Swift Basic data types

1 // Playground-noun: a place where people can play
  2 
  3 import UIKit
  4 // ----------------------------------------------- ------------------------
  5 // 1. String output
  6 var str = "world"
  7 println ("hello, \ (str)")
  8 
  9 //----------------------------------------------- ------------------------
 10 // 2. Type alias
 11 typealias audioSample = UInt16
 12
 13 // ----------------------------------------------- ------------------------
 14 // 3. Yuanzu tuples
 15 // Definition 1
 16 let http404Error = (404, "Not Found")
 17 let (statusCode, statusMessage) = http404Error
 18 let (justTheStatusCode, _) = http404Error // Only one value
 19
 20 // Definition 2
 21 let http200Status = (statusCode: 200, descirption: "OK")
 twenty two 
 23 // Access mode 1
 24 println ("\ (statusCode), \ (statusMessage)")
 25
 26 // Access mode 2
 27 println ("\ (http404Error.0), \ (http404Error.1)")
 28
 29 // Access mode 3
 30 println ("\ (http200Status.statusCode), \ (http200Status.descirption)")
 31
 32 // ----------------------------------------------- ------------------------
 33 // 4 Optionals
 34 // Optional value means either a certain value or nothing
 35 let possibleNumber = "123"
 36 var surveyAnswer: String? // The default is nil
 37 let converedNumber = possibleNumber.toInt () // converedNumber is optional
 38
 39 // Optional value binding
 40 if let actualNumber = converedNumber {
 41 println ("\ (possibleNumber) has numbers \ (actualNumber)")
 42} else {
 43 println ("\ (possibleNumber) cannot be converted to integer")
 44}
 45
 46 //4.1 nil
 47 // Object-C: nil represents a pointer to a non-existent object
 48 // swift: nil means a certain type of value, any optional value type and object type can be set to nil
 49
 50 //4.2 Implicity Unwrapped Optionals
 51 // Unpack each use
 52 let possibleString: String? = "An optional string."
 53 println (possibleString!)
 54
 55 // Whether it is used or not, it is automatically unpacked
 56 let assumeString: String! = "An implicitly unwrapped optional string."
 57 println (assumeString)
 58
 59 // ------------------------------------------------ ------------------------
 60 // 5 Assertions
 61 // The assertion checks whether a certain situation is true at run time. If it is true, the code continues to execute, and if it is false, the code is no longer executed
 62 let age = 3
 63 assert (age> = 0, "age cannot be less than 0")
 64
 65 // ------------------------------------------------ ------------------------
 66 // 6 basic operators
 67 //6.1 Range Operators
 68 //6.1.1 Closed Range Operator (a ... b), which is mathematically [a, b]
 69 for index in 1 ... 5 {
 70 println ("\ (index) times is \ (5 * index)")
 71}
 72 //6.1.2 Half-Closed Range Operator (a..b), namely (a, b)
 73 // for index in 1..5 {
 74 // println ("\ (index) times is \ (5 * index)")
 75 //}
 76
 77 // ----------------------------------------------- ------------------------
 78 // 7. String Literals
 79 var emptyString = String ()
 80 if emptyString.isEmpty {
 81}
 82
 83 //7.1 escape character
 84 / **
 85 * \ 0 null character
 86 * \\ backslash
 87 * \ t horizontal tab
 88 * \ n newline
 89 * \ r return
 90 * \ "double quotes
 91 * \ ‘single quote
 92 * /
 93
 94 // 7.2 Strings in swift are value types
 95 // When passing a string to a function, or assigning a string to another string, a copy of the string value is passed, not the address or reference of the string. A new copy of the string is created. The newly created copy is passed to the function or other string instead of the original string. This copy is created lazily and will only be created when necessary, so it is very efficient.
 96
 97 // Note that this is different from NSString in Cocoa, NSString passes reference.
 98
 99 // 7.3 Traverse Character in String
100 // Each character in the String is a single Unicode character
101 for character in "abcdef" {
102 println (character)
103}
104
105 // 7.4 Count the number of characters in the string countElements
106 let string = "abcdef"
107 println (countElements (string))
108
109 // 7.5 string concatenation
110 let string1 = "hello"
111 let string2 = "world"
112 let character1: Character = "!"
113 let multipier = 3
114
115 let stringPlusString = string1 + "" + string2 + String (character1)
116 let message = "\ (multipier * 2) times \ (stringPlusString)"
117
118 // 7.6 String comparison
119 if string1 == string2 {
120 println ("\ (string1) and \ (string2) contain the same character in the same position")
121}
122
123 // 7.7 hasPrefix, hasSuffix
124 var hasPrefix: Bool = stringPlusString.hasPrefix (string1)
125
126 // 7.8 case conversion
127 let upper = string1.uppercaseString
128 let lower = upper.lowercaseString
129
130 // 7.9 Unicode encoding
131
132 // Unicode is an international encoding, it can represent any character in any language through a standard format. In Unicode, any character can be represented by one or more unicode scalars (scalars: scalar, that is, non-vector, only numeric size, no direction) A unicode scalar is a unique 21-bit number (or name), for example U + 0061 means LOWERCASE LATIN LETTER A ("a")
133
134 // Swift's String and Character are fully compatible with Unicode encoding, it supports a series of different Unicode encoding
135
136 // UTF-8
137 // Get the utf8 representation of the character through the utf8 attribute of the character UTF8View
138 let dog = "Dog!"
139 for codeUnit in dog.utf8 {
140 print (codeUnit)
141}
142 // UTF-16
143 for codeUnit in dog.utf16 {
144 print (codeUnit)
145}
146 // Unicode Scalars
147 // Get the UnicodeScalar representation of the character through the unicodeScalars attribute of the type UnicodeScalarView
148 for scalar in dog.unicodeScalars {
149 print (scalar)
150} 

Swift Basic data types