假设我们有一个名为imageFile的自定义类,这个类包含两个属性:

class imageFile  {
    var fileName = String()
    var fileID = Int()
}

很多都存储在一个数组中:

var images : Array = []

var aImage = imageFile()
aImage.fileName = "image1.png"
aImage.fileID = 101
images.append(aImage)

aImage = imageFile()
aImage.fileName = "image1.png"
aImage.fileID = 202
images.append(aImage)

我如何排序的图像数组由'fileID'升序或降序?


当前回答

如果你不使用自定义对象,而是使用值类型来实现可比协议(Int, String等),你可以简单地这样做:

myArray.sort(>) //sort descending order

一个例子:

struct MyStruct: Comparable {
    var name = "Untitled"
}

func <(lhs: MyStruct, rhs: MyStruct) -> Bool {
    return lhs.name < rhs.name
}
// Implementation of == required by Equatable
func ==(lhs: MyStruct, rhs: MyStruct) -> Bool {
    return lhs.name == rhs.name
}

let value1 = MyStruct()
var value2 = MyStruct()

value2.name = "A New Name"

var anArray:[MyStruct] = []
anArray.append(value1)
anArray.append(value2)

anArray.sort(>) // This will sort the array in descending order

其他回答

从fileID属性返回一个排序的数组,方法如下:

斯威夫特2

let sortedArray = images.sorted({ $0.fileID > $1.fileID })

Swift 3或4

let sortedArray = images.sorted(by: { $0.fileID > $1.fileID })

斯威夫特5.0

let sortedArray = images.sorted {
    $0.fileID < $1.fileID
}

Swift 4.0, 4.1和4.2:

首先,我创建了imageFile类型的可变数组,如下所示

var arr = [imageFile]()

创建类型为imageFile的可变对象图像,并为属性赋值,如下所示

var image = imageFile()
image.fileId = 14
image.fileName = "A"

现在,将这个对象追加到数组arr

arr.append(image)

现在,将不同的属性分配给相同的可变对象,即图像

image = imageFile()
image.fileId = 13
image.fileName = "B"

现在,再次将image object追加到数组arr中

arr.append(image)

现在,我们将对数组arr对象中的fileId属性应用升序。使用<符号按升序排列

arr = arr.sorted(by: {$0.fileId < $1.fileId}) // arr has all objects in Ascending order
print("sorted array is",arr[0].fileId)// sorted array is 13
print("sorted array is",arr[1].fileId)//sorted array is 14

现在,我们将在数组arr对象中的fileId属性上应用降序。降序使用>符号

arr = arr.sorted(by: {$0.fileId > $1.fileId}) // arr has all objects in Descending order
print("Unsorted array is",arr[0].fileId)// Unsorted array is 14
print("Unsorted array is",arr[1].fileId)// Unsorted array is 13

在Swift 4.1和4.2中,用于排序使用

let sortedArr = arr.sorted { (id1, id2) -> Bool in
  return id1.fileId < id2.fileId // Use > for Descending order
}

[为Swift 3更新了sort(by:)]这,利用一个尾随闭包:

images.sorted { $0.fileID < $1.fileID }

根据ASC或DESC分别使用<或>。如果你想修改图像数组,那么使用以下命令:

images.sort { $0.fileID < $1.fileID }

如果你要重复这样做,并且更喜欢定义一个函数,一种方法是:

func sorterForFileIDASC(this:imageFile, that:imageFile) -> Bool {
  return this.fileID < that.fileID
}

然后用as:

images.sort(by: sorterForFileIDASC)
var students = ["Kofi", "Abena", "Peter", "Kweku", "Akosua"]

students.sort(by: >)

print(students)

彼得Prints:“[””、“科菲Kweku”、“”、“Akosua Abena”、“]”

在Swift 5中,Array有两个方法,分别是sorted()和sorted(by:)。第一个方法sorted()有如下声明:

返回排序后的集合元素。

func sorted() -> [Element]

第二个方法,排序(通过:),有如下声明:

返回集合的元素,使用给定的谓词作为元素之间的比较进行排序。

func sorted(by areInIncreasingOrder: (Element, Element) throws -> Bool) rethrows -> [Element]

# 1。对可比较的对象进行升序排序

如果集合中的元素类型符合Comparable协议,则可以使用sorted()以升序对元素进行排序。下面的Playground代码展示了如何使用sorted():

class ImageFile: CustomStringConvertible, Comparable {

    let fileName: String
    let fileID: Int
    var description: String { return "ImageFile with ID: \(fileID)" }

    init(fileName: String, fileID: Int) {
        self.fileName = fileName
        self.fileID = fileID
    }

    static func ==(lhs: ImageFile, rhs: ImageFile) -> Bool {
        return lhs.fileID == rhs.fileID
    }

    static func <(lhs: ImageFile, rhs: ImageFile) -> Bool {
        return lhs.fileID < rhs.fileID
    }

}

let images = [
    ImageFile(fileName: "Car", fileID: 300),
    ImageFile(fileName: "Boat", fileID: 100),
    ImageFile(fileName: "Plane", fileID: 200)
]

let sortedImages = images.sorted()
print(sortedImages)

/*
 prints: [ImageFile with ID: 100, ImageFile with ID: 200, ImageFile with ID: 300]
 */

# 2。对可比较的对象按降序排序

如果集合中的元素类型符合Comparable协议,则必须使用sorted(by:)以降序对元素进行排序。

class ImageFile: CustomStringConvertible, Comparable {

    let fileName: String
    let fileID: Int
    var description: String { return "ImageFile with ID: \(fileID)" }

    init(fileName: String, fileID: Int) {
        self.fileName = fileName
        self.fileID = fileID
    }

    static func ==(lhs: ImageFile, rhs: ImageFile) -> Bool {
        return lhs.fileID == rhs.fileID
    }

    static func <(lhs: ImageFile, rhs: ImageFile) -> Bool {
        return lhs.fileID < rhs.fileID
    }

}

let images = [
    ImageFile(fileName: "Car", fileID: 300),
    ImageFile(fileName: "Boat", fileID: 100),
    ImageFile(fileName: "Plane", fileID: 200)
]

let sortedImages = images.sorted(by: { (img0: ImageFile, img1: ImageFile) -> Bool in
    return img0 > img1
})
//let sortedImages = images.sorted(by: >) // also works
//let sortedImages = images.sorted { $0 > $1 } // also works
print(sortedImages)

/*
 prints: [ImageFile with ID: 300, ImageFile with ID: 200, ImageFile with ID: 100]
 */

# 3。对不可比较的对象按升序或降序排序

如果集合中的元素类型不符合Comparable协议,则必须使用sorted(by:)以升序或降序对元素进行排序。

class ImageFile: CustomStringConvertible {

    let fileName: String
    let fileID: Int
    var description: String { return "ImageFile with ID: \(fileID)" }

    init(fileName: String, fileID: Int) {
        self.fileName = fileName
        self.fileID = fileID
    }

}

let images = [
    ImageFile(fileName: "Car", fileID: 300),
    ImageFile(fileName: "Boat", fileID: 100),
    ImageFile(fileName: "Plane", fileID: 200)
]

let sortedImages = images.sorted(by: { (img0: ImageFile, img1: ImageFile) -> Bool in
    return img0.fileID < img1.fileID
})
//let sortedImages = images.sorted { $0.fileID < $1.fileID } // also works
print(sortedImages)

/*
 prints: [ImageFile with ID: 300, ImageFile with ID: 200, ImageFile with ID: 100]
 */

注意,Swift还提供了两个方法sort()和sort(by:)作为sorted()和sorted(by:)的对应,如果你需要对你的集合进行就地排序。