Difference between revisions of "NULL KEY"
Mako Nozaki (talk | contribs) m (I think it is overkill...) |
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|type=string | |type=string | ||
|value="00000000-0000-0000-0000-000000000000" | |value="00000000-0000-0000-0000-000000000000" | ||
|desc= | |desc=<span style="color:red;">'''NULL_KEY is a [[string]].'''</span> However it is only really useful as a [[key]]. | ||
Despite fitting the syntax criteria to be a valid [[key]], when fed to a {{LSLGC|Conditional}} as a key it executes as [[FALSE]]. | Despite fitting the syntax criteria to be a valid [[key]], when fed to a {{LSLGC|Conditional}} as a key it executes as [[FALSE]]. | ||
Revision as of 04:54, 23 May 2010
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Description
Constant: string NULL_KEY = "00000000-0000-0000-0000-000000000000";The string constant NULL_KEY has the value "00000000-0000-0000-0000-000000000000"
NULL_KEY is a string. However it is only really 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
All Issues
~ Search JIRA for related Issues
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SVC-5772 | A | NULL_KEY is no longer a NULL_KEY when passed to a function |
Signature |
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string NULL_KEY = "00000000-0000-0000-0000-000000000000"; |