# Constants Use constant rules when the boundary is best described by a framework or library constant. ```ruby models.cannot_reference_constants "ActionController", "ActionView" ``` Rule id: `constants.forbid` This fails when a file in the component references the constant or anything under it. For component-to-component boundaries, prefer [dependency rules](/archspec/rules/dependencies/).

Constants

Use constant rules when the boundary is best described by a framework or library constant.

Rule id: constants.forbid

This fails when a file in the component references the constant or anything under it.

For component-to-component boundaries, prefer dependency rules.