stupid-gopher-tricks.md

Stupid Gopher Tricks

Andrew Gerrand's talk "Stupid Gopher Tricks" at the Golang UK conference.

Type literals

Type declaration:

type Foo struct {
    i int
    s string
}

The latter part of a type declaration is the type literal:

struct {
    i int
    s string
}

An unnamed struct literal is often called an anonymous struct:

var t struct {
    i int
    s string
}

Anonymous structs

Template data

data := struct {
    Title               string
    Firstname, Lastname string
    Rank                int
}{
    "Dr", "Carl", "Sagan", 7,
}
if err := tmpl.Execute(os.Stdout, data); err != nil {
    log.Fatal(err)
}

JSON

• Encode and decode JSON objects.

b, err := json.Marshal(struct {
    ID   int
    Name string
}{42, "The answer"})
if err != nil {
    log.Fatal(err)
}
fmt.Printf("%s\n", b)

var data struct {
    ID   int
    Name string
}
err := json.Unmarshal([]byte(`{"ID": 42, "Name": "The answer"}`), &data)
if err != nil {
    log.Fatal(err)
}
fmt.Println(data.ID, data.Name)

• Structs can be nested to describe more complex JSON objects

var data struct {
    ID int
    Person struct {
        Name string
        Job string
    }
}

const s = `{"ID":42,"Person":{"Name":"George Costanza","Job":"Architect"}}`
err := json.Unmarshal([]byte(s), &data)
if err != nil {
    log.Fatal(err)
}
fmt.Println(data.ID, data.Person.Name, data.Person.Job)

Repeated literals and struct names

type Foo struct {
    i int
    s string
}

var s = []Foo{
    {6 * 9, "Question"},
    {42, "Answer"},
}

var m = map[int]Foo{
    7: {6 * 9, "Question"},
    3: {42, "Answer"},
}

• Combined with anonymous structs, this convenience shortens the code dramatically:

var s = []struct {
    i int
    s string
}{
    struct {
        i int
        s string
    }{6 * 9, "Question"},
    struct {
        i int
        s string
    }{42, "Answer"},
}

var t = []struct {
    i int
    s string
}{
    {6 * 9, "Question"},
    {42, "Answer"},
}

... [WIP]