Extensions

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An arbitrary Unicode string value.Unicode-Correct ===============Swift strings are designed to be Unicode-correct. In particular, the APIs make it easy to write code that works correctly, and does not surprise end-users, regardless of where you venture in the Unicode character space. For example,

• The == operator checks for Unicode canonical equivalence, so two different representations of the same string will always compare equal.
• String elements are Characters (Unicode extended grapheme clusters), a unit of text that is meaningful to most humans.

Locale-Insensitive ==================The fundamental operations on Swift strings are not sensitive to locale settings. That’s because, for example, the validity of a Dictionary<String, T> in a running program depends on a given string comparison having a single, stable result. Therefore, Swift always uses the default, un-tailored Unicode algorithms for basic string operations.Importing Foundation endows swift strings with the full power of the NSString API, which allows you to choose more complex locale-sensitive operations explicitly.Value Semantics ===============Each string variable, let binding, or stored property has an independent value, so mutations to the string are not observable through its copies::

var a = foo var b = a b[b.endIndex.predecessor()] = x println(a=\(a), b=\(b)) // a=foo, b=fox

Strings use Copy-on-Write so that their data is only copied lazily, upon mutation, when more than one string instance is using the same buffer. Therefore, the first in any sequence of mutating operations may cost O(N) time and space, where N is the length of the string’s (unspecified) underlying representation,.Growth and Capacity ===================When a string’s contiguous storage fills up, new storage must be allocated and characters must be moved to the new storage. String uses an exponential growth strategy that makes append a constant time operation when amortized over many invocations.Objective-C Bridge ==================String is bridged to Objective-C as NSString, and a String that originated in Objective-C may store its characters in an NSString. Since any arbitrary subclass of NSSString can become a String, there are no guarantees about representation or efficiency in this case. Since NSString is immutable, it is just as though the storage was shared by some copy: the first in any sequence of mutating operations causes elements to be copied into unique, contiguous storage which may cost O(N) time and space, where N is the length of the string representation (or more, if the underlying NSString is has unusual performance characteristics).

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struct String

A 64-bit signed integer value type.

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struct Int : SignedIntegerType

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A value type whose instances are either true or false.

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struct Bool

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Undocumented

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Undocumented

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Undocumented

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