# decode(_:) Starts or continues decoding a UTF-8 sequence. ``` mutating func decode(_ input: inout I) -> UnicodeDecodingResult where I : IteratorProtocol, I.Element == UInt8 ``` ## Parameters `input` An iterator of code units to be decoded. `input` must be the same iterator instance in repeated calls to this method. Do not advance the iterator or any copies of the iterator outside this method. ## Return Value A `UnicodeDecodingResult` instance, representing the next Unicode scalar, an indication of an error, or an indication that the UTF sequence has been fully decoded. ## Discussion To decode a code unit sequence completely, call this method repeatedly until it returns `UnicodeDecodingResult.emptyInput`. Checking that the iterator was exhausted is not sufficient, because the decoder can store buffered data from the input iterator. Because of buffering, it is impossible to find the corresponding position in the iterator for a given returned `Unicode.Scalar` or an error. The following example decodes the UTF-8 encoded bytes of a string into an array of `Unicode.Scalar` instances. This is a demonstration only—if you need the Unicode scalar representation of a string, use its `unicodeScalars` view. ``` let str = "✨Unicode✨" print(Array(str.utf8)) // Prints "[226, 156, 168, 85, 110, 105, 99, 111, 100, 101, 226, 156, 168]" var bytesIterator = str.utf8.makeIterator() var scalars: [Unicode.Scalar] = [] var utf8Decoder = UTF8() Decode: while true { switch utf8Decoder.decode(&bytesIterator) { case .scalarValue(let v): scalars.append(v) case .emptyInput: break Decode case .error: print("Decoding error") break Decode } } print(scalars) // Prints "["\u{2728}", "U", "n", "i", "c", "o", "d", "e", "\u{2728}"]" ``` --- 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)