在 Swift 中，如何对数组中的值求和

Question

这是我的代码：

import Foundation

struct Movie {
    var title = ""
    var year = 0
    var isImportant: Bool
    var isFinished: Bool
    
    init(title: String, year: Int, isImportant: Bool, isFinished: Bool) {
        self.title = title
        self.year = year
        self.isImportant = isImportant
        self.isFinished = isFinished
    }

    static let list1 = [
        Movie(title: "The Shawshank Redemption", year: 1994, isImportant: false, isFinished: false),
        Movie(title: "The Godfather", year: 1972, isImportant: false, isFinished: false),
        Movie(title: "The Dark Knight", year: 2008, isImportant: false, isFinished: false),
        Movie(title: "The Godfather: Part II", year: 1974, isImportant: false, isFinished: false),
        Movie(title: "Avengers: Infinity War", year: 2018, isImportant: false, isFinished: false),
        Movie(title: "Schindler's List", year: 1993, isImportant: false, isFinished: false)
        ]
    
    static let list2 = [
        Movie(title: "The Lord of the Rings: The Fellowship of the Ring", year: 2001, isImportant: false, isFinished: false),
        Movie(title: "Inception", year: 2010, isImportant: false, isFinished: false),
        Movie(title: "Forrest Gump", year: 1994, isImportant: false, isFinished: false),
        Movie(title: "Fight Club", year: 1999, isImportant: false, isFinished: false)
        ]
    
    static let list3 = [list1, list2]
    
    static let nomsDesRepas: [String] = ["Petit Déjeuner", "Collation 11h"]
}


var list2Dim = Movie.list3
var list1 = Movie.list1

我必须从“list1”字典中总结年份，而不是直接从“list1”中总结。我需要通过“list2dim”词典。我的意思是 (1994+1972+ ... +1993)

Answer 1

I don't know how to navigate in it! Could you help me please?

索引是相同的，无论数组中有什么，包括其他数组，所以“导航”它只是重复索引。你知道如何从你的问题中索引 .

在 playground 中尝试以下操作并确保您理解每一行输出：

let list1 = [1, 2]
let list2 = [3, 4, 5]
let list3 = [6]

let listlist1 = [list1, list2]
let listlist2 = [list3]

let listlistlist = [listlist1, listlist2]

// print what we have produced
print(listlistlist)

// "navigate" into the structure, one step at a time
let result1 = listlistlist[0]
print(result1)
let result2 = result1[1]
print(result2)
let result3 = result2[2]
print(result3)

// indexing is left-associative, navigate in one step
let result012 = listlistlist[0][1][2]
print(result012)

如果您不确定 left-associative 读的是什么 Operator associativity。

在上面的例子中，最终结果是一个数字，从你之前的如果最终结果是一个对象，你知道你可以访问它的属性。

在您的问题的答案中，您了解了如何使用 map 通过对现有数组的每个元素应用函数来生成新数组。

如果像 map 这样按照某种模式处理整个数组的函数存在于库中，库中可能没有其他函数也按照其他模式处理整个数组吗？因此，请查找 map 的文档，然后通读文档的那个区域，看看您找到了什么——您可能不会失望，并且离您的年值求和目标更近了一步。

如果您在旅程的中途遇到困难，请提出一个新问题，包括您到那时为止设计的代码，描述您遇到的错误或您无法弄清楚的步骤，并包括一个link 回到这个问题，以便读者可以阅读您的问答。下一步肯定会有人帮助你。

继续学习、阅读和实践！ HTH

Answer 2

我终于找到了问题的答案：

struct Movie {
    var title = ""
    var year = 0
    var isImportant: Bool
    var isFinished: Bool
    
    init(title: String, year: Int, isImportant: Bool, isFinished: Bool) {
        self.title = title
        self.year = year
        self.isImportant = isImportant
        self.isFinished = isFinished
    }

    static let list1 = [
        Movie(title: "The Shawshank Redemption", year: 1994, isImportant: false, isFinished: false),
        Movie(title: "The Godfather", year: 1972, isImportant: false, isFinished: false),
        Movie(title: "The Dark Knight", year: 2008, isImportant: false, isFinished: false),
        Movie(title: "The Godfather: Part II", year: 1974, isImportant: false, isFinished: false),
        Movie(title: "Avengers: Infinity War", year: 2018, isImportant: false, isFinished: false),
        Movie(title: "Schindler's List", year: 1993, isImportant: false, isFinished: false)
        ]
    
    static let list2 = [
        Movie(title: "The Lord of the Rings: The Fellowship of the Ring", year: 2001, isImportant: false, isFinished: false),
        Movie(title: "Inception", year: 2010, isImportant: false, isFinished: false),
        Movie(title: "Forrest Gump", year: 1994, isImportant: false, isFinished: false),
        Movie(title: "Fight Club", year: 1999, isImportant: false, isFinished: false)
        ]
    
    static let list3 = [list1, list2]
    
    static let nomsDesRepas: [String] = ["Petit Déjeuner", "Collation 11h"]
}

var list2Dim = Movie.list3

func sumSectionCalorie(Liste liste: Int) -> Int {
var total = 0
let number = list2Dim[liste].count
    for xxx in 0 ..< number {
    
        total += list2Dim[liste][xxx].year
}
    return total
}

let total = sumSectionCalorie(Liste: 0)
print(total)

谢谢CARD给我提示

在 Swift 中，如何对数组中的值求和

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