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In an application that allows realtime chat between clients, I aim to integrate functionality that allows to define messages that are delivered at future points in time.
In the following example, I am able to insert messages, which are inserted directly into the template. However, I would like to display only messages that have a time smaller or equal to the current time, but automatically display messages that have future time points as soon as the time is reached. For example, if I insert a message from the console, which should be displayed 30 seconds in the future by calling Meteor.call("createMessage", 30000, "hello in 30 seconds"), the message should be automatically displayed after 30 seconds.
I started restricting the query in the publish function to time: {'$lt': new Date()}. However, I have trouble in making this reactive. I unsuccessfully tried several combinations of Tracker.autorun and cursor.observe.
Can anybody give me a hint how I accomplish the desired reactivity within the following running example?
1) html file
<body>
{{> chat}}
</body>
<template name="chat">
{{#each chatMessages}}
{{time}} - {{message}} <br>
{{/each}}
</template>
2) js file
//server and client
Messages = new Mongo.Collection("messages"); //{time: Sun Nov 02 2014 22:17:32 GMT+0100 (CET), message: "hello"}
//server
if(Meteor.isServer){
Meteor.methods({
'createMessage': function(timeOffset, message){
Messages.insert({
time: new Date(new Date().getTime() + timeOffset),
message: message
});
}
});
Meteor.publish("messages", function(){
return Messages.find({
//time: {'$lt': new Date()}
});
});
}
//client
if (Meteor.isClient) {
Template.chat.helpers({
chatMessages: function(){
return Messages.find({});
}
});
Tracker.autorun(function (){
mySub = Meteor.subscribe('messages');
});
}
992
If Date() was a reactive datasource, it would work but it's not.
You can create a Timer at server side that will handle it. The best design I see id: pick the next message future date and set a Timer with the time difference and also get the next message time. Of course it's dependes on how your application works.
Read more about Timers in Meteor: https://docs.meteor.com/#/full/timers
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