Factorio Forums

TL;DR

If a train arrives at a station because of an interrupt with wildcard, there should be an option to read the wildcard instantiation from the station

What?

In the train station circuit GUI, there should be a checkbox that says "Read wildcard condition"
If a train arrives at the station due to an interrupt with a X wildcard condition, the station will output the following for as long as the train is stopped there:
- item wildcard: a signal referring to the item that triggered the interrupt with the count of the item
- fluid wildcard: a signal referring to the fluid that triggered the interrupt with the quantity of the fluid
- signal wildcard: the same exact signal with the same exact value
- fuel wildcard: a signal with fuel count

Why?

Thanks to wildcards, it's very easy and satisfying to design a supply-based train network - where train gets an item and then figures out where it should go. It's way harder to implement a demand-based system where trains are dispatched to fetch a specific item.
Reading wildcards would give us a tool for implementing such systems without implementing global circuit networks. It would also give trains more uses that right now seem to be monopolized by bots (like unloading landing pads)

Examples:
1. On Fulgora, you are building independent outposts dedicated to manufacturing and you're tired of trying to connect logistics networks together, so you consider each outpost having its own network. You could resupply these networks via a train, but instead of having the train carrying all the items needed by default, you can have it empty by default and only bring in items the logistic network demands.

2. On Nauvis, you could unload the landing pod with a train. Train gets dispatched with an electromagnetic science wildcard, arrives at the stop next to the landing pad and thanks to the signal emitted from the station, all inserter filters are set to electromagnetic science only. Setting filters based on wildcard probably would have lots of applications.

3. You could implement a universal manufacturing hub with trains. Product X is requested, X's ingredients are sent to a train station and a train can fetch the exact quantity of each ingredient via the signal wildcard.