04_adding_arguments.md

title	summary
Adding arguments	Add arguments to your fields, queries, and mutations

Working with generic types

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[info] You are viewing docs for silverstripe/graphql 4.x. If you are using 3.x, documentation can be found in the github repository [/info]

Adding arguments

Fields can have arguments, and queries are just fields, so let's add a simple way of influencing our query response:

app/_graphql/schema.yml

  queries:
    'readCountries(limit: Int!)': '[Country]'

[hint] In the above example, the limit argument is required by making it non-nullable. If you want to be able to get an un-filtered list, you can instead allow the argument to be nullable by removing the !: 'readCountries(limit: Int)': '[Country]' [/hint]

We've provided the required argument limit to the query, which will allow us to truncate the results. Let's update the resolver accordingly.

    public static function resolveReadCountries($obj, array $args = [])
    {
        $limit = $args['limit'];
        $results = [];
        $countries = Injector::inst()->get(Locales::class)->getCountries();
        $countries = array_slice($countries, 0, $limit);
        foreach ($countries as $code => $name) {
            $results[] = [
                'code' => $code,
                'name' => $name
            ];
        }

        return $results;
    }

Now let's try our query again. This time, notice that the IDE is telling us we're missing a required argument. We need to add the argument to our query:

query {
  readCountries(limit: 5) {
    name
    code
  }
}

This works pretty well, but maybe it's a bit over the top to require the limit argument. We want to optimise performance, but we also don't want to burden the developer with tedium like this. Let's give it a default value.

app/_graphql/schema.yml

  queries:
    'readCountries(limit: Int = 20)': '[Country]'

Rebuild the schema and try the query again without adding a limit in the query. Notice that the IDE is no longer yelling at you for a limit argument, but the result list is limited to the first 20 items.

Let's take this a step further by turning this in to a proper paginated result.

Further reading

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