addListener(harvest, callback) {
    let query = Harvests.find({_id: harvest._id});

    // First, check to see if there is already a listener defiend. If there is,
    // remove it.
    if(_.has(this.observers, harvest._id)) {
      this.removeListener(harvest);
    }

    // Create a new observer and store it in this.observers
    this.observers[harvest._id] = query.observe({
      changed: callback
    });
  }
/**
   * Add a listener that lsitens for any changes in harvest and executes
   * callback when a change occurs.
   */
Add a listener that lsitens for any changes in harvest and executes
callback when a change occurs.
Add a listener that lsitens for any changes in harvest and executes callback when a change occurs .
addListener(harvest, callback) {
    let query = Harvests.find({_id: harvest._id});
    if(_.has(this.observers, harvest._id)) {
      this.removeListener(harvest);
    }
    this.observers[harvest._id] = query.observe({
      changed: callback
    });
  }
addListener ( harvest , callback ) { let query = Harvests . find ( { _id : harvest . _id } ) ; if ( _ . has ( this . observers , harvest . _id ) ) { this . removeListener ( harvest ) ; } this . observers [ harvest . _id ] = query . observe ( { changed : callback } ) ; }
Add a listener that lsitens for any changes in harvest and executes
 callback when a change occurs.
Add a listener that lsitens for any changes in harvest and executes callback when a change occurs .
// First, check to see if there is already a listener defiend. If there is, // remove it. // Create a new observer and store it in this.observers