LlJsonGetValue

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/LSL

JsonGetValue

llJsonGetValue

Summary

Function: string llJsonGetValue( string json, list specifiers );

0.0	Forced Delay
10.0	Energy

Gets the value indicated by specifiers from the json string.
Returns a string made by parsing json, a string representing json and traversing as specified by specifiers.

• string	json
• list	specifiers

When the input is invalid or no result can be found this function returns JSON_INVALID. If the result is null the function returns JSON_NULL.

Specification

See Json_usage_in_LSL

Caveats

llJsonGetValue() is significantly slower than reading a value from a list with llList2String(). And llJsonGetValue() gets exponentially worse for with longer lists/arrays.

Reading all single values from a Json with llJsonGetValue() takes roughly 0.5*values times as long as reading all single values from a list with llList2String().

• This means; a Json with 10 values takes 2x as long to read an average value from, than reading an average value from a list with 10 entries.
• This means; a Json with 100 values takes 20x as long to read an average value from, than reading an average value from a list with 100 entries.

"average values" because it appears that reading a right value with a high specifier# from a Json takes longer than reading a value with a low specifier# from a Json. The "left values" get read faster, but still read slower than any from a list, where value# does not seem to matter at all for reading speed.

Examples

<lsl> JGetValTest(){

   string j="[[1,2],[4,5,6]]";            //JSON may be written directly as a string like this in sl.
   string k;                              //this will change with each command below;
   k=llJsonGetValue(j,[]);                //returns the whole array of a JSON. It might just be one entry or a whole nested array or whole nested object.
   //if "j" is a single JSON_STRING, this may return what the string represents as a JSON within a string; a JSON_NUMBER , JSON_TRUE, TRUE ...

   k=llJsonGetValue("\"3.14\"",[]);       //==k="3,14" (float that was stored in a JSON_STRING within a JSON. and not as JSON_NUMBER for no good reason)
   k=llJsonGetValue("\"TRUE\""     ,[]);  //==k="TRUE" (the value was stored as a JSON_STRING and is thus returned verbatim)
   k=llJsonGetValue(j,[0]);               //returns only the first entry (at offset 0). An entry can be any JSON type,
                                          //each entry being separated by a comma from other entries.
                                          //array and object entries may contain multiple comma separated entries within them.
   k=llJsonGetValue(j,[1]);//returns only the second entry... (all the above still applies) k="[4,5,6]";
   k=llJsonGetValue(llJsonGetValue(j,[1]),[2]);
                                          //instead of getting an entry from "j" we get a sub-entry from llJsonGetValue(j,[1]), 
                                          //assuming the sub-entry is a JSON_ARRAY. It returns the 3rd sub-entry of the second entry, 
                                          //that is an array with 3 entries. it would make k="6". 
                                          //it will return JSON_INVALID if there is no 3rd entry in the 2nd sub-array,
                                          //or no 2nd sub-array.
   k=llJsonGetValue(j,[1,2]);             //Shorter way to do the same as in the previous example.
   k=llJsonGetValue("true",[]);           //Sets k to JSON_TRUE
   k=llJsonGetValue("True",[]);           //Sets k to JSON_INVALID because the JSON constant for 'true' is all lower case
   k=llJsonGetValue("TRUE",[]);           //Sets k to JSON_INVALID because the JSON constant for 'true' is all lower case
   k=llJsonGetValue(JSON_TRUE,[]);        //Sets k to JSON_INVALID. The JSON_xxxx constants are not supposed to be part of
                                          // a JSON string, just values to test against.

} </lsl>

See also llJsonValueType for examples where the value type is checked before getting the value as that type.

See Also

Functions

•	llList2Json
•	llJson2List
•	llJsonSetValue
•	llJsonValueType

Articles

•

Typecast

Deep Notes

History

Date of Release 20/05/2013

Signature
function string llJsonGetValue( string json, list specifiers );