16 replies

How to make Service/Context generic?

I want to add a type parameter to the Context. For example, I’ll take code directly from the tutorial

import { Effect, Context } from "effect"
 
class Random extends Context.Tag("MyRandomService")<
  Random,
  { readonly next: Effect.Effect<number> }
>() {}

import { Effect, Context } from "effect"
 
class Random extends Context.Tag("MyRandomService")<
  Random,
  { readonly next: Effect.Effect<number> }
>() {}

But what if I want to parameterize the output type of

next()

next()

import { Effect, Context } from "effect"
 
class Random extends Context.Tag("MyRandomService")<
  Random,
  { readonly next: Effect.Effect<T> } // 👈 HOW??
>() {}

import { Effect, Context } from "effect"
 
class Random extends Context.Tag("MyRandomService")<
  Random,
  { readonly next: Effect.Effect<T> } // 👈 HOW??
>() {}

Guideline says avoid X/Y questions so I won’t post my attempts, but I basically tried

class Random<T>

class Random<T>

and

function<T>(){ return class …}

function<T>(){ return class …}

style but they didn’t work

Effect Community•2y ago•

16 replies

ingun37

How to make Service/Context generic?

I want to add a type parameter to the Context. For example, I’ll take code directly from the tutorial

import { Effect, Context } from "effect"
 
class Random extends Context.Tag("MyRandomService")<
  Random,
  { readonly next: Effect.Effect<number> }
>() {}

import { Effect, Context } from "effect"
 
class Random extends Context.Tag("MyRandomService")<
  Random,
  { readonly next: Effect.Effect<number> }
>() {}

But what if I want to parameterize the output type of

next()

next()

import { Effect, Context } from "effect"
 
class Random extends Context.Tag("MyRandomService")<
  Random,
  { readonly next: Effect.Effect<T> } // 👈 HOW??
>() {}

import { Effect, Context } from "effect"
 
class Random extends Context.Tag("MyRandomService")<
  Random,
  { readonly next: Effect.Effect<T> } // 👈 HOW??
>() {}

Guideline says avoid X/Y questions so I won’t post my attempts, but I basically tried

class Random<T>

class Random<T>

and

function<T>(){ return class …}

function<T>(){ return class …}

style but they didn’t work

How to make Service/Context generic?

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