golang类型断言的实现示例

value, ok := interfaceValue.(ConcreteType)

package main

import (
    "fmt"
)

func main() {
    var i interface{} = "Hello, World!"

    // 类型断言
    s, ok := i.(string)
    if ok {
        fmt.Println("String value:", s) // 输出: String value: Hello, World!
    } else {
        fmt.Println("Not a string")
    }
}

package main

import (
    "fmt"
)

func main() {
    var i interface{} = 42

    s, ok := i.(string)
    if !ok {
        fmt.Println("Not a string") // 输出: Not a string
    }
    fmt.Println("Value:", s) // 输出: Value:
}

package main

import (
    "fmt"
)

func printType(i interface{}) {
    switch v := i.(type) {
    case string:
        fmt.Println("String:", v)
    case int:
        fmt.Println("Integer:", v)
    case float64:
        fmt.Println("Float:", v)
    default:
        fmt.Println("Unknown type")
    }
}

func main() {
    printType("Hello")
    printType(123)
    printType(3.14)
    printType(true) // 输出: Unknown type
}

package main

import (
    "fmt"
)

func main() {
    var i interface{} = "Direct assertion"

    s := i.(string) // 直接断言
    fmt.Println(s)  // 输出: Direct assertion

    // 如果断言失败，将导致 panic
    // i = 42
    // s = i.(string) // 运行时错误: interface conversion: interface {} is int, not string
}