Catch decorator in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the @Catch decorator in NestJS?

The @Catch decorator is used to define an exception filter that handles specific exceptions thrown in the application, allowing centralized error handling.

beginner

How do you specify which exceptions a filter should catch using the @Catch decorator?

You pass one or more exception classes as arguments to the @Catch decorator. The filter will only handle those exceptions.

intermediate

What method must be implemented in a class decorated with <code>@Catch</code> to handle exceptions?

The class must implement the <code>catch(exception: any, host: ArgumentsHost)</code> method, which contains the logic to handle the caught exception.

intermediate

Can the @Catch decorator be used without arguments? What does that mean?

Yes, if used without arguments, the filter will catch all exceptions, acting as a global catch-all error handler.

intermediate

How do you apply a class with the <code>@Catch</code> decorator globally in a NestJS application?

You provide the filter class in the <code>app.useGlobalFilters(new YourFilter())</code> method inside the main bootstrap function.

What does the @Catch(HttpException) decorator do?

A Catches all exceptions

B Does nothing without a catch method

C Catches exceptions except HttpException

D Catches only HttpException errors

The decorator catches only exceptions of type HttpException.

Which method handles the exception inside a class decorated with @Catch?

A catch()

B handle()

C process()

D execute()

The catch() method is required to handle exceptions.

If you want to catch all exceptions, how do you use the @Catch decorator?

A <code>@Catch(null)</code>

B <code>@Catch(AllExceptions)</code>

C <code>@Catch()</code> with no arguments

D <code>@Catch(Error)</code>

Using @Catch() without arguments catches all exceptions.

How do you register a catch filter globally in NestJS?

A Use <code>app.useGlobalFilters()</code>

B Add it to <code>providers</code> in a module

C Use <code>app.use()</code>

D Add it to <code>imports</code> in a module

Global filters are registered with app.useGlobalFilters().

What argument does the catch() method receive besides the exception?

A Request object

B ArgumentsHost object

C Response object

D Next function

The catch() method receives the exception and an ArgumentsHost to access request/response.

Explain how the @Catch decorator works in NestJS and how you create a custom exception filter.

Think about how you tell NestJS which errors to handle and where you write the handling code.

Describe the steps to apply a custom exception filter globally in a NestJS application.

Focus on how to make the filter work for the whole app, not just one controller.