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title | summary |
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Adding pagination | Add the pagination plugin to a generic query |
Working with generic types
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Adding pagination
We've created a simple generic query for our Country
type called readCounties
that takes a limit
argument.
query {
readCountries(limit: 5) {
name
code
}
}
Let's take this a step further and paginate it using a plugin.
The "paginate" plugin
Since pagination is a fairly common task, we can take advantage of some reusable code here and just add a generic plugin for paginating.
[notice]
If you're paginating a DataList, you might want to consider using models with read operations, which paginate
by default using the paginateList
plugin. This will work, too, but requires a bit of code.
[/notice]
Let's add the plugin to our query:
app/_graphql/schema.yml
queries:
readCountries:
type: '[Country]'
plugins:
paginate: {}
Right now the plugin will add the necessary arguments to the query, build and update the return types. But we still need to provide this generic plugin a way of actually limiting the result set, so we need a resolver.
app/_graphql/schema.yml
queries:
readCountries:
type: '[Country]'
plugins:
paginate:
resolver: ['MyProject\Resolvers\Resolver', 'paginateCountries']
Let's write that resolver code now:
public static function paginateCountries(array $context): Closure
{
$maxLimit = $context['maxLimit'];
return function (array $countries, array $args) use ($maxLimit) {
$offset = $args['offset'];
$limit = $args['limit'];
$total = count($countries);
if ($limit > $maxLimit) {
$limit = $maxLimit;
}
$limitedList = array_slice($countries, $offset, $limit);
return PaginationPlugin::createPaginationResult($total, $limitedList, $limit, $offset);
};
}
A couple of things are going on here:
-
Notice the new design pattern of a context-aware resolver. Since the plugin be configured with a
maxLimit
parameter, we need to get this information to the function that is ultimately used in the schema. Therefore, we create a dynamic function in a static method by wrapping it with context. It's kind of like a decorator. -
As long as we can do the work of counting and limiting the array, the
PaginationPlugin
can handle the rest. It will return an array includingedges
,nodes
, andpageInfo
.
Rebuild the schema, and test it out:
query {
readCountries(limit:3, offset:4) {
nodes {
name
}
}
}
Further reading
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