End-to-end type safety with GraphQL, Apollo, TypeScript, and React
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Buzzwords!
What are we really talking about?
Leveraging a GraphQL schema as a source of truth can elevate confidence, improve quality, and hyper charge velocity
Mike DeWitt
Director of Engineering, First Dollar
AKA: It's a bank account
What is First Dollar?
State of JS: 2020
https://2020.stateofjs.com/en-US/
State of JS: 2020
https://2020.stateofjs.com/en-US/
State of JS: 2020
https://2020.stateofjs.com/en-US/
GraphQL
- Describe your data (Schema)
- Query, mutate, or subscribe
- Ask only for what you need
Simple GraphQL Schema
type Query {
books: [Book!]!
}
type Mutation {
addBookToCart(bookId: String!): Book!
}
type Book {
id: String!
inStock: Boolean!
title: String!
author: String!
thumbnail: String!
description: String!
price: String!
}TypeScript
- Brings static typing to JavaScript
- Provides compile time errors instead of runtime errors
- TypeScript plays great with React
Book Type Safety
type Book = {
id: string
inStock: boolean
title: string
author: string
thumbnail: string
description: string
price: string
}
const myBook: Book = {
id: "fk903",
title: "Untamed",
price: "$25.99",
inStock: false,
author: "Glennon Doyle",
description: "description",
thumbnail: "https://pic.com",
}
// Valid
myBook.title.toLowerCase()
// TS Failure: Property 'salePrice' does not exist on type 'Book'
myBook.salePrice.toLowerCase()
// TS Failure: Property 'toLowerCase' does not exist on type 'boolean'.
myBook.inStock.toLowerCase()We have to define a schema for GraphQL, and we want type safety on the frontend...
https://graphql-code-generator.com/
GraphQL Code Generator
- Install and Configure
- NPM Scripts
- Import types to components
Demo #1
Thumbnail is not required, and we forgot to add price
Demo #2
We should probably write tests
currentUserProfile
- Called in 14 components
- Mocked in 8 tests
First Dollar React App
Other facts
- 37 total queries, 36 mutations
- We have a small/medium sized app
query AccountTransfers($fromDate: String, $toDate: String, $page: PageInput) {
accountTransfers(fromDate: $fromDate, toDate: $toDate, page: $page) {
transfers {
node {
id
createdAt
linkedBankAccountId
direction
amount
amountCurrency
amountForDisplay
note
contributionType
contributionYear
withdrawalCategoryCode
withdrawalExpenseDate
withdrawalReceipts {
bucket
fullPath
}
status
effectiveDate
errorCode
}
}
pageInfo {
hasNextPage
endCursor
}
}
}Demo #3
Better feedback eslint-plugin-graphql
Is your client safe to ship?
- When you deploy the production GQL server, export the schema and keep in cloud storage
- When deploying client, download latest production schema and eslint it
- This should prevent you from ever shipping clients that are querying things on your dev server that haven't been released to prod
Worth mentioning... With a Node.js backend, this same tooling can be applied, in reverse!
In closing...
Thanks! Questions?
Demo
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