SOLVED: Writing to an array inside a dictionary?

@lululucaschae

Jul '22

Hi, happy Friday!

I was working with some data of type <Int, [String]>

Here's a sample data,

var myDictionary: Dictionary<Int, [String]> = [
1: ["apple", "banana", "cranberries"],
2: ["tiger", "dog", "cat"],
3: ["crow", "goose", "sparrow"]
]

Now, what I want to do is to add a new item to an array of a specified key. (e.g. add "eagle" to myDictionary[3])

I do have a code that works but as you can see, I had to manually read and write the values by declaring a new variable.

var temp = myDictionary[3]
temp!.append("eagle")
myDictionary[3] = temp

print(myDictionary)

// [1: ["apple", "banana", "cranberries"],  2: ["tiger", "dog", "cat"], 3: ["crow", "goose", "sparrow", "eagle"],]

I was wondering if this is the only way to write to an array inside a dictionary, or if there's one-line command that does the same work. Thank you!

@roosterboy HWS+

Jul '22

myDictionary[3, default: []].append("eagle")

This will fetch the item with key of 3 or return an empty array [] if that key doesn't exist in myDictionary.

Then it appends a new value either to the returned array corresponding to the key 3 or to the empty array [].

Finally, it sets the value of the key 3 to the newly appended array.

@Azzaknight

Jul '22

You could also use optional chaining

myDictionary[3]?.append("eagle")

where if 3 is a key, then it will extract the array and append "eagle" else it will return nil

Sponsor Hacking with Swift and reach the world's largest Swift community!

Archived topic

This topic has been closed due to inactivity, so you can't reply. Please create a new topic if you need to.

All interactions here are governed by our code of conduct.