Constant NOOP 

pub const NOOP: FunctionDescriptor;

Does nothing and returns a successful Unit result; useful as a default zero-argument callback.

It is a concrete function value, so it can be stored in Button.action without a string callback name or a host effect.

Signature

func noop() -> Res[Unit, DataError]

Default action

noop is assignable to a zero-argument recoverable callback.

let action: func() -> Res[Unit, DataError] = noop;
action()?;