Swift Basic syntax

1. Automatic type inference for constant volume

Let-age = 20 constant immutable

var num = 24 variable

num =

Let count:Int = 2

Double(count) type conversions

2. String

Swift's string operation is more complex and often turns into OC nsstring

Let name:String = "Hrrrrrrrrr"

var addr:string = string()  

Print(name)

Print("My name is \(name)")  

Name. EndIndex

(name as nsstring). Substringtoindex(5)

(name as nsstring). Substringwithrange(nsmakerange(5, 2))

(name as nsstring). Length

3. The array can only hold one type, and OC is not the same

var heightarray:array<Int> = array()

Heightarray. Append(3)

Heightarray. Insert(2, Atindex: 1)

HEIGHTARRAY[0]

4. Dictionaries

Let numberoflegs:[String:Int] = ["Cat":4,"Duck":2]

5.bool type True False

6. Optional value optional

var temp:String? Nil

Temp = "Test " "Test"

Print(temp) "Optional (" test ") \ n"

Automatically add a question mark to indicate that temp exists, exists to do, does not exist, does not

Print(temp?. endIndex) "Optional (4) \ n"

var temp:string! Must have

7.for in loop

For index in 1... 5{

Print(index)

}

For name in namesarray{

print(name)

}

Let numberoflegs:[String:Int] = ["Cat":4,"Duck":2]

For (Name,legs) in numberoflegs{

　　One pair to take out

}

Swift Basic syntax