CopyString

This method copies the value of a key into a variable of the data type STRING, which can be of any length. The method returns the length of the copied string (including null termination). If the destination buffer is too small, it is emptied by a null termination and returned as length 0.

Syntax

METHOD CopyString : UDINT
VAR_INPUT
  v    : SJsonValue;
END_VAR
VAR_IN_OUT CONSTANT
  pStr : STRING;
  nStr : UDINT;
END_VAR

Return value

Name	Type
CopyString	UDINT

Inputs

Name	Type
v	SJsonValue (note possible invalidity)

/ Inputs/outputs

Name	Type
pStr	STRING
nStr	UDINT

Sample call:

The following JSON document is to be loaded into the DOM memory:

sMessage := ' {"serialNumber":"123","batteryVoltage":"1547mV","clickType":"SINGLE"}';

The value of the key "clickType" is to be extracted and stored in a variable of data type STRING. First, the JSON document is iteratively searched for the property "clickType".

jsonDoc         := fbJson.ParseDocument(sMessage);
jsonIterator    := fbJson.MemberBegin(jsonDoc);
jsonIteratorEnd := fbJson.MemberEnd(jsonDoc);
WHILE jsonIterator <> jsonIteratorEnd DO
  sName         := fbJson.GetMemberName(jsonIterator);
  jsonValue     := fbJson.GetMemberValue(jsonIterator);
  IF sName = 'clickType' THEN
    fbJson.CopyString(jsonValue, sString, SIZEOF(sString));
  END_IF
  jsonIterator  := fbJson.NextMember(jsonIterator);
END_WHILE

After this run, the sString variable has the following content:

SINGLE