<Query> component

In this section, we will implement GraphQL Queries and integrate with the UI. With Apollo Client, you can send queries in 2 different ways.

  1. Using the query method directly and then process the response.
  2. React's render prop API

The more convenient method is to use the render prop method, where you will just pass your GraphQL query as prop and <Query /> component will fetch the data automatically and will present it in the component's render prop function.

Great! Now let's define the graphql query to be used:

Create a file called src/GraphQLQueries.re and add the following code:

// GraphQL query module for getting my todos
module GetMyTodos = [%graphql
query getMyTodos {
todos(where: { is_public: { _eq: false} }, order_by: { id: desc }) {
module GetMyTodosQuery = ReasonApollo.CreateQuery(GetMyTodos);

In the above code,

  • GetMyTodos is a query module built from plain query string using graphql_ppx. If you are coming from JS, it is analogous to wrapping the query in gql
  • GetMyTodosQuery is a typed React component that makes the GraphQL query and provides the request state and the GraphQL data in a render prop. It is similar to the <Query> component in react-apollo.

What does this query do?

The query fetches todos with a simple condition; is_public must be false. We sort the todos descending by its created_at time according to the schema. We specify which fields we need for the todos node.

The query is now ready, let's integrate it with our code.

Firstly, let us remove the sample todos.

-// sample data
-let sampleTodos = [|
- {
- id: 1,
- title: "This is private todo 1",
- is_completed: true,
- is_public: false,
- user: None,
- },
- {
- id: 2,
- title: "This is private todo 2",
- is_completed: false,
- is_public: false,
- user: None
- }

Now let us use the React Component GetMyTodosQuery to load the personal todos from the GraphQL server. We will consume the GraphQL response object from the GraphQL response instead of the sample data.

+ <GraphQLQueries.GetMyTodosQuery>
+ ...{
+ ({result}) => switch(result) {
+ | Data(data) => {
let filteredTodos =
- sampleTodos
+ data##todos
|> Array.to_list
|> List.filter((todo) => switch(todo##is_completed) {
| true => state.filter === "all" || state.filter === "complete"
| false => state.filter === "all" || state.filter === "active"
|> List.map((t) => <TodoItem todo={t} />);
// filter callback
let filterTodos = (f) => {
// return JSX
<div className="todoListWrapper">
| _ => ReasonReact.null
+ }
+ <GraphQLQueries.GetMyTodosQuery>

Woot! You have written your first GraphQL integration with ReasonReact. Easy isn't it?

How does this work?

When you wrapped your return with <GetMyTodosQuery> component, Apollo provides the render prop function with a Union type of Loading, Error(error) and Data(data). You can pattern match over the argument of the render prop and figure out the status of the GraphQL request. Currently, we are rendering data only if it matches with Data(data), in the next section, we will handle the Loading and Error states.

Data(data): A type containing the result of your GraphQL query. This will contain our actual data from the server. In our case, it will be the todo data.

Using the data prop, we are parsing the results from the server. In our query, data prop has an array todos which can be mapped over to render each TodoItem.

If you noted, there has been some client side filtering to the todos that are displayed.

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