Golang Basic Knowledge 1

This is a creation in Article, where the information may have evolved or changed.

1.slice and Array

Package Main

Import (
"FMT"
)

Func Main () {
s: = []int{1, 2, 3}
SS: = s[1:]
For I: = range SS {
Ss[i] + =//slice Change the value of the array to change the value in the original array
}
Fmt. PRINTLN (s)
SS = Append (ss, 4) after the value of//append is assigned to the variable SS, the SS does not point to the original array
Fmt. PRINTLN (SS)
For I: = range SS {
Ss[i] + = 10
}
Fmt. PRINTLN (SS)
Fmt. PRINTLN (s)
}

Results

[1 12 13]
[12 13 4]
[22 23 14]
[1 12 13]

2.:= and Var

: = must be used within Func, VAR can generate a global variable

Not declared and declared can be used: =, but not declared cannot be used directly =:

  x, _ := f() //错，x已经声明不需要用 :=

  x, _ = f()　　 //对, x已经声明可以直接使用 =

  x, y := f()　　//对， y没有声明

  x, y = f()　　　//错， y没有声明，不能直接使用 =

How to use 3.map correctly

使用map,必须使用make生成map,否则不能初始化map的值。
var m make(map[string]int)　　 //使用make来初始化map
m["b"]; ok { //使用ok来判断遍历的正确是否，不用其他方式

　　println(v)

  }


4.strct 的初始化和调用

Defining a struct

Type Student struct {id      intname    stringaddress stringage     int}

1.赋值方式：

var s *student = new (Student) s.id = 101s.name = "Mikle" s.address = "Hongqi South Road" S.age = 18

2.var S1 *student = &student{102, "John", "Nanjing Road", 19}
Both of these are pointer types.package main

type S struct { m string}func f() *S { return &S{"foo"} //A}func main() { p := *f() //B，这里加*是表示返回的是指针类型 *&正好中和，*是获取指针的值。 print(p.m) //print "foo"}

5.传参是传指针还是具体的变量。

如果参数func(p *interface{}) 则只能传指针类型，

interface{}) 可以传指针和具体变量。

package maintype S struct {}func f(x interface{}) {}func g(x *interface{}) {}func main() {    s := S{}    p := &s    f(s) //A correct    g(s) //B incorrect    f(p) //C correct    g(p) //D incorrect}

6.存指针的map的方式，指针是*int
m := make(map[int]*int)
7.for循环的i，获取临时变量的指针，由于go的闭包属性，

Package Main

Const N = 3

Func Main () {
M: = Make (Map[int]*int)

For I: = 0; i < N; i++ {
M[i] = &i//a
}

For _, V: = range m {
Print (*V)
}
}

Because of the closure relationship, the last value that is referenced is the last. So to change this situation, it is best to re-common a variable within the for loop

package mainconst N = 3func main() {m := make(map[int]*int)for i := 0; i < N; i++ {j := int(i)    //这是一个新的变量，因此不会被后来者覆盖。m[i] = &j}for _, v := range m {print(*v)}}

 8.var 的全局变量定义

The type of the variable must be declared, for example: var s int