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<a class="" href="../getting-started/">Getting Started</a>
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<li class="toctree-l3"><a href="#type-system">Type System</a></li>
<li class="toctree-l3"><a href="#type-definition-styles">Type Definition Styles</a></li>
<li class="toctree-l3"><a href="#type-registry">Type Registry</a></li>
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<a class="" href="object-types/">Object Types</a>
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<a class="" href="scalar-types/">Scalar Types</a>
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<h1 id="type-system">Type System</h1>
<p>To start using GraphQL you are expected to implement a type hierarchy and expose it as <a href="../type-system/schema/">Schema</a>. </p>
<p>In <strong>graphql-php</strong> <code>type</code> is an instance of internal class from
<code>GraphQL\Type\Definition</code> namespace: <code>ScalarType</code>, <code>ObjectType</code>, <code>InterfaceType</code>,
<code>UnionType</code>, <code>InputObjectType</code> (or one of it's subclasses).</p>
<p>But most of the types in your schema will be <a href="../type-system/object-types/">object types</a>.</p>
<h1 id="type-definition-styles">Type Definition Styles</h1>
<p>Several styles of type definitions are supported depending on your preferences.</p>
<p>Inline definitions:</p>
<pre><code class="php">&lt;?php
namespace MyApp;
use GraphQL\Type\Definition\ObjectType;
use GraphQL\Type\Definition\Type;
$myType = new ObjectType([
'name' =&gt; 'MyType',
'fields' =&gt; [
'id' =&gt; Type::id()
]
]);
</code></pre>
<p>Class per type:</p>
<pre><code class="php">&lt;?php
namespace MyApp;
use GraphQL\Type\Definition\ObjectType;
use GraphQL\Type\Definition\Type;
class MyType extends ObjectType
{
public function __construct()
{
$config = [
// Note: 'name' is not needed in this form:
// it will be inferred from class name by omitting namespace and dropping &quot;Type&quot; suffix
'fields' =&gt; [
'id' =&gt; Type::id()
]
];
parent::__construct($config);
}
}
</code></pre>
<p>You can also mix-and-match styles for convenience. For example:</p>
<pre><code class="php">&lt;?php
namespace MyApp;
use GraphQL\Type\Definition\ObjectType;
use GraphQL\Type\Definition\Type;
class BlogPostType extends ObjectType
{
public function __construct()
{
$config = [
'fields' =&gt; [
'body' =&gt; new ObjectType([
'name' =&gt; 'BlogPostBody',
'fields' =&gt; [
'html' =&gt; Type::string(),
'text' =&gt; Type::string(),
]
])
]
];
parent::__construct($config);
}
}
</code></pre>
<h1 id="type-registry">Type Registry</h1>
<p>Every type must be presented in Schema by single instance (<strong>graphql-php</strong>
throws when it discovers several instances with the same <code>name</code> in schema).</p>
<p>Therefore if you define your type as separate PHP class you must ensure that only one
instance of that class is added to schema.</p>
<p>Typical way to do this is to create registry of your types:</p>
<pre><code class="php">&lt;?php
namespace MyApp;
class TypeRegistry
{
private $myAType;
private $myBType;
public function myAType()
{
return $this-&gt;myAType ?: ($this-&gt;myAType = new MyAType($this));
}
public function myBType()
{
return $this-&gt;myBType ?: ($this-&gt;myBType = new MyBType($this));
}
}
</code></pre>
<p>And use this registry in type definition:</p>
<pre><code class="php">&lt;?php
namespace MyApp;
use GraphQL\Type\Definition\ObjectType;
class MyAType extends ObjectType
{
public function __construct(TypeRegistry $types)
{
parent::__construct([
'fields' =&gt; [
'b' =&gt; $types-&gt;myBType()
]
]);
}
}
</code></pre>
<p>Obviously you can automate this registry as you wish to reduce boilerplate or even
introduce Dependency Injection Container if your types have other dependencies.</p>
<p>Alternatively all methods of registry could be static if you prefer - then there is no need
to pass it in constructor - instead just use use <code>TypeRegistry::myAType()</code> in your type definitions.</p>
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