mirror of
https://github.com/silverstripe/silverstripe-framework
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112 lines
3.1 KiB
Markdown
112 lines
3.1 KiB
Markdown
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---
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title: Adding pagination
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summary: Add the pagination plugin to a generic query
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---
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# Working with generic types
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[CHILDREN asList]
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[alert]
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You are viewing docs for a pre-release version of silverstripe/graphql (4.x).
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Help us improve it by joining #graphql on the [Community Slack](https://www.silverstripe.org/blog/community-slack-channel/),
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and report any issues at [github.com/silverstripe/silverstripe-graphql](https://github.com/silverstripe/silverstripe-graphql).
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Docs for the current stable version (3.x) can be found
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[here](https://github.com/silverstripe/silverstripe-graphql/tree/3)
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[/alert]
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## Adding pagination
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We've created a simple generic query for our `Country` type called `readCounties` that takes a `limit` argument.
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```graphql
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query {
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readCountries(limit: 5) {
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name
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code
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}
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}
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```
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Let's take this a step further and paginate it using a plugin.
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### The "paginate" plugin
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Since pagination is a fairly common task, we can take advantage of some reusable code here and just add a generic
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plugin for paginating.
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[notice]
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If you're paginating a DataList, you might want to consider using models with read operations, which paginate
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by default using the `paginateList` plugin. This will work, too, but requires a bit of code.
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[/notice]
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Let's add the plugin to our query:
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**app/_graphql/schema.yml**
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```yaml
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queries:
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readCountries:
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type: '[Country]'
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plugins:
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paginate: {}
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```
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Right now the plugin will add the necessary arguments to the query, build and update the return types. But
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we still need to provide this generic plugin a way of actually limiting the result set, so we need a resolver.
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**app/_graphql/schema.yml**
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```yaml
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queries:
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readCountries:
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type: '[Country]'
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plugins:
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paginate:
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resolver: ['MyProject\Resolvers\Resolver', 'paginateCountries']
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```
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Let's write that resolver code now:
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```php
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public static function paginateCountries(array $context): Closure
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{
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$maxLimit = $context['maxLimit'];
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return function (array $countries, array $args) use ($maxLimit) {
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$offset = $args['offset'];
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$limit = $args['limit'];
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$total = count($countries);
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if ($limit > $maxLimit) {
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$limit = $maxLimit;
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}
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$limitedList = array_slice($countries, $offset, $limit);
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return PaginationPlugin::createPaginationResult($total, $limitedList, $limit, $offset);
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};
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}
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```
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A couple of things are going on here:
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* Notice the new design pattern of a **context-aware resolver**. Since the plugin be configured with a `maxLimit`
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parameter, we need to get this information to the function that is ultimately used in the schema. Therefore,
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we create a dynamic function in a static method by wrapping it with context. It's kind of like a decorator.
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* As long as we can do the work of counting and limiting the array, the `PaginationPlugin` can handle the rest. It will reutrn an array including `edges`, `nodes`, and `pageInfo`.
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Rebuild the schema, and test it out:
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```graphql
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query {
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readCountries(limit:3, offset:4) {
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nodes {
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name
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}
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}
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}
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```
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### Further reading
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[CHILDREN]
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