Go Basic-map

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

/*

Features of 1.map:

A.map is a built-in reference type for the go language, so when multiple maps point to the same underlying situation, a value changes and all changes

B.map are unordered, and the order of each iteration is indeterminate.

C.map only Len has no cap.

D.map is not thread-safe and is used in multiple go-routine to lock.

E.map[key]value

Key must support operations for operators (= =,! =), such as Number/string/pointer/array/struct/interface

Value can be of any type.

Creation of 2.map:

A. New to create

MapA: = new (map[int]string)

*mapa = map[int]string{}

(*mapa) [112] = "112"

(*mapa) [110] = "110"

B. Direct declaration creation

var map1 map[int]string = map[int]string{}

MAP2: = map[int]string{

11: "11",

12: "12",

13: "13",

}

C.make to create

MAP3: = Make (map[int]string, 1000)//1000 is the capacity of the map, this is the same as slice, the pre-application of a piece of memory, to avoid frequent expansion later, improve performance

Some basic operations of 3.MAP

A. Determine if the key value exists

If V, OK: = Map1[5]; OK = = true {

Fmt. PRINTLN ("This key is Exit", V)

} else {

Fmt. PRINTLN ("This key isn't Exit")

}

B. Increase

Map[key] = value

C. Modifications

Map when modifying value

If value is a value type, you need to replace it all if you want to change it (value for value)

If it is a reference type, you can directly assign a value to replace

MapS: = map[string]person{}

maps["xuhh"] = Person{name: "Xuhh", old:26}

maps["xuhh"].name = "Xuhehe"//Error  cannot assign to maps["Xuhh"].name

D. Delete

Key-value pairs can be safely removed during iteration

Delete (map, key)

E. Iterative traversal

For k, V: = Range Map {

Fmt. Println ("key =", K, "value =", V)

}

*/
Package Mainimport ("FMT") the type person struct {name string old Int}func main () {//new is created MapA: = new (M        ap[int]string) *mapa = map[int]string{} (*mapa) [*mapa] = "the" [[]] = "A" for V: = Range *mapa { Fmt. Println (v)}//directly created, can be initialized directly: var map1 map[int]string = map[int]string{} map2: = map[int]string{11: "11 ",": "", "" "," "," FMT. " Println (MAP2) map1[2] = "222" map1[3] = "333" map1[1] = "111" map1[6] = "666" map1[8] = "888" map1[5] = "555" FMT. PRINTLN (MAP1)//Make create MAP3: = Made (map[int]string, +) map3[22] = "$" FMT. PRINTLN (MAP3)//Map operation//Find if V, OK: = Map1[5]; OK = = true {fmt. PRINTLN ("This key is Exit", V)} else {fmt. PRINTLN ("This key was not exit")}//add map1[5] = "Exit" FMT. Println (map1[5])//modify MapS: = map[string]person{} maps["xuhh"] = Person{name: "Xuhh", old:26}//maps["Xuh H "].name =" XuheHe "//error cannot assign to maps[" Xuhh "].name//map when operating value, if value is a value type, to change the value, you need to replace all (value for value), if not a reference type , you can directly assign a value to replace//delete Delete (MAP1, 5) If _, OK: = Map1[5];!ok {fmt. PRINTLN ("This key is deleted")}//Iterate over for k, V: = Range Map1 {fmt. Println ("key =", K, "value =", V)}}