What is the usage of golang range?

As an efficient and concise programming language, Golang (also known as Go) continues to win more and more supporters and developers. Its rich libraries and concise syntax make Golang very convenient and pleasant to use. In this article, we will introduce the usage of range in Golang in detail to better utilize Golang for programming!

What is range?

Range is a built-in function in Golang. It can directly take out each element in the collection (array, slice, map, etc.), which is very convenient to use. In the actual programming process, we often use the range function to traverse the data collection for calculation, printing, filtering and other operations.

Basic syntax for using range

The basic syntax for range is as follows:

for index, value := range collection {

// 针对value和index进行操作

}

Where index represents the index of the current element traversed, and value represents the current element traversed.

For example, we can use range to traverse an integer array:

package main

import "fmt"

func main() {

nums := []int{2, 3, 4}
sum := 0
for _, num := range nums {
    sum += num
}
fmt.Println("sum: ", sum)

}

Result output: sum: 9

In the above code, we traverse each element in the array nums in turn, and accumulate according to =, Finally the sum of the elements is calculated.

Using indexes in range

In range, we can use subscripts (indexes) to traverse collection elements while outputting element subscripts and values:

package main

import "fmt"

func main() {

nums := []int{2, 3, 4}
for i, num := range nums {
    fmt.Printf("index: %d, value: %d\n", i, num)
}

}

When you run this program, you will get the following output:

index: 0, value: 2
index: 1, value: 3
index: 2, value: 4

Ignore index in range

If we don't need to use an index in the range, we can ignore it and use "_" instead.

package main

import "fmt"

func main() {

nums := []int{2, 3, 4}
for _, num := range nums {
    fmt.Println("value: ", num)
}

}

Output result:

value: 2
value: 3
value: 4

Using map in range

In addition to processing arrays and slices in range, we can also process Mapping (Map), the specific implementation is as follows:

package main

import "fmt"

func main() {

kvs := map[string]string{"a": "apple", "b": "banana"}
for k, v := range kvs {
    fmt.Printf("%s -> %s\n", k, v)
}

}

Output result:

a -> apple
b -> banana

It can be seen that in range we can not only process arrays and slices, but also easily traverse Map.

Using channel in range

In addition to arrays, slices and mappings, we can also traverse channels (Channel) in range. The sample code is as follows:

package main

import "fmt"

func main() {

c := make(chan int, 2)
c <- 1
c <- 2
close(c)
for v := range c {
    fmt.Println(v)
}

}

Output result:

1
2

In the above example code, we define a channel c with a capacity of 2, put the two values ​​1 and 2 into the channel, and finally close the channel through the close() function. When using a channel in a range, the loop will automatically exit when the channel is closed.

Summary

In Golang, range is a very convenient way to traverse various data structures. Through the range function, we can easily traverse various data types to obtain the data we need. Whether dealing with arrays, slices, maps, or channels, using range is an efficient and elegant way to help us achieve the true meaning of our program.

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