Production GraphQL workshop

Strawberry Overview

Let's see how Strawberry works by taking a look at our current API.

import strawberry

from .podcasts.query import PodcastsQuery


@strawberry.type
class Query(PodcastsQuery):
    hello: str = strawberry.field(resolver=lambda: "Hello World!")

For the time being we'll be ignoring the imports, they are there to make the structure of the code manageable.

Let's focus on the the Query class. Every GraphQL API needs to have at least one root type, which is usually called Query. This is the entry point for fetching data in our API.

Let's break the code down, we have a class called Query, that has one field called hello, its type is str and we are using strawberry.field to add some metadata to this field.

strawberry.type

Finally we have a @strawberry.type decorator at the beginning of the class, this decorator is what transform your python class to a GraphQL type.

@strawberry.type does a few things, the most important ones are the following:

  1. it uses dataclasses.dataclass to make your class a dataclass
  2. it finds all the fields on the class and creates a GraphQL type from it

Using dataclasses.dataclass makes your class easier to use, since you'll be getting useful methods without having to write any code (for example __init__, __repr__ and __eq__)

The creation of the GraphQL type is done by mapping every python type to a GraphQL type. For example our query class will become the following GraphQL type:

type Query {
  hello: String!
}

Resolvers

When we created the class above we used strawberry.field and passed a "resolver" to our hello field. Resolvers are python functions that are called when a GraphQL field is requested.

In our example we passed resolver=lambda: "Hello World!", this means that every time we want to fetch our hello field, we'll be calling that lambda function.

Try it out!

Feel free to try to change what the lambda function does, you can return a different text or maybe add the current time to the returned value.