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                <li class="toctree-l3"><a href="#user-types">User Types</a></li>
                
                    <li><a class="toctree-l4" href="#register-user-type-with-constructor">Register user type with constructor</a></li>
                
                    <li><a class="toctree-l4" href="#register-user-type-without-constructor">Register user type without constructor</a></li>
                
                    <li><a class="toctree-l4" href="#usage-in-lua">Usage in Lua</a></li>
                
                    <li><a class="toctree-l4" href="#manually-constructing-a-user-type">Manually constructing a user type</a></li>
                
                    <li><a class="toctree-l4" href="#registry-names">Registry names</a></li>
                
            
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                <h1 id="user-types">User Types</h1>
<p>A user type is a collection of class members bundled into a metatable. Before user types can be used
in Lua, you must register such metatable in Lua's registry.</p>
<p>The following examples work on this class:</p>
<pre><code class="c++">struct Point {
    double x, y;

    Point(double x, double y):
        x(x), y(y)
    {
        std::cout &lt;&lt; &quot;Construct Point(&quot; &lt;&lt; x &lt;&lt; &quot;, &quot; &lt;&lt; y &lt;&lt; &quot;)&quot; &lt;&lt; std::endl;
    }

    ~Point() {
        std::cout &lt;&lt; &quot;Destruct Point(&quot; &lt;&lt; x &lt;&lt; &quot;, &quot; &lt;&lt; y &lt;&lt; &quot;)&quot; &lt;&lt; std::endl;
    }

    void scale(double f) {
        x *= f;
        y *= f;
    }

    std::string __tostring() {
        return &quot;&lt;Point(&quot; + std::to_string(x) + &quot;, &quot; + std::to_string(y) + &quot;)&gt;&quot;;
    }
};
</code></pre>

<h2 id="register-user-type-with-constructor">Register user type with constructor</h2>
<p><a href="../reference/namespaceluwra.html#a683f6075862f8fc5cad0d76445f2f607">registerUserType&lt;S&gt;</a> allows
you to register a metatable and constructor in the global namespace. The template parameter to
<code>registerUserType</code> is a signature in the form of <code>U(A...)</code> where <code>U</code> is your user type and <code>A...</code>
the parameter types to the constructor which you want to register.</p>
<p>By default, the function generates a garbage-collector hook and a string representation function.
If you add a <code>__gc</code> or <code>__tostring</code> meta method to your type, these auto-generated functions will be
overridden.</p>
<p>See this example:</p>
<pre><code class="c++">luwra::registerUserType&lt;Point(double, double)&gt;(
    lua,

    // Constructor name
    &quot;Point&quot;,

    // Methods need to be declared here
    {
        LUWRA_MEMBER(Point, scale),
        LUWRA_MEMBER(Point, x),
        LUWRA_MEMBER(Point, y)
    },

    // Meta methods may be registered aswell
    {
        LUWRA_MEMBER(Point, __tostring)
    }
);
</code></pre>

<p>Parameter 3 and 4 are instances of
<a href="../reference/namespaceluwra.html#ac090722c6d5d6b88b31895aad64788c2">FieldVector</a>. The <code>LUWRA_MEMBER</code> macro
generates a <code>std::pair&lt;Pushable, Pushable&gt;</code> expression.</p>
<pre><code class="c++">LUWRA_MEMBER(Point, scale) === {&quot;scale&quot;, LUWRA_WRAP(Point::scale)}
</code></pre>

<p><code>Pushable</code> has an implicit constructor, which makes it convenient to add other types of fields:</p>
<pre><code class="c++">luwra::registerUserType&lt;Point(double, double)&gt;(
    lua,

    // Constructor name
    &quot;Point&quot;,

    // Methods need to be declared here
    {
        {&quot;scale&quot;, LUWRA_WRAP(Point::scale)},
        {&quot;x&quot;,     LUWRA_WRAP(Point::x)},
        {&quot;y&quot;,     LUWRA_WRAP(Point::y)},
        {&quot;magic&quot;, luwra::FieldVector {
            {&quot;number&quot;, 1337},
            {&quot;string&quot;, &quot;Hello World&quot;}
        }}
    },

    // Meta methods may be registered aswell
    {
        {&quot;__tostring&quot;, LUWRA_WRAP(Point::__tostring)}
    }
);
</code></pre>

<h2 id="register-user-type-without-constructor">Register user type without constructor</h2>
<p>To register only the metatable associated with a user type, simply omit the constructor parameters
and name from the call to <code>registerUserType</code>.</p>
<pre><code class="c++">luwra::registerUserType&lt;Point&gt;(
    lua,

    // Methods need to be declared here
    {
        {&quot;scale&quot;, LUWRA_WRAP(Point::scale)},
        {&quot;x&quot;,     LUWRA_WRAP(Point::x)},
        {&quot;y&quot;,     LUWRA_WRAP(Point::y)},
        {&quot;magic&quot;, luwra::FieldVector {
            {&quot;number&quot;, 1337},
            {&quot;string&quot;, &quot;Hello World&quot;}
        }}
    },

    // Meta methods may be registered aswell
    {
        {&quot;__tostring&quot;, LUWRA_WRAP(Point::__tostring)}
    }
);
</code></pre>

<p>It is still possible to provide a constructor using the <code>LUWRA_WRAP_CONSTRUCTOR</code> macro:</p>
<pre><code class="c++">lua_CFunction ctor = LUWRA_WRAP_CONSTRUCTOR(Point, double, double);
luwra::setGlobal(lua, &quot;Point&quot;, ctor);
</code></pre>

<h2 id="usage-in-lua">Usage in Lua</h2>
<p>After you have registered your user type using one of the given methods, you can start using it in
Lua:</p>
<pre><code class="lua">-- Instantiate 'Point'
local point = Point(13, 37)

-- Invoke 'scale' method
point:scale(1.5)

-- Convert to string via '__tostring' meta method
print(point)

-- Read properties 'x' and 'y'
print(point:x(), point:y())

-- Set property 'x'
point:x(point.magic.number)
</code></pre>

<h2 id="manually-constructing-a-user-type">Manually constructing a user type</h2>
<p>Provided you already registered your user type, one can create it from the C++ side aswell.
<a href="../reference/namespaceluwra.html#af079dcca8e67d88e5cfdc7e8872cf5d7">construct&lt;U&gt;</a> provides this
functionality. Given the user type and constructor parameters, it will construct the user type on
top of the stack:</p>
<pre><code class="c++">Point&amp; my_point = luwra::construct&lt;Point&gt;(lua, 13.37, 73.31);

// Changes on C++ side will be visible in Lua
my_point.scale(2);
</code></pre>

<h2 id="registry-names">Registry names</h2>
<p>When registering the metatable for a user type, an automatically generated name will be used to
store it in the registry. When Luwra is used in a single executable or shared library, name
collisions should not happen. If your application consists of multiple seperate compiled units, it
is highly recommended to prevent name collisions by defining the <code>LUWRA_REGISTRY_PREFIX</code> macro
before including the Luwra headers. This macro changes the prefix for auto-generated registry names.</p>
<pre><code class="c++">#define LUWRA_REGISTRY_PREFIX &quot;MyProject#&quot;
#include &lt;luwra.hpp&gt;
</code></pre>

<p>Another way to prevent collisons is to give each user type its individual registry name. This can be
done using the <code>LUWRA_DEF_REGISTRY_NAME</code> macro.</p>
<pre><code class="c++">struct MyUserType {
    // ...
};

LUWRA_DEF_REGISTRY_NAME(MyUserType, &quot;MyUserType&quot;)
</code></pre>

<p>Choosing this method will not prefix the registry name with the value of <code>LUWRA_REGISTRY_PREFIX</code>.</p>
              
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