NULL KEY

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/LSL

NULL_KEY

Description

Constant: string NULL_KEY = "00000000-0000-0000-0000-000000000000";

The string constant NULL_KEY has the value "00000000-0000-0000-0000-000000000000"

While technically a string constant, it is only useful as a key.

Despite fitting the syntax criteria to be a valid key, when fed to a Conditional as a key it executes as FALSE.

Caveats

Related Articles

Functions

•	llAvatarOnSitTarget
•	llDetectedKey
•	llGetNotecardLine
•	llGetLandOwnerAt
•	llGetPermissionsKey
•	llGetTexture
•	llListen

Events

•

attach

Examples

<lsl>integer isKey(key in) {

   if(in) return 2;
   return (in == NULL_KEY);

}//returns 2 if it's a valid key, 1 if it's NULL_KEY</lsl> <lsl>// NULL_KEY itself is evaluated as FALSE only when it is casted as a key. default {

   state_entry() {
       if (NULL_KEY) { llOwnerSay("NULL_KEY is TRUE");  }// Correct.
       else          { llOwnerSay("NULL_KEY is FALSE"); }// Never.
       
       if ((key) NULL_KEY) { llOwnerSay("Casted NULL_KEY is TRUE");  }// Never.
       else                { llOwnerSay("Casted NULL_KEY is FALSE"); }// Correct.
   }

}</lsl>

Notes

Like any LSO string constants longer then 3 characters and used in multiple places in the code, they should be stored in a global variable. The result will be a considerable memory savings. This does not apply to scripts compiled with Mono. See LSL Constants vs Globals for more information about this and examples.
In most situations NULL_KEY isn't needed; an empty string ("") will suffice. To take advantage of this certain practices have to be avoided. In many applications keys are checked against NULL_KEY to determine if they are valid; this is bad practice.

LSL makes it easy to check if a key is valid. Simply use the key as the parameter for a conditional.

That is, instead of if(uuid != NULL_KEY), use if(uuid). if(uuid) will only return TRUE if it is a valid key that is also not a null key.

Deep Notes

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Signature
string NULL_KEY = "00000000-0000-0000-0000-000000000000";