Swift Syntax 100

1. Print Statements

2. Defining Constants and variables

Define a string constant with a variable let constantstring:string = "Hello"  //Let constant name: String type = "String" var variblestring:string = "World"   // var variable name: String type = "string"

3. Constants and variable types are automatically inferred, and types can be omitted when using declarations

Let Constantint:int = 1              //Common type has Int double Float stringvar pi = 3.14                         //compiler will automatically infer that pi is a double type

4. Type must match

5. The OUTPUT statement

Print (Constantint)                    //1print ("π value is: \ (pi)")                 

6. Type conversion

Let three = 3                         //Hold option, move the mouse over the variable name, click to view the constant type var pointonefour = 0.14               //system auto-infer the type of Pointonefour is: Doublepi = Double (three) + Pointonefour     //Only type can be manipulated, conversion format: type name (variable or constant) let piint = Int (pi)                   //double to int, the system automatically ignores the number after the decimal point, Will lose precision

7. Tuples

Tuples: Multiple sets of colors that can be of different types let Http404error = (404, "not Found")//Type: (Int, String), element types in tuples can be different lets (code, message) = Http404error    //Assign a tuple to a constant print ("Code:\ (Code), message:\ (Message)")//code:404, Message:not Foundlet (_, errormessage) = Http404error  //_ Can play the role of Ellipsis, which is widely applied in swift print (Http404error.1)                 //Not Found by subscript access element let ErrorCode = ( requesterror:401, 402, 403)//When defining tuples, you can name individual elements                

8. Optional type, if it is possible to assign a value of nil, it must be declared as an optional type

1. Optional type: The two state var errorcode:int used to represent a value or a value that is not valued? = 404              //Add one after type? print (ErrorCode)                       //Optional (404) ErrorCode = nil                        //assign nil to non-selectable type print (ErrorCode)                       //Nil

9. Use! Must not be nil in the inside

3. Using the IF statement to force resolution, the optional type cannot be directly used to convert if errorCode! = nil {                  //To determine the optional type contains the value can be added after the variable name! Force parsing  Print (errorcode!)                    404}

10. Optional binding, assigning an optional type to a temporary variable or constant

If let code = ErrorCode {    print (code)/                        /output: 404, Auto Parse}else {//    print (Code)                      //?, code is the local variable    print ( ErrorCode)                   //If ErrorCode = nil here outputs nil}

11. Implicit parsing of optional types: Because there must be value, so you can eliminate the trouble of parsing

" A "       // format: Optional type? change to! Print (assumedstring)                   //  Aif let tempstring = assumedstring {    //  Implicit parsing optional types can be used as normal optional types to use    print (tempstring)                  //  A}

12. Whether the string is empty

Emptystring2.isempty                   //True, the IsEmpty method is used to determine whether an empty

13. Traversing all characters of a string

The for char in emptystring1.characters {  //For loop will be followed by a verbose    print (char)                        //output all characters in EmptyString1}

14. Get the length of a string

EmptyString1.characters.count          //9, gets the number of characters in a string including spaces

15. Links to Strings

var string3 = string1 + string2        //Hello World, connect two strings by "+" String1.append ("!")                   Hello world!, stitching let messages = "Hello \ (string2) by append () Method!"    Hello World! By putting a constant or variable in \ ()

16. Interception of strings

Let Messchar = Messages[messages.startindex]  //H, gets the character by the index of the first character let FirstIndex = Messages.index (after: Messages.startindex)  //1, index of the first character let LastIndex = Messages.index (before:messages.endIndex)  //13, Index of last character let index = Messages.index (Messages.startindex, Offsetby:4)  //4, initial position offset 4messages[index]                        //O, The characters obtained by the index are OMESSAGES[MESSAGES.ENDINDEX]            //?, note: Indexes cannot be crossed

17. Creation of arrays

var arrtitle = [String] ()

18. Adding the array

Arrtitle.append ("Great value outing"), Arrtitle.append ("Select Tickets"), Arrtitle.append ("Enjoy the Tour");

19. Iterating the array

For Arritem in twodouble {//             traverse print    (arritem)                     ////print each element sequentially through a for In loop}

for (index, value) in twoDouble.enumerated() { // 使用迭代器获取数组元素以及索引号 print("索引:\(index), 元素:\(value)") // 依次打印索引号及元素 索引号:0, 元素:3.0 ...} 

20. Statement of the Dictionary

var chardict = ["Char1": "A", "char2": "B"]  //system will make automatic type inference, type can also be omitted

21. Adding a dictionary

chars["CHAR3"] = "C"  

21. Removal of the dictionary

22. Updating the dictionary

Chars.updatevalue ("B", Forkey: "Char2")    //Update key value pair, if this key does not exist, it will add a

23. The traversal of a dictionary

For (key, value) in Chardict {             //traverse all keys in dictionary value    print ("\ (key): \ (value)")              //char2:b newline char1:a}for key In Chardict.keys {                 //traverse all key in dictionary    print (key)                             //CHAR2 wrap char1}for value in Chardict.values {             //Traverse dictionary for all Value    Print (value)                           //B line break A}

Operation of 24.for Loops

For num in 1...5 {                     //To assign values in the closed interval [1, 5] to num    print (num)                         //Output 5 digits sequentially}

25.if/else

num = 3if num = = 3 {                          //If after Judgment statement returns to True, execute {} after {}    print (num)                         //If statement {} cannot omit}else {                                //If after Judgment statement returns FALSE, execute else after {}< C7/>print ("num is not equeal to 3")}

26.switch

num = 12switch num {case 2:    print ("num equals 2")                  //Each case branch must contain at least one statement    print ("num equals 2")                  //  The case branch end does not need to write a break and will not occur through the case 3, 4, 5:                         /////////////(,) to separate the    print ("num = = 3 or 4 or 5") between the multiple values, with (,). Case 6..<10:                          // The case statement also supports interval    print ("num is greater than or equal to 6 and less than ten") case 10..<19 where num% 3 = = 0:      //Use the Where statement to add additional judgment to    print (" Num is greater than or equal to 10 and less than 19 and divisible by 3 ") Default:    print (" None of the above ")}

27. Basic function: A separate code snippet to complete a specific task

Func Minmax (CurrentArray Array:[int]), (min:int,max:int) {                var currentmin = array[0];        var currentmax = array[0];        For Arritem in array {            if Arritem < currentmin            {                currentmin = Arritem;            }                        if (Arritem>currentmax)            {                Currentmax = Arritem;            }        }        Return (Currentmin,currentmax)    }

28. Functions that do not determine the number of parameters:

Computes the number of averages of the Func avaragenum (_ num:double ...), Double {///parameter appended ... Indicates that there are more than one parameter    var total:double = 0 for number in    num {total        + + #    }    return total/double (Num.coun T)}avaragenum (2, 6, 4, 8, 7)               //5.4, unlimited number of parameters Avaragenum (5)                           //Note: A function can have only one variable parameter

27. Network Request Framework

Alamofire.request ("Http://wimg.mangocity.com/bms/api/app/index/index.json", Method:. Get, Parameters:nil, encoding : Jsonencoding.default)            . DownloadProgress (Queue:DispatchQueue.global (QoS:. Utility)) {Progress in                print (" Progress: \ (progress.fractioncompleted)            }}            . Validate {Request, response, data in                debugprint (response)                return. Success            }            . Responsejson {response in                debugprint (response)        }

　　

　

　

Swift Syntax 100