Swift selectable type and optional chain

One, optional type

Sometimes expressions in swift programs can be seen, and! symbols, which represent what they mean, are related to the optional type.

Sometimes a variable and a constant are used, and the value it holds may or may not

1. To assign nil to a variable, you need to assign a value to the following expression

Class empoyee{

var int: = 0

var name:string = ""

var job:string = ""

}

var emp:employee? = nil//followed by the number can accept null value, not add? Null value cannot be assigned

Emp1=employee ()

println (emp!. No

2. Reference Code

Emp1?. no=1000

Emp1?. Name= "Zhang San"

Emp1?. job= "Clerk"

3. See the example again

Func divided (n1:int,n2:int)->double? {

If n2==0{

return Nil

}

Double (N1)/double (N2)

}

Let result:double? = Divide (100,200)

This article is from the "Ordinary Road" blog, please be sure to keep this source http://linjohn.blog.51cto.com/1026193/1621250

Swift selectable type and optional chain