How to Update the Value for a Key in a Dictionary in Swift - Step by Step Examples

How to Update the Value for a Key in a Dictionary in Swift ?

Answer

To update the value for a key in a dictionary in Swift, you can use the subscript syntax to assign a new value to the key. If the key does not exist, it will be added to the dictionary with the specified value.

✐ Examples

1 Updating the Value for a Key Using Subscript Syntax

We can update the value for a key in a dictionary in Swift using subscript syntax. This example demonstrates how to update the value for an existing key and add a new key-value pair if the key does not exist.

For example,

We start by declaring and initializing a dictionary named myDictionary with integer keys and string values.
We update the value for an existing key using subscript syntax.
We add a new key-value pair using subscript syntax.
We print the dictionary contents to verify the updates.

Swift Program

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

// Update the value for an existing key
myDictionary[2] = "Two Updated"

// Add a new key-value pair
myDictionary[4] = "Four"

// 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 Updated
Key: 3, Value: Three
Key: 4, Value: Four

2 Updating the Value for a Key Using the `updateValue(_:forKey:)` Method

We can update the value for a key in a dictionary in Swift using the `updateValue(_:forKey:)` method. This example demonstrates how to update the value for an existing key and add a new key-value pair using the `updateValue(_:forKey:)` method.

For example,

We start by declaring and initializing a dictionary named myDictionary with integer keys and string values.
We update the value for an existing key using the `updateValue(_:forKey:)` method.
We add a new key-value pair using the `updateValue(_:forKey:)` method.
We print the dictionary contents to verify the updates.

Swift Program

var myDictionary: [String: Double] = [
    "A": 1.1,
    "B": 2.2,
    "C": 3.3
]

// Update the value for an existing key
myDictionary.updateValue(2.5, forKey: "B")

// Add a new key-value pair
myDictionary.updateValue(4.4, forKey: "D")

// 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: 2.5
Key: C, Value: 3.3
Key: D, Value: 4.4

Summary

In this tutorial, we learned How to Update the Value for a Key in a Dictionary in Swift language with well detailed examples.

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How to Update the Value for a Key in a Dictionary in Swift - Step by Step Examples