Swift Novice Tutorial 3-strings String

Original blog, reproduced please indicate the source

String
In Swfit, string is Unicode-compatible. The usage is similar to the C language.
Attention

In cocoa and cocoa touch, Swift's string, and NSString in the foundation are compatible, and all NSString-amount APIs can invoke the string type


String constants
1, with escape characters: such as \n,\t, etc.
2, single-byte Unicode scalar, \XMM
3, double-byte Unicode scalar, \ummmm
4, four-byte Unicode scalar, \ummmmmmmm
The m here is the hexadecimal number

Let myname = "HWC"//hwclet myname = "\" hwc\ ""//"HWC"

Initialize

var emptystring = ""//empty string var sameemptystring = string ()//empty string var notemptystring = "First"

Value Passing
In the Swfit. A value is passed when a string is assigned to a function or is passed as a parameter. This means that a copy is passed, not a reference to itself.

This is different from Cocoa's nsstring.


Strings often use operations
1 IsEmpty Properties
Infer whether it is empty

Let str = "" If Str.isempty{println ("This Is empty")}

2 StartIndex EndIndex countelements
Returns the Index of the last character, returns the value type String.index

Let str = "Hello World" println (Str.endindex)//11

println (countelements (str))

3 ToInt ()
return int? That is, if the conversion succeeds, the return value is int, otherwise nil

var str = "123" var result = Str.toint () if result! = Nil{println ("Success")}

4 Sub-string

  Substringfromindex (Index:String.index)  substringtoindex (index:String.index)  Substringwithrange (arange: Range ())

Here to use a advance function: Advance (start:t,n:distance)
is the offset distance distance relative to T. Due to temporary not finding an int to string.index the appropriate API
StackOverflow found some information, it seems that Swift's API has a lot of non-intact places
In the end. I'll talk about how to extend a class, and then give a sample of the substring

var str = "Hello World" str.substringfromindex (Advance (str.startindex,6))//hellostr.substringtoindex (Advance ( str.startindex,5))//worldstr.substringwithrange (Range (Start:advance (str.startindex,2), End:advance ( str.startindex,8))//llo wo

5 string concatenation

Very simple answer, with Plus + or string interpolation

var str1 = "Hello" var str2 = "World" var str = str1 + str2

var str2 = "\ (str1) HWC and the \ (str2)"//hello HWC and the world

6 uppercase and lowercase conversions

Str.uppercasestring//hello World str.lowercasestring//hello World

7 prefix suffix equals
Bool Hasprefix (prefix:string)
Bool Hassuffix (suffix:string)

var str = "Hello HWC" str.hasprefix ("Hello")//truestr.hassuffix ("123")//false

var str1 = "Jack"

if  str = = str1{println ("Equal")}

8 processing substrings

void Insert (NEWELEMEMT:CHARACTER,ATINDEX:STRING.INDEX)//insert character void Removeatindex (I:string.index)//delete character void RemoveRange (subrange:range<string.index>)//delete an interval void Replacerange (SUBRANGE:RANGE<STRING.INDEX> WITH:C)

9 formatting merged strings
String Stringbyappendingformat (Format:string,arguments:cvarargtype ...)

var str = "Hello World" Str.stringbyappendingformat ("%d", 4)//hello World4

Ten UTF8 UTF16 properties

Str.utf8//Returns a collection of UTF8 representations of STR

STR.UTF16//Returns a collection of utf17 representations of STR

Extended string

By extending the Swifr class, you can provide new methods without changing the original class. Here are a few extension functions that expand the

Get substrings by subscript

and three overloads of substring

Extension string {    subscript (r:range<int>), String {         get {            Let Substart = Advance ( Self.startindex, R.startindex, Self.endindex)             Let SubEnd = Advance (Substart, R.endindex-r.startindex, Self.endindex)              return Self.substringwithrange (Range (Start:substart, end:subend))         }   }    func substring (from:int), String {  & nbsp;     Let end = Countelements (self)         return self[ From.. <end]   }    func substring (from:int, length:int), String {   & nbsp;    let end = from + LENGTH&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSp Return Self[from. <end]   }    func substring (from:int, to:int)->string    {         return Self[from. <to]   }}var str = "Hello world" var str1 = str.substring (6) var str2 = str.substring (0,to:5) var str3 = s Tr.substring (0,length:5)

On the right side of the playground, you can see

Output

Hello

Hello

World

Swift Novice Tutorial 3-strings String