AddJsonKeyValueFromSymbol
This method generates the JSON representation of a PLC data structure on an FB_JsonSaxWriter object. The method receives as its input parameters the instance of the FB_JsonSaxWriter function block, the data type name of the structure, and the address and size of the source structure instance. As a result, the FB_JsonSaxWriter instance contains a valid JSON representation of the structure. Unlike the method AddJsonValueFromSymbol(), the elements of the source structure are nested here in a JSON sub-object whose name can be specified via the input/output parameter sKey.
Syntax
METHOD AddJsonValueFromSymbol : BOOL
VAR_IN_OUT
fbWriter : FB_JsonSaxWriter;
END_VAR
VAR_IN_OUT CONSTANT
sKey : STRING;
sDatatype : STRING;
END_VAR
VAR_INPUT
nData : UDINT;
pData : PVOID;
END_VAR
VAR_OUTPUT
hrErrorCode : HRESULT;
END_VAR
Return value
Name | Type |
|---|---|
AddJsonValueFromSymbol | BOOL |
Inputs
Name | Type |
|---|---|
nData | UDINT |
pData | PVOID |
/ Inputs/Outputs
Name | Type |
|---|---|
fbWriter | FB_JsonSaxWriter |
sKey | STRING |
sDatatype | STRING |
Outputs
Name | Type |
|---|---|
hrErrorCode | HRESULT |
A complete sample of how to use this method can be found in section Tc3JsonXmlSampleJsonDataType.
Sample call:
fbJsonSaxWriter.ResetDocument()
fbJsonDataType.AddJsonKeyValueFromSymbol(fbJsonSaxWriter, 'Values','ST_Values',SIZEOF(stValues), ADR(stValues));