Essential typing techniques required for manipulating data retrieved from GraphQL

My headless CMS is responsible for generating all types in my GraphQL schema.

Upon querying, I receive a result that contains an array which I can manipulate.

However, when attempting to use filter, map, or find methods on the returned array, an error message stating 'Property 'filter/map/find' does not exist on type 'TypeName'' is received.

To resolve this, a quick fix through Visual Studio can be applied, but it generates the types in an automatically generated file. Alternatively, I extended the types in a separate file and found success.

import { DataEntity } from './__generated__/graphql'

interface DataEntityWithMethods extends DataEntity {
    filter(arg0?: (grouping: DataEntity) => DataEntity): unknown
    find(arg0?: (group: DataEntity) => boolean): unknown
    map(arg0?: (group: DataEntity) => void): unknown
}

export type { DataEntityWithMethods }

Though effective, I question if this is the best approach. It seems odd that I need to manually add default JavaScript methods to the created types.

Does TypeScript typically function in this manner?

Answer №1

Absolutely not!

Ensuring a variable containing an array is properly typed in TypeScript requires adding [] at the end to specify that it is indeed an array and not just an Object.

For example:

let info: InfoEntity[]

By doing this, there is no need to declare any additional methods for the object.

It's crucial to be aware that TypeScript may not initially detect this issue and provide a quick fix that does not accurately resolve the problem.

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