Go language learning, structure

Come on, Wuhan!

Let's move on to the structure of go

For example, we want to store a student's information, such as student number, name, age, gender, etc. according to our previous storage habits, we will define different types of fields to represent different fields and different data types.

This method is feasible, but it is relatively troublesome, and is not conducive to data management.

But in GO language, we can store data in the form of structure. Let's look at the definition of structure:

package main import "fmt" //Define the structure outside the function, and act globally. //Definition of structure //type name struct{ //Structure member list //} type Student struct { id int name string sex string age int addr string } func main() { //Define structure variables by structure name var stdu Student //Structure variable name. Member name stdu.id = 111 stdu.name = "Zhang San" stdu.sex = "male" stdu.age = 26 stdu.addr = "Chengdu" fmt.Println(stdu) }

Output results:

Another way to define:

When writing structure parameters, it is fixed to write according to the defined structure order

func main() { var stdu Student=Student fmt.Println(stdu) }

Let's see how automatic derivation types define structs

stdu_1:= Student

When we define a structure with an auto derived type, we need to add parameters in the structure before defining variables.

2, Assignment and comparison of structures

package main import "fmt" type Student struct { id int name string sex string age int addr string } func main() { s:= Student //Structure variable assignment s1:=s fmt.Println(s1) //Changing values in a structure s1.age=26 fmt.Println(s1) //Let's see if the modified value will affect our original s fmt.Println(s) }

Result:

We can see that we assign the structure s to s1 for printing, s1, and get the same information as the structure s

After changing the age of s1 to 26, printing s1 and printing s, you can see that changing the value of s1 will not change the value of S.

Structure comparison

//In the structure, for comparison, use "= =" or "! =" to compare, which cannot be greater than or less than. if s1!=s{ fmt.Println("Inequality") }else { fmt.Println("identical") }

Result:

In a structure, you can only use "= =" or "! =" for comparison, and cannot use greater than, less than, etc. as comparison of the structure.

Greater than less than can be used to compare structural members.

if s.age>s1.age{ fmt.Println("s Older than s1 Age") }else { fmt.Println("s Less than s1 Age") }

Result:

3, Structure array slicing defined in

We have already introduced the definition and basic use of structure.

1. Structure array

package main import "fmt" type student struct { id int name string sex string age int score int addr string } func main() { //var structure variable name structure type //Define structure array //var structure array name [number of elements] structure type var arr[5]student // Len (array name) calculates the number of array elements //fmt.Println(len(arr)) for i:=0; i<len(arr) ;i++{ fmt.Scan(&arr[i].id,&arr[i].name,&arr[i].sex,&arr[i].age,&arr[i].score,&arr[i].addr) } fmt.Println(arr) }

Result:

Input the above data and print the contents of the structure array.

Output the data content of the structure in a circular way

//fmt.Println(arr) //Output each item of the structure through circulation for i:=0; i<len(arr); i++ { fmt.Println(arr[i]) }

Result:

2. Sorting operation based on member information of structure (bubble sorting algorithm)

package main import "fmt" type student struct { id int name string sex string age int score int addr string } func main() { //var structure variable name structure type //Define structure array //var structure array name [number of elements] structure type var arr[5]student // Len (array name) calculates the number of array elements //fmt.Println(len(arr)) for i:=0; i<len(arr) ;i++{ fmt.Scan(&arr[i].id,&arr[i].name,&arr[i].sex,&arr[i].age,&arr[i].score,&arr[i].addr) } //fmt.Println(arr) //Output each item of the structure through circulation fmt.Println("Before sorting:") for i:=0; i<len(arr); i++ { fmt.Println(arr[i]) } //According to the member information of the structure, we use bubble sorting algorithm for i:=0; i< len(arr)-1; i++{ for j:=0;j<len(arr)-1-i;j++{ //The information, age and score of the members of the comparative structure can be sorted if arr[j].age>arr[j+1].age{ //Exchange members by comparison arr[j],arr[j+1]=arr[j+1],arr[j] } } } fmt.Println("After sorting:") for i:=0; i<len(arr); i++ { fmt.Println(arr[i]) } }

Result:

The elements in the array allow the operation of assigning values to each other, and exchange all the data in the members of the structure.

3, Use automatic type derivation to create a structure

package main import "fmt" type students struct { id int name string sex string age int score int addr string } func main() { //Creating structure information using automatic type inference arr:=[3]students{ , , , } for i,v:=range arr{ //Print type //fmt.Printf("%T",v) fmt.Println(i,v) } }

Result:

4. Definition of slice structure:

Difference: [number of elements] array [] slice

arr:=[]students{ , , , }

It can also run printing.

package main import "fmt" type students struct { id int name string sex string age int score int addr string } func main() { //Creating structure information using automatic type inference // [number of elements] array [] slice arr:=[]students{ , , , } //Adding data information to slices arr = append(arr,students) for i,v:=range arr{ //Print type //fmt.Printf("%T",v) fmt.Println(i,v) } }

Result:

4, Structure as value in Map

package main import "fmt" type stu struct { name string age int score int } func main() { //Define a map m:=make(map[int]stu) m[1] = stu{"Ha-ha", 50,88} m[2] = stu{"tick",51,88} fmt.Println(m) }

Result:

Loop through values in map

for k,v:=range m{ fmt.Println(k,v) }

Result:

5, Slice of structure as value in map

package main import "fmt" type stu struct { name string age int score int } func main() { //Slice of structure as value in map m:=make(map[int][]stu) // map structure slice assignment m[1] = append(m[1],stu{"Ha ha 1",51,81}, stu{"Da Da 1",61,91}) m[2] = append(m[2],stu{"Ha ha 2",52,82}, stu{"Da Da 2",62,82}) m[3] = append(m[3],stu{"Ha ha 3",53,83}, stu{"Da Da 3",63,93}) //Ergodic operation for k,v:=range m{ //At this time, the type of V is, structure slice. //Traversing slice information for i,data:=range v{ fmt.Println("key:",k,"index:",i,"value:",data) } } }

Result:

6, Structure as function parameter

package main import "fmt" type person struct { id int name string score int sex string } func test(s person){ fmt.Println(s.name) fmt.Println(s.score) fmt.Println(s.sex) } func main() { stu:=person //Structure as function parameter test(stu) }

Result:

Structure as function parameter is value transfer

package main import "fmt" type person struct { id int name string score int sex string } func test(s person){ s.name = "Da da da" } func main() { stu:=person //Structure as function parameter test(stu) //As a function parameter, structure is a value transfer. fmt.Println(stu) }

Result: the structure name is not changed, and the value is passed.

Value transfer, parameter unit and parameter unit are different storage areas, and modification will not affect other values. (note here that all slice types are address passing)

Structure slice, passed as parameter address.

package main import "fmt" type person struct { id int name string score int sex string } //All slices are address passing func test(stu []person){ stu[0].name = "tick" } func main() { //Defining structural slices stu:=[]person{, } //Add data to slice stu = append(stu,person) //Structure slice as function parameter is address passing //Structure array as function parameter is value passing test(stu) fmt.Println(stu) }

Result:

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1 February 2020, 03:00 | Views: 1722