make 和 new 的区别

make_and_new.go

package main

import (
	"fmt"
)

type Foo struct {
	age  int
	name string
}

func main() {
	p1 := new(int)
	fmt.Printf("p1 --> %#v \n ", p1)
	fmt.Printf("p1 --> %#v \n ", *p1)

	var p2 *int
	i := 0
	p2 = &i
	fmt.Printf("p2 --> %#v \n ", p2)
	fmt.Printf("p2 --> %#v \n ", *p2)

	var s1 []int
	if s1 == nil {
		fmt.Printf("s1 is nil --> %#v \n ", s1)
	}

	s2 := make([]int, 3)
	if s2 == nil {
		fmt.Printf("s2 is nil --> %#v \n ", s2)
	} else {
		fmt.Printf("s2 is not nill --> %#v \n ", s2)
	}

	modifySlice(s2)
	fmt.Printf("s2 is not nill --> %#v \n ", s2)

	var m1 map[int]string
	if m1 == nil {
		fmt.Printf("m1 is nil --> %#v \n ", m1)
	}

	m2 := make(map[int]string)
	if m2 == nil {
		fmt.Printf("m2 is nil --> %#v \n ", m2)
	} else {
		fmt.Printf("m2 is not nill --> %#v \n ", m2)
	}

	modifyMap(m2)
	fmt.Printf("m2 is not nill --> %#v \n ", m2)

	var c1 chan string
	if c1 == nil {
		fmt.Printf("c1 is nil --> %#v \n ", c1)
	}

	c2 := make(chan string)
	if c2 == nil {
		fmt.Printf("c2 is nil --> %#v \n ", c2)
	} else {
		fmt.Printf("c2 is not nill --> %#v \n ", c2)
	}

	go modifyChan(c2)
	fmt.Printf("c2 is not nill --> %#v\n ", <-c2)

	var foo1 Foo
	fmt.Printf("foo1 --> %#v\n ", foo1)
	foo1.age = 1
	fmt.Println(foo1.age)
	foo2 := Foo{}
	fmt.Printf("foo2 --> %#v\n ", foo2)
	foo2.age = 2
	fmt.Println(foo2.age)

	foo3 := &Foo{}
	fmt.Printf("foo3 --> %#v\n ", foo3)
	foo3.age = 3
	fmt.Println(foo3.age)

	foo4 := new(Foo)
	fmt.Printf("foo4 --> %#v\n ", foo4)
	foo4.age = 4
	fmt.Println(foo4.age)

	var foo5 *Foo = new(Foo)
	fmt.Printf("foo5 --> %#v\n ", foo5)
	foo5.age = 5
	fmt.Println(foo5.age)

	modifyFooPointer(foo5)
	fmt.Println("foo5", foo5.age)

	modifyFoo(foo1)
	fmt.Println("foo1", foo1.age)
}

func modifySlice(s []int) {
	s[0] = 1
}

func modifyMap(m map[int]string) {
	m[0] = "string"
}

func modifyChan(c chan string) {
	c <- "string"
}

func modifyFooPointer(f *Foo) {
	f.age = 10
}

//f 是 foo 的一个拷贝
func modifyFoo(f Foo) {
	foo := &f
	foo.age = 10
}