What you get here is the documentation for StringProtocol
func hasPrefix(_ prefix: String) -> Bool
This is enough information for a quickhelp.
There is also a documentation for Generic Instance Method of Substring, much more detailed. But this is not the one called in quickHelp
Returns a Boolean value indicating whether the string begins with the specified prefix.
Language
Swift
SDK
Xcode 10.0+
Framework
Swift Standard Library
On This Page
- Declaration
- Parameters
- Return Value
- Discussion
func hasPrefix<Prefix>(_ prefix: Prefix) -> Bool where Prefix : StringProtocol
prefix
A possible prefix to test against this string.
true
if the string begins with
prefix
; otherwise,
false
.
The comparison is both case sensitive and Unicode safe. The case-sensitive comparison will only match strings whose corresponding characters have the same case.
let cafe = "Café du Monde" // Case sensitive print(cafe.hasPrefix("café")) // Prints "false"
The Unicode-safe comparison matches Unicode extended grapheme clusters rather than the code points used to compose them. The example below uses two strings with different forms of the
"é"
character—the first uses the composed form and the second uses the decomposed form.
// Unicode safe let composedCafe = "Café" let decomposedCafe = "Cafe\u{0301}" print(cafe.hasPrefix(composedCafe)) // Prints "true" print(cafe.hasPrefix(decomposedCafe)) // Prints "true"
