Swift Learning notes-1

Apple Official Development Brochure address:

Https://developer.apple.com/library/prerelease/ios/referencelibrary/GettingStarted/LandingPage/index.html

Syntax overview

1 Simple Values

Constant definition: let

Variable definition: var

Constant or variable type is consistent with the initial value:   var myvariable =   myvariable =   Myconstant = 42 can also be explicitly specified type: let  explicitdouble:d ouble = 70

Type conversion, for example, String ():

   Let label = ' the width is ' let   width = 94 let   Widthlabel = label + String (width)

Print constant/variable values using \()

    Let apples = 3 let    oranges = 5 let    applesummary = "I has \ (apples) apples."    Let fruitsummary = "I had \ (apples + oranges) pieces of fruit."

Create an array or dictionary. Use []:

    var shoppinglist = ["Catfish", "water", "tulips", "Blue paint"]    shoppinglist[1] = "Bottle of water"    var occupation s = [    "Malcolm": "Captain",    "Kaylee": "Mechanic",    ]    occupations["Jayne"] = "Public Relations"

Initialize an empty array or dictionary:

    Let Emptyarray = string[] () let    emptydictionary = dictionary<string, float> ()

2 Control Flow

Conditional Inference If/switch

loop control for-in for while Do-while

    Let individualscores = [103, +,]    var teamscore = 0 for    score in Individualscores {    if score > 5 0 {    Teamscore + = 3    } else {    Teamscore + 1    }    }    Teamscore

Switch case

    Let vegetable = ' red pepper '    switch vegetable {case    ' celery ': let    vegetablecomment = ' Add some raisins and Make ants on a log. "    Case ' cucumber ', ' watercress ': let    vegetablecomment = ' would make a good tea sandwich. '    Case Let X where X.hassuffix ("Pepper"): let    vegetablecomment = "is it a spicy \ (x)?"
'    default: let    vegetablecomment = ' Everything tastes good in soup. '    }

For-in

    Let interestingnumbers = [    "Prime": [2, 3, 5, 7, one, +],    "Fibonacci": [1, 1, 2, 3, 5, 8],    "Square": [1, 4, 9, [+],    ]    var largest = 0    for (kind, numbers) in Interestingnumbers {for number in    numbers {    if num ber > Largest {    largest = number    }}}    largest

While/do-while

var m = 2do {m = m * 2} while M < 100m

For

Traditional format: var secondforloop = 0for var i = 0; I < 3; ++i {Secondforloop + = 1}secondforloop

New format: var firstforloop = 0for I in 0..3 {firstforloop + = I}firstforloop

3 Functions and Closures

    Function name (parameter 1, parameter 2), return type    func greet (name:string, day:string), String {    return ' Hello \ (name), today is \ (day). "    }    Greet (" Bob "," Tuesday ")

Returns multiple parameters:

    Func getgasprices () (double, double, double) {    return (3.59, 3.69, 3.79)    }    getgasprices ()

Variable number of parameters:

    Func sumof (Numbers:int ...)-Int {    var sum = 0 for number in    numbers {    sum + = number    }    return sum    }    Sumof ()    sumof (42, 597, 12)

Function nesting:

    Func Returnfifteen (), Int {    var y = ten    func Add () {    y + = 5    }    Add ()    return y    }
   
    returnfifteen ()
   

Returns the return value of a nested function:

    Func makeincrementer () (int-int) {    func addone (number:int), int {    return 1 + number    }    re Turn AddOne    }    var increment = makeincrementer ()    increment (7) <pre name= "code" class= "OBJC" >    Class Namedshape {    var numberofsides:int = 0    var name:string    init (name:string) {    self.name = Name
   }    func simpledescription (), String {    return "A shape with \ (numberofsides) sides."    }    }

There is a function to use as a parameter:

    Func hasanymatches (list:int[], condition:int-bool), BOOL {for    item in list {    if condition (item) {
   return true    }    }    return False    }    func Lessthanten (number:int), Bool {    return number < Ten    }    var numbers = [7, a, +]    hasanymatches (numbers, Lessthanten)

Use of {} and $

Numbers.map ({number in 3 * number})

Sort ([1, 5, 3, 2]) {$ > $}

4 Objects and Classes

Class implementation. Construct and destructor Init/deinit

    Class Namedshape {    var numberofsides:int = 0    var name:string    init (name:string) {       self.name = name       }    <code class= "Code-voice" >deinit</code> () {}     func simpledescription ()-String {          return "A shape with \ (numberofsides) sides."       }    }

Class uses:

    var shape = shape ()    shape.numberofsides = 7    var shapedescription = shape.simpledescription ()

Class inheritance and function overloading:

<pre name= "code" class= "OBJC" >class equilateraltriangle:namedshape {   var sidelength:double = 0.0   Initialize in subclass need to run:   1) Set subclass property Value   2) Parent class initialization   3) Set parent class Property value   init (sidelength:double, name:string) {     Self.sidelength = Sidelength     super.init (name:name)     numberofsides = 3  } var perimeter:double {  get {
   return 3.0 * Sidelength  }  set {    sidelength = newvalue/3.0  }}override func simpledescription ()- > String {    return ' an equilateral triagle with sides of length \ (sidelength). '  }}

Pre-set Willset and Didset

Willset {square.sidelength = newvalue.sidelength}

When working with optional values, you can write ?Before operations like methods, properties, and subscripting. If the value before the ?Is nil, everything after the ?

is ignored and the value of the whole expression is nil . Otherwise, the optional value is unwrapped, and everything after the?

Acts on the unwrapped value. In both cases, the value of the whole expression was an optional value.

    Let Optionalsquare:square? = Square (sidelength:2.5, name: "Optional square") let    sidelength = Optionalsquare?. Sidelength

5 enumerations and structures

Definition and use of enum

    Enum Rank:int {case    aces = 1 Case    -Three, four, Five, Six, Seven, Eight, Nine, Ten case    Jack, Queen, King    func simpledescription (), String {    switch self {case    . Ace:    return "Ace" case    . Jack:    return "Jack" case    . Queen:    return "Queen" Case    . King:    return "King"    default:    return String (Self.toraw ())}}    } let    ace = Rank.ace let    acerawvalue = Ace.toraw ()

Conversion of enum values and raw values (Toraw and Fromraw)

    If Let Convertedrank = Rank.fromraw (3) {let    threedescription = Convertedrank.simpledescription ()    }

struct and class differences:

A struct is a copy when it is used. Class is quoted when it is used.

6 Protocols and Extensions

Declare a protocol

  Protocol Exampleprotocol {    var simpledescription:string {get}    mutating func adjust ()    }

Protocol use:

   Class Simpleclass:exampleprotocol {    var simpledescription:string = "A very simple class."    var anotherproperty:int = 69105    func adjust () {    simpledescription + = "Now 100% adjusted."    }    }    var a = Simpleclass ()    a.adjust () let    adescription = a.simpledescription    struct simplestructure: Exampleprotocol {    var simpledescription:string = "A simple structure"    mutating func adjust () {    Simpledescription + = "(adjusted)"    }    }    var b = simplestructure ()    b.adjust () let    bdescription = B.simpledescription

Notice the use of the keyword in the declaration's to mutating SimpleStructure mark a method, that modifies the structure.

Use of extension add functionality to an existing type

    Extension Int:exampleprotocol {    var simpledescription:string {    return "the number \ (self)    }    mutating Func adjust () {self    + =    -    simpledescription}}   

7 generics

Types of parameters to be determined:

    Func repeat<itemtype> (Item:itemtype, Times:int), itemtype[] {    var result = itemtype[] () for    i in 0. . times {    result + = Item    }    return result    }    repeat ("knock", 4)

Use whereTable with the list of references:

    Func anycommonelements <t, U where t:sequence, U:sequence, t.generatortype.element:equatable, T.GeneratorType.Eleme NT = = u.generatortype.element> (Lhs:t, rhs:u), Bool {for    Lhsitem in LHS {to    Rhsitem in RHS {    if L Hsitem = = Rhsitem {    return True    }}    }    return False    }    anycommonelements ([1, 2, 3], [3])

Swift Learning notes-1