Resolver service. (#18)

Signed-off-by: Pavel Patrin <[email protected]>

container.go

@@ -48,6 +48,9 @@ func New(factories ...*Factory) (result Container, err error) {
 	// Prepare services registry instance.
 	registry := &registry{events: events}
 
+	// Prepare service resolver instance.
+	resolver := &resolver{ctx: ctx, registry: registry}
+
 	// Prepare service container instance.
 	container := &container{
 		ctx:      ctx,
@@ -70,6 +73,11 @@ func New(factories ...*Factory) (result Container, err error) {
 		return nil, fmt.Errorf("failed to register events service: %w", err)
 	}
 
+	// Register service resolver instance in the registry.
+	if err := container.registry.registerFactory(ctx, NewService[Resolver](resolver)); err != nil {
+		return nil, fmt.Errorf("failed to register service resolver: %w", err)
+	}
+
 	// Register provided factories in the registry.
 	for _, factory := range factories {
 		if err := container.registry.registerFactory(ctx, factory); err != nil {

resolver.go

@@ -0,0 +1,31 @@
+package gontainer
+
+import (
+	"context"
+	"fmt"
+	"reflect"
+)
+
+// Resolver defines service resolver interface.
+type Resolver interface {
+	// Resolve returns specified dependency.
+	Resolve(any) error
+}
+
+// resolver implements resolver interface.
+type resolver struct {
+	ctx      context.Context
+	registry *registry
+}
+
+// Resolve returns specified dependency.
+func (r *resolver) Resolve(varPtr any) error {
+	value := reflect.ValueOf(varPtr).Elem()
+	ins := []reflect.Type{value.Type()}
+	outs, err := r.registry.getFactoryInValues(r.ctx, ins)
+	if err != nil {
+		return fmt.Errorf("failed to get service: %s", err)
+	}
+	value.Set(outs[0])
+	return nil
+}

resolver_test.go

@@ -0,0 +1,35 @@
+package gontainer
+
+import (
+	"testing"
+	"time"
+)
+
+// TestResolverService tests resolver service.
+func TestResolverService(t *testing.T) {
+	container, err := New(
+		NewFactory(func() string { return "string" }),
+		NewFactory(func(resolver Resolver) {
+			var depExists string
+			equal(t, resolver.Resolve(&depExists), nil)
+			equal(t, depExists, "string")
+
+			var depNotExists int
+			equal(t, resolver.Resolve(&depNotExists) != nil, true)
+			equal(t, depNotExists, 0)
+		}),
+	)
+	equal(t, err, nil)
+	equal(t, container == nil, false)
+
+	// Start all factories in the container.
+	equal(t, container.Start(), nil)
+
+	// Let async service function launch.
+	time.Sleep(time.Millisecond)
+
+	// Close all factories in the container.
+	equal(t, container.Close(), nil)
+
+	<-container.Done()
+}