Variables and constants of Go learning notes

This is a creation in Article, where the information may have evolved or changed.

1 Variables

1-1 statement

Declaring variables using the keyword var in the Go language

For example

var int_a int; In most cases, semicolons can be omitted

When there is no initialization value at the time of the Declaration, Go sets the default value for the underlying type.

int 0
int8 0
Int32 0
Int64 0
UINT 0x0
The actual type of Rune 0//rune is int32
The actual type of byte 0x0//byte is uint8
float32 0//Length 4 byte
Float64 0//Length 8 byte
BOOL False
String ""

Declarations can also be assigned initialization, such as

var int_a int =1

Declaring simultaneous assignments can be simply abbreviated to

Int_a: = 1

More than 1-2 declarations of the same type

Multiple declarations of the same type can be abbreviated as

var A, b, C int

You can also assign values at the same time

var A, b, c int = 1, 2, 3

can also be shortened to

A, B, c: = 1, 2, 3

More than 1-3 different types of declarations

Several different types of declarations can be abbreviated as

VAR (

a int

B string

)

You can also assign values at the same time

VAR (

a int = 1

b string = "abc"

)

1-4 Special Empty ID _

Any assigned null identifier _ will be discarded, generally used to make the return value has multiple values, but may only use a few of them, only the use of values, the other values can be discarded.

A, _, c: = 1, 2, 3

The value 2 will be discarded.

2 Constants

2-1 statement

Declaring a variable in the Go language uses the keyword const, and the value of a constant can only be one of the bool, string, or numeric types.

For example

const a int = 1

Because the declaration constants must be initialized, the type can be omitted, i.e.

Const A = 1

More than 2-2 declarations of the same type

Multiple declarations of the same type can be abbreviated as

Const A, b = 1, 2

2-More than 3 different types of declarations

Several different types of declarations can be abbreviated as

Const (

A = 1

b = "ABC"

c = False

)

2-4 Special Keyword Iota

Go has a keyword iota, which is used when declaring an enum, with a default starting value of 0, plus 1 for each call

Const (

A = iota//a = 0

b//b = 1

c//C = 2

)

Iota can also participate in operations, such as

Const (
A = 1 << iota//A = 1 (Iota has been reset) 1*2^0
b = 1 << iota//b = 2 1*2^1
c = 1 << iota//c = 4 1*2^2
)

Resources

"Go language. Cloud Power"

"Go Web Programming"