Placeholder

A placeholder in the Library Manager is a reference on a definite library version. Placeholders simplify the maintenance of library hierarchies. In the CODESYS environment there are the following places where you can define placeholders.

Device Description:

For device-dependent libraries (Depending on the runtime system version)

Library Profile:

For CODESYS features (Depending on the compiler version)

Library Support Package:

For CODESYS features (Depending on the version of the related package)

Application:

For so called “unbound” placeholders. CODESYS takes care of the correct handling of this “unbound” placeholders, which are neither defined in a device description nor in a library profile.

Note

As of and including version CODESYS SP17, the library profile is no longer supported. This means that all placeholders that are not resolved via the device description or a library support package are so-called free placeholders.

Consequent usage of placeholders allows to change libraries at a lower level of the dependencies hierarchy (e.g. update, bug-fix, …) without the need to adapt all libraries of the higher levels or to adapt the device descriptions.

For more information see also the descriptions of the various possibilities to reference a Library.

The search order is as follows:

  1. Application related “unbound” Placeholders

  2. Device Description

  3. Library Support Package

  4. Library Profile

Important

It is always possible to overwrite the resolution of a placeholder in the application context.

Note

The namespace of a library can be changed in the context of an library manager. But the name of a placeholder can not be changed and therefore it is highly recommended to select a name with a high probability that no other one will select this again.