: 45, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "John", lastName: "Webb", age: 28, hasDriverLicense: true, isAmerican: true), 
 Person(firstName: "Charlie", lastName: "Webb", age: 10, hasDriverLicense: false, isAmerican: true), 
 Person(firstName: "Alex", lastName: "Zunino", age: 34, hasDriverLicense: true, isAmerican: true)]

作者

感谢

非常感谢 Jérôme Alves (elegantswift.com) 提出了正确的模型，以允许对具有异构类型的多个属性进行排序。