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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
extension String {
/// Subscripting strings with integers is not available.
///
/// The concept of "the `i`th character in a string" has
/// different interpretations in different libraries and system
/// components. The correct interpretation should be selected
/// according to the use case and the APIs involved, so `String`
/// cannot be subscripted with an integer.
///
/// Swift provides several different ways to access the character
/// data stored inside strings.
///
/// - `String.utf8` is a collection of UTF-8 code units in the
/// string. Use this API when converting the string to UTF-8.
/// Most POSIX APIs process strings in terms of UTF-8 code units.
///
/// - `String.utf16` is a collection of UTF-16 code units in
/// string. Most Cocoa and Cocoa touch APIs process strings in
/// terms of UTF-16 code units. For example, instances of
/// `NSRange` used with `NSAttributedString` and
/// `NSRegularExpression` store substring offsets and lengths in
/// terms of UTF-16 code units.
///
/// - `String.unicodeScalars` is a collection of Unicode scalars.
/// Use this API when you are performing low-level manipulation
/// of character data.
///
/// - `String.characters` is a collection of extended grapheme
/// clusters, which are an approximation of user-perceived
/// characters.
///
/// Note that when processing strings that contain human-readable
/// text, character-by-character processing should be avoided to
/// the largest extent possible. Use high-level locale-sensitive
/// Unicode algorithms instead, for example,
/// `String.localizedStandardCompare()`,
/// `String.localizedLowercaseString`,
/// `String.localizedStandardRangeOfString()` etc.
@available(
*, unavailable,
message: "cannot subscript String with an Int, use a String.Index instead."
)
public subscript(i: Int) -> Character {
Builtin.unreachable()
}
/// Subscripting strings with integers is not available.
///
/// The concept of "the `i`th character in a string" has
/// different interpretations in different libraries and system
/// components. The correct interpretation should be selected
/// according to the use case and the APIs involved, so `String`
/// cannot be subscripted with an integer.
///
/// Swift provides several different ways to access the character
/// data stored inside strings.
///
/// - `String.utf8` is a collection of UTF-8 code units in the
/// string. Use this API when converting the string to UTF-8.
/// Most POSIX APIs process strings in terms of UTF-8 code units.
///
/// - `String.utf16` is a collection of UTF-16 code units in
/// string. Most Cocoa and Cocoa touch APIs process strings in
/// terms of UTF-16 code units. For example, instances of
/// `NSRange` used with `NSAttributedString` and
/// `NSRegularExpression` store substring offsets and lengths in
/// terms of UTF-16 code units.
///
/// - `String.unicodeScalars` is a collection of Unicode scalars.
/// Use this API when you are performing low-level manipulation
/// of character data.
///
/// - `String.characters` is a collection of extended grapheme
/// clusters, which are an approximation of user-perceived
/// characters.
///
/// Note that when processing strings that contain human-readable
/// text, character-by-character processing should be avoided to
/// the largest extent possible. Use high-level locale-sensitive
/// Unicode algorithms instead, for example,
/// `String.localizedStandardCompare()`,
/// `String.localizedLowercaseString`,
/// `String.localizedStandardRangeOfString()` etc.
@available(
*, unavailable,
message: "cannot subscript String with an integer range, use a String.Index range instead."
)
public subscript<R: RangeExpression>(bounds: R) -> String where R.Bound == Int {
Builtin.unreachable()
}
}
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