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graphql - graphql-php 入门：如何将解析器函数从 .graphql 文件添加到模式？

问题描述

我对 GraphQL 完全陌生，想玩一下 graphql-php 以构建一个简单的 API 来开始。我目前正在阅读文档并尝试示例，但我一开始就被卡住了。

我希望我的架构存储在一个schema.graphql文件中，而不是手动构建它，所以我按照文档说明了如何做到这一点，它确实有效：

<?php
// graph-ql is installed via composer
require('../vendor/autoload.php');

use GraphQL\Language\Parser;
use GraphQL\Utils\BuildSchema;
use GraphQL\Utils\AST;
use GraphQL\GraphQL;

try {
    $cacheFilename = 'cached_schema.php';
    // caching, as recommended in the docs, is disabled for testing
    // if (!file_exists($cacheFilename)) {
        $document = Parser::parse(file_get_contents('./schema.graphql'));
        file_put_contents($cacheFilename, "<?php\nreturn " . var_export(AST::toArray($document), true) . ';');
    /*} else {
        $document = AST::fromArray(require $cacheFilename); // fromArray() is a lazy operation as well
    }*/

    $typeConfigDecorator = function($typeConfig, $typeDefinitionNode) {
        // In the docs, this function is just empty, but I needed to return the $typeConfig, otherwise I got an error
        return $typeConfig;
    };
    $schema = BuildSchema::build($document, $typeConfigDecorator);

    $context = (object)array();

    // this has been taken from one of the examples provided in the repo
    $rawInput = file_get_contents('php://input');
    $input = json_decode($rawInput, true);
    $query = $input['query'];
    $variableValues = isset($input['variables']) ? $input['variables'] : null;
    $rootValue = ['prefix' => 'You said: '];
    $result = GraphQL::executeQuery($schema, $query, $rootValue, $context, $variableValues);
    $output = $result->toArray();
} catch (\Exception $e) {
    $output = [
        'error' => [
            'message' => $e->getMessage()
        ]
    ];
}
header('Content-Type: application/json; charset=UTF-8');
echo json_encode($output);

这是我的schema.graphql文件的样子：

schema {
    query: Query    
}

type Query {
    products: [Product!]!
}

type Product {
    id: ID!,
    type: ProductType
}

enum ProductType {
    HDRI,
    SEMISPHERICAL_HDRI,
    SOUND
}

例如，我可以查询它

query {
  __schema {types{name}}
}

这将按预期返回元数据。但当然现在我想查询实际的产品数据并从数据库中获取，为此我需要定义一个解析器函数。

http://webonyx.github.io/graphql-php/type-system/type-language/上的文档状态：“默认情况下，这样的模式是在没有任何解析器的情况下创建的。我们必须依赖默认字段解析器和根值为了对此模式执行查询。” - 但没有这样做的例子。

如何为每个类型/字段添加解析器函数？

标签： graphqlgraphql-php

解决方案

这种方法无需实例化服务器即可工作。在我的例子中，我已经有一个服务器并且可以读取 HTTP 数据，我所需要的只是读取 GraphQL 模式并运行查询。首先，我从文件中读取架构：

        $schemaContent = // file_get_contents or whatever works for you

        $schemaDocument = GraphQL\Language\Parser::parse($schemaContent);
        $schemaBuilder = new GraphQL\Utils\BuildSchema($schemaDocument);
        $schema = $schemaBuilder->buildSchema();

然后我执行通过自定义字段解析器的查询：

        $fieldResolver = function() {
            return call_user_func_array([$this, 'defaultFieldResolver'], func_get_args());
        };

        $result = GraphQL\GraphQL::executeQuery(
            $schema,
            $query,        // this was grabbed from the HTTP post data
            null,
            $appContext,   // custom context
            $variables,    // this was grabbed from the HTTP post data
            null,
            $fieldResolver // HERE, custom field resolver
        );

字段解析器如下所示：

private static function defaultFieldResolver(
    $source,
    $args,
    $context,
    \GraphQL\Type\Definition\ResolveInfo $info
) {
    $fieldName = $info->fieldName;
    $parentType = $info->parentType->name;

    if ($source === NULL) {
        // this is the root value, return value depending on $fieldName
        // ...
    } else {
        // Depending on field type ($parentType), I call different field resolvers.
        // Since our system is big, we implemented a bootstrapping mechanism
        // so modules can register field resolvers in this class depending on field type
        // ...

        // If no field resolver was defined for this $parentType,
        // we just rely on the default field resolver provided by graphql-php (copy/paste).
        $fieldName = $info->fieldName;
        $property = null;

        if (is_array($source) || $source instanceof \ArrayAccess) {
            if (isset($source[$fieldName])) {
                $property = $source[$fieldName];
            }
        } else if (is_object($source)) {
            if (isset($source->{$fieldName})) {
                $property = $source->{$fieldName};
            }
        }

        return $property instanceof \Closure
            ? $property($source, $args, $context)
            : $property;
    }
}

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