Declaration and assignment of go variables

Go Declaration and assignment of variables

Three forms of declaring variables

1. var Variable name Variable type

Example :

var name int = 0 // Declared a int Type variables , Its identifier is name
println(int)

2. var Variable name ： Declare variables by declaring variable types , The compiler will infer the variable type by initializing the value .

Example ： The variable type is omitted , Then the initial value must be given at the time of declaration , Can let the compiler judge its type , Otherwise the syntax is wrong missing variable type or initializationsyntax.

var name = 0
var name1 = "Hello go"
println(name, name1) // Output is 0 Hello go
print(fmt.Sprintf("%T---%T", name, name1))// Print the types of the two variables 
//int---string name by int type ,name1 by string type 

3. Use := Declare variables and assign initial values

Example ：

name := "Hello go"
println(name)

The above code is equivalent to :

var name string 
name = "Hello go"
println(name)

Be careful ： Use := It is equivalent to declaring variables and initializing variables at the same time , So for expressions name:="Hello go", If the variable name It has been stated before , It is not allowed to declare again . If you declare , The syntax detector will display an error no new variables on left side of :=.

Multivariable declaration

If you want to declare multiple variables of the same type at the same time , The following types can be used ：

var name1, name2, name3 int = 1, 2, 3

If you want to declare multiple variables of the same or different types at the same time , It can take the form of :

var name1, name2, name3 = 123, 2.0, "Hello go"

assignment , Multiple numbers or strings to the right of the equal sign depend on their relative positions , Assign values to the variables to the left of the equal sign

Declaration of global variables

Global variables can still be declared using the three variable declaration methods described above . Here is another way to write a global variable declaration ：

var(
    name1 int
    name2 string
    name3 float32
)

Considerations for local variables

• For local variables , Its declaration is in the function body , Once declared , Then it must be used in the following code segment , Otherwise, compilation errors will occur .

• And for global variables , It can be declared without being used .

identifier _

For designators _, Often used to discard unwanted values . Like functions func Returns two values a, b, Unwanted b Value , Then you can write like this :

a, _ = func()

And python Of _ similar . however Go Medium _ Cannot be read , Only values can be written to this variable . And in the python in , Can read _ The value in .

Reference material

• https://www.runoob.com/go/go-variables.html