Catalog

1、Slice section

2、Map

Summary

---

Learning notes , Where is where .

1、Slice section

Slice and java Medium ArrayList similar ,Go The length of the language array cannot be changed ,Slice Its length is not fixed , Appendable element .

The definition can be ：

var identifier []type

You can also use make function

var slice1 []type = make([]type, len)

The sample code is as follows

package main

import "fmt"

// section 
func test_slice() {
	a := [...]int{1, 2, 3}
	b := a[:]
	fmt.Printf("a:%T,b%T\na=%v,b=%v\n", a, b, a, b)
	c := a[:2]
	fmt.Println(c)
	s := make([]string, 0)
	s = append(s, "haha")
	s = append(s, "haha1", "haha2")
	fmt.Println(s, len(s), cap(s))

	printSlice := func(x []int) { fmt.Printf("len=%d,cap=%d,slice=%v\n", len(x), cap(x), x) }
	var d []int
	if d == nil {
		printSlice(d)
	}

	copyS := make([]string, cap(s)*2)
	copy(copyS, s)
	fmt.Println(copyS, s)

}

func main() {
	test_slice()
}

Execution results

a:[3]int,b[]int
a=[1 2 3],b=[1 2 3]
[1 2]                                   
[haha haha1 haha2] 3 3                  
len=0,cap=0,slice=[]                    
[haha haha1 haha2   ] [haha haha1 haha2]

Be careful

1、 It can be seen that a It's an array ,b Yes, it will a Array to slice .

2、c yes a The index of the array is 0 To 2-1 The elements of , As a slice .

3、 have access to copy function , Copy slice elements .

4、 Use len()、cap() Built in functions , You can get the length and maximum capacity of the slice .

5、 Use append() Function can append slice elements .

2、Map

and java Medium map similar , Creating map You also need to specify the key value type .

Define the way ：

var map_variable map[key_data_type]value_data_type

map_variable := make(map[key_data_type]value_data_type)

The sample code is as follows

package main

import "fmt"

func testMap() {
	var a = make(map[string]int)
	a[" Xiao Huang "] = 10
	a[" Xiaohong "] = 18
	for s, i := range a {
		fmt.Println(s, i)
	}
	b, ok := a[" Xiaolan "]
	fmt.Println(b, ok)
	a[" floret "] = 21
	delete(a, " Xiao Huang ")
	fmt.Println(a)
}

func main() {
	testMap()
}

Execution results

 Xiao Huang  10
 Xiaohong  18
0 false             
map[ Xiaohong :18  floret :21]

Be careful

1、 In obtaining map At a certain value , Will return two return values , The second return value is bool type , If the key value pair does not exist , Then for false.

2、 have access to delete() Function to delete key value pairs .

Summary

The way of use is also relatively rigorous , They are more conventional data types in work .