How do you add schema middleware (hooks) and instance methods in NestJS Mongoose?

Add pre/post hooks and instance methods directly on the schema object returned by SchemaFactory.createForClass() before it is registered in the module. Pre-save hooks are the standard location for password hashing. Extend the document type with a TypeScript interface to get typed access to instance methods.

Pre-save hook, instance method, and virtual

Mongoose hooks and methods rules:

Apply hooks and methods to the schema object before registering it in MongooseModule.forFeature().
Use regular functions (not arrow functions) in hooks and methods — arrow functions do not bind this.
this.isModified('field') in pre-save hooks avoids rehashing an already-hashed password.
Extend the document interface to get TypeScript typing for instance methods.
Virtuals are not included in JSON output by default — set { toJSON: { virtuals: true } } on the schema.

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How do you add schema middleware (hooks) and instance methods in NestJS Mongoose?

Pre-save hook, instance method, and virtual

Mongoose hooks and methods rules:

Apply hooks and methods to the schema object before registering it in MongooseModule.forFeature().
Use regular functions (not arrow functions) in hooks and methods — arrow functions do not bind this.
this.isModified('field') in pre-save hooks avoids rehashing an already-hashed password.
Extend the document interface to get TypeScript typing for instance methods.
Virtuals are not included in JSON output by default — set { toJSON: { virtuals: true } } on the schema.