Minecraft – Inventory Slot Detection

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In Sethbling's snapshot 14w07b video, he uses a command block to give him jump boost while he is wearing his Boots of Leaping.

I am trying to imitate this for a multiplayer map I am making. Wearing golden boots called "Stealth Boots" is supposed to give that player invisibility. I am using this command:

/effect @a[Inventory:[{Slot:100b,tag:{display:{Name:"Stealth Boots"}}}]] 14 30000 200

I do know that in the video he is using a /testfor command, but since I'm making a multiplayer map in order to use this technique I'd have to define a scoreboard variable for each player – and even then, the players would be finite. Thus, I want to be able to use the command DIRECTLY.

When I use that command, it either says "That player cannot be found" or "The entity UUID provided is in an invalid format" – the former of which I'm familiar with; the later I've barely ever seen before.

So, my method doesn't seem to work – how do I fix it?

Best Answer

As of 14w10c, this is possible using scoreboard values.

First, you need to set up a dummy scoreboard variable. I used "sneaky" as my variable, but you can really use whatever you want (as long as you change the commands as appropriate). To set this up, you just need to use the command /scoreboard objectives add sneaky dummy. You only need to do this once.

I had to set up the command blocks in a very specific pattern for them to work, as shown:

Command block setup

I think this has something to do with how command blocks handle firing off "simultaneously". The comparator in this setup is in subtraction mode, creating a "comparator clock" which pulses very quickly.

The command blocks on the left are your scoreboard related commands. The one on the bottom left sets "sneaky" to 0 for all players:

/scoreboard players set @a sneaky 0

The command block on the top left sets "sneaky" to 1 for all players with the stealth boots equipped:

/scoreboard players set @a sneaky 1 {Inventory:[{Slot:100b,tag:{display:{Name:"Stealth Boots"}}}]}

The command blocks on the right are your effect commands. They give players the invisibility effect, or take it away, as appropriate. The one on the bottom clears the invisibility effect from all players without the stealth boots:

/effect @a[score_sneaky=0] 14 0 0

The top one gives the invisibility effect to all players with the stealth boots:

/effect @a[score_sneaky_min=1] 14 30000

Related Solutions

Minecraft – Select players with empty inventory slot

We're going to use the fact that you are checking for boots to our advantage, since boots are not stackable and there can normally only be 0 or 1 item in that slot.

Set up a dummy scoreboard objective called boots and run the following two Commands on a setblock/fill clock.

scoreboard players set @a boots 0
scoreboard players set @a boots 1 {Inventory:[{Slot:100b,Count:1b}]}

For example, you can use a setup like this one.

Full setup

This will set the boots score to 1 for everyone having exactly one item in their foot inventory slots. From there, you can use @a[score_boots=0] to detect barefoot players.

A general answer for every inventory slot is more difficult, because checking for Count:0b does not work, since for the game, "no item" is different from "0 items of any kind".

Minecraft – Entity Inventory Slot Detection

The error you are getting simply means that no entity can be found that matches your target selector. Basically, the target selector then returns NULL, which is not a valid UUID, hence the message.

As to why your command fails, you have confused target selector arguments with data tags, which represent NBT data. While some target selector arguments duplicate checking for NBT data, for example [name=Bob] <-> {CustomName:Bob}, these are different things. In particular, some commands are unable to check NBT data altogether, such as execute (scoreboard does, and is therefore a common very workaround to turn NBT into a target selector).

Luckily, testfor is able to check matching NBT data as an optional argument:

testfor <player> [dataTag]

There is another issue with your command, which is that the Inventory data tag is only valid for players. Mobs have an Equipment tag instead, which is a list of 5 Item tags (Hand, Feet, Legs, Chest, Head). Due to Minecraft's partial tag matching, you can leave the other 4 tags empty:

In order to make your command work, you should use

/testfor @e[name=Skeletor] {Equipment:[{},{},{},{},{id:minecraft:golden_helmet}]}

For reasons unknown to me, you need to use the full item id, including the minecraft: prefix. Using only id:golden_helmet does not work.

Best Answer

Related Solutions

Minecraft – Select players with empty inventory slot

Minecraft – Entity Inventory Slot Detection

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