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container.go
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container.go
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package gioc
import (
"errors"
"reflect"
"sync"
)
var container map[reflect.Type]binding
var mu *sync.Mutex
func init() {
container = make(map[reflect.Type]binding)
mu = &sync.Mutex{}
}
type binding struct {
singleton bool
resolved bool
resolver interface{}
instance interface{}
}
// Singleton binds a resolver to an abstraction once
func Singleton(resolver interface{}) {
Bind(resolver, true)
}
// Bind binds a resolver to an abstraction
func Bind(resolver interface{}, singleton bool) {
mu.Lock()
defer mu.Unlock()
resolverType := reflect.TypeOf(resolver)
if resolverType.Kind() != reflect.Func {
panic("ioc resolver should be a function")
}
if resolverType.NumOut() != 2 {
panic("ioc resolver should have two return types")
}
if resolverType.Out(1) != reflect.ValueOf(new(error)).Elem().Type() {
panic("ioc resolver second return type should be error")
}
container[reflect.TypeOf(resolver).Out(0)] = binding{
singleton: singleton,
resolved: false,
resolver: resolver,
}
}
// Make loads given parameter's value from container
func Make(receiver interface{}) error {
receiverType := reflect.TypeOf(receiver)
return resolveType(receiverType, receiver)
}
func getBindingFor(t reflect.Type) (binding, bool) {
b, ok := container[t]
if !ok {
if reflect.Ptr == t.Kind() {
b, ok = container[t.Elem()]
}
}
return b, ok
}
func (b binding) resolve() (interface{}, error) {
if b.singleton && b.resolved {
return b.instance, nil
}
args, err := getArgumentsOf(b.resolver)
if err != nil {
return nil, err
}
values := reflect.ValueOf(b.resolver).Call(args)
if values[1].Interface() != nil {
return nil, values[1].Interface().(error)
}
if b.singleton && !b.resolved {
b.instance = values[0].Interface()
b.resolved = true
}
return values[0].Interface(), nil
}
func getArgumentsOf(function interface{}) ([]reflect.Value, error) {
fType := reflect.TypeOf(function)
argsCount := fType.NumIn()
args := make([]reflect.Value, argsCount)
for i := 0; i < argsCount; i++ {
abstract := fType.In(i)
var instance interface{}
if err := resolveType(abstract, &instance); err != nil {
return nil, err
}
args[i] = reflect.ValueOf(instance)
}
return args, nil
}
func resolveType(t reflect.Type, receiver interface{}) error {
b, ok := getBindingFor(t)
if !ok {
return errors.New("binding not found")
}
concrete, err := b.resolve()
if err != nil {
return err
}
reflect.ValueOf(receiver).Elem().Set(reflect.ValueOf(concrete))
return nil
}