dependency-injection - 异步工厂的依赖注入(inject)解析

Question

通过 di.dart 将数据库连接注入(inject)类时遇到一些问题包裹。具体来说，解决 toFactory 中的异步依赖。选项。
两次尝试都导致
NoSuchMethodError: Class '_Future' has no instance method 'query'.
错误，目前还不清楚正确的前进道路。我宁愿保留 conn没有被包裹在 Future 中的属性。我尝试在类构造函数中对 Future 进行解包，但此时 Dart 中不允许使用异步构造函数。

import 'package:postgresql/pool.dart';
import 'package:postgresql/postgresql.dart';
import 'package:di/di.dart';

main() async {
  var uri = "postgres://username:password@localhost:5432/database";
  var pool = new Pool(uri, minConnections: 2, maxConnections: 5);
  await pool.start();

  Module module = new Module();
  module.bind(TestQuery);
  module.bind(TestController);
  module.bind(Pool, toValue: pool);
  module.bind(Connection, toFactory: (pool) => pool.connect(), inject: [Pool]);

  var injector = new ModuleInjector([module]);

  var html = await injector.get(TestController).index(); 
  print(html);
}

class BaseQuery {
  Connection conn;

  BaseQuery(Connection this.conn);
}

class TestQuery extends BaseQuery {
  TestQuery(Connection conn) : super(conn); // type '_Future' is not a subtype of type 'Connection' of 'conn' where

  run() async {
    var results =  await conn.query("select 1").toList();

    // Do some data manipulation

    return results;
  }
}

class TestController {
  TestQuery testQuery;

  TestController(TestQuery this.testQuery);

  index() async {
    var results = await testQuery.run();

    var html = "<pre>" + results.toString() + "</pre>";

    return html;
  }
}

Answer 1

我可以重现，但是当我将线路更改为

var conn = await injector.get(Connection);
var res = await conn.query("select 1").toList();

它工作正常。

我认为您的代码也应该可以正常工作。