# subscript(_:default:) Accesses the value with the given key, falling back to the given default value if the key isn’t found. ``` subscript(key: Key, default defaultValue: @autoclosure () -> Value) -> Value { get set } ``` ## Parameters `key` The key the look up in the dictionary. `defaultValue` The default value to use if `key` doesn’t exist in the dictionary. ## Return Value The value associated with `key` in the dictionary; otherwise, `defaultValue`. ## Overview Use this subscript when you want either the value for a particular key or, when that key is not present in the dictionary, a default value. This example uses the subscript with a message to use in case an HTTP response code isn’t recognized: ``` var responseMessages = [200: "OK", 403: "Access forbidden", 404: "File not found", 500: "Internal server error"] let httpResponseCodes = [200, 403, 301] for code in httpResponseCodes { let message = responseMessages[code, default: "Unknown response"] print("Response \(code): \(message)") } // Prints "Response 200: OK" // Prints "Response 403: Access forbidden" // Prints "Response 301: Unknown response" ``` When a dictionary’s `Value` type has value semantics, you can use this subscript to perform in-place operations on values in the dictionary. The following example uses this subscript while counting the occurrences of each letter in a string: ``` let message = "Hello, Elle!" var letterCounts: [Character: Int] = [:] for letter in message { letterCounts[letter, default: 0] += 1 } // letterCounts == ["H": 1, "e": 2, "l": 4, "o": 1, ...] ``` When `letterCounts[letter, default: 0] += 1` is executed with a value of `letter` that isn’t already a key in `letterCounts`, the specified default value (`0`) is returned from the subscript, incremented, and then added to the dictionary under that key. > Note: Do not use this subscript to modify dictionary values if the > dictionary’s `Value` type is a class. In that case, the default value > and key are not written back to the dictionary after an operation. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)