Variables

A hierarchy of QueryFragments can take a struct of variables. This struct must implement QueryVariables which can be derived:

#![allow(unused)]
fn main() {
#[derive(cynic::QueryVariables)]
struct FilmVariables {
    id: Option<cynic::Id>,
}
}

Using QueryVariables

To use any fields of this struct as an argument to a QueryFragment, the struct must provide a variables parameter that points to the FilmArguments struct. This allows variables to be passed in using the arguments attribute on the fields where you wish to pass them.

#![allow(unused)]
fn main() {
#[derive(cynic::QueryFragment, Debug)]
#[cynic(
    schema_path = "examples/starwars.schema.graphql",
    graphql_type = "Root",
    variables = "FilmVariables"
)]
struct FilmQuery {
    #[arguments(id: $id)]
    film: Option<Film>,
}
}

This example uses our FilmVariables at the root of the query to specify which film we want to fetch.

It's also possible to pass variables down to lower levels of the query using the same technique. Though it's worth noting that all the QueryFragments from the Root to the point that requires arguments must define the same variables in their cynic attribute. If no nested QueryFragments require any variables then it's OK to omit variables.