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by murbard2
4045 days ago
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Yes, thanks, sort of! The pattern you use is basically the one I would naturally do, but it doesn't feel "meteoritic"... the client side manipulation of the db really seems centric to the magic of it. Regarding the concurrent store, forget event about the client. You need to check whether or not the inventory has been depleted and then update the inventory, and create the client's invoice. That means blocking calls, double staged commits, and a whole lot of nasty things that have nothing to do with reactivity and everything to do with integrity. |
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In the prototyping sense, yes. I've been working with Meteor for about two years and the pattern I shared above still feels magical when you realize what it's doing in just a few minutes of work. The client-side writes are still okay. The big problem is remembering to specify the correct allow/deny rules.
The pattern above is a sort of brute force approach to saying "I'm an idiot, I'll forget to set rules, let's make this a non-issue." Of note, I recall some chatter about dropping allow/deny rules altogether in the future, so there's likely a better solution on the horizon.
> You need to check whether or not the inventory has been depleted and then update the inventory, and create the client's invoice.
This isn't as big of a problem as it's being made out to be. Really just a few lines of code, e.g.:
```
// Fetch just makes this an array instead of a Mongo cursor.
// The fields part just strips the returned object(s) back
// with only those fields + the _id of the object.
var inventoryAvailable = Inventory.find({product: productName}, {fields: {"available": 1}}).fetch();
if ( inventoryAvailable.available > 1 ) { // Call some purchase function. } else { // Throw an error back to the client. }
```
Re: the concern around race conditions between customers, Meteor could actually have a leg up on this. Because you have reactivity, if say there was only 1 of an item left, if one customer completed the purchase before another, you could throw up an overlay on the slower customers screen saying "uh oh, the last one of these just got snatched up...get on the waiting list?"
A lot of ways to skin this cat :)