分支语句
1. 条件语句 if-else ，基本语法形式如下，其中 “[]” 中 的部分可以省略。
- if boolean-expression {
- statement1;
- } [else if boolean-expression {
- statement2;
- } ] [else {
- statement3;
- } ]
实例：
- var number1 = 0;
- var number2 = 1;
- var max = 0;
- if number1 >number2 {
- max = number1;
- } else if number1 < number2 {
- max = number2;
- } else {
- max = number1;
- }
- println("Themaximum is (max)")
2 ．多分支语句 switch 它的语法形式如下：
- switch some value to consider {
- case value 1:
- respond to value 1 case value 2, value 3:
- respond to value 2 or 3
- default:
- otherwise, do something else
- }
每个 case 不需要显式地添加 break ，每个 case 至少有 一条语句。
可以比较任何类型。
实例１：
- let someCharacter: Character ="e" switch someCharacter {
- case "a", "e", "i","o", "u":
- println("(someCharacter) isa vowel")case "b", "c", "d", "f", "g", "h", "j", "k", "l","m", "n", "p", "q", "r", "s", "t", "v", "w", "x", "y", "z":
- println("(someCharacter) is a consonant")
- default:
- println("(someCharacter) is not a vowel or a consonant")
- }
实例２：
- let count = 3_000
- let countedThings = "stars inthe Milky Way"varnaturalCount: String
- switch count {
- case 0:
- naturalCount ="no" case 1...3:
- naturalCount ="a few" case 4...9:
- naturalCount ="several"
- case 10...99:
- naturalCount ="tens of" case 100...999:
- naturalCount ="hundreds of" case 1000...999_999:
- naturalCount ="thousands of"
- default:
- naturalCount = "millions and millions of"
- }
- println("There are (naturalCount) (countedThings).")
循环语句
while语句
do-while语句
for语句
for in语句
while 循环
- while condition{
- statements
- }
- vari = 100 varr = 0 vars= 0 vart = 0
- while i < 1000 {
- r= i / 100
- s=( i - r* 100 ) / 10
- t= i - r* 100 - s* 10
- if( i == r * r* r + s* s *s + t* t * t){
- println ( "i = (i)" )
- }
- i++
- }
- do while 循环
- do {
- statements
- } while condition
- vari = 100 varr = 0 vars= 0 vart = 0
- do {
- r= i / 100
- s=( i - r* 100 ) / 10
- t= i - r* 100 - s* 10
- if( i == r * r* r + s* s *s + t* t * t){
- println ("i = (i)" )
- }
- i++
- } while i < 1000
for 循环
- for initialization; condition; increment {
- statements
- }
- vari= 8 varr = 0 vars= 0
- forvarj =0; j <=i; j++{
- r = j * j
- s=j * j * j
- println (" 整数为 :(j) ");
- println (" 对应的平方和 :( r)")
- println ( " 对应的立方和 : ( s ) " )
- }
for in 循环
用于遍历集合。
1. 遍历范围
- forindex in1...5{
- println( " (index) times 5 is (index * 5 )" )
- }
2. 忽略循环变量
- letbase = 3
- letpower = 10 varanswer = 1
- for_ in 1...power {
- answer *=base
- }
- println (" (base )to the power of (power )is (answer ) " )
3. 遍历数组
- letnames =[ "Anna" ,"Alex" , "Brian" ,"Jack"]
- forname innames {
- println( "Hello, (name) !" )
- }
4. 遍历字典
- letnumberOfLegs =[ "spider" :8 , "ant" :6 , "cat" : 4]
- for(animalName, legCount) innumberOfLegs {
- println( " (animalName) s have (legCount) legs" )
- }
5 .遍历字符串
- letnumberOfLegs =[ "spider" :8 , "ant" :6 , "cat" : 4]
- for(animalName, legCount) innumberOfLegs {
- println( " (animalName) s have (legCount) legs" )
- }
- letnumberOfLegs =[ "spider" :8 , "ant" :6 , "cat" : 4]
- for(animalName, legCount) innumberOfLegs {
- println( " (animalName) s have (legCount) legs" )
- }
1.12.3 跳转语句
• continue
• break
• fallthrough
• return
1.continue 实例：
- for var i = 0; i < 100; i++ {
- if i % 10 == 0 {
- continue;
- }
- println("i = (i)");
- }
2. break 实例：
- for var i = 0; i < 10;i++ {
- if i == 3 {
- break;
- }
- println("i = (i)");
- }
- println("Game Over!");
3. fallthrough 实例：
- let integerToDescribe = 5
- var description = "Thenumber (integerToDescribe) is"
- switchintegerToDescribe {
- case 2, 3, 5, 7, 11, 13, 17, 19:
- description += " a prime number, and also"fallthrough
- default:
- description += " an integer."
- }
- println(description)
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