You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.Dismiss alert
{{ message }}
This repository has been archived by the owner on Jul 16, 2024. It is now read-only.
The proposed flatMapError function would take an effect self and a mapping function fn that transforms the error type E to a new effect. The function signature can be either:
The key takeaway is that the flatMapError function allows you to handle errors from an effect and transform them into a new effect. This can be useful for error recovery or for chaining effects that may produce different error types.
Example article
Proposing a Effect.flatMapError Function
The Effect.flatMapError function is a proposed addition to the Effect-TS ecosystem. It allows you to handle errors in a more flexible way by providing a mapping function that transforms the error type of an effect.
Function Signature
The function signature of Effect.flatMapError is as follows:
This function takes an effect self with an error type E, and a mapping function fn that takes an error of type E and returns a new effect with an error type E2. The resulting effect has the same success type A as the original effect.
Example Usage
Here's an example of how you can use Effect.flatMapError:
import{Effect}from'@effect/io'// An effect that may fail with an errorconsteffect: Effect<unknown,string,number>=Effect.fail('Oops!')// A mapping function that transforms the error typeconstmappingFn=(error: string)=>Effect.succeed(error.length)// Using flatMapError to handle the errorconstresult=Effect.flatMapError(effect,mappingFn)// Running the effect and handling the resultresult.run().then(console.log)// Output: 5
In this example, the effect can fail with an error of type string. We define a mapping function mappingFn that takes the error message and returns a new effect that succeeds with the length of the error message. We use Effect.flatMapError to apply the mapping function to the original effect, resulting in a new effect with the transformed error type. Finally, we run the effect and handle the result.
Handling Eventually Raised Errors
One question that arises is how Effect.flatMapError should handle eventually raised errors from the effect returned by the mapping function. One approach is to force the effect to never raise errors by using never as the error type. This ensures that any errors raised by the mapping function are treated as defects and cause the effect to fail.
In this example, the mapping function mappingFn returns an effect that fails with a new error message. Since we use never as the error type for the effect returned by mappingFn, any errors raised by that effect are treated as defects and cause the overall effect to fail.
Conclusion
The proposed Effect.flatMapError function provides a convenient way to handle errors in a flexible manner by allowing you to transform the error type of an effect. This can be useful in scenarios where you need to handle errors in a specific way or perform additional computations based on the error.
Summary
The proposed
flatMapError
function would take an effectself
and a mapping functionfn
that transforms the error typeE
to a new effect. The function signature can be either:or
The key takeaway is that the
flatMapError
function allows you to handle errors from an effect and transform them into a new effect. This can be useful for error recovery or for chaining effects that may produce different error types.Example article
Proposing a
Effect.flatMapError
FunctionThe
Effect.flatMapError
function is a proposed addition to the Effect-TS ecosystem. It allows you to handle errors in a more flexible way by providing a mapping function that transforms the error type of an effect.Function Signature
The function signature of
Effect.flatMapError
is as follows:This function takes an effect
self
with an error typeE
, and a mapping functionfn
that takes an error of typeE
and returns a new effect with an error typeE2
. The resulting effect has the same success typeA
as the original effect.Example Usage
Here's an example of how you can use
Effect.flatMapError
:In this example, the
effect
can fail with an error of typestring
. We define a mapping functionmappingFn
that takes the error message and returns a new effect that succeeds with the length of the error message. We useEffect.flatMapError
to apply the mapping function to the original effect, resulting in a new effect with the transformed error type. Finally, we run the effect and handle the result.Handling Eventually Raised Errors
One question that arises is how
Effect.flatMapError
should handle eventually raised errors from the effect returned by the mapping function. One approach is to force the effect to never raise errors by usingnever
as the error type. This ensures that any errors raised by the mapping function are treated as defects and cause the effect to fail.In this example, the mapping function
mappingFn
returns an effect that fails with a new error message. Since we usenever
as the error type for the effect returned bymappingFn
, any errors raised by that effect are treated as defects and cause the overall effect to fail.Conclusion
The proposed
Effect.flatMapError
function provides a convenient way to handle errors in a flexible manner by allowing you to transform the error type of an effect. This can be useful in scenarios where you need to handle errors in a specific way or perform additional computations based on the error.Discord thread
https://discord.com/channels/795981131316985866/1144164954526715964
The text was updated successfully, but these errors were encountered: