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Preconditions
Precondition logic is the same as it is for Text-based commands.
A list of attributes and usage is still given for people who are new to both.
There are two types of Preconditions you can use:
- PreconditionAttribute can be applied to Modules, Groups, or Commands.
- ParameterPreconditionAttribute can be applied to Parameters.
You may visit their respective API documentation to find out more.
Bundled Preconditions
@Discord.Interactions ships with several bundled Preconditions for you
to use.
- @Discord.Interactions.RequireContextAttribute
- @Discord.Interactions.RequireOwnerAttribute
- @Discord.Interactions.RequireBotPermissionAttribute
- @Discord.Interactions.RequireUserPermissionAttribute
- @Discord.Interactions.RequireNsfwAttribute
- @Discord.Interactions.RequireRoleAttribute
Using Preconditions
To use a precondition, simply apply any valid precondition candidate to
a command method signature as an attribute.
[!code-csharpPrecondition usage]
ORing Preconditions
When writing commands, you may want to allow some of them to be
executed when only some of the precondition checks are passed.
This is where the Group property of a precondition attribute comes in
handy. By assigning two or more preconditions to a group, the command
system will allow the command to be executed when one of the
precondition passes.
Example - ORing Preconditions
[!code-csharpOR Precondition]
Custom Preconditions
To write your own Precondition, create a new class that inherits from
either PreconditionAttribute or ParameterPreconditionAttribute
depending on your use.
In order for your Precondition to function, you will need to override
the CheckPermissionsAsync method.
If the context meets the required parameters, return
PreconditionResult.FromSuccess, otherwise return
PreconditionResult.FromError and include an error message if
necessary.
[!NOTE]
Visual Studio can help you implement missing members
from the abstract class by using the "Implement Abstract Class"
IntelliSense hint.