Meteor：来自观察回调的Meteor.call（）不会执行

Question

Is there any possibility of calling a server method from within a observe callback in Meteor?

I put together an example that reproduces the issue, that a Meteor.call() called from within a callback of myCursor.observe() does not execute. When called from within the observe callback, the Meteor.method itself also does not callback with an error, it just returns Undefined .

Stop ignoring me, Meteor.call() :) Any help is very appreciated!

observe.js

items=new Meteor.Collection("Items");

if (Meteor.isClient) {
    Meteor.subscribe("Items");
    Meteor.startup(function(){
        itemsCursor=items.find();
        itemsHandle=itemsCursor.observe({
            added : function(doc){
                console.log("added "+doc.text);
                Meteor.call('aMethod',doc.text,function(e,r){
                    if(e){
                        console.log("error from server: "+e);
                    }else{
                        console.log("response from server: "+r);
                    }
                });
            },
            removed : function(doc){
                console.log("removed "+doc.text);
                Meteor.call('aMethod',doc.text,function(e,r){
                    if(e){
                        console.log("error from server: "+e);
                    }else{
                        console.log("response from server: "+r);
                    }
                });
            }
        });
    });

    Template.test.items=function(){
        return items.find();
    }
    Template.test.events({
        'click #add':function(){
            items.insert({"text":"Timestamp: "+(new Date().getTime())});
        },
        'click #remove':function(){
            items.remove(items.findOne()._id);
        }
    });
}

if (Meteor.isServer) {
    Meteor.publish("Items",function(){
        return items.find();
    });
    items.allow({
        insert : function(userId,doc){
            return true;
        },
        update : function(userId,doc){
            return true;
        },
        remove : function(userId,doc){
            return true;
        }
    });
    Meteor.methods({
        aMethod:function(text){
            console.log("Got it! "+text);
            return "Got it! "+text;
        }
    });
}

observe.html

<head>
  <title>observe</title>
</head>

<body>
  {{> test}}
</body>

<template name="test">
  <button id="add">add item</button>
  <button id="remove">remove item</button>
    <ol>
        {{#each items}}
        <li>{{text}}</li>
        {{/each}}
    </ol>
</template>

Answer 1

This might be a known issue, i'm not sure since I've not tried it myself, but it looks like there might be a workaround (see https://github.com/meteor/meteor/issues/907 )

Add your Meteor.call into an instantaneous setTimeout callback:

added: function(doc) {
    console.log("added "+doc.text);
    setTimeout(function() {
        Meteor.call('aMethod',doc.text,function(e,r){
            if(e){
                console.log("error from server: "+e);
            }else{
                console.log("response from server: "+r);
            }
        });
    },0);
}

Answer 2

Btw Tarang's answer also works when calling from a client method. Essentially I have a file in the client scope. And this file is a method definition. Inside my method definition I call a method at the server.

I was having problems because only the client stub of the server call is being called and the server method does not get called. The fix was this one:

Meteor.methods({  
    assignUserSession: function(options) {
        setTimeout(function() { // https://stackoverflow.com/questions/18645334/meteor-meteor-call-from-within-observe-callback-does-not-execute
            // Find all the base_accounts of this user and from there decide which view to prioritize.
            Meteor.call('user_base_accounts', {user_id: Meteor.userId()}, function(error,result){
                ....
                //server is then called due to logs shown in the command prompt
                ....
            });
        });
    }
});

Thanks for pointing this out!