javascript - Angular 2 ES6/7 Eventemitter 更新其他组件

Question

我想在组件之间共享数据，所以我实现了一个具有 EventEmitter 的服务。

我的服务如下所示:

@Injectable()
export class LanguageService {



  constructor() {
    this.languageEventEmitter = new EventEmitter();
    this.languages = [];

    this.setLanguages();
  }

  setLanguages() {

    var self = this;

    axios.get('/api/' + api.version + '/' + api.language)
      .then(function (response) {
        _.each(response.data, function (language) {
          language.selected = false;
          self.languages.push(language);
        });
        self.languageEventEmitter.emit(self.languages);
      })
      .catch(function (response) {
      });
  }

  getLanguages() {
    return this.languages;
  }

  toggleSelection(language) {
    var self = this;
    language.selected = !language.selected;
    self.languages.push(language);
    self.languageEventEmitter.emit(self.languages);
  }

}

我必须订阅服务的组件如下:

self.languageService.languageEventEmitter.subscribe((newLanguages) => {
  _.each(newLanguages, function (language) {
    self.updateLanguages(language);
  });
});

当两个组件都加载时，语言数组就会按照我的意愿填充。

这是第一个组件:

export class LanguageComponent {

  static get parameters() {
    return [[LanguageService]];
  }

constructor(languageService) {
  var self = this;

  this.languageService = languageService;
  this.languages = [];

  this.setLanguages();
}

setLanguages() {

  var self = this;

  self.languageService.languageEventEmitter.subscribe((newLanguages) => {
    _.each(newLanguages, function (language) {
      self.updateLanguages(language);
    })
  });

}

updateLanguages(newLanguage) {
  var self = this;

  if (!newLanguage) {
    return;
  }

  var match = _.find(self.languages, function (language) {
    return newLanguage._id === language._id;
  });

  if (!match) {
    self.languages.push(newLanguage);
  }

  else {
    _.forOwn(newLanguage, function (value, key) {
      match[key] = value;
    })
  }

  toggleLanguageSelection(language) {
    var self = this;
    self.languageService.toggleSelection(language)
  }

}

当LanguageComponent执行由点击事件触发的函数toggleLanguageSelection()时，另一个组件的订阅如下:

self.languageService.languageEventEmitter.subscribe((newLanguages) => {
  _.each(newLanguages, function (language) {
    self.updateLanguages(language);
  })
});

不会收到有关更改的通知。我认为发生这种情况是因为两个组件都获得了我的 LanguageService 的不同实例，但我对此不确定。我也尝试创建一个单例，但是 Angular'2 di 不再工作了。这个问题的原因是什么？我该如何解决这个问题？

Answer 1

您需要在引导应用程序时定义共享服务:

bootstrap(AppComponent, [ SharedService ]);

并且不在组件的 providers 属性中再次定义它。这样，您将拥有整个应用程序的服务的单个实例。组件可以利用它来一起通信。

这是因为 Angular2 的“分层注入(inject)器”特性。有关更多详细信息，请参阅此问题:

• What's the best way to inject one service into another in angular 2 (Beta)?