Nodes (Functions)
Last updated
Last updated
Nodes are the key building blocks for any kind of application logic within Heisenware. They can perform a wide range of actions, including:
Fetching and sending data
Processing and manipulating data
Creating objects
Creating and managing database tables
There are different types of functions with different properties and origins.
Static functions are standard and don't have any context or state, meaning that each of these functions is independent and does not rely on any previous information.
Object functions, also referred to as member functions, are the actions an is able to perform. As they always belong to a specific object, they have context and can include previous information. In order to use an object function, you need to create an object using a create
function first.
Custom functions can perform any action and generally behave like either static or object functions. They can be used by integrating custom code with the . This implies that these functions are not inherently part of the App Builder, but rather extend its functionality.
Each function has a status indicator showing its condition. The status indicator, a colored circle, can be found right next to the function handler. The status can be:
Green: everything okay
Red: an exception or error has occurred
Gray: function not available or offline
Blue: function execution takes very long to finish (> 2 seconds)
Yellow: the underlying object of this function does not exist (yet)
Hover above the indicator to get details about the function's condition.
Built-in functions provide documentation. Hover above the function name to read it.
Functions added via the Code Adapter can automatically provide documentation if the original code has been documented properly with block comments.
Extensions allow on-the-fly data processing for function output. There are four extensions:
To add a function to an app:
Search the function in the functions panel.
Drag and drop it to the desired section within the logic board.
That's it. You can now start to configure and link the function.
Each part of a function, including extensions, can be configured and linked separately, allowing for maximum flexibility and almost limitless data processing options. Linking possibilities include:
Application logic to user interface
Function to page or subpage
Application logic to application logic
Function to function
Function with same function
Function to file
To see existing links, hover above one part of a function. Any existing link to and from this part is indicated by a light shadow within another function. Links to widgets are indicated by a border around the widget. Additionally, the status lamp of the linked function will glow yellow and next to the each section, the number of linked functions in the respective section is indicated.
When creating apps with many functions, it is always helpful to comment functions so that it is easier to understand what action a particular function performs. To comment a function:
Right-click on the function name.
Click Comment
in the context menu.
Add a comment.
To change a comment, click on the comment and start typing.
To move a function to a new position, drag and drop it with its handle icon. You can only move functions within the same section. The position of a function does not affect its functionality and links.
To delete a function:
Right-click on the function name.
Click Delete
in the context menu.
When deleting a function, its links and configuration will be deleted with it. This action can't be undone.
Typically, a function consists of one or more , a , and an . In some cases, for example when using a read function to fetch sensor data, the function does not need an input argument to work properly.
: Allows modifying data with JavaScript and JSONata.
: Enables condition-based interruption or continuation of flows using JavaScript.
: Records data in InfluxDB.
: Enables processing of exceptions thrown by a function.
Function to and vice versa
To create a link, drag and drop the part of a function onto the item you want to link it to. When linking to the user interface, you first select the and then drag and drop the relevant part of the function onto it.
Flows consist of chained functions where data or data serves as an for subsequent functions. The creation of flows involves linking functions together. Flows are typically triggered by the update or change of output data, automatically initiating a sequence of connected functions. within flows act as switches, altering the flow's direction based on the output data. They can interrupt or continue flows in a specific direction depending on the specified conditions.
Application logic and user interface communicate by connecting function , or with . Through this connection, functions can both set and receive widget properties. The link between a widget and the part of the function determines the direction of data exchange, specifying which data or events are transferred.