akoenig

//
// This is a code example from the blog post:
//
// https://andrekoenig.de/articles/pattern-matching-in-typescript
//

import { P, match } from "ts-pattern";

type ProductWasAddedToCartEvent = Readonly<{
  type: "ProductWasAddedToCart";

akoenig

Keybase proof

I hereby claim:

• I am akoenig on github.
• I am andrekoenig (https://keybase.io/andrekoenig) on keybase.
• I have a public key ASAP9kw2P5vzONNZiY8kA4JgNR_tAq7sahvVNtBXnZ3-ewo

To claim this, I am signing this object:

akoenig

const aFieldResolver = (parent, args, context, info) => "beeeeeeeeep";

const myCustomMiddleware = async (parent, args, context, info) => {
    // Will be executed before the resolver
};

const middleware = (middlewares, resolver) => async (...args) => {
    for (const middleware of middlewares) {
        await middleware(...args);

akoenig

telemetry-consumer:
     schemaPath: ./binding/telemetry.graphql
     extensions:
+      prepare-binding:
+        output: ./binding/telemetry.ts
+        generator: binding-ts
       endpoints:
         telemetry: 'https://kqxrmk1pr7.lp.gql.zone/graphql'

akoenig

mkdir telemetry-consumer && cd $_

# Create directory for the binding
mkdir binding

# Install the `graphql-cli` locally
yarn add graphql-cli

yarn graphql init
? Enter project name (Enter to skip): telemetry-consumer

akoenig

// path: resolvers/mutation/index.ts

import { helmet } from "../helmet";

import { login } from "./login";

const Mutation = {
  login: helmet(login)
  // ...
};

akoenig

// path: resolvers/helmet.ts

import { FatalError } from "./errors/FatalError";

const helmet = (resolver) => async (...args) => {
  try {
    //
    // Try to execute the actual resolver and return
    // the result immediately.
    //

akoenig

import { GraphQLServer, Options } from "graphql-yoga";
import { formatError } from "apollo-errors";

const options: Options = {
  formatError
};

const server = new GraphQLServer({ typeDefs, resolvers })
server.start(options, () => console.log('GraphQL API is running on localhost:4000'))

akoenig

{
  "data": {},
  "errors": [
    {
      "message":"The provided credentials are invalid.",
      "name":"WrongCredentialsError",
      "time_thrown":"2018-02-14T00:40:50.954Z",
    }
  ]
}

akoenig

// path: resolvers/mutation/login/index.ts

import { WrongCredentialsError } from "./errors/WrongCredentialsError";

interface LoginInput {
  username: string;
  password: string;
}

const login = await (parent, args: LoginInput, context: Context, info) {