Solve golang error: undefined name 'x' (cannot refer to unexported name), solution

Solution to golang error: undefined name 'x' (cannot refer to unexported name), solution

When using golang to write programs, we often encounter various problems Various error reports. One of the common errors is "undefined name 'x' (cannot refer to unexported name)". This error indicates that an error occurred when accessing an unexported variable or function. So how to solve this problem? This article will introduce you in detail how to solve this error.

First of all, we need to understand the access permission rules in golang. In golang, the access permission of a variable or function is related to the case of its first letter. If the first letter of a variable or function is uppercase, then it is exported and can be accessed and used in other packages; if the first letter of a variable or function is lowercase, then it is unexported and can only be accessed and used in other packages. Accessed and used within the current package. When we access an unexported variable or function in another package, an "undefined name" error occurs.

The following is a simple sample code to simulate the situation where this error occurs:

package main

import "fmt"

type person struct {
    name string
    age  int
}

func main() {
    p := person{name: "Alice", age: 20}
    fmt.Println(p.name) // 会报错："undefined name 'name'"
}

In the above code, we define a structure person, in which Contains two fields: name and age. In the main function, we create an instance p of person and try to access its name field. However, since the name field is not exported (the first letter is lowercase), it is not accessible in other packages, which results in an error.

To solve this error, just change the first letter of the field or function that needs to be accessed to uppercase. The modified code is as follows:

package main

import "fmt"

type Person struct { // 注意这里的首字母大写
    Name string     // 注意这里的首字母大写
    Age  int        // 注意这里的首字母大写
}

func main() {
    p := Person{Name: "Alice", Age: 20} // 注意这里的结构体名称也要修改为大写
    fmt.Println(p.Name) // 不再报错，能够正确访问"name"字段
}

In the above modified code, we changed the structure person to Person, and also changed name## The # and age fields are changed to Name and Age. Since the Name field is exported (the first letter is capitalized), we can access and use it correctly in other packages.

In addition to the fields in the structure, the access permissions of functions also follow the same rules. If a function needs to be used in other packages, the first letter of its name must also be capitalized. If a function is only used internally within the current package, the first letter of its name can be lowercase.

To summarize, when we encounter "golang error: undefined name 'x' (cannot refer to unexported name)", we only need to change the first letter of the variable, structure field or function to uppercase. This will solve this error. This way they can be accessed and used correctly in other packages.

I hope the introduction in this article can help you solve the problem of "golang error: undefined name 'x' (cannot refer to unexported name)". When writing golang programs, we need to pay attention to the access permissions of variables and functions and follow the specifications to avoid such errors.

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