injector.go

package di

import (
	"fmt"
	"reflect"
)

func (container *Container) Inject(servicePtr interface{}) error {
	ptrValue := reflect.ValueOf(servicePtr)

	// Ensure that servicePtr is a pointer to a struct
	if ptrValue.Kind() != reflect.Ptr || ptrValue.Elem().Kind() != reflect.Struct {
		return fmt.Errorf("Inject: Must pass a pointer to a struct")
	}

	// Get the type of the struct from the pointer
	structType := ptrValue.Elem().Type()
	serviceName := structType.Name()
	structValue := ptrValue.Elem()
	// Iterate through the fields of the struct
	for i := 0; i < structValue.NumField(); i++ {
		field := structValue.Type().Field(i)
		fieldValue := structValue.Field(i)
		dependencyName, ok := field.Tag.Lookup("di")
		if ok {
			defaultName := field.Type.String()
			fallbackName := dependencyName
			dependency, err := invokeByName(serviceName, container, defaultName, fallbackName)
			if err != nil {
				return err
			}

			if !fieldValue.CanSet() {
				return fmt.Errorf("Field is not settable %s", field.Name)
			}

			if dependency == nil {
				return fmt.Errorf(
					"Dependency not found. Field: %s, Dependency: %s",
					field.Name,
					dependencyName,
				)
			}

			fieldValue.Set(reflect.ValueOf(dependency))
		}
	}

	return nil

}