Tags and introspection (reflect)

---

• We can add "free-text" tags to the elements of the struct, but it is better to use key-value pairs in there.
• We can use introspection to look at the content of the tags.

examples/struct-tags/struct_tags.go

package main

import (
    "fmt"
    "reflect"
)

type aPerson struct {
    id       int    `unique:"true"`
    name     string `required:"true" max:"100"`
    children []string
}

func main() {
    t := reflect.TypeOf(aPerson{})
    field, ok := t.FieldByName("id")
    if ok {
        fmt.Printf("id: %v\n", field.Tag)
        fmt.Println(field.Tag.Get("unique"))
        fmt.Println(field.Tag.Get("required"))

        value, ok := field.Tag.Lookup("unique")
        if ok {
            fmt.Printf("unique value: %v\n", value)
        }
    }
    field, ok = t.FieldByName("children")
    if ok {
        fmt.Printf("children: %v\n", field.Tag)
    }

    a := aPerson{
        id: 1,
    }
    fmt.Println(a)
}

id: unique:"true"
true

unique value: true
children: 
{1  []}