How to update client UI after ApplyModifier?

[sinful inlet]

I have a modifier to increase strength:

ability:ApplyDataDrivenModifier(caster, caster, "modifier_strange_amulet_activate_str", { duration = duration })    
caster:SetModifierStackCount("modifier_strange_amulet_activate_str", ability, charges)

but after item starts I should use ability or do another action to update UI and see new strength value. How should I notify client to update values from lua?

[inland inlet]

The parameters for SetModifierStackCount is modifier name, caster, stack count.

You're doing modifier name, ability, stack count. Could this be the issue?

https://moddota.com/api/#!/vscripts?search=SetModifierStackCount

Are you seeing the stacks being set?

Also: a little general tip - you should not use datadriven anymore. It's very old and barely supported

[sinful inlet]

What should I use instead?

[inland inlet]

Lua abilities. You can learn lua via the tutorial here https://github.com/Elfansoer/dota-2-lua-abilities/wiki

[sinful inlet]

I fixed the issue with adding caster:CalculateStatBonus(true) after SetModifierStackCount

[sinful inlet]

So how do you know that CDOTA_Item_DataDriven is barely supported, but CDOTA_Ability_Lua is better?

[inland inlet]

Common knowledge. DataDriven was introduced when the arcade was introduced, and ever since it got no new capabilities, no APIs, nothing. It works but apart from that it stayed in the same state for years

Additionally, DataDriven is known to be very limited. You can only do very basic things with it. Lua is much more dynamic and can do complex abilities and modifiers.