How to modify the value of key in nested array of struct in swift5?

Question

How to modify the value of key from struct that is under nested of array of struct. I found one of possible solution from stackoverflow but it is only for one level. I am wondering if there is any better solution? and what if the key is optional?

struct Article {
    var id: Int
    var book: [Book]
}
struct Book {
    var page: Int
    var author: [Author]
}
struct Author {
    var visited: Bool
}
// update value of visited key in nested array of struct
var a = Article(id: 1, book: [Book(page: 11, author: [Author(visited: true)])])
print(a)
a.book.modifyElement(atIndex: 0) {$0.author.modifyElement( atIndex: 0) {$0.visited = false}}
print(a)

Changing The value of struct in an array

Why did you not include func modifyElement…? Why is book not books and author not authors? — user652038
– user652038, Commented Oct 25, 2022 at 23:18
have you tried this: a.book[0].author[0].visited = false, works for me. — workingdog support Ukraine
– workingdog support Ukraine, Commented Oct 25, 2022 at 23:21

workingdog support Ukraine · Accepted Answer · 2022-10-26 00:01:27Z

1

"How to modify the value of property from struct that is under nested of array of struct". Try this approach, a better more compact solution than what you have:

 var a = Article(id: 1, book: [Book(page: 11, author: [Author(visited: true)])])
 print("\n---> before a: \(a)")
 
 a.book[0].author[0].visited = false    // <-- here
 print("\n--->  after a: \(a)")

answered Oct 26, 2022 at 0:01

workingdog support Ukraine

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4 Comments

jacobcan118 Over a year ago

thinking about a more dynamic way to do it. but this one works

workingdog support Ukraine Over a year ago

what do you mean a more dynamic way? What is that?

jacobcan118 Over a year ago

lets say I need to modify the value under different path of key in different struct i do not want to write something likea.book[0].author[0].visited x.book.author.x.y[0].z = ""

workingdog support Ukraine Over a year ago

I think, no matter how you skin the cat, eventually you need to determine which book you want to change, which author you want to change and which property you want to change. If you want to change a range of books and/or authors, then you can use a for loop. You can wrap some of these steps into pre-canned functions, but that's just more code to do something simple.

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