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askaale
askaale

Reputation: 1199

Remove value from Array of Dictionaries

How I can remove a dict from an array of dictionaries?

I have an array of dictionaries like so: var posts = [[String:String]]() - and I would like to remove a dictionary with a specific key, how would I proceed? I know that I can remove a value from a standard array by doing Array.removeAtIndex(_:) or a dictionary key by doing key.removeValue(), but an array of dictionaries is more tricky.

Thanks in advance!

Upvotes: 1

Views: 5380

Answers (2)

Alexander
Alexander

Reputation: 63264

Removing all Dictionaries with a given key

let input = [
    [
        "Key 1" : "Value 1",
        "Key 2" : "Value 2",
    ],
    [
        "Key 1" : "Value 1",
        "Key 2" : "Value 2",
    ],
    [
        "Key 1" : "Value 1",
        "Key 2" : "Value 2",
        "Key 3" : "Value 3",
    ],
]

let keyToRemove = "Key 3"

//keep dicts only if their value for keyToRemove is nil (meaning key doesn't exist)
let result = input.filter{ $0[keyToRemove] == nil }

print("Input:\n")
dump(input)
print("\n\nAfter removing all dicts which have the key \"\(keyToRemove)\":\n")
dump(result)

You can see this code in action here.

Removing the only the first Dictionary with a given key

var result = input
//keep dicts only if their value for keyToRemove is nil (meaning key doesn't exist)
for (index, dict) in result.enumerate() {
    if (dict[keyToRemove] != nil) { result.removeAtIndex(index) }
}

print("Input:\n")
dump(input)
print("\n\nAfter removing all dicts which have the key \"\(keyToRemove)\":\n")
dump(result)

You can see this code in action here.

Upvotes: 3

Sash Zats
Sash Zats

Reputation: 5466

If I understood you questions correctly, this should work

var posts: [[String:String]] = [
    ["a": "1", "b": "2"],
    ["x": "3", "y": "4"],
    ["a": "5", "y": "6"]
]

for (index, var post) in posts.enumerate() {
    post.removeValueForKey("a")
    posts[index] = post
}

/* 
This will posts = [
    ["b": "2"], 
    ["y": "4", "x": "3"], 
    ["y": "6"]
]
*/

Since both your dictionary and the wrapping array are value types just modifying the post inside of the loop would modify a copy of dictionary (we created it by declaring it using var), so to conclude we need to set the value at index to the newly modified version of the dictionary

Upvotes: 4

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