A slice of a string.
- Xcode 9.0+Beta
- Swift Standard Library
When you create a slice of a string, a
Substring instance is the result. Operating on substrings is fast and efficient because a substring shares its storage with the original string. The
Substring type presents the same interface as
String, so you can avoid or defer any copying of the string’s contents.
The following example creates a
greeting string, and then finds the substring of the first sentence:
You can perform many string operations on a substring. Here, we find the length of the first sentence and create an uppercase version.
Converting a Substring to a String
This example defines a
raw string with some unstructured data, and then uses the string’s
prefix(while:) method to create a substring of the numeric prefix:
When you need to store a substring or pass it to a function that requires a
String instance, convert it using the
Calling this initializer copies the contents of the substring to a new string.