Go Joiner

A generic strings.Join implementation that uses the go generate command from Go 1.4. See this post for details.

Try the example

Install this package:

go install github.com/bslatkin/joiner

Go into the example directory:

go generate
go run *.go

You should see:

My favorite Simpsons Characters:
main.Person{FirstName:"Sideshow", LastName:"Bob", HairColor:"red"}
main.Person{FirstName:"Homer", LastName:"Simpson", HairColor:"n/a"}
main.Person{FirstName:"Lisa", LastName:"Simpson", HairColor:"blonde"}
main.Person{FirstName:"Marge", LastName:"Simpson", HairColor:"blue"}
main.Person{FirstName:"Mr", LastName:"Burns", HairColor:"gray"}
My favorite numbers:
10
33
24
47
My favorite places:
San Francisco
Katmandu
Sydney

Generate your own joiners

Add this to the top of a file where you want to generate joiners:

//go:generate joiner $GOFILE

Annotate your types with // @joiner to generate the code:

// @joiner
type MyData struct{
    X float32
    Y float32
}

Then in your project directory run the generate command:

go generate

This will generate a set of files in the same directory with the generated code. If your types already satisfy fmt.Stringer in the same file then it won't auto-generate the stringer method.

func (t MyData) String() string {
    return fmt.Sprintf("%#v", t)
}

type JoinMyData []MyData

func (j JoinMyData) With(sep string) string {
    all := make([]string, 0, len(j))
    for _, s := range j {
        all = append(all, s.String())
    }
    return strings.Join(all, sep)
}

To use the joiner, just do:

JoinMyData(dataArray).With("\n")

The Join* prefixed type conversion will always be defined for your types. The With method indicates the separator string to use. The return type is a string.

About

By Brett Slatkin