golang “undefined” function declared in another file?

问题

I'm trying to write a basic go program that calls a function on a different file, but a part of the same package. However, it returns:

undefined: NewEmployee

Here is the source code:

main.go:

package main

func main() {
emp := NewEmployee()    
}

employee.go:

package main

type Employee struct {
    name string
    age int
}   

func NewEmployee() *Employee {
    p := &Employee{}
    return p
}

func PrintEmployee (p *Employee)  {
    return "Hello world!"
}

回答1:

Please read "How to Write Go Code".

Don't use /src in your GOPATH. Packages are located in $GOPATH/src.

For build or install you need to have your files in a package directory.

For go run, you need to supply all files as argument:

go run main.go employee.go

But, you should almost always use go install, or go build (and preferably the former, as go build causes confusion when working with non-main packages)

回答2:

I just had the same problem in GoLand (which is Intellij IDEA for Go) and worked out a solution. You need to change the Run kind from File to Package or Directory. You can choose this from a drop-down if you go into Run/Edit Configurations.

Eg: for package ~/go/src/a_package, use a Package path of a_package and a Directory of ~/go/src/a_package and Run kind of Package or Directory.

回答3:

If you're using go run, do go run *.go. It will automatically find all go files in the current working directory, compile and then run your main function.

回答4:

You can try one of followings.

Method 01 : assume that your project name is MyProject

go to you path, type go build and hit enter.
it will creates an executable file as your project name ("MyProject")
then in your terminal type ./MyProject and hit enter

you can do both steps at once by typing go build && ./MyProject. it will run your project properly with all go files.

Method 02

just type go run *.go and hit enter. this will execute all your go files.

Hope this will help to someone.

回答5:

If you want to call a function from another go file and you are using Goland, then find the option 'Edit configuration' from the Run menu and change the run kind from File to Directory. It clears all the errors and allows you to call functions from other go files.

回答6:

I ran into the same issue with Go11, just wanted to share how I did solve it for helping others just in case they run into the same issue.

I had my Go project outside $GOPATH, so I had to turned on GO111MODULE=on without this option turned on, it will give you this issue; even if you you try to build or test the whole package or directory it won't be solved without GO111MODULE=on

回答7:

If your source folder is structured /go/src/blog (assuming the name of your source folder is blog).

cd /go/src/blog ... (cd inside the folder that has your package)
go install
blog

That should run all of your files at the same time, instead of you having to list the files manually or "bashing" a method on the command line.

来源：https://stackoverflow.com/questions/28153203/golang-undefined-function-declared-in-another-file

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