package main
import (
"fmt"
)
func main() {
exampleDefault()
exampleCustomTypedCollection()
}
func exampleDefault() {
c := Collection{data: make(map[int]Identifiable)}
c.Set(Item{ID: 123})
c.Set(Foo{ID: 234})
fmt.Printf("%#v\n", c)
entity, ok := c.Get(123)
fmt.Printf("%#v %v\n", entity, ok)
entity, ok = c.Get(234)
fmt.Printf("%#v %v\n", entity, ok)
entity, ok = c.Get(999)
fmt.Printf("%#v %v\n", entity, ok)
}
func exampleCustomTypedCollection() {
c := NewFooCollection()
c.Set(Foo{ID: 123})
fmt.Printf("%#v\n", c)
entity, ok := c.Get(123)
fmt.Printf("%#v %v\n", entity, ok)
entity, ok = c.Get(456)
fmt.Printf("%#v %v\n", entity, ok)
}
// Interfaces.
type Identifiable interface {
Identify() int
}
type Collectable interface {
Get(id int) (entity Identifiable, ok bool)
Set(entity Identifiable)
}
// Base collection.
type Collection struct {
data map[int]Identifiable
}
func (collection Collection) Get(id int) (entity Identifiable, ok bool) {
entity, ok = collection.data[id]
return
}
func (collection Collection) Set(entity Identifiable) {
collection.data[entity.Identify()] = entity
}
// Collection item.
type Item struct {
ID int
Value string
}
func (item Item) Identify() int {
return item.ID
}
// Typed collection.
type FooCollection struct {
Collection
}
func NewFooCollection() FooCollection {
return FooCollection{Collection: Collection{data: make(map[int]Identifiable)}}
}
// Typed collection item.
type Foo struct {
ID int
Data string
}
func (foo Foo) Identify() int {
return foo.ID
}
