Where is it best to handle the business logic in m

2020-07-27 15:45发布

问题:

So I've got a pure Polymer app. Currently, in some elements I have methods that call to my Firebase database, and handle related processing and whatnot, which I then <template repeat=...> into my element. This doesn't seem right, as it's encouraged that Polymer elements are reusable. I also do things like dependency injection e.g. <my-element app="{{app}}"> so I have access to global settings and such.

What I end up with is a structure like:

index.dart -> <my-app-as-an-element app=... -> <child-elements app=...

Is there a better way to architect things? Like, should the business logic happen in lib/src/some_controller.dart which is imported into index.dart and has the business logic methods? How would I pass that through to the child elements that need access to those methods? Basically, some best practices and approaches would be helpful.

Code: http://github.com/davenotik/dart-stack/tree/dev

回答1:

I use Model classes which are structured in a way that reflects the GUI structure and I bind them to the Polymer elements like shown below. Similar with the controllers but this would get out of proportion for an SO answer.

I didn't test this code - this is just to demonstrate the idea.

import 'package:polymer/polymer.dart';

class AppModel {
  var loginModel = new LoginModel();
  var moviesModel = new MoviesModel();
  var actorsModel = new ActorsModel();
}

class LoginModel extends Observable {
  @observable bool isAuthenticated;
  @observable String userName;
  @observable String email;
}

class MoviesModel {
  final List<MovieModel> movies = toObservable(<MovieModel>[]);
}

class MovieModel extends Observable {
  @observable String id;
  @observable String name;
  @observable int rating;
  final List<ActorModel> actors = toObservable(<ActorModel>[]);
}

class ActorsModel {
  final List<ActorModel> actors = toObservable(<ActorModel>[]);
}

class ActorModel extends Observable {
  @observable String id;
  @observable String firstName;
  @observable String middleName;
  @observable String lastName;
  @observable DateTime birthDate;
  final List<MovieModel> movies = toObservable(<MovieModel>[]);
}

.

<polymer-element name="login-dropdown">
  <template>
    <template if="model.isAuthenticated">
      <label for="userName"><input id="userName" value="{{model.userName}}" disabled></label>
      <label for="email"><input id="email" value="{{model.email}}" disabled></label>
      <button on-click="{{handleSignOut}}">Sign out</button>
    </template>
    <template if="!model.isAuthenticated">
      <label for="userName"><input id="userName" value="{{model.userName}}"></label>
      <button on-click="{{handleSignIn}}">Sign out</button>
    </template>
  </template>
  <script type="application/dart">
    import 'package:polymer/polymer.dart';
    import 'model.dart';
    @CustomTag('login-dropdown')
    class LoginDropdown extends PolymerElement {
      LoginDropdown.created() : super.created();

      @PublishedProperty(reflect: true) MoviesModel model;
    }
  </script>
</polymer-element>

<polymer-element name="app-element">
  <template>
    <header-toolbar>
      <login-dropdown-button>
        <login-dropdown model="{{model.loginModel}}"></login-dropdown>
      </login-dropdown-button>
    </header-toolbar>
    <tab-control>

      <tab-panel label="Movies">
        <movies-panel model="{{model.moviesModel}}"></movies-panel>
      </tab-panel>

      <tab-panel label="Actors">
        <actors-panel model="{{model.actorsModel}}"></actors-panel>
      </tab-panel>

    </tab-control>

  </template>
  <script type="application/dart">
    import 'package:polymer/polymer.dart';
    import 'model.dart';

    @CustomTag('app-element')
    class AppElement extends PolymerElement {
      AppElement.created() : super.created();

      AppModel model = new AppModel();
    }
  </script>
</polymer-element>

<polymer-element name="movies-panel">
  <template>
    <template repeat="{{movie in model.movies}}">
      <movie-panel model="{{movie}}"></movie-panel>
    </template>
  </template>
  <script type="application/dart">
    import 'package:polymer/polymer.dart';
    import 'model.dart';

    @CustomTag('movies-panel')
    class MoviesPanel extends PolymerElement {
      MoviesPanel.created() : super.created();

      @PublishedProperty(reflect: true) MoviesModel model;
    }
  </script>
</polymer-element>

<polymer-element name="movie-panel">
  <template>
    <div data-id="{{model.id}}">
      <div><span>Name:</span><span>{{model.name}}</span></div>
      <div><span>Rating:</span><span>{{model.rating}}</span></div>
    </div>

    <template repeat="{{actor in model.actors}}">
      <actor-panel model="{{actor}}"></actor-panel>
    </template>

  </template>
  <script type="application/dart">
    import 'package:polymer/polymer.dart';
    import 'model.dart';

    @CustomTag('movies-panel')
    class MoviesPanel extends PolymerElement {
      MoviesPanel.created() : super.created();

      @PublishedProperty(reflect: true) MoviesModel model;
    }
  </script>
</polymer-element>

<polymer-element name="actors-panel">
  <template>
    <template repeat="{{actor in model.actors}}">
      <actor-panel model="{{actor}}"></actor-panel>
    </template>
  </template>
  <script type="application/dart">
    import 'package:polymer/polymer.dart';
    import 'model.dart';

    @CustomTag('actors-panel')
    class ActorsPanel extends PolymerElement {
      ActorsPanel.created() : super.created();

      @PublishedProperty(reflect: true) ActorsModel model;
    }
  </script>
</polymer-element>

<polymer-element name="actor-panel">
  <template>
    <div data-id="{{model.id}}">
      <div><span>First name:</span><span>{{model.firstName}}</span></div>
      <div><span>Middle name:</span><span>{{model.middleName}}</span></div>
      <div><span>Last name:</span><span>{{model.lastName}}</span></div>
      <div><span>Date of birth:</span><span>{{model.birthDate}}</span></div>
    </div>

    <template repeat="{{movie in model.movies}}">
      <movie-panel model="{{movie}}"></movie-panel>
    </template>

  </template>
  <script type="application/dart">
    import 'package:polymer/polymer.dart';
    import 'model.dart';

    @CustomTag('actor-panel')
    class ActorPanel extends PolymerElement {
      ActorPanel.created() : super.created();

      @PublishedProperty(reflect: true) ActorModel model;
    }
  </script>
</polymer-element>   

See also Use a class as attribute for a dart polymer element for more interesting options.