learn swift codecademy

If you're an iOS developer, or you're looking to enter the industry, Swift offers you a great opportunity. Swift's design is elegant, easier to learn than obj-c, and of course very powerful.To guide developers using Swift for development, Apple has released a series of technical documents such as the Swift programming

line unless there is a very clear need.We find that each volume is prefixed with a let or var keyword, so what type are they? In fact, the swift language has a type inference mechanism (Tyoe inference), that is, by initializing the value to infer the actual type of the volume, for example, in the above example, two is inferred by Swift as an int type, you can use the option key to see the amount of the rea

letorangesAreOrange=truelet turnipsAreDelicious=false When we write conditional statements, such as the IF statement, the Boolean value is very useful1 if turnipsaredelicious {2 3 print ("Mmm,tasty turnips!") 4 5} else {6 7 print ("Eww,turnips is horrible. ") 8 9}//output" Eww, turnips is horrible. " 10 11 Meta-groupTuples combine multiple values into a single composite value. The values within a tuple can be any type and do not require the same typeLet Http404error = (404,

Learn Swift from scratch (Day 52)-Cocoa error handling modeThe Swift error handling mode is different in Swift1.x and Swift 2.0. The error handling mode of Swift 1.x Code adopts the Cocoa framework error handling mode. Currently, Objective-C still adopts this mode, while the

the program is not validA case can be matched with multiple objects, separated by commas:Switch Anothercharacter {case "B", "C", "D": println ("Output BCD") case "a", "E", "F": println ("Output AEF") Default: println ("not Found") the}//program outputs: Output AEFBecause when executing the program, compared with the three objects in the first case, we find that we do not want it, and then we execute the second case and compare it with the multiple objects.Tuples in switch are used:Writ

call wrapper is asserted at run time, so that no error is thrown. If the error is actually thrown, a run-time error is triggered.Enum Customerror:errortype {case someerror}func willonlythrowiftrue (value:bool) throws { If value {throw Custo Merror.someerror}}do { try Willonlythrowiftrue (true)} catch { print ("Error")}try! Willonlythrowiftrue (True) //Run-time errorFinishing ActionUse the defer statement to execute a series of statements. This allows you to perform some necessa

simple.Accessing properties with optional chained callslet someAddress = Address()someAddress.buildingNumber"29"someAddress.street"Acacia Road"john.residence?.address = someAddressInvoking a method with an optional chained callifnil { print("It was possible to print the number of rooms."else { print("It was not possible to print the number of rooms.")}Access subscript via optional chained calljohn.residence?[0] = Room(name"Bathroom")To access the subscript for an optional typevar testScor

model, each country must have the capital, each city must belong to a country. This allows the two properties to be accessed directly after initialization (no optional expansion is required), while avoiding circular references. To meet this requirement, the Capitalcity property of country is declared as an implicit parsing of an optional type's property by adding an exclamation point (city!) at the end of the type. This means that, like other optional types, the default value of the Capitalcity

struct or enumeration's properties in a specific method, you can choose the mutation (mutating) method, and the method can change its properties from within the method, and any changes it makes will remain in the original structure at the end of the method. The method can also assign an entirely new instance to its implied self property, and the new instance will replace the original instance after the method finishes. struct PointS {var x = 0.0, y = 0.0 mutating func movebyx (deltax:dou

characters similar to identifiers. Defined by the language itself. You can't use it for him. Unless you enclose it with an accent sign ('). Swift language Common keyword have the following 4 species. keyword related to the declaration: class , Deinit , enum and so on. break Span style= "font-family: Arial" >, case , continue expression and type keyword: as catch , dynamictype , false keyword used in a specific context

A few days ago to learn the next Tabbar, with you to share the study content, welcome everyone to make suggestions.As a beginner, there is no customization involved. There is no code involved.1. First drag a tab to the controller to the interface650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M02/6D/76/wKiom1VkmWuxcWcDAADU7yt25nc147.jpg "title=" 1.jpg " alt= "Wkiom1vkmwuxcwcdaadu7yt25nc147.jpg"/>2. You can see that Xcode automatically generated

]/ /return 915699632[5] //return 615699632[6] //Return 5Nested TypesExtensions can add new nested types to existing classes, structs, and enumerations:Extension Int { enum Kind {case negative, Zero, Positive } var kind:kind { switch self {case 0: return. Zero case let number where number > 0: return. Positive Default: return. Negative } }}func printintegerkinds (numbers: [Int]) {for number in

object. The sample code is as follows:Let Host:cfhost =cfhostcreatewithname (Kcfallocatordefault, "127.0.0.1"). Takeretainedvalue () Let hostnames: Cfarray =cfhostgetnames (host, nil)!. Takeunretainedvalue ()Welcome to follow Dongsheng Sina Weibo@tony_Dongsheng. Learn about the latest technical articles, books, tutorials and information on the public platform of the smart Jie classroom650) this.width=650; "title=" 00.png "src=" http://s3.51cto.com/wy

the button.If you call the following parameter-free method:Func OnClick () {}The calling code is as follows:Button.addtarget (Self, Action: "OnClick", êforcontrolevents:uicontrolevents.touchupinside)The difference is that the action parameter "OnClick" method name differs, and the colon of the action parameter method name implies that the method name should have several parameters. If the method to be called is the following 3 parameter forms:Func OnClick (Sender:anyobject, Forevent even

an employee Employee different. Welcome to follow Dongsheng Sina Weibo@tony_Dongsheng. Learn about the latest technical articles, books, tutorials and information on the public platform of the smart Jie classroom650) this.width=650; "title=" 00.png "alt=" Wkiol1bwsd6gjs1raaas2mbeznc134.png "src=" http://s5.51cto.com/wyfs02/M00/ 7c/ae/wkiol1bwsd6gjs1raaas2mbeznc134.png "/>More ProductsIOS,Cocos, mobile Design course please pay attention to the officia

() Let Hostnames:cfarray = Cfhostgetnames (host, nil)!. Takeunretainedvalue ()Welcome to follow Dongsheng Sina Weibo@tony_Dongsheng. Learn about the latest technical articles, books, tutorials and information on the public platform of the smart Jie classroom?More ProductsIOS,Cocos, mobile Design course please pay attention to the official website of Chi Jie Classroom:http://www.zhijieketang.comSmart-Jie Classroom Forum Website:http://51work6.c

discarded after the decimal point.Variable varVariables are declared with Var. After the declaration can be modifiedvar v = 20v = 30But note that you can only change the same type. With object-oriented thinking, the initialization is equivalent to birth, and after a pig is born you can't make him a person ... Can't just become a person can change that is eight commandments ...Tip, we cannot copy the string type to the int type, which means that Swift

the above code, its Swift syntax is defined as follows: Init? (Contentsofurl url:nsurl, encoding enc:uint, error Error:nserrorpointer)the last parameter of the constructor isNserrorpointer(i.e.Nserrorpointer), then in the actual call we need to passErrvariable address (that is,err),is a fetch address character. When the method call is complete, if there is an errorErrThe variable is assigned a value. Welcome to follow Dongsheng

Daoerror:errortype {case NoData case Primarykeynull}NoData indicates no data condition, Primarykeynull represents the primary key of the table ( Primary Key ) is an empty case. Then we can catch the error with the following code.Do {//try accesses a data table function or method} catch Daoerror.nodata {print ("no data. ")} catchdaoerror.primarykeynull {print (" PRIMARY key is empty. ")}Welcome to follow Dongsheng Sina Weibo@tony_Dongsheng. Learn abou

\ (day)."}Hello ("Adomikao", "Monday")Functions can be nested, and nested functions can access variables of the outer function. Use nested functions to reconstruct complex functions.A function can be used as a return value for another function, and can be passed as a parameter to another function.A function is a closure that can be used to create an anonymous closure, use in to split a parameter, and return a type. such as: Numbers.map ({(Number:int)->int inLet result = 7*numberRetrun result})U