Swift Tutorials

How to Add a Key-Value Pair to a Dictionary in Swift

How to Add a Key-Value Pair to a Dictionary in Swift ?

Answer

To add a key-value pair to a dictionary in Swift, you can use the subscript syntax or the `updateValue(_:forKey:)` method.

✐ Examples

1 Adding a Key-Value Pair Using Subscript Syntax

We can add a key-value pair to a dictionary in Swift using subscript syntax. This example demonstrates how to add key-value pairs to a dictionary and print its contents.

For example,

We start by declaring and initializing an empty dictionary named myDictionary.
We add key-value pairs to the dictionary using subscript syntax.
We print the dictionary contents to verify the key-value pairs.

Swift Program

var myDictionary: [Int: String] = [:]

// Add key-value pairs to the dictionary
myDictionary[1] = "One"
myDictionary[2] = "Two"
myDictionary[3] = "Three"

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

Output

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

2 Adding or Updating a Key-Value Pair Using `updateValue(_:forKey:)`

We can add or update a key-value pair in a dictionary in Swift using the `updateValue(_:forKey:)` method. This example demonstrates how to add or update key-value pairs in a dictionary and print its contents.

For example,

We start by declaring and initializing an empty dictionary named myDictionary.
We add or update key-value pairs in the dictionary using the `updateValue(_:forKey:)` method.
We print the dictionary contents to verify the key-value pairs.

Swift Program

var myDictionary: [String: Double] = [:]

// Add or update key-value pairs in the dictionary
myDictionary.updateValue(1.1, forKey: "A")
myDictionary.updateValue(2.2, forKey: "B")
myDictionary.updateValue(3.3, forKey: "C")

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

Output

Dictionary contents:
Key: A, Value: 1.1
Key: B, Value: 2.2
Key: C, Value: 3.3

Summary

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

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How to Add a Key-Value Pair to a Dictionary in Swift