Swift Entry-Looping statements

Begin to share the looping statements in the swift introductory chapter.

One: Circular statements

1:for usage 2:for in usage 3:while usage 4:do while  usage

For usage

General format

Common formats: (for many formats) for  variables; variables < a value; variable + +

Example

------for a usage for var i = 0; I<5 i++ {    println ("i=\ (i)")    }//-------for two uses var j = 0for j = 0; j<5; j + + {        println ("I=\ (j)")    }

Usage of for in

The format for variable or temporary  variable  in the collection description: When the For statement is executed, the corresponding value in the collection is assigned to the variable or temporary variable in turn

Example

The first usage  string traversal for

------------the first usage string of for in is to  traverse var str = "ABC"//str is a string variable even if the character set/*1:STR is a character set, temp is a temporary variable (no need to define) 2: When the program executes the for-in statement Assigned the characters in the character set to the temporary variable temp*/for temp in  str {    println ("temp=\ (temp)")}

Run results

Temp=atemp=btemp=c

The 2nd usage of for in  iterates over the sequence:
Let's start with a concept sequence in Swift for shaping ...  Three points to indicate

var  A = 1...5//... Three dots represent a sequence  of 1 to 5  

Example

The second usage of------------for in traversal sequence/*1:1 ... 5 represents a sequence of 1 to 5, that is, the set of 1-5 2:temp is a temporary variable 3: Executes a For in statement that is the corresponding value in the set of 1-5, assigned to the temporary variable temp*/for  temp in  1...5{    println ( Temp)}

Run results

12345

While statement

Format  while Boolean {} Description: Stop the While statement only if the Boolean value after the while is false, or the while statement is always executed

Import Foundationvar  i = 0/* jumps out of the while statement */while (i<3) {    println ("i=\ (i)")    i++} Run results only if i<3 is false i=0i= 1i=2

Do While statement

3: If the Boolean value behind the while statement stops the  do while statement, the Do and do statement is executed  

Import Foundationvar i = 1/*1: Executes the DO {} inside Statement 2: Then the value while Statement 3: When the i< 3, the Do While statement stops */do {println ("i=\ (i)") I=i+1}while (i <3) Run result i=5i=4

Conditional statements

If statement (already mentioned earlier) if not clear, please go to swift Introductory article-basic type (3)

Switch statement

Format: switch (variable) {case variable Value:    execution method Case  variable Value:    execution method Default:  Execute Method} Description: 1:switch conditional statement with at least one case statement and default Statements must be followed by the execution Method 3: Variable values can be multiple or one, multiple variables separated by commas 4: Variable value can be any type of 2:case

Example

var  i = 1switch (i) {case 0:  //case followed by a variable  when i=0 is executing the corresponding method under the case statement    println ("i=\ (i)") Case    1, 2: 
   
    //case  followed by two variables, multiple variables separated by commas when I=1 and 2 execute the corresponding method under the case statement     println ("i=\ (i)")    Default:    //If I is not equal to 0,1,2, Execute the corresponding method under the default statement    println ("Default")} to run the result I=1
   

Switch sequence Matching

-------The first usage  range matches var  i = 75switch (i) {case 1...50:  //case followed by a sequence, the sequence is a set variable   when I is executing in the range 1 to 50　The case statement below corresponds to the method    println ("1...50-> i=\ (i)") Case    50...100:  //case   followed by a sequence, the sequence is a set variable  When I executes a case statement under the range 1 to 100, the corresponding method     println ("50...100->  i=\ (i)") is    default:    //If I is not equal to 1 to 100 range, execute The default statement below corresponds to the method    println ("Default")}

Run results

50...100-> i=75

Switch tuple matching

Import foundation//-------The first usage  tuple match let  str = (UP)//STR is a tuple variable switch (str) {case (0...1,0...1)://If the range of tuple variable str (0 to 1, 0 to 1)        println ("(0...1,0...1)-->str=\ (str)") Case (1...2,1...2): If the range of the tuple variable str (1 to 2, 1 to 2)        println ("( 1...2,1...2)-->str=\ (str) ")    default:    println (" Default ")}

Run results

(1...2,1...2)-->str= (1, 2)

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Swift Entry-Looping statements