​带你试用 Go 1.18beta1 之泛型入门

安装 Go 1.18beta1

1. 运行以下命令安装 1.18beta1

$ go install golang.org/dl/go1.18beta1@latest
go: downloading golang.org/dl v0.0.0-20211214194107-65ed43b8dfff

2 . 运行以下命令进行更新

$ go1.18beta1 download
Downloaded   0.0% (    16384 / 143162528 bytes) ...
Downloaded   5.2% (  7454704 / 143162528 bytes) ...
Downloaded  11.9% ( 16973760 / 143162528 bytes) ...
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Downloaded  32.1% ( 46006032 / 143162528 bytes) ...
Downloaded  39.0% ( 55852640 / 143162528 bytes) ...
Downloaded  46.1% ( 66059792 / 143162528 bytes) ...
Downloaded  52.5% ( 75169264 / 143162528 bytes) ...
Downloaded  59.0% ( 84458912 / 143162528 bytes) ...
Downloaded  65.1% ( 93224256 / 143162528 bytes) ...
Downloaded  70.4% (100744512 / 143162528 bytes) ...
Downloaded  77.2% (110591200 / 143162528 bytes) ...
Downloaded  83.9% (120159376 / 143162528 bytes) ...
Downloaded  90.7% (129842224 / 143162528 bytes) ...
Downloaded  95.2% (136264736 / 143162528 bytes) ...
Downloaded 100.0% (143162528 / 143162528 bytes)
Unpacking /Users/xxx/sdk/go1.18beta1/go1.18beta1.darwin-amd64.tar.gz ...
Success. You may now run 'go1.18beta1'

3 . 测试 go1.18beta1 是否安装成功

$ go1.18beta1 version
go version go1.18beta1 darwin/amd64

4 . 为了我们更方便的使用 Go 命令，我们可以给 go1.18beta1 重命名。

$ alias go=go1.18beta1
$ go version
go version go1.18beta1 darwin/amd64

入门：项目实战

1. 初始化项目

$ mkdir generics
$ cd generics
$ go mod init github.com/yangwenmai/generics
go: creating new go.mod: module github.com/yangwenmai/generics

2 . 创建文件，编写 Go 代码

$ vim main.go

本示例来自于 Go 官网：https://go.dev/doc/tutorial/generics

package main

import "fmt"

type Number interface {
    int64 | float64
}

func main() {
    // Initialize a map for the integer values
    ints := map[string]int64{
        "first": 34,
        "second": 12,
    }

    // Initialize a map for the float values
    floats := map[string]float64{
        "first": 35.98,
        "second": 26.99,
    }

    fmt.Printf("Non-Generic Sums: %v and %v\n",
        SumInts(ints),
        SumFloats(floats))

    fmt.Printf("Generic Sums: %v and %v\n",
        SumIntsOrFloats[string, int64](ints),
        SumIntsOrFloats[string, float64](floats))

    fmt.Printf("Generic Sums, type parameters inferred: %v and %v\n",
        SumIntsOrFloats(ints),
        SumIntsOrFloats(floats))

    fmt.Printf("Generic Sums with Constraint: %v and %v\n",
        SumNumbers(ints),
        SumNumbers(floats))
}

// SumInts adds together the values of m.
func SumInts(m map[string]int64) int64 {
    var s int64
    for _, v := range m {
        s += v
    }
    return s
}

// SumFloats adds together the values of m.
func SumFloats(m map[string]float64) float64 {
    var s float64
    for _, v := range m {
        s += v
    }
    return s
}

// SumIntsOrFloats sums the values of map m. It supports both floats and integers
// as map values.
func SumIntsOrFloats[K comparable, V int64 | float64](m map[K]V) V {
    var s V
    for _, v := range m {
        s += v
    }
    return s
}

// SumNumbers sums the values of map m. Its supports both integers
// and floats as map values.
func SumNumbers[K comparable, V Number](m map[K]V) V {
    var s V
    for _, v := range m {
        s += v
    }
    return s
}

你还可以直接在 Go Playground 上直接测试以上代码。

https://go.dev/play/?v=gotip

如图：

疑惑

我核对了当前安装的 go1.18beta1 的版本，是修改 interface{} 为 any，但是当我尝试把 type Number interface 改为 type Number any 会直接报错：./main.go:21:17: syntax error: unexpected { after top level declaration，有谁知道这是为什么？

欢迎各位留言评论~

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文章来源：https://mp.weixin.qq.com/s/AycBUNLWymayKDafDD22xw