内置Go中“必备”模式的帮助器

Question

Is there a more built-in wrapper to make a function that returns (X, error) successfully execute or abort, like regexp.MustCompile?

I'm talking about something like this, but more "built-in".

Answer 1

There is not. The best you'll get is something like this:

func Must(fn func() (interface{}, error)) interface{} {
    v, err := fn()
    if err != nil {
        log.Fatalln(err)
    }
    return v
}

Then to use it:

Must(func() (interface{}, error) {
    return template.ParseGlob(pattern)
}).(*template.Template)

Assuming that template.ParseGlob(pattern) is the call you wanted to wrap.

Go does not have parametric polymorphism, so this kind of code will end up requiring type assertions to restore the original type and so (in my opinion) is more effort than it's worth. The tidiest, idiomatic error handling you'll get for long chains of potential failure is simply to check for an error, and return it. Defer your cleanup handlers:

func MyFunc() (err error) {
    a, err := blah1()
    if err != nil {
        return
    }
    defer a.Close()
    b, err := blah2(a)
    if err != nil {
        return
    }
    defer b.Close()
    // ad nauseam
}

Long and tedious, but at least it's explicit and easy to follow. Here are two modules I wrote that are crying out for parametric polymorphism that might give you some ideas for dealing without it:

• bitbucket.org/anacrolix/dms/futures
• bitbucket.org/anacrolix/dms/cache