Swift Signs and constants

Apple launched Swift also for some time, the internet also appeared a lot of information, very grateful to the great gods.

Swift's syntax differs greatly from the OC syntax, in which we create a class that generates both an. h file and a. m file, and only one. Swift file in Swift.

Grammatical differences also want to be large, such as constants and variables:

var a = 1

With Var, a is a variable name, 1 is a value, and if you need to change the value of a, you only need to:

A = 2

Note In Swift's language, there is no need to write ";" The

Swift has type inference, A is actually an int type, but we can omit it or omit it:

var a:int = 1a = 2

VAR is used to declare a variable, and if you need to declare a constant, you need to declare it with let:

Let B = 3

b is a variable, and you can't change its value at this time.

The name of Swift also no longer conforms to the identifier specification, the name can be encoded in Unicode, that is, when we declare a variable or constant, you can use Chinese as the variable name.

var Chinese = "China"

"China" is a variable name, the program will not error.

Type conversions:

var interValue = 10
var doubleValue = 9.0
doubleValue = Double (interValue)
println (doubleValue)

Swift does not support implicit type conversions. It is also for security reasons, so you need to cast the type.
Casting requires adding the converted type before the value being converted, and then adding parentheses, as in the code above:


Tuple:

Tuples combine multiple values into a composite value. The values in the tuple can be of any type, and are not required to be of the same type.
such as:

("age", 18)
This is a tuple, and the values in it can be of any type and in any order;
The value of a tuple can be broken down into separate variables / constants for use:

let stu = ("age", 18)
println (stu.0)
println (stu.1)

The background output at this time is:
stu.0 represents the first value of the tuple, stu.1 represents the second value of the tuple, and the subscript starts from 0;

We can add a label to each tuple, so that we can use the label directly when using:

let stu = (a: "age", b: 18)
println (stu.a)
println (stu.b)

The output at this time does not change;

If we only need to use a part of the value of the tuple, we can replace the part to be ignored with "_"

let (a, _, _) = stu


Welcome the guidance of various gods to learn together.

[Swift first look] Swift variables and constants