Go语言：获取结构体方法函数指针的实用指南

package main

import "fmt"

// 独立函数
func hello(a int) {
    fmt.Printf("hello called with %d\n", a)
}

func main() {
    f1 := hello // 直接获取函数引用
    fmt.Printf("独立函数引用类型: %T, 值: %+v\n", f1, f1)
    f1(10)
}

package main

import "fmt"

type x struct {}
func (self *x) hello2(a int) {
    fmt.Printf("hello2 called with %d on receiver %p\n", a, self)
}

func main() {
    // 错误示例：直接引用方法会编译失败
    // f2 := hello2 // 编译错误：undefined: hello2
    // i := &x{}
    // f2 := &i.hello2 // 编译错误：method i.hello2 is not an expression, must be called
    // f2 := x.hello2 // 编译错误：invalid method expression x.hello2 (needs pointer receiver: (*x).hello2)
}

package main

import "fmt"

type x struct {}
func (self *x) hello2(a int) {
    fmt.Printf("hello2 called with %d on receiver %p\n", a, self)
}

func main() {
    // 获取方法表达式
    // f2 的类型将是 func(*x, int)
    f2 := (*x).hello2
    fmt.Printf("方法表达式类型: %T, 值: %+v\n", f2, f2)

    // 调用方法表达式：第一个参数是接收者实例，后续参数是方法本身的参数
    receiver1 := &x{}
    f2(receiver1, 123) // 输出：hello2 called with 123 on receiver 0xc...

    // 也可以直接创建匿名接收者调用
    f2(&x{}, 456)      // 输出：hello2 called with 456 on receiver 0xc...
}

package main

import "fmt"

type x struct {}
func (self *x) hello2(a int) {
    fmt.Printf("hello2 called with %d on receiver %p\n", a, self)
}

func main() {
    // 接受接收者作为参数的闭包
    // f3 的类型将是 func(*x, int)
    f3 := func(val *x, a int) {
        val.hello2(a)
    }
    fmt.Printf("接受接收者参数的闭包类型: %T, 值: %+v\n", f3, f3)

    receiver2 := &x{}
    f3(receiver2, 789) // 输出：hello2 called with 789 on receiver 0xc...
    f3(&x{}, 999)      // 输出：hello2 called with 999 on receiver 0xc...
}

package main

import "fmt"

type x struct {}
func (self *x) hello2(a int) {
    fmt.Printf("hello2 called with %d on receiver %p\n", a, self)
}

func main() {
    // 捕获现有接收者的闭包
    val := &x{} // 捕获一个特定的接收者实例
    // f4 的类型将是 func(int)
    f4 := func(a int) {
        val.hello2(a) // 闭包捕获了 val 变量
    }
    fmt.Printf("捕获现有接收者的闭包类型: %T, 值: %+v\n", f4, f4)

    f4(101) // 输出：hello2 called with 101 on receiver 0xc... (同一个 val 实例)
    f4(202) // 输出：hello2 called with 202 on receiver 0xc... (同一个 val 实例)
}