Custom tool class

A custom tool class defines the behavior of a Nova tool that can be instantiated.

The class for a tool is created by the Tool.register function. An execute method must be added to it to define its behavior, along with additional optional extension methods.

Within the extension methods, instance variables (like tool parameters) can be accessed.

Extension methods

Tools are specialized with extension methods that define their behavior. Every ToolClass must have an execute method that performs the tool’s tasks, and there are other extension methods that can be added for specific purposes.

Extension methods are added to the table returned from Tool.register.

Example: Defining the execute extension method. The arguments to Tool.register are omitted.

_MyTool = Tool.register{
  -- ...
}

function _MyTool:execute(input, output)
  output:add("Pass", true)
end

The following extension methods are supported.

function ToolClass:constructor()

The constructor is called on new instance of a tool.

Optional: A constructor should only be added to a tool in specific circumstances.

If a tool has this method, it will be called on the instance when the tool type is instantiated for any reason, for example due to:

• a user adding it in the Nova user interface

• a user loading a Nova configuration with instances of this tool in the initial job

• a switch of the active job to a job with instances of this tool.

A constructor is only necessary if the automated default initialization of parameters for the tool is insufficient, for example:

• to do initial (per tool instance) setup of a Crown that the execution uses

• to adapt parameters from a loaded Nova configuration saved with an older version of the tool, for backwards compatibility.

• to initialize variables that shouldn’t be saved with configurations, and therefore are not part of the tool parameters

function ToolClass:destructor()

The destructor is called when a tool instance is removed.

Optional: A destructor should only be added to a tool in specific circumstances.

If a tool has this method, it will be called on instances of this tool type when they are deleted for any reason, for example due to:

• a user deleting the tool instance in the user-interface

• a switch away from the current job

• loading a new configuration, replacing the current tool

function ToolClass:execute(input, output)

The execute extension method is called when a tool instance should perform its task.

Required: A Tool must have an execute method.

param input:

input

param output:

output

This method must be attached to a ToolClass and should implement the behavior of the tool, see the MyTool.execute example in Building plug-in tools for SICK Nova.

Methods

self:getText(label)

Used within extension methods to get the translated text for a label. See Localization for details on translation.

param label:

string The label

return:

string The text for the label in the selected language or fallback language.

Instance variables

The following properties are available on ToolClass instances. Properties give access to the parameters and thresholds interfaces, and are used within the extension methods.

self.parameters

Type: parameters

Provides access to the current values of the parameters defined in the call to Tool.register for the tool instance.

• See the parameters interface documentation for usage.

• See Parameter types for the types of parameters that can be registered.

self.thresholds

Type: thresholds

Provides access to the current thresholds for tool results for an instance of the Tool. The available thresholds are defined in the call to Tool.register.

• See the thresholds interface documentation for usage.

• See threshold types for the types of thresholds that can be registered.

Example syntax

Example definition of a tool class named “_MyTool”

local Tool = require("Nova.Tool")

 _MyTool = Tool.register{
   category="Analysis",
   results={{name="Pass", type="bool"}}
 }

 function _MyTool:execute(input, output)
   output:add("Pass", true)
 end