Swift Convert String to Byte Array: utf8 and UInt8

Converts String to a byte array with the utf8 property. Convert the UInt8 array back into a String.

String, byte array. In Swift a byte is called a UInt8—an unsigned 8 bit integer. A byte array is a UInt8 array. In ASCII we can treat chars as UInt8 values.

With the utf8 String property, we get a UTF8View collection. We can convert his to a byte array. Then we can manipulate bytes. We can convert those bytes into a String.

An example. This example takes a String with value "Codex" and gets its UTF8View. Then it creates a byte array from the UTF8View with an array creation statement.

Next: It changes the first value in the byte array. It increments it, changing "p" to "q."

String: Finally the program uses an "if let" statement to create a String from the byte array. It specifies ASCII encoding.

Swift program that converts string to byte array import Foundation // An input string. let name = "Codex" // Get the String.UTF8View. let bytes = name.utf8 print(bytes) // Get an array from the UTF8View. // ... This is a byte array of character data. var buffer = [UInt8](bytes) // Change the first byte in the byte array. // ... The byte array is mutable. buffer[0] = buffer[0] + UInt8(1) print(buffer) // Get a string from the byte array. if let result = String(bytes: buffer, encoding: NSASCIIStringEncoding) { print(result) } Output Codex [113, 101, 114, 108, 115] qerls

Create string, bytes. It is possible to create a String from a sequence of bytes. We can specify these directly in the program. This allows dynamic creation of strings.

Here: We create an empty byte array (with the UInt8 type). We add 3 UInt8 values to the array.

Result: Our resulting string has the value "abc" from the bytes added to the buffer. We use ASCII encoding.

Swift program that creates string from bytes import Foundation // An empty UInt8 byte array. var buffer = [UInt8]() // Add some bytes to the byte array. buffer.append(UInt8(97)) buffer.append(UInt8(98)) buffer.append(UInt8(99)) // Get a string from the byte array. if let result = String(bytes: buffer, encoding: NSASCIIStringEncoding) { print(result) } Output abc

In Swift, Strings are hard to manipulate. Using a UInt8 array to create certain kinds of strings (like those meant for machines) is a good strategy to improve performance and gain clarity.Strings

Some notes. In Swift 2 we have access to a utf8 property. This is key to converting Strings to byte arrays. We use the UInt8 type to indicate a byte in this language.

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Swift Convert String to Byte Array: utf8 and UInt8

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