golang map increase

Golang is a very popular programming language that is popular for processing large-scale data. The map is an efficient data structure used to store key-value pairs, which can achieve fast search and retrieval. Although the use of map is very convenient, in actual applications, there may be situations where new key-value pairs need to be added. So how can you add new key-value pairs to Golang map? This article will introduce you to three methods.

Method 1: Direct assignment

In Golang, the simplest way to add a new key-value pair to a map is to directly assign a value to the target key. This can be achieved using the following code:

package main

import "fmt"

func main() {
    // 声明并初始化map
    scores := make(map[string]int)
    scores["Tom"] = 90
    scores["Jerry"] = 80
    scores["Alice"] = 95
    
    fmt.Println(scores)
    
    // 增加新键值对
    scores["Bob"] = 85
    
    fmt.Println(scores)
}

The running results are as follows:

map[Tom:90 Jerry:80 Alice:95]
map[Tom:90 Jerry:80 Alice:95 Bob:85]

In the above code, we first initialize a map, which contains three key-value pairs. Then, we add a new key-value pair by assigning a value to a new key. Finally, we print out the complete added map, which contains the original three key-value pairs and the new key-value pair.

This method is suitable for adding new key-value pairs in the map, and multiple key-value pairs can be quickly added through loop statements according to actual needs. But please note that if the key we assign already exists in the map, its value will be overwritten.

Method 2: Use the update method of map

In Golang, there is also a special method that can be used to simultaneously determine whether a key exists and add a new key-value pair. This method uses the update method of map, and the implementation code is as follows:

package main

import "fmt"

func main() {
    // 声明并初始化map
    scores := make(map[string]int)
    scores["Tom"] = 90
    scores["Jerry"] = 80
    scores["Alice"] = 95
    
    fmt.Println(scores)
    
    // 增加新键值对
    updateMap("Bob", 85, &scores)
    
    fmt.Println(scores)
}

func updateMap(key string, value int, scores *map[string]int) {
    if _, ok := (*scores)[key]; !ok {
        (*scores)[key] = value
    }
}

The running results are as follows:

map[Tom:90 Jerry:80 Alice:95]
map[Tom:90 Jerry:80 Alice:95 Bob:85]

In the above code, we define an updateMap function, which accepts three parameters: key , value and a pointer to the map. Inside the function, we use map's update method to determine whether the key to be added already exists, and formulate a new key-value pair if it does not exist. Finally, we call the updateMap function to add a new key-value pair to the map.

Although this method is slightly more complicated than the first method, it is more flexible. It allows us to perform additional operations on the operation of adding a new key, such as updating the value of an existing key-value pair or printing out the details of the new key-value pair.

Method 3: Use the assignment operator of map

Another method is to use the assignment operator of Golang map. The implementation code is as follows:

package main

import "fmt"

func main() {
    // 声明并初始化map
    scores := make(map[string]int)
    scores["Tom"] = 90
    scores["Jerry"] = 80
    scores["Alice"] = 95
    
    fmt.Println(scores)
    
    // 增加新键值对
    scores = map[string]int{
        "Bob": 85,
    }
    
    fmt.Println(scores)
}

The running results are as follows:

map[Tom:90 Jerry:80 Alice:95]
map[Bob:85]

In this method, we directly use the assignment operator of map to add new key-value pairs. In this example, we first initialize a map using the make function, and then use the map assignment operator to add new key-value pairs to the map. Similar to the first method, this method can also be used to add new key-value pairs in batches in a loop.

This method is simpler than the first two methods, but it is only suitable for replacing the original map with a new map. If you need to add new key-value pairs to an existing map, you still need to use the first or second method.

To sum up, the functions implemented by these three methods are to add new key-value pairs to the Golang map. Which method to choose depends on the specific scenario. Hope the above content is helpful to you!

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