Swift Tutorials

How to Check if a Key Exists in a Dictionary in Swift

How to Check if a Key Exists in a Dictionary in Swift ?

Answer

To check if a key exists in a dictionary in Swift, you can use the `keys.contains` method or optional binding with `if let` to safely check for the presence of a key.

✐ Examples

1 Checking if a Key Exists Using `keys.contains` Method

We can check if a key exists in a dictionary in Swift using the `keys.contains` method. This example demonstrates how to check for the presence of a key and print a message based on the result.

For example,

We start by declaring and initializing a dictionary named myDictionary with integer keys and string values.
We use the `keys.contains` method to check if a key exists in the dictionary.
We print a message based on whether the key exists or not.

Swift Program

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

// Key to check
let keyToCheck = 2

// Check if the key exists using the keys.contains method
if myDictionary.keys.contains(keyToCheck) {
    print("Key \(keyToCheck) exists in the dictionary.")
} else {
    print("Key \(keyToCheck) does not exist in the dictionary.")
}

Output

Key 2 exists in the dictionary.

2 Checking if a Key Exists Using Optional Binding

We can check if a key exists in a dictionary in Swift using optional binding with `if let`. This example demonstrates how to check for the presence of a key and print a message based on the result.

For example,

We start by declaring and initializing a dictionary named myDictionary with integer keys and string values.
We use optional binding with `if let` to check if a key exists in the dictionary.
We print a message based on whether the key exists or not.

Swift Program

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

// Key to check
let keyToCheck = 4

// Check if the key exists using optional binding
if let _ = myDictionary[keyToCheck] {
    print("Key \(keyToCheck) exists in the dictionary.")
} else {
    print("Key \(keyToCheck) does not exist in the dictionary.")
}

Output

Key 4 does not exist in the dictionary.

Summary

In this tutorial, we learned How to Check if a Key Exists in a Dictionary in Swift language with well detailed examples.

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How to Check if a Key Exists in a Dictionary in Swift