How to solve golang error: assignment to entry in nil map

How to solve golang errors: assignment to entry in nil map

In the development process of golang, we often encounter various errors. One of the common errors is "assignment to entry in nil map". This error means that an assignment operation was performed in an uninitialized map. In this article, we will describe the causes of this problem and provide solutions.

Cause of the problem:
The reason for this error is very simple, that is, an assignment operation was performed in an uninitialized map. In golang, map is an unordered collection of key-value pairs that must be initialized before use. If you do not initialize the map and assign it directly, this error will be triggered.

Solution:
To solve this problem, we need to initialize the map first and then perform the assignment operation. The following are several common solutions:

1. Use the make function to initialize the map:

   m := make(map[string]int)
   m["key"] = 10

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2. Use the literal to initialize the map:

   m := map[string]int{"key": 10}

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3. Use nil to determine whether the map is empty:

   var m map[string]int
   if m == nil {
    m = make(map[string]int)
   }
   m["key"] = 10

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It should be noted here that using nil to determine whether the map is empty can only be used to determine whether the map is empty. is nil, and it cannot be determined whether the map has been initialized. Because an uninitialized map is still nil, an error will still be triggered in this case. Therefore, before determining whether the map is empty, you must ensure that the map has been initialized.

In addition, if you have declared the map variable before using map instead of declaring it when you need to use it, you can initialize it at the same time as the declaration to avoid the problem of uninitialized map errors. The following is a sample code:

var m = map[string]int{"key": 10}

Summary:
In the development of golang, if you encounter the error "assignment to entry in nil map", it must be because of an assignment operation to an uninitialized map. To solve this problem, we need to initialize the map before using it. You can use the make function or literal method to initialize, or you can use nil to determine whether the map is empty, but you must pay attention to ensure that the map has been initialized. By following these principles, you can easily solve this common map error problem.

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