How to modify map in golang

During the development process, using Golang’s Map structure is a very common operation. Map is an unordered collection of key-value pairs that can be used to store and find data. If you want to modify the data in the Map, it is also very easy. Let's explore how to modify Map in Golang.

First, let us take a look at the declaration and initialization method of Map in Golang:

// 声明一个 Map，键是字符串类型，值是整数类型
var m map[string]int

// 初始化 Map
m = make(map[string]int)

In the above code, we define a variable m, which is a Map type . The keys of this Map are string types and the values ​​are integer types. Then we use the make function to initialize this Map.

Next let's take a look at how to add data to the Map:

m["apple"] = 2
m["banana"] = 3
m["orange"] = 4

The above code adds three key-value pairs to m. Through this example, we can see that adding data to Map is very simple in Golang.

Now let’s take a look at how to modify the data in Map. Suppose we already have a Map:

m := make(map[string]int)
m["apple"] = 2
m["banana"] = 3
m["orange"] = 4

We want to modify the value of orange to 5. It can be implemented in the following way:

m["orange"] = 5

As shown above, the modification can be completed by assigning values ​​using the keys in the Map. If the key-value pair does not exist in the Map, it will be added automatically.

Of course, there is one situation that requires special attention. If you directly modify a non-existent key, the program will throw an exception:

m["pear"] = 1 // 这里会抛出异常，因为 pear 键不存在

If the key to be modified may not exist, you can check first:

if v, ok := m["pear"]; ok {
    // 如果 pear 键存在，修改其值
    m["pear"] = v + 1
} else {
    // 如果 pear 键不存在，创建并设置其值为 1
    m["pear"] = 1
}

We use the above code Use ok mode to check if the pear key exists. If the key exists, we can update the value of the key using the old value plus one. If the key does not exist, we create a new key-value pair and set its value to 1.

Finally, it should be noted that when multiple threads access Map at the same time, thread-safe processing needs to be performed to avoid problems such as data competition.

The above is a detailed introduction to modifying Map in Golang. Although it is very simple to operate, there are still many details that need to be paid attention to. For beginners, you can gradually master the usage through practice.

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