Swift Control statements

Branch statements

1. Conditional statements If-else, basic grammatical forms such as the following. The part of "[]" can be omitted.

If boolean-expression {statement1;  }  [Else if Boolean-expression    {statement2;}  ] [Else  {statement3;  }  

Instance:

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. The multi-branch statement switch its syntax forms such as the following:

Switch some value to consider {case value 1:respond to value 1 case value 2,                value 3:respond to value 2 or 3default: Otherwise, do something else}

Each case does not need to explicitly join the break, with at least one statement per case.

To be able to compare whatever type.

Example 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":p rintln ("\ (som Echaracter) is a consonant ") default:println (" \ (Somecharacter) are not  a  vowel   or  

Example 2:

Let count = 3_000 let countedthings = "stars inthe Milky a" varnaturalcount:stringswitch count {case 0:naturalcount = " No ' case 1...3:naturalcount = ' A few ' case 4...9:naturalcount = ' several ' case 10...99:naturalcount = ' tens of ' case 100...9 99:naturalcount = "Hundreds of" case 1000...999_999:naturalcount = "thousands of" Default:naturalcount = "millions and mill Ions of "  } println (" There is \ (Naturalcount) \ (countedthings). ")

Looping statements

While statement

Do-while statements

For statement

In statement

While loop

While condition{statements}vari = Varr = 0 vars= 0 vart = 0while I < + {r= i/100 s= (i-r*)/t= I -R* 100-s* if (i = = R * r* r + s* s *s + t* T * t) {println ("i = \ (i)")}i++}do while loop do {statements} while Conditionvari = Varr = 0 vars= 0 vart = 0do {r= i/100 s=      (i-r*)/t= i-r* 100-s* if (i = = R * r* R + s* s *s + t* T * t) {println ("i = \ (i)")} i++} while I < 1000

For loop

for initialization; Condition Increment {statements}vari= 8 Varr = 0 vars= 0forvarj = 0; J <=i; j++{r = J * J S=j * J * JPRINTLN ("integer: \ (j)"); println ("corresponding squared sum: \ (r)") println ("corresponding cubic and: \ (s)")}

For In loop

Used to traverse the collection.

1. Traversing range

Forindex in1 ... 5{println ("\ (index) times 5 is \ (Index * 5)")}

2. Ignore loop variables

Letbase = 3letpower = Varanswer = 1for_ in 1...power {answer *=base} println ("\ (base) to the power of \ (power) is \ (answer) " )

3. Iterating through an array

Letnames =["Anna", "Alex", "Brian", "Jack"] forname innames {println ("Hello, \ (name)!")}

4. Traversing a dictionary

Letnumberoflegs =["Spider": 8, "Ant": 6, "Cat": 4] for (Animalname, Legcount) innumberoflegs {println ("\ (animalname) S has \ (legcount) legs ")}

5. Traversing a string

Letnumberoflegs =["Spider": 8, "Ant": 6, "Cat": 4] for (Animalname, Legcount) innumberoflegs {println ("\ (animalname) S has \ (legcount) legs ")} letnumberoflegs =[" Spider ": 8," Ant ": 6," Cat ": 4] for (Animalname, Legcount) innumberofl EGS {println ("\ (animalname) s has \ (legcount) legs")}

1.12.3 Jump Statement

? Continue

? Break

? Fallthrough

? Return

1.continue instance:

for var i = 0; I < 100; i++ {if I% = = 0 {continue;} println ("i = \ (i)");}

2. Break instance:

for var i = 0; I < 10;i++ {if i = = 3 {break;} println ("i = \ (i)");} println ("Game over!");

3. Fallthrough Example:

Let Integertodescribe = 5 var description = ' thenumber \ (integertodescribe) is ' switchintegertodescribe {case 2, 3, 5, 7, One, all, 19:description + = "A prime number, and also" fallthroughdefault:description + = "an Integer."} println (description)

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Swift Control statements