Why is My Go Function 'undefined' When Declared in Another File?

"undefined" Function Declared in Another File?

Problem:

When attempting to call a function defined in a separate file within the same package, you encounter the following error: "undefined: NewEmployee."

Solution:

To resolve this issue, it is essential to understand Go's module system and package management approach.

Go Modules and Packages

Go organizes code into modules and packages. Each module contains one or more packages, and each package represents a single unit of functionality. In the given example, both main.go and employee.go belong to the same package, as they both use package main.

Building and Installing Packages

When working with packages, it's important to use the appropriate commands for building and installing them. The recommended approach is to use go build or go install within the package directory. This ensures that the package is properly built and made available for import.

Running Programs

For executing programs, it's generally advisable to use go run . within the package directory. This command runs the program using the current package's build state.

File Arguments

Using file arguments for go build or go install is not recommended. Instead, provide an import path for the package. Similarly, while you can use file arguments for go run, it's better practice to build the package first, using either go run . or go install.

By following these guidelines and understanding Go's module and package system, you can avoid the "undefined" function error and work effectively with multiple files in your Go programs.

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