Meteor run a function when a mongo collection gets updated

问题

I am trying to do a simple prototype using Meteor (I am very new to Meteor).

I have the following in an isClient block

    Template.imageList.helpers({
    images: function() {
        return Images.find({});
  },
}
);

Then for quick demo purposes I am inserting data with meteor mongo and the following

db.images.insert({ imgSrc: "http://mysite/img1.png", createdAt: new Date() })

This works and I can see the change reflected on the ui but I need to also run a client side javascript function when this occurs. I have been trying things like pub/sub and Tracker but can't get anything to work.

Any guidance would be great.

回答1:

Use observeChanges :

Images.find().observeChanges({
   added: function (id, fields) {
       runFunction();
   },
   changed: function (id, fields) {
       runFunction();
   },
   removed: function (id) {
       runFunction();
  }
});

See here for more: http://docs.meteor.com/#/full/observe_changes

回答2:

Using meteor-collections-hooks its the more easy way to accomplish this.

meteor add matb33:collection-hooks

For example.

Images = new Mongo.Collection('Images')
example = function(){
  console.log("updated")
}
if (Meteor.isClient) {
  Images.before.update(function(userId, doc, fieldNames, modifier, options){
     example();
  })
}

the example() function will run each time the Images collection get updated.

回答3:

Run function on the client's template helper, like:

Template.imageList.helpers({
  images: function() {
    imgs = Images.find({});
    yourFunction();
    return images;
  }
});

Or use Tracker.autorun wrapper:

Tracker.autorun(
   Images.find({});
   yourFunction();
)

来源：https://stackoverflow.com/questions/29596256/meteor-run-a-function-when-a-mongo-collection-gets-updated

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meteor