avoid_as

Avoid using as.

This rule has been removed as of the latest Dart releases.

Details

AVOID using as.

If you know the type is correct, use an assertion or assign to a more narrowly-typed variable (this avoids the type check in release mode; as is not compiled out in release mode). If you don’t know whether the type is correct, check using is (this avoids the exception that as raises).

BAD:

(pm as Person).firstName = 'Seth';

GOOD:

if (pm is Person)
  pm.firstName = 'Seth';

but certainly not

BAD:

try {
   (pm as Person).firstName = 'Seth';
} on CastError { }

Note that an exception is made in the case of dynamic since the cast has no performance impact.

OK:

HasScrollDirection scrollable = renderObject as dynamic;

Usage

To enable the avoid_as rule, add avoid_as under linter > rules in your analysis_options.yaml file:

linter:
  rules:
    - avoid_as