golang 反射

参考

https://www.cnblogs.com/jiujuan/p/17142703.html
https://deepinout.com/go/go-examples/g_reflect-select-function-in-golang-with-examples.html

float反射示例

package main

import (
	"fmt"
	"reflect"
)

func main() {
	var x float64 = 1.2345

	fmt.Println("==TypeOf==")
	t := reflect.TypeOf(x)
	fmt.Println("type: ", t)
	fmt.Println("kind:", t.Kind())

	fmt.Println("==ValueOf==")
	v := reflect.ValueOf(x)
	fmt.Println("value: ", v)
	fmt.Println("type:", v.Type())
	fmt.Println("kind:", v.Kind())
	fmt.Println("value:", v.Float())
	fmt.Println(v.Interface())
	fmt.Printf("value is %5.2e\n", v.Interface())

	y := v.Interface().(float64)
	fmt.Println(y)
    
    fmt.Println("===kind===")
	type MyInt int
	var m MyInt = 5
	v = reflect.ValueOf(m)
    fmt.Println("kind:", v.Kind()) // Kind() 返回底层的类型 int
    fmt.Println("type:", v.Type()) // Type() 返回类型 MyInt
}

struct反射示例

package main

import (
	"fmt"
	"reflect"
)

type student struct {
	Name string `json:"name"`
	Age  int    `json:"age" id:"1"`
}

func main() {
	stu := student{
		Name: "hangmeimei",
		Age:  15,
	}

	valueOfStu := reflect.ValueOf(stu)
	// 获取struct字段数量
	fmt.Println("NumFields: ", valueOfStu.NumField())
	// 获取字段 Name 的值
	fmt.Println("Name value: ", valueOfStu.Field(0).String(), ", ", valueOfStu.FieldByName("Name").String())
	// 字段类型
	fmt.Println("Name type: ", valueOfStu.Field(0).Type())

	typeOfStu := reflect.TypeOf(stu)
	for i := 0; i < typeOfStu.NumField(); i++ {
		// 获取字段名
		name := typeOfStu.Field(i).Name
		fmt.Println("Field Name: ", name)

		// 获取tag
		if fieldName, ok := typeOfStu.FieldByName(name); ok {
			tag := fieldName.Tag

			fmt.Println("tag-", tag, ", ", "json:", tag.Get("json"), ", id", tag.Get("id"))
		}
	}
}

channel反射示例

package main

import (
	"fmt"
	"reflect"
)

func fibonacci(ch chan<- int, n int) {
	x, y := 0, 1

	for i := 0; i < n; i++ {
		ch <- x
		x, y = y, x+y
	}
	
	close(ch)
}

func fanIn(channels []reflect.Value, out chan int) {
	cases := make([]reflect.SelectCase, len(channels))

	for i, ch := range channels {
		cases[i] = reflect.SelectCase{
			Dir:  reflect.SelectRecv,
			Chan: ch,
		}
	}

	for i := 0; i < len(channels); i++ {
		chosen, value, ok := reflect.Select(cases)
		if !ok {
			channels[chosen] = reflect.ValueOf(nil)
			continue
		}
		out <- value.Interface().(int)
	}
	
	close(out)
}

func main() {
	ch1 := make(chan int)
	ch2 := make(chan int)

	go fibonacci(ch1, 10)
	go fibonacci(ch2, 10)

	out := make(chan int, 20)
	fanIn([]reflect.Value{reflect.ValueOf(ch1), reflect.ValueOf(ch2)}, out)

	for x := range out {
		fmt.Println(x)
	}
}