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We want to build a new frontend for our existing app with elements shown or hidden based on a users role.

Are there any common patterns for this? I see two ways of doing this.

  • The backend sends the user role to the fronted, the frontend knows about what roles can see what elements.
  • Or the backend knows about the elements in the frontend and gives a mapping of what should be shown or hidden.

Are there any preferences, or other ways of going about this? Either way involves coupling of the frontend and backend.

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Basically, you want to run the business logic on a client. This may be dangerous, but sometimes it's inevitable — people want to have nice dynamic reactive UI. Be aware of the following issues:

  1. Some business logic may slip into front-end and stay there. Consequences may range from inconsistent UI to dangerous security holes.

  2. Code duplication may cause discrepancy between back-end and front-end. If you are lucky to use same language on both sides, this problem can be partially mitigated — still, there will be cases when front-end does not have all required information.

  3. This may leak security-related implementation details and other users' data. Helping potential attacker is not a good idea.

Sending plain roles/permissions will cause maximum coupling. It makes more sense to send sets of flags that describe availability of operations: "CanEditOrder", "CanDeleteOrder". Just remember that if you're doing any validation on client-side, you have to to repeat it in the back-end.

(As a side note, there is one trick I found when developing CRM/ERP with lots of complex rules. Put a button somewhere, that may be activated by IT or advanced users. It calls back-end to run all possible validations in current component and return resulting errors to display in a dialog. Solves lots of "why can't I do that?".)

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