This method is used for parsing of a JSON-formatted data. The parsing of the data is done in several blocks. The block-size is specified by the global parameter udiJsonMaxNumOfBytesPerCycle.
The parsing is completed if the one of the outputs q_xDone or q_xError indicates TRUE. You must cyclically call the method while the output q_xBusy is TRUE.
Depending on the data size and the specified block-size, the parsing can take several program cycles. While the parsing is in progress, no other method or property of the function block instance is processed.
If an error was detected use the properties Result and ResultMsg to obtain the result of the method.
|
Input |
Data type |
Description |
|---|---|---|
|
i_anyDataToParse |
ANY |
Assign a variable containing the JSON-formatted data. Variables of type STRING or ARRAY OF BYTE are supported. |
|
i_sJPath |
STRING [255] |
Not supported. Assign a null string. |
|
Output |
Data type |
Description |
|---|---|---|
|
q_xBusy |
BOOL |
If this output is set to TRUE, the method execution is in progress. |
|
q_xDone |
BOOL |
If this output is set to TRUE, the method execution has been completed successfully. |
|
q_xError |
BOOL |
If this output is set to TRUE, an error has been detected. For details, refer to q_etResult and q_etResultMsg. |
NOTE: For performance reasons, the validity of the input parameters of the function blocks will be verified only in the first cycle after triggering the method execution. Do not modify these values while the parsing is in progress. By executing this method, a previously detected error indicated by the corresponding properties and the information related to previous parsing operation are reset. The function block performs a basic syntax verification of the data to parse. Ensure that the data is formed according to the JSON specification.
Following example shows how to implement an asynchronous parse and to retrieve one value out of the parsed JSON-formatted string:
PROGRAM SR_Main_Async
VAR
xGetValueOutOfJsonString : BOOL;
sCity : STRING;
sJsonString : STRING[500] := '{"Library": "FileFormatUtility","Namespace": "FFU","Forward Compatible": true,"Supported Formats": ["JSON", "XML", "CSV"],"Company": "Schneider Electric","Address":{"Street": "Schneiderplatz","House Number": 1,"Postal Code": "97828","City": "Marktheidenfeld","Country": "Germany"}}';
fbJsonUtilities : FFU.FB_JsonUtilities;
xBusy : BOOL;
xDone : BOOL;
xError : BOOL;
etResult : FFU.ET_Result;
sResultMsg : STRING;
END_VAR
IF xGetValueOutOfJsonString THEN
//Parse JSON formatted string
fbJsonUtilities.ParseAsync(i_anyDataToParse := sJsonString, i_sJPath := '', q_xBusy => xBusy, q_xDone => xDone, q_xError => xError);
IF xDone THEN
xGetValueOutOfJsonString := FALSE;
//Select element containing requested value
IF NOT(fbJsonUtilities.Select(i_sJPath := '.Address.City')) THEN
//Error handling for failed Parse process.
etResult := fbJsonUtilities.Result;
sResultMsg := fbJsonUtilities.ResultMsg
RETURN;
END_IF
//Get value of item
sCity := fbJsonUtilities.ValueOfSelected;
IF fbJsonUtilities.Error THEN
//Error handling for failed Parse process.
etResult := fbJsonUtilities.Result;
sResultMsg := fbJsonUtilities.ResultMsg
RETURN;
END_IF
ELSIF xError THEN
xGetValueOutOfJsonString := FALSE;
//Error handling for failed Parse process.
etResult := fbJsonUtilities.Result;
sResultMsg := fbJsonUtilities.ResultMsg
RETURN;
END_IF
END_IF
