Swift Learning notes-tutorials to learn two strings and characters (Strings and characters)

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2.1string literalString Literals

string literals are represented by double quotation marks ( "" ) wrapped with a fixed-order text character set.

Let somestring = "Some string literal value"

2.2initializing an empty stringInitializing an Empty String

var emptystring = ""//empty string literal

var anotheremptystring = String ()//construction method

The two strings are both empty and equivalent.

2.3string VariabilityString mutability

(with Let a string assigned to a constant can no longer be modified.

2.4string is a value typeStrings is Value Types

Because a string is a value type, the assignment, copy, and pass process does not affect the original string, it creates a new copy and passes or assigns the new copy.

2.5using charactersworking with characters

by marking a Character type and the character literal to assign the value,

Let Exclamationmark:character = "!"

Let catcharacters: [Character] = ["C", "a", "T", "!", "??"]

Let catstring = String (catcharacters)

Print (catstring)

Prints "Cat!??"

2.6connection strings and charactersconcatenating Strings and characters

Let string1 = "Hello"

Let string2 = "there"

var welcome = string1 + string2

Welcome now equals "Hello there."

var instruction = "Look over"

Instruction + = string2

Instruction now equals "look over there."

Let Exclamationmark:character = "!

Welcome.append (Exclamationmark)

Welcome now equals "Hello there!."

2.7string Interpolation(String interpolation)

string interpolation is a way to construct a new string that can contain constants, variables, literals, and expressions. Each entry for the string literal that you insert is in parentheses prefixed with a backslash:

Let multiplier = 3

Let message = "\ (multiplier) times 2.5 is \ (Double (multiplier) * 2.5)"

Message is ' 3 times 2.5 is 7.5

2.8 UnicodeUnicodeScalar (Unicode scalars)

Swiftof theStringtype is based onUnicodescalarestablished. Unicodea scalar is the only one that corresponds to a character or modifier. +bit numbers, such asu+0061the Latin alphabet that represents lowercase(LATIN SMALL letter A) ("a"),u+1f425expression of a chick(front-facing BABY chick) ("?").

special characters for string literals(special characters in String literals)

String literals can contain the following special characters:

• Escape character (null character), \ \ (backslash), \ t (horizontal tab), \ n (newline character), \ r (carriage return), \ "(double quotation mark), \ ' (single quotation mark).

Unicode scalar, written as \u{n} (U is lowercase), where n is any one to eight hexadecimal digits and the available Unicode bit code.

Scalable Glyph Clusters(Extended grapheme Clusters)

Let Eacute:character = "\u{e9}"//é

Let Combinedeacute:character = "\u{65}\u{301}"//E-followed by?

Eacute isé, Combinedeacute is E?

2.9calculating the number of charactersCounting characters

If you want to get a string in the Character the number of strings that can be used characters property of Count Properties:

Note: The extensible character clouds set can form one or more Unicode scalars.

The length property of the NSString is the 16-bit code unit number represented by the UTF-16.

var word = "Cafe"

Print ("The number of characters in \ (word) is \ (Word.characters.count)")

Prints "The number of characters in Cafe is 4"

Word + = "\u{301}"//combining ACUTE ACCENT, u+0301

Print ("The number of characters in \ (word) is \ (Word.characters.count)")

Prints "The number of characters in cafe? is 4 "

2.10Accessing and modifying stringsAccessing and modifying a StringString IndexString Indices

each one String value has an associated index type, String.index that corresponds to each of the characters in the string Character the location.

Let greeting = "Guten tag!"

Greeting[greeting.startindex]

G

Greeting[greeting.endindex.predecessor ()]

// !

Greeting[greeting.startindex.successor ()]

U

Let index = greeting.startIndex.advancedBy (7)

Greeting[index]

A

Greeting[greeting.endindex]//Error

Greeting.endIndex.successor ()//Error

For index in Greeting.characters.indices {

Print ("\ (Greeting[index])", Terminator: "")

}

Prints "G U t e n T a G!"

inserting and deletingInserting and removing

Insert (_:atindex:), Insertcontentsof (_:at:), Removeatindex (_:)

var welcome = "Hello"

Welcome.insert ("!", AtIndex:welcome.endIndex)

Welcome now equals "Hello!"

Welcome.insertcontentsof ("there". Characters, At:welcome.endIndex.predecessor ())

Welcome now equals "Hello there!"

Welcome.removeatindex (Welcome.endIndex.predecessor ())

Welcome now equals "Hello there"

To remove a substring at a specified range, use the RemoveRange (_:) Method:

Let range = Welcome.endIndex.advancedBy (-6): <welcome.endindex

Welcome.removerange (Range)

Welcome now equals "Hello"

2.11Comparing Strings(comparing Strings)string/Word typeface, etc.(String and Character equality)

equals ( == ) and not equal to ( != )

Let quotation = "We ' re a lot alike, you and I."

Let samequotation = "We ' re a lot alike, you and I."

If quotation = = Samequotation {

Print ("These strings is considered equal")

}

Print output "These strings is considered equal"

"Voulez-vous un café?" using LATIN SMALL letter E with ACUTE

Let eacutequestion = "voulez-vous un caf\u{e9}?"

"Voulez-vous un cafe?" using LATIN SMALL letter E and combining ACUTE ACCENT

Let combinedeacutequestion = "voulez-vous un caf\u{65}\u{301}?"

if eacutequestion = = combinedeacutequestion {

Print ("These strings is considered equal")

}

prefix/suffix equal(Prefix and Suffix equality)

Let Romeoandjuliet = [

"Act 1 Scene 1:verona, A public Place",

"Act 1 Scene 2:capulet ' s Mansion",

ACT 1 Scene 3: A Capulet ' s Mansion ",

"Act 1 Scene 4:a Street outside Capulet ' s mansion",

"Act 1 Scene 5:the great Hall in Capulet ' s mansion",

"Act 2 Scene 1:outside Capulet ' s Mansion",

"Act 2 Scene 2:capulet ' s Orchard",

"Act 2 Scene 3:outside friar Lawrence ' s Cell",

"Act 2 Scene 4:a Street in Verona",

"Act 2 Scene 5:capulet ' s Mansion",

"Act 2 Scene 6:friar Lawrence ' s Cell"

]

You can call Hasprefix (_:) method to calculate the number of scenes in the first act of a play:

var act1scenecount = 0

For scene in Romeoandjuliet {

If Scene.hasprefix ("Act 1") {

Act1scenecount + = 1

}

}

Print ("There is \ (Act1scenecount) scenes in Act 1")

Prints "There is 5 scenes in Act 1"

Similarly, you can use Hassuffix (_:) method to calculate the number of scenes that occur in different places:

var mansioncount = 0

var cellcount = 0

For scene in Romeoandjuliet {

If Scene.hassuffix ("Capulet ' s Mansion") {

Mansioncount + = 1

} else if Scene.hassuffix ("Friar Lawrence ' s cell") {

Cellcount + = 1

}

}

Print ("\ (mansioncount) mansion scenes; \ (cellcount) cell scenes ")

Prints "6 mansion scenes; 2 cell scenes "

of the stringUnicodeRepresentation (Unicode representations of Strings)

When a Unicode string is written into a text file or other storage, the Unicode scalar in the string is encoded in several encoding formats defined by Unicode. The small block encoding in each string is called a code unit. The encoding format includes the UTF-8 encoding format (a code unit with an encoded string of 8 bits), a UTF-16 encoding format (a code unit with an encoded string of 16 bits), and a UTF-32 encoding format (a code unit with an encoded string of 32 bits).

utf-8 Code Unit Collection (accessed using the UTF8 property of the string)

utf-16 Code Unit Collection (accessed using the Utf16 property of the string)

• 21-bit Unicode scalar value collection, which is the UTF-32 encoding format of the string (accessed using the Unicodescalars property of the string)

Let dogstring = "Dog???" (u+1f436)

UTF-8 Representation

For CodeUnit in Dogstring.utf8 {

Print ("\ (CodeUnit)", Terminator: "")

}

Print ("")

68 111 103 226 128 188 240 159 144 182

UTF-16 Representation

For CodeUnit in Dogstring.utf16 {

Print ("\ (CodeUnit)", Terminator: "")

}

Print ("")

68 111 103 8252 55357 56374

Unicode Scalar Representation

For scalar in Dogstring.unicodescalars {

Print ("\ (Scalar.value)", Terminator: "")

}

Print ("")

68 111 103) 8252 128054

For scalar in Dogstring.unicodescalars {

Print ("\ (scalar)")

}

D//O//g//? // ??

Swift Learning notes-tutorials to learn two strings and characters (Strings and characters)