How to gather from a building?

[Noctosphere]

Hello
So yeah, well...
I'm trying to make my worker to gather a specific building.
In short, Lumber isn't in my game, it is replaced by food.
I have a building called Field, I want workers to be able to gather food (lumber) from it.
However, even if it is targeted as Tree (in combat) and its unit classification is Tree (in stat), in-game, when I order worker to gather from the Field, it says it requires to target ressources.
Does anyone know how I can make my worker to gather lumber from a building?
Thanks

EDIT : Nevermind, I wanted to make Field building owned by a player, but I think I'll rather make it a neutral building like Tree.

 

[Mechanical Man]

you can still erect a destructible where the farm is.

 

[Spellbound]

Keep an eye out for ConstructableFarm when it updates. It requires JNGP with an updated JassHelper. I haven't checked how you can customise it to be neutral, but it should be a matter of changing the spell's targeting parameters.

Alternatively, since you don't have lumber in your game, just make your Tree a destructible and all the other trees to be not-trees so a normal lumber harvesting skill will only work on the custom Tree.