Difference between revisions of "NULL KEY"
| Line 6: | Line 6: | ||
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. | ||
|examples= | |examples= | ||
<lsl> | <lsl>integer isKey(key in) { | ||
integer isKey(key in) { | |||
if(in) return 2; | if(in) return 2; | ||
return (in == NULL_KEY); | return (in == NULL_KEY); | ||
}//returns 2 if it's a valid key, 1 if it's NULL_KEY | }//returns 2 if it's a valid key, 1 if it's NULL_KEY</lsl> | ||
</lsl> | |notes=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 and that is used to assume if they are valid; this is a bad practice. LSL makes it easy to check if a key is valid, all that is required is to use it as the parameter for a conditional. So instead of <code>if(uuid != NULL_KEY)</code> use <code>if(uuid)</code>, it will only return true if it is a valid key that is not NULL_KEY. | ||
|notes= | |||
|functions= | |functions= | ||
{{LSL DefineRow||[[llAvatarOnSitTarget]]|}} | {{LSL DefineRow||[[llAvatarOnSitTarget]]|}} | ||
Revision as of 07:48, 8 July 2008
| LSL Portal | Functions | Events | Types | Operators | Constants | Flow Control | Script Library | Categorized Library | Tutorials |
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>
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 and that is used to assume if they are valid; this is a bad practice. LSL makes it easy to check if a key is valid, all that is required is to use it as the parameter for a conditional. So instead of if(uuid != NULL_KEY) use if(uuid), it will only return true if it is a valid key that is not NULL_KEY.