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Swift: Append an element to an array in a dictionary value, creating the array/value if needed
import Foundation
extension Dictionary where Value: RangeReplaceableCollection {
public mutating func append(element: Value.Iterator.Element, toValueOfKey key: Key) -> Value? {
var value: Value = self[key] ?? Value()
value.append(element)
self[key] = value
return value
}
}
var books: [String: [String]] = [
"Phillip K Dick": [
"Do Androids Dream of Electric Sheep?",
"The Man in the High Castle",
],
"Cory Doctorow": [
"Down and Out in the Magic Kingdom",
"Makers",
]
]
books.append(element: "Eastern Standard Tribe", toValueOfKey: "Cory Doctorow")
books
/*
[
"Phillip K Dick": [
"Do Androids Dream of Electric Sheep?",
"The Man in the High Castle",
],
"Cory Doctorow": [
"Down and Out in the Magic Kingdom",
"Makers",
"Eastern Standard Tribe",
]
]
*/
books.append(element: "Parable of the Sower", toValueOfKey: "Octavia Butler")
books
/*
[
"Phillip K Dick": [
"Do Androids Dream of Electric Sheep?",
"The Man in the High Castle",
],
"Cory Doctorow": [
"Down and Out in the Magic Kingdom",
"Makers",
"Eastern Standard Tribe",
],
"Octavia Butler": [
"Parable of the Sower",
]
]
*/
@HaMaDaRaOuF
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@asmallteapot actully it's greate extention but when i try to use it that's what i found i hope if u help me
Result of call to 'append(element:toValueOfKey:)' is unused

@tadeha
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tadeha commented Oct 23, 2019

@asmallteapot actully it's greate extention but when i try to use it that's what i found i hope if u help me
Result of call to 'append(element:toValueOfKey:)' is unused

It just returns the value you added to the dictionary value part. You can silence that warning using these 2 ways:

1- Ignore the result by adding _ = in front of the function call
2- Add @discardableResult to the declaration of the function to silence the compiler

@hiteshsuthar1410
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Saved my day thankss!!

@Fazlis
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Fazlis commented Mar 28, 2023

if you want add element in [String] to your dictionary like [String : [String]] use methods @AtishPapa. That methods helped me

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