golang函数可变数量参数传参

开发过程中发现 fun(opts...) 的用法，于是学习函数可变数量参数传参

package main

import (
    "fmt"
)

type Foo struct {
    Number int
    Text   string
    Name   string
}

func print(list ...int) {
    for index, a := range list {
        fmt.Printf("%d: %v \n", index, a)  // print 0:1  1:3  2:4
    }
}

func main() {
    arr := []int{1, 3, 4}
    print(arr...)
}

如果是复杂的多种类型入参

涉及知识点

1. 数组对象类型定义
2. interface用法
3. []interface{} 和 []T{}类型的区别

notices: a variable with type []interface{} is not an interface! 注意: 变量类型[]interface{} 不是 一个interface

package main

import (
    "fmt"
)

type Foo struct {
    Number int
    Text   string
    Name   string
}

func print(list ...interface{}) {
    for index, a := range list {
        fmt.Printf("%d: %v \n", index, a)
    }
}

func main() {
    arr := []Foo{{Number: 1, Text: "pie"}, {Name: "ssss", Number: 15, Text: "fish"}, {Number: 30, Text: "orange"}}
    print(arr...)  // compiler error: cannot use arr (variable of type []Foo) as []interface{} 
}

[]Foo 并不能当成[]interface{}类型, 原因是[]Foo长度不固定 []interface{}编译时并不知道参数数量

参考文章1

参考文章2

修改后

package main

import (
    "fmt"
)

type Foo struct {
    Number int
    Text   string
    Name   string
}

func print(list ...interface{}) {
    for index, a := range list {
        fmt.Printf("%d: %v \n", index, a)
    }
}

func main() {
    arr := []Foo{{Number: 1, Text: "pie"}, {Name: "ssss", Number: 15, Text: "fish"}, {Number: 30, Text: "orange"}}
    var interfaceSlice []interface{} = make([]interface{}, len(arr)) // 增加[]interface{}类型变量，并确定长度
    for i, d := range arr {
        interfaceSlice[i] = d
    }
    print(interfaceSlice...)
}