JSON Module

The json variables will be available to the process that created them from the moment they were initialized. They will not reset per message or per transaction. If you want to use the on a per message basis you should initialize them each time.

The grammar that describes the id is:

id = name(identifier)*

identifier = key | index

key = /string | /$var

index = [integer] | [$var] | []

The "[]" index represents appending to the array. It should only be used when trying to set a value and not when trying to get one.

Negative indexes can be used to access an array starting from the end. So "[-1]" signifies the last element.

IMPORTANT: The id strictly complies to this grammar. You should be careful when using spaces because they will NOT be ignored. This was done to allow keys that contain spaces.

Variables can be used as indexes or keys. Variables that will be used as indexes must contain integer values. Variables that will be used as keys should contain string values.

Trying to get a value from a non-existing path (key or value) will return the NULL value and notice messages will be placed in the log describing the value of the json and the path used.

Trying to replace or insert a value in a non-existing path will cause an error in setting the value and notice messages will be printed in the log describing the value of the json and the path used

...
$json(obj1/key) = "value"; #replace or insert the (key,value)
			   #pair into the json object;
			   
$json(matrix1[1][2]) = 1;  #replace the element at index 2 in the element
			   #at index 1 in an array

xlog("$json(name/key1[0][-1]/key2)"); # a more complex example

...
		

...

$json(ar1) := "[1,2,3,4]";

$var(i) = 0;

while( $json(ar1[$var(i)]) )
{

	#print each value
	xlog("Found:[$json(ar1[$var(i)])]\n");

	#increment each value
	$json(ar1[$var(i)])  = $json(ar1[$var(i)]) + 1 ;

	$var(i) = $var(i) + 1;

}


...
		

Dynamic traversal of a JSON object or array is possible by using a for each statement, similarly to the indexed pseudo variables iteration. However, note that indexing the $json variable is not supported in any other statements (this refers to indexing the entire variable and not to the indexes accepted in the grammar of the id).

In order to explicitly iterate over a JSON object keys or values, you can use the .keys or .values suffix for the path specified in the id.

...
$json(foo) := "{\"a\": 1, \"b\": 2, \"c\": 3}";
for ($var(k) in $(json(foo.keys)[*]))
    xlog("$var(k) ");
...
		

...
$json(foo) := "{\"a\": 1, \"b\": 2, \"c\": 3}";
for ($var(v) in $(json(foo.values)[*]))
    xlog("$var(v) ");

# equivalent to:

$json(foo) := "{\"a\": 1, \"b\": 2, \"c\": 3}";
for ($var(v) in $(json(foo)[*]))
    xlog("$var(v) ");
...
		

...
$json(foo) := "[1, 2, 3]";
for ($var(v) in $(json(foo)[*]))
    xlog("$var(v) ");
...
		

If the value specified by the id is an integer it will be returned as an integer value.

If the value specified by the id is a string it will be returned as a string.

If the value specified by the id is any other type of json ( null, boolean, object, array ) the serialized version of the object will be returned as a string value. Using this and the ":=" operator you can duplicate json objects and put them in other json objects ( for string or integer you may use the "=" operator).

If the id does not exist a NULL value will be returned.

There are 2 operators available for this variable.

...
$json(array1[]) = 1;
...
			

...
$json(array1[-1]) = NULL;
...
			

...
$json(object1/some_key) = "some_value";
...
			

...
$json(array1) := "[]";
...
			

...
$json(array1[]) := "null";
$json(array1[]) := "true";
$json(array1[]) := "false";
...
			

...

$json(array) := "[1,2,3]";
$json(object) := "{}";
$json(object/array) := $json(array) ;
...