Use of switch statement in go language learning

Catalog

Basic grammar

fallthrough Usage method

Multiple condition matching

Judgment interface (interface) type

Empty interface

Get the actual type

Basic grammar

It's about if-else Already mentioned when , If there are multiple criteria ,Go The language provides Switch-Case The way . If switch The following without conditions is equivalent to switch true

// Convert hexadecimal character to an int value switch { case '0' <= c && c <= '9': return c - '0' case 'a' <= c && c <= 'f': return c - 'a' + 10 case 'A' <= c && c <= 'F': return c - 'A' + 10 } return 0fallthrough Usage method

By default ,case It will be carried out after meeting the requirements break, Back case Even if the conditions are met, it will not cycle , If you want to continue , You need to add fallthrough,

package mainimport "fmt"func main() { i := 3 switch i { case i > 0: fmt.Println("condition 1 triggered") fallthrough case i > 2: fmt.Println("condition 2 triggered") fallthrough default: fmt.Println("Default triggered") }}

All the case Will be executed

condition 1 triggered
condition 2 triggered
Default triggered

Multiple condition matching

If the same condition is met , You can also list the same conditions in this way , Equivalent to or condition

switch i { case 0, 1: f() default: g()} Judgment interface (interface) type Empty interface

We will talk about interfaces later , adopt switch It can be done to type Judge , Get the real type of the interface .

package mainimport "fmt"func main() { var value interface{} switch q:= value.(type) { case bool: fmt.Println("value is of boolean type") case float64: fmt.Println("value is of float64 type") case int: fmt.Println("value is of int type") default: fmt.Printf("value is of type: %T", q) }}

In the example above , We define an empty interface

var value interface{}

Use at the same time switch To judge the type

switch q:= value.(type) {

Because the empty interface has no content , So the type is nil, Triggered default

value is of type: <nil> Get the actual type

Let's transform the above example , At the same time, let the empty interface have the actual value , Let's take a look at the effect of implementation

package mainimport "fmt"func valueType(i interface{}) { switch q:= i.(type) { case bool: fmt.Println("value is of boolean type") case float64: fmt.Println("value is of float64 type") case int: fmt.Println("value is of int type") default: fmt.Printf("value is of type: %T\n", q) }}func main() { person := make(map[string]interface{}, 0) person["name"] = "Alice" person["age"] = 21 person["height"] = 167.64 fmt.Printf("%+v\n", person) for _, value := range person { valueType(value) }}

Here are some knowledge points that have not been mentioned ：

How to define a function

Defined a map, But the type of the value is null interface , This means that it can be any type of value , This will be explained in detail in the interface chapter , So don't get tangled up here , Keep looking down

assignment , Specially value Different types , string/int/float type

Finally, the variable is passed to through the loop valueType function , See what the program outputs

map[age:21 height:167.64 name:Alice]
value is of type: string
value is of int type
value is of float64 type

This is about Go Language learning Switch This is the end of the article on the use of statements , More about Go Language Switch Please search the previous articles of software development network or continue to browse the relevant articles below. I hope you will support software development network more in the future ！