在外部函数中访问Go结构的值

Question

I have the following function declararion, which works and prints out correctly.

import (
    "fmt"
    "github.com/google/go-github/github"
)

func LatestTag(user, project string) {

    client := github.NewClient(nil)
    releases, _, err := client.Repositories.ListTags(user, project, nil)

    if err != nil {
        fmt.Printf("error: %v
", err)
    } else {
        release := releases[0]
        fmt.Printf("Version: %+v
", *release.Name)
    }

}

EDIT

I have modified the function to return a string (I don't think this is right) but hopefully it can help shed some light on what I am trying to do.

import (
    "fmt"
    "github.com/google/go-github/github"
)

func LatestTag(user, project string) string {

    client := github.NewClient(nil)
    releases, _, err := client.Repositories.ListTags(user, project, nil)
    var release string

    if err != nil {
        fmt.Printf("error: %v
", err)
    } else {
        release := releases[0]
    }
    return *release.Name
}

I would like to return the value of *release.Name rather than just print it out so that I can access the value from another function but I don't understand how returning works in this case (very new to Go).

I was thinking I could just return the struct as a string but get errors when I run it.

release.Name undefined (type string has no field or method Name)

Which makes me think that I'm not approaching this correctly. Can somebody point me in the right direction?

Answer 1

One problem is here:

var release string
...
if err != nil {
...
} else {
    release := releases[0]  // <-- here
}

At the line indicated you define a new variable called release equal to releases[0] which is scoped only to the else clause (use of :=). That then goes out of scope immediately. I'm surprised you don't get an unused variable warning. Looks like you also need to change the type of release to github.RepositoryTag. Try:

var release github.RepositoryTag
...
if err != nil {
...
} else {
    release = releases[0]  // note equals sign
}

However a more idiomatic way to do this would be something like (untested):

func LatestTag(user, project string) (string, error) {
    client := github.NewClient(nil)
    if releases, _, err := client.Repositories.ListTags(user, project, nil); err != nil {
        return "", err
    } else {
        release := releases[0]
        return *release.Name, nil
    }
}