等待我的班级初始化（或如何等待未来完成）？ [英] Waiting for my class to initialize (or how to wait for a Future to complete)?

问题描述

Dart的未来是我的存在的痛苦。

我有一个类，调用一个async（Future）函数来启动数据库实例，如下所示：

< pre class =lang-dart prettyprint-override> class DataManager {
bool DbIsReady = false;
Db _db;

DataManager（）{
init_mongo_db（）;
}

void init_mongo_db（）{
print（Initializing MongoDB）;
_db = new Db（mongodb：//127.0.0.1/test）;
_db.open（）。then（（_）{
DbIsReady = true;
}）;
}

Future< List> attemptLogin（String username，String password）{
users = _db.collection（users）;

return // ...为了清晰起见，余下的代码
}
}


这在服务器端工作，因为当服务器首次启动时，数据库被初始化。在用户实际尝试登录时，数据库已初始化，一切正常。但是，当我尝试为此创建集成测试时，这会失败。当我创建类时，数据库尚未初始化，因此运行AttemptLogin例程失败。

  DataManager db = new DataManager（）; 
 //这可能会失败，因为db还没有初始化。 
 db.AttemptLogin（test，test）; 
  

更糟的是，代码使用Dart DI框架，所以我实际上没有直接控制初始化DataManager类。这是类的实际设置：

  setUp（（）{
 app .addModule（new Module（）
 ..bind（DataManager）
 app.setUp（）; 
}）; 
  

然后这是调用测试登录功能，最终调用attemptLogin函数失败：

  var req = new MockRequest（/ user / login，contentType：'JSON'，method：'POST'，
 body：JSON.encode 
 {username：'test'，
password：'test'}））; 
  

如何处理数据库init的异步性质，并仍然进行模拟测试？具体来说，是否有一种方法强制attemptLogin（）Future以某种方式等待DataManager类初始化完成？

感谢您的帮助，
Greg

解决方案

使用@lrn的解决方案如何使用

  setUp （）{
 return DataManager.createNew（）。then（（dm）{
 app.addModule（new Module（）
 ..bind（DataManager，toValue：dm）; 
 app.setUp（）; 
} 
}）; 
  

这样你已经传递了一个初始化的 DataManager 实例进入DI。如果您以后请求，您总是可以确定它已经初始化。

Futures in Dart are the bane of my existence.

I have a class, which calls an async (Future) function to start up the database instance like so:

class DataManager {
  bool DbIsReady = false;
  Db _db;

  DataManager() {
    init_mongo_db();
  }

  void init_mongo_db() {
    print("Initializing MongoDB");
    _db = new Db("mongodb://127.0.0.1/test");
    _db.open().then((_) {
      DbIsReady = true;
    });
  }  

  Future<List> attemptLogin(String username, String password) {
    users = _db.collection("users");

    return // ... rest of code cut out for clarity
  }
}

This works OK server-side because when the server first starts up, the database is initialized. By the time a user actually attempts to log in, the database has been initialized and all is well. However, this fails miserably when I try to create an integration test for this. When I create the class, the database isn't yet initialized, so running the AttemptLogin routine fails.

DataManager db = new DataManager();
// This fails miserably, because db hasn't initialized yet.
db.AttemptLogin("test", "test"); 

Worse, the code uses the Dart DI framework, so I don't actually have direct control over the initialization of the DataManager class. This is the actual setup of the class:

setUp(() {
  app.addModule(new Module()
            ..bind(DataManager)
  app.setUp();
});

And then this is the call to test the login functionality, which ultimately calls the attemptLogin function which fails:

var req = new MockRequest("/user/login", contentType: 'JSON', method:'POST',
    body:JSON.encode(
      {"username" : 'test',
       "password" : 'test' }));

How does one deal with the async nature of the the database init and still do mock testing? Specifically, is there a way to force the attemptLogin() Future to somehow wait for the completion of the DataManager class initialization?

Thanks for your help, Greg

解决方案

what about using @lrn s solution like

setUp(() {
  return DataManager.createNew().then((dm) {
    app.addModule(new Module()
            ..bind(DataManager, toValue: dm);
    app.setUp();
  }
});

This way you already pass an initialized DataManager instance into the DI. If you request it later on you always can be sure it is already initialized.

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