Modification and extension by inheritance

In the vertical division of the project structure into Plastic Base Application and Sample Code, the extension is implemented using IEC 61131-3 inheritance. This means that the machine-specific part (Sample Code) is freely adaptable, but can build on the implemented algorithms of the Plastic Base Application.

The consistent use of inheritance for changes to the machine controller also enables updates to the Plastic Base Application to be applied directly by Beckhoff Automation.

Editing the Plastic Base Application not recommended Editing the Plastic Base Application is quite possible. However, the option of support from Beckhoff Automation in terms of adaptations and extensions is thereby forfeited. Normally, you only edit the machine-specific part (Sample Code) and use the Plastic Base Application as a library.

Concept of object-oriented programming It is recommended to deal in detail with the concept of object-oriented programming according to IEC 61131-3 in order to be able to use the advantages effectively. Further information on object-oriented programming can be found in the documentation for TwinCAT 3 PLC programming

In Plastic Application, there are a total of four cases where an inheriting class (EXTENDS) can extend, modify or remove the inherited class:

• Runtime memory in the class variable declaration
• Extension possible with EXTENDS
• Add, overwrite and extend properties or methods
• Extension possible with SUPER^. call
• Extend, modify and disable inner procedures
• Extension possible with FB_AdaptableSequence
• Extend and modify HMI parallel class
• Extending the interface and the parallel class with EXTENDS possible