How to Remove a Key-Value Pair from a Dictionary in Swift - Step by Step Examples

How to Remove a Key-Value Pair from a Dictionary in Swift ?

Answer

To remove a key-value pair from a dictionary in Swift, you can use the `removeValue(forKey:)` method or set the key's value to `nil`. Both methods remove the element with the specified key from the dictionary.

✐ Examples

1 Removing a Key-Value Pair Using `removeValue(forKey:)` Method

We can remove a key-value pair from a dictionary in Swift using the `removeValue(forKey:)` method. This example demonstrates how to remove a key-value pair by specifying the key and print the dictionary contents before and after the removal.

For example,

We start by declaring and initializing a dictionary named myDictionary with integer keys and string values.
We print the dictionary contents before removing a key-value pair.
We use the `removeValue(forKey:)` method to remove a key-value pair by specifying the key.
We print the dictionary contents after removing the key-value pair.

Swift Program

var myDictionary: [Int: String] = [
    1: "One",
    2: "Two",
    3: "Three"
]

// Print the dictionary contents before removal
print("Dictionary contents before removal:")
for (key, value) in myDictionary {
    print("Key: \(key), Value: \(value)")
}

// Key to remove
let keyToRemove = 2

// Remove the key-value pair using the removeValue(forKey:) method
myDictionary.removeValue(forKey: keyToRemove)

// Print the dictionary contents after removal
print("Dictionary contents after removal:")
for (key, value) in myDictionary {
    print("Key: \(key), Value: \(value)")
}

Output

Dictionary contents before removal:
Key: 1, Value: One
Key: 2, Value: Two
Key: 3, Value: Three
Dictionary contents after removal:
Key: 1, Value: One
Key: 3, Value: Three

2 Removing a Key-Value Pair by Setting the Key's Value to `nil`

We can remove a key-value pair from a dictionary in Swift by setting the key's value to `nil`. This example demonstrates how to remove a key-value pair by specifying the key and setting its value to `nil`, and print the dictionary contents before and after the removal.

For example,

We start by declaring and initializing a dictionary named myDictionary with integer keys and string values.
We print the dictionary contents before removing a key-value pair.
We set the key's value to `nil` to remove the key-value pair.
We print the dictionary contents after removing the key-value pair.

Swift Program

var myDictionary: [Int: String] = [
    1: "One",
    2: "Two",
    3: "Three"
]

// Print the dictionary contents before removal
print("Dictionary contents before removal:")
for (key, value) in myDictionary {
    print("Key: \(key), Value: \(value)")
}

// Key to remove
let keyToRemove = 2

// Remove the key-value pair by setting the key's value to nil
myDictionary[keyToRemove] = nil

// Print the dictionary contents after removal
print("Dictionary contents after removal:")
for (key, value) in myDictionary {
    print("Key: \(key), Value: \(value)")
}

Output

Dictionary contents before removal:
Key: 1, Value: One
Key: 2, Value: Two
Key: 3, Value: Three
Dictionary contents after removal:
Key: 1, Value: One
Key: 3, Value: Three

3 Checking for Key Existence Before Removing Using `removeValue(forKey:)` Method

We can check if a key exists before attempting to remove a key-value pair in a dictionary in Swift using the `removeValue(forKey:)` method. This example demonstrates how to check for key existence and remove the key-value pair if it exists, then print the dictionary contents before and after the removal.

For example,

We start by declaring and initializing a dictionary named myDictionary with integer keys and string values.
We print the dictionary contents before removing a key-value pair.
We check if the key exists and use the `removeValue(forKey:)` method to remove the key-value pair if it exists.
We print the dictionary contents after removing the key-value pair.

Swift Program

var myDictionary: [Int: String] = [
    1: "One",
    2: "Two",
    3: "Three"
]

// Print the dictionary contents before removal
print("Dictionary contents before removal:")
for (key, value) in myDictionary {
    print("Key: \(key), Value: \(value)")
}

// Key to remove
let keyToRemove = 4

// Check if the key exists and remove it if it does
if myDictionary[keyToRemove] != nil {
    myDictionary.removeValue(forKey: keyToRemove)
    print("Key \(keyToRemove) was removed from the dictionary.")
} else {
    print("Key \(keyToRemove) does not exist in the dictionary.")
}

// Print the dictionary contents after removal
print("Dictionary contents after removal:")
for (key, value) in myDictionary {
    print("Key: \(key), Value: \(value)")
}

Output

Dictionary contents before removal:
Key: 1, Value: One
Key: 2, Value: Two
Key: 3, Value: Three
Key 4 does not exist in the dictionary.
Dictionary contents after removal:
Key: 1, Value: One
Key: 2, Value: Two
Key: 3, Value: Three

Summary

In this tutorial, we learned How to Remove a Key-Value Pair from a Dictionary in Swift language with well detailed examples.

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How to Remove a Key-Value Pair from a Dictionary in Swift - Step by Step Examples