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===== Type switch =====

==== What is it? ====
A **type switch** lets you execute different code depending on the **concrete type** stored inside an interface value at runtime.

Syntax:
`switch v := i.(type) { ... }`

==== What is it used for? ====
  * Handle multiple possible concrete types in one function.
  * Safely branch logic without multiple chained type assertions.
  * Implement polymorphic behavior for `any` / `interface{}` inputs.

==== Example ====
<code go>
package main

import "fmt"

func handle(i any) {
    switch v := i.(type) {
    case int:
        fmt.Println("int:", v+1)
    case string:
        fmt.Println("string:", v+"!")
    default:
        fmt.Println("unknown type")
    }
}

func main() {
    handle(10)
    handle("go")
    handle(true)
}
</code>

==== Notes / pitfalls ====
  * A type switch works only on interface values (including `any`).
  * The variable `v` inside each case has the concrete type for that case.
  * Use type switches sparingly—prefer interfaces with methods when possible.

==== Related pages ====
  * [[go:data_structures:interface|Interface]]
  * [[go:data_structures:type_assertion|Type assertion]]
  * [[go:data_structures:type_switch|Type switch]]
  * [[go:data_structures:empty_interface|any / interface{}]]

==== Hard words (English) ====
  * **type switch** /taɪp swɪtʃ/: switch theo kiểu
  * **concrete type** /ˈkɑːnkriːt taɪp/: kiểu thật bên trong interface
  * **interface** /ˈɪntərfeɪs/: giao diện
  * **runtime** /ˈrʌntaɪm/: lúc chương trình đang chạy
  * **polymorphic** /ˌpɑːlɪˈmɔːrfɪk/: đa hình
  * **sparingly** /ˈsperɪŋli/: dùng hạn chế