FB_JsonDomParser

This function block is derived from the same internal function block as FB_JsonDynDomParser and thus offers the same interface.

The two derived function blocks differ only in their internal memory management. FB_JsonDomParser is optimized for the fast and efficient parsing and creation of JSON documents that are only changed a little. The function block FB_JsonDynDomParser is recommended for JSON documents to which many changes are made (e.g. the cyclic changing of a specific value in the JSON document).

WARNING

Use of router memory

The function block occupies new memory with each change, e.g. with the methods SetObject() or SetJson(). As a result, the amount of router memory used can grow enormously after repeated actions. This allocated memory is only released again by calling the NewDocument() or ParseDocument() methods.

	Strings in UTF-8 format The variables of type STRING used here are based on the UTF-8 format. This STRING formatting is common for MQTT communication as well as for JSON documents. In order to be able to receive special characters and texts from a wide range of languages, the character set in the Tc3_IotBase and Tc3_JsonXml libraries is not limited to the typical character set of the data type STRING. Instead, the Unicode character set in UTF-8 format is used in conjunction with the data type STRING. If the ASCII character set is used, there is no difference between the typical formatting of a STRING and the UTF-8 formatting of a STRING. Further information on the UTF-8 STRING format and available display and conversion options can be found in the documentation for the Tc2_Utilities PLC library.

Syntax

FUNCTION_BLOCK FB_JsonDomParser
VAR_OUTPUT
  initStatus     : HRESULT;
END_VAR

Outputs

Name	Type
initStatus	HRESULT

Methods

Name	Description
AddArrayMember	Adds an Array member to a JSON object.
AddBase64Member	Adds a Base64 member to a JSON object.
AddBoolMember	Adds a Bool member to a JSON object.
AddDateTimeMember	Adds a DateTime member to a JSON object.
AddDcTimeMember	Adds a DcTime member to a JSON object.
AddDoubleMember	Adds a Double member to a JSON object.
AddFileTimeMember	Adds a FileTime member to a JSON object.
AddHexBinaryMember	Adds a HexBinary member to a JSON object.
AddInt64Member	Adds an Int64 member to a JSON object.
AddIntMember	Adds an Int member to a JSON object.
AddJsonMember	Adds a JSON member to a JSON object.
AddNullMember	Adds a NULL member to a JSON object.
AddObjectMember	Adds an Object member to a JSON object.
AddStringMember	Adds a String member to a JSON object.
AddUint64Member	Adds an UInt64 member to a JSON object.
AddUintMember	Adds an UInt member to a JSON object.
ArrayBegin	Returns the first element of an array.
ArrayEnd	Returns the last element of an array.
ClearArray	Deletes the contents of an array.
CopyDocument	Copies the contents of the DOM memory into a variable of data type STRING.
CopyJson	Extracts a JSON object from a key and stores it in a variable of data type STRING.
CopyString	Copies the value of a key into a variable of data type STRING.
FindMember	Searches for a specific property in a JSON document.
FindMemberPath	Searches for a specific property in a JSON document (path-specific).
GetArraySize	Returns the number of elements in a JSON array.
GetArrayValue	Returns the value at the current iterator position of an array.
GetArrayValueByIdx	Returns the value of an array at a specified index.
GetBase64	Decodes a Base64 value from a JSON property.
GetBool	Returns the value of a property of the data type BOOL.
GetDateTime	Returns the value of a property of the data type DATE_AND_TIME.
GetDcTime	Returns the value of a property of the data type DCTIME.
GetDocument	Returns the content of the DOM memory as the data type STRING(255).
GetDocumentLength	Returns the length of a JSON document in the DOM memory.
GetDocumentRoot	Returns the root node of a JSON document in the DOM memory.
GetDouble	Returns the value of a property of the data type LREAL.
GetFileTime	Returns the value of a property of the data type DCTIME.
GetHexBinary	Decodes the HexBinary content of a property and writes it to a certain memory address,
GetInt	Returns the value of a property of the data type DINT.
GetInt64	Returns the value of a property of the data type LINT.
GetJson	Returns the value of a property of the data type STRING(255).
GetJsonLength	Returns the length of a property if this is a JSON document.
GetMaxDecimalPlaces	Returns the current setting for MaxDecimalPlaces.
GetMemberName	Returns the name of a JSON property member at the position of the current iterator,
GetMemberValue	Returns the value of a JSON property member at the position of the current iterator,
GetString	Returns the value of a property of the data type STRING(255).
GetStringLength	Returns the length of a property if its value is a string.
GetType	Returns the type of a property value.
GetUint	Returns the value of a property of the data type UDINT.
GetUint64	Returns the value of a property of the data type ULINT.
HasMember	Checks whether a certain property is present in the DOM memory.
IsArray	Checks whether a given property is an array.
IsBase64	Checks whether the value of a given property is of the data type Base64.
IsBool	Checks whether the value of a given property is of the data type BOOL.
IsDouble	Checks whether the value of a given property is of the data type Double (PLC: LREAL).
IsFalse	Checks whether the value of a given property is FALSE.
IsHexBinary	Checks whether the value of a property is in the HexBinary format.
IsInt	Checks whether the value of a given property is of the data type Integer (PLC: DINT) .
IsInt64	Checks whether the value of a given property is of the data type LINT.
IsISO8601TimeFormat	Checks whether the value of a given property has a time format according to ISO8601.
IsNull	Checks whether the value of a given property is NULL.
IsNumber	Checks whether the value of a given property is a numerical value.
IsObject	Checks whether the given property is a further JSON object.
IsString	Checks whether the value of a given property is of the data type STRING.
IsTrue	Checks whether the value of a given property is TRUE.
IsUint	Checks whether the value of a given property is of the data type UDINT.
IsUint64	Checks whether the value of a given property is of the data type ULINT.
LoadDocumentFromFile	Loads a JSON document from a file.
MemberBegin	Returns the first child element below a JSON property.
MemberEnd	Returns the last child element below a JSON property.
NewDocument	Generates a new empty JSON document in the DOM memory.
NextArray	Returns the next element in an array.
NextMember	Returns the next property in a JSON document.
ParseDocument	Loads a JSON object into the DOM memory for further processing.
PopbackValue	Deletes the element at the end of an array.
PushbackBase64Value	Appends a Base64 value to the end of an array.
PushbackBoolValue	Appends a Base64 value to the end of an array.
PushbackDateTimeValue	Appends a value of the data type DATE_AND_TIME to the end of an array.
PushbackDcTimeValue	Appends a value of the data type DCTIME to the end of an array.
PushbackDoubleValue	Appends a value of the data type Double to the end of an array.
PushbackFileTimeValue	Appends a value of the data type FILETIME to the end of an array.
PushbackHexBinaryValue	This method appends a HexBinary-coded value to the end of an array.
PushbackInt64Value	Appends a value of the data type Int64 to the end of an array.
PushbackIntValue	Appends a value of the data type INT to the end of an array.
PushbackJsonValue	Appends a JSON document to the end of an array.
PushbackNullValue	Appends a NULL value to the end of an array.
PushbackStringValue	Appends a value of the data type String to the end of an array.
PushbackUint64Value	Appends a value of the data type UInt64 to the end of an array.
PushbackUintValue	Appends a value of the data type UInt to the end of an array.
RemoveAllMembers	Removes all child elements from a given property.
RemoveArray	Deletes the value of the current array iterator.
RemoveMember	Deletes the property at the current iterator.
RemoveMemberByName	Removes a child element from a given property.
SaveDocumentToFile	Saves a JSON document in a file.
SetArray	Sets the value of a property to the type "Array".
SetBase64	Sets the value of a property to a Base64-coded value.
SetBool	Sets the value of a property to a value of the data type BOOL.
SetDateTime	Sets the value of a property to a value of the data type DATE_AND_TIME.
SetDcTime	Sets the value of a property to a value of the data type DCTIME.
SetDouble	Sets the value of a property to a value of the data type Double.
SetFileTime	Sets the value of a property to a value of the data type FILETIME.
SetHexBinary	Sets the value of a property to a HexBinary-coded value.
SetInt	Sets the value of a property to a value of the data type INT
SetInt64	Sets the value of a property to a value of the data type Int64.
SetJson	Inserts a further JSON document into the value of a property.
SetMaxDecimalPlaces	Sets the current setting for MaxDecimalPlaces.
SetNull	Sets the value of a property to the value NULL.
SetObject	Sets the value of a property to the type "Object".
SetString	Sets the value of a property to a value of the data type STRING.
SetUint	Sets the value of a property to a value of the data type UInt.
SetUint64	Sets the value of a property to a value of the data type UInt64.

Requirements

TwinCAT version	Hardware	Libraries to be integrated
TwinCAT 3.1, Build 4022	x86, x64, ARM	Tc3_JsonXml

Further Information