Google Git
Sign in
vanadium / third_party / refs/heads/discovery / . / csrc / node-v0.10.24 / doc / api / addons.html
blob: 296ffd784d5d162266d61d545ea0109f3b2660df [file] [log] [blame]
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Addons Node.js v0.10.24 Manual &amp; Documentation</title>
<link rel="stylesheet" href="assets/style.css">
<link rel="stylesheet" href="assets/sh.css">
<link rel="canonical" href="http://nodejs.org/api/addons.html">
</head>
<body class="alt apidoc" id="api-section-addons">
<div id="intro" class="interior">
<a href="/" title="Go back to the home page">
<img id="logo" src="http://nodejs.org/images/logo-light.png" alt="node.js">
</a>
</div>
<div id="content" class="clearfix">
<div id="column2" class="interior">
<ul>
<li><a href="/" class="home">Home</a></li>
<li><a href="/download/" class="download">Download</a></li>
<li><a href="/about/" class="about">About</a></li>
<li><a href="http://npmjs.org/" class="npm">npm Registry</a></li>
<li><a href="http://nodejs.org/api/" class="docs current">Docs</a></li>
<li><a href="http://blog.nodejs.org" class="blog">Blog</a></li>
<li><a href="/community/" class="community">Community</a></li>
<li><a href="/logos/" class="logos">Logos</a></li>
<li><a href="http://jobs.nodejs.org/" class="jobs">Jobs</a></li>
</ul>
<p class="twitter"><a href="http://twitter.com/nodejs">@nodejs</a></p>
</div>
<div id="column1" class="interior">
<header>
<h1>Node.js v0.10.24 Manual &amp; Documentation</h1>
<div id="gtoc">
<p>
<a href="index.html" name="toc">Index</a> |
<a href="all.html">View on single page</a> |
<a href="addons.json">View as JSON</a>
</p>
</div>
<hr>
</header>
<div id="toc">
<h2>Table of Contents</h2>
<ul>
<li><a href="#addons_addons">Addons</a><ul>
<li><a href="#addons_hello_world">Hello world</a></li>
<li><a href="#addons_addon_patterns">Addon patterns</a><ul>
<li><a href="#addons_function_arguments">Function arguments</a></li>
<li><a href="#addons_callbacks">Callbacks</a></li>
<li><a href="#addons_object_factory">Object factory</a></li>
<li><a href="#addons_function_factory">Function factory</a></li>
<li><a href="#addons_wrapping_c_objects">Wrapping C++ objects</a></li>
<li><a href="#addons_factory_of_wrapped_objects">Factory of wrapped objects</a></li>
<li><a href="#addons_passing_wrapped_objects_around">Passing wrapped objects around</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
<div id="apicontent">
<h1>Addons<span><a class="mark" href="#addons_addons" id="addons_addons">#</a></span></h1>
<p>Addons are dynamically linked shared objects. They can provide glue to C and
C++ libraries. The API (at the moment) is rather complex, involving
knowledge of several libraries:
</p>
<ul>
<li><p>V8 JavaScript, a C++ library. Used for interfacing with JavaScript:
creating objects, calling functions, etc. Documented mostly in the
<code>v8.h</code> header file (<code>deps/v8/include/v8.h</code> in the Node source
tree), which is also available
<a href="http://izs.me/v8-docs/main.html">online</a>.</p>
</li>
<li><p><a href="https://github.com/joyent/libuv">libuv</a>, C event loop library.
Anytime one needs to wait for a file descriptor to become readable,
wait for a timer, or wait for a signal to be received one will need
to interface with libuv. That is, if you perform any I/O, libuv will
need to be used.</p>
</li>
<li><p>Internal Node libraries. Most importantly is the <code>node::ObjectWrap</code>
class which you will likely want to derive from.</p>
</li>
<li><p>Others. Look in <code>deps/</code> for what else is available.</p>
</li>
</ul>
<p>Node statically compiles all its dependencies into the executable.
When compiling your module, you don&#39;t need to worry about linking to
any of these libraries.
</p>
<p>All of the following examples are available for
<a href="https://github.com/rvagg/node-addon-examples">download</a> and may be
used as a starting-point for your own Addon.
</p>
<h2>Hello world<span><a class="mark" href="#addons_hello_world" id="addons_hello_world">#</a></span></h2>
<p>To get started let&#39;s make a small Addon which is the C++ equivalent of
the following JavaScript code:
</p>
<pre><code>module.exports.hello = function() { return &#39;world&#39;; };</code></pre>
<p>First we create a file <code>hello.cc</code>:
</p>
<pre><code>#include &lt;node.h&gt;
#include &lt;v8.h&gt;
using namespace v8;
Handle&lt;Value&gt; Method(const Arguments&amp; args) {
HandleScope scope;
return scope.Close(String::New(&quot;world&quot;));
}
void init(Handle&lt;Object&gt; exports) {
exports-&gt;Set(String::NewSymbol(&quot;hello&quot;),
FunctionTemplate::New(Method)-&gt;GetFunction());
}
NODE_MODULE(hello, init)</code></pre>
<p>Note that all Node addons must export an initialization function:
</p>
<pre><code>void Initialize (Handle&lt;Object&gt; exports);
NODE_MODULE(module_name, Initialize)</code></pre>
<p>There is no semi-colon after <code>NODE_MODULE</code> as it&#39;s not a function (see <code>node.h</code>).
</p>
<p>The <code>module_name</code> needs to match the filename of the final binary (minus the
.node suffix).
</p>
<p>The source code needs to be built into <code>hello.node</code>, the binary Addon. To
do this we create a file called <code>binding.gyp</code> which describes the configuration
to build your module in a JSON-like format. This file gets compiled by
<a href="https://github.com/TooTallNate/node-gyp">node-gyp</a>.
</p>
<pre><code>{
&quot;targets&quot;: [
{
&quot;target_name&quot;: &quot;hello&quot;,
&quot;sources&quot;: [ &quot;hello.cc&quot; ]
}
]
}</code></pre>
<p>The next step is to generate the appropriate project build files for the
current platform. Use <code>node-gyp configure</code> for that.
</p>
<p>Now you will have either a <code>Makefile</code> (on Unix platforms) or a <code>vcxproj</code> file
(on Windows) in the <code>build/</code> directory. Next invoke the <code>node-gyp build</code>
command.
</p>
<p>Now you have your compiled <code>.node</code> bindings file! The compiled bindings end up
in <code>build/Release/</code>.
</p>
<p>You can now use the binary addon in a Node project <code>hello.js</code> by pointing <code>require</code> to
the recently built <code>hello.node</code> module:
</p>
<pre><code>var addon = require(&#39;./build/Release/hello&#39;);
console.log(addon.hello()); // &#39;world&#39;</code></pre>
<p>Please see patterns below for further information or
</p>
<p><a href="https://github.com/arturadib/node-qt">https://github.com/arturadib/node-qt</a> for an example in production.
</p>
<h2>Addon patterns<span><a class="mark" href="#addons_addon_patterns" id="addons_addon_patterns">#</a></span></h2>
<p>Below are some addon patterns to help you get started. Consult the online
<a href="http://izs.me/v8-docs/main.html">v8 reference</a> for help with the various v8
calls, and v8&#39;s <a href="http://code.google.com/apis/v8/embed.html">Embedder&#39;s Guide</a>
for an explanation of several concepts used such as handles, scopes,
function templates, etc.
</p>
<p>In order to use these examples you need to compile them using <code>node-gyp</code>.
Create the following <code>binding.gyp</code> file:
</p>
<pre><code>{
&quot;targets&quot;: [
{
&quot;target_name&quot;: &quot;addon&quot;,
&quot;sources&quot;: [ &quot;addon.cc&quot; ]
}
]
}</code></pre>
<p>In cases where there is more than one <code>.cc</code> file, simply add the file name to the
<code>sources</code> array, e.g.:
</p>
<pre><code>&quot;sources&quot;: [&quot;addon.cc&quot;, &quot;myexample.cc&quot;]</code></pre>
<p>Now that you have your <code>binding.gyp</code> ready, you can configure and build the
addon:
</p>
<pre><code>$ node-gyp configure build</code></pre>
<h3>Function arguments<span><a class="mark" href="#addons_function_arguments" id="addons_function_arguments">#</a></span></h3>
<p>The following pattern illustrates how to read arguments from JavaScript
function calls and return a result. This is the main and only needed source
<code>addon.cc</code>:
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#include &lt;node.h&gt;
using namespace v8;
Handle&lt;Value&gt; Add(const Arguments&amp; args) {
HandleScope scope;
if (args.Length() &lt; 2) {
ThrowException(Exception::TypeError(String::New(&quot;Wrong number of arguments&quot;)));
return scope.Close(Undefined());
}
if (!args[0]-&gt;IsNumber() || !args[1]-&gt;IsNumber()) {
ThrowException(Exception::TypeError(String::New(&quot;Wrong arguments&quot;)));
return scope.Close(Undefined());
}
Local&lt;Number&gt; num = Number::New(args[0]-&gt;NumberValue() +
args[1]-&gt;NumberValue());
return scope.Close(num);
}
void Init(Handle&lt;Object&gt; exports) {
exports-&gt;Set(String::NewSymbol(&quot;add&quot;),
FunctionTemplate::New(Add)-&gt;GetFunction());
}
NODE_MODULE(addon, Init)</code></pre>
<p>You can test it with the following JavaScript snippet:
</p>
<pre><code>var addon = require(&#39;./build/Release/addon&#39;);
console.log( &#39;This should be eight:&#39;, addon.add(3,5) );</code></pre>
<h3>Callbacks<span><a class="mark" href="#addons_callbacks" id="addons_callbacks">#</a></span></h3>
<p>You can pass JavaScript functions to a C++ function and execute them from
there. Here&#39;s <code>addon.cc</code>:
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#include &lt;node.h&gt;
using namespace v8;
Handle&lt;Value&gt; RunCallback(const Arguments&amp; args) {
HandleScope scope;
Local&lt;Function&gt; cb = Local&lt;Function&gt;::Cast(args[0]);
const unsigned argc = 1;
Local&lt;Value&gt; argv[argc] = { Local&lt;Value&gt;::New(String::New(&quot;hello world&quot;)) };
cb-&gt;Call(Context::GetCurrent()-&gt;Global(), argc, argv);
return scope.Close(Undefined());
}
void Init(Handle&lt;Object&gt; exports, Handle&lt;Object&gt; module) {
module-&gt;Set(String::NewSymbol(&quot;exports&quot;),
FunctionTemplate::New(RunCallback)-&gt;GetFunction());
}
NODE_MODULE(addon, Init)</code></pre>
<p>Note that this example uses a two-argument form of <code>Init()</code> that receives
the full <code>module</code> object as the second argument. This allows the addon
to completely overwrite <code>exports</code> with a single function instead of
adding the function as a property of <code>exports</code>.
</p>
<p>To test it run the following JavaScript snippet:
</p>
<pre><code>var addon = require(&#39;./build/Release/addon&#39;);
addon(function(msg){
console.log(msg); // &#39;hello world&#39;
});</code></pre>
<h3>Object factory<span><a class="mark" href="#addons_object_factory" id="addons_object_factory">#</a></span></h3>
<p>You can create and return new objects from within a C++ function with this
<code>addon.cc</code> pattern, which returns an object with property <code>msg</code> that echoes
the string passed to <code>createObject()</code>:
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#include &lt;node.h&gt;
using namespace v8;
Handle&lt;Value&gt; CreateObject(const Arguments&amp; args) {
HandleScope scope;
Local&lt;Object&gt; obj = Object::New();
obj-&gt;Set(String::NewSymbol(&quot;msg&quot;), args[0]-&gt;ToString());
return scope.Close(obj);
}
void Init(Handle&lt;Object&gt; exports, Handle&lt;Object&gt; module) {
module-&gt;Set(String::NewSymbol(&quot;exports&quot;),
FunctionTemplate::New(CreateObject)-&gt;GetFunction());
}
NODE_MODULE(addon, Init)</code></pre>
<p>To test it in JavaScript:
</p>
<pre><code>var addon = require(&#39;./build/Release/addon&#39;);
var obj1 = addon(&#39;hello&#39;);
var obj2 = addon(&#39;world&#39;);
console.log(obj1.msg+&#39; &#39;+obj2.msg); // &#39;hello world&#39;</code></pre>
<h3>Function factory<span><a class="mark" href="#addons_function_factory" id="addons_function_factory">#</a></span></h3>
<p>This pattern illustrates how to create and return a JavaScript function that
wraps a C++ function:
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#include &lt;node.h&gt;
using namespace v8;
Handle&lt;Value&gt; MyFunction(const Arguments&amp; args) {
HandleScope scope;
return scope.Close(String::New(&quot;hello world&quot;));
}
Handle&lt;Value&gt; CreateFunction(const Arguments&amp; args) {
HandleScope scope;
Local&lt;FunctionTemplate&gt; tpl = FunctionTemplate::New(MyFunction);
Local&lt;Function&gt; fn = tpl-&gt;GetFunction();
fn-&gt;SetName(String::NewSymbol(&quot;theFunction&quot;)); // omit this to make it anonymous
return scope.Close(fn);
}
void Init(Handle&lt;Object&gt; exports, Handle&lt;Object&gt; module) {
module-&gt;Set(String::NewSymbol(&quot;exports&quot;),
FunctionTemplate::New(CreateFunction)-&gt;GetFunction());
}
NODE_MODULE(addon, Init)</code></pre>
<p>To test:
</p>
<pre><code>var addon = require(&#39;./build/Release/addon&#39;);
var fn = addon();
console.log(fn()); // &#39;hello world&#39;</code></pre>
<h3>Wrapping C++ objects<span><a class="mark" href="#addons_wrapping_c_objects" id="addons_wrapping_c_objects">#</a></span></h3>
<p>Here we will create a wrapper for a C++ object/class <code>MyObject</code> that can be
instantiated in JavaScript through the <code>new</code> operator. First prepare the main
module <code>addon.cc</code>:
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#include &lt;node.h&gt;
#include &quot;myobject.h&quot;
using namespace v8;
void InitAll(Handle&lt;Object&gt; exports) {
MyObject::Init(exports);
}
NODE_MODULE(addon, InitAll)</code></pre>
<p>Then in <code>myobject.h</code> make your wrapper inherit from <code>node::ObjectWrap</code>:
</p>
<pre><code>#ifndef MYOBJECT_H
#define MYOBJECT_H
#include &lt;node.h&gt;
class MyObject : public node::ObjectWrap {
public:
static void Init(v8::Handle&lt;v8::Object&gt; exports);
private:
explicit MyObject(double value = 0);
~MyObject();
static v8::Handle&lt;v8::Value&gt; New(const v8::Arguments&amp; args);
static v8::Handle&lt;v8::Value&gt; PlusOne(const v8::Arguments&amp; args);
static v8::Persistent&lt;v8::Function&gt; constructor;
double value_;
};
#endif</code></pre>
<p>And in <code>myobject.cc</code> implement the various methods that you want to expose.
Here we expose the method <code>plusOne</code> by adding it to the constructor&#39;s
prototype:
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#include &lt;node.h&gt;
#include &quot;myobject.h&quot;
using namespace v8;
Persistent&lt;Function&gt; MyObject::constructor;
MyObject::MyObject(double value) : value_(value) {
}
MyObject::~MyObject() {
}
void MyObject::Init(Handle&lt;Object&gt; exports) {
// Prepare constructor template
Local&lt;FunctionTemplate&gt; tpl = FunctionTemplate::New(New);
tpl-&gt;SetClassName(String::NewSymbol(&quot;MyObject&quot;));
tpl-&gt;InstanceTemplate()-&gt;SetInternalFieldCount(1);
// Prototype
tpl-&gt;PrototypeTemplate()-&gt;Set(String::NewSymbol(&quot;plusOne&quot;),
FunctionTemplate::New(PlusOne)-&gt;GetFunction());
constructor = Persistent&lt;Function&gt;::New(tpl-&gt;GetFunction());
exports-&gt;Set(String::NewSymbol(&quot;MyObject&quot;), constructor);
}
Handle&lt;Value&gt; MyObject::New(const Arguments&amp; args) {
HandleScope scope;
if (args.IsConstructCall()) {
// Invoked as constructor: `new MyObject(...)`
double value = args[0]-&gt;IsUndefined() ? 0 : args[0]-&gt;NumberValue();
MyObject* obj = new MyObject(value);
obj-&gt;Wrap(args.This());
return args.This();
} else {
// Invoked as plain function `MyObject(...)`, turn into construct call.
const int argc = 1;
Local&lt;Value&gt; argv[argc] = { args[0] };
return scope.Close(constructor-&gt;NewInstance(argc, argv));
}
}
Handle&lt;Value&gt; MyObject::PlusOne(const Arguments&amp; args) {
HandleScope scope;
MyObject* obj = ObjectWrap::Unwrap&lt;MyObject&gt;(args.This());
obj-&gt;value_ += 1;
return scope.Close(Number::New(obj-&gt;value_));
}</code></pre>
<p>Test it with:
</p>
<pre><code>var addon = require(&#39;./build/Release/addon&#39;);
var obj = new addon.MyObject(10);
console.log( obj.plusOne() ); // 11
console.log( obj.plusOne() ); // 12
console.log( obj.plusOne() ); // 13</code></pre>
<h3>Factory of wrapped objects<span><a class="mark" href="#addons_factory_of_wrapped_objects" id="addons_factory_of_wrapped_objects">#</a></span></h3>
<p>This is useful when you want to be able to create native objects without
explicitly instantiating them with the <code>new</code> operator in JavaScript, e.g.
</p>
<pre><code>var obj = addon.createObject();
// instead of:
// var obj = new addon.Object();</code></pre>
<p>Let&#39;s register our <code>createObject</code> method in <code>addon.cc</code>:
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#include &lt;node.h&gt;
#include &quot;myobject.h&quot;
using namespace v8;
Handle&lt;Value&gt; CreateObject(const Arguments&amp; args) {
HandleScope scope;
return scope.Close(MyObject::NewInstance(args));
}
void InitAll(Handle&lt;Object&gt; exports, Handle&lt;Object&gt; module) {
MyObject::Init();
module-&gt;Set(String::NewSymbol(&quot;exports&quot;),
FunctionTemplate::New(CreateObject)-&gt;GetFunction());
}
NODE_MODULE(addon, InitAll)</code></pre>
<p>In <code>myobject.h</code> we now introduce the static method <code>NewInstance</code> that takes
care of instantiating the object (i.e. it does the job of <code>new</code> in JavaScript):
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#ifndef MYOBJECT_H
#define MYOBJECT_H
#include &lt;node.h&gt;
class MyObject : public node::ObjectWrap {
public:
static void Init();
static v8::Handle&lt;v8::Value&gt; NewInstance(const v8::Arguments&amp; args);
private:
explicit MyObject(double value = 0);
~MyObject();
static v8::Handle&lt;v8::Value&gt; New(const v8::Arguments&amp; args);
static v8::Handle&lt;v8::Value&gt; PlusOne(const v8::Arguments&amp; args);
static v8::Persistent&lt;v8::Function&gt; constructor;
double value_;
};
#endif</code></pre>
<p>The implementation is similar to the above in <code>myobject.cc</code>:
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#include &lt;node.h&gt;
#include &quot;myobject.h&quot;
using namespace v8;
Persistent&lt;Function&gt; MyObject::constructor;
MyObject::MyObject(double value) : value_(value) {
}
MyObject::~MyObject() {
}
void MyObject::Init() {
// Prepare constructor template
Local&lt;FunctionTemplate&gt; tpl = FunctionTemplate::New(New);
tpl-&gt;SetClassName(String::NewSymbol(&quot;MyObject&quot;));
tpl-&gt;InstanceTemplate()-&gt;SetInternalFieldCount(1);
// Prototype
tpl-&gt;PrototypeTemplate()-&gt;Set(String::NewSymbol(&quot;plusOne&quot;),
FunctionTemplate::New(PlusOne)-&gt;GetFunction());
constructor = Persistent&lt;Function&gt;::New(tpl-&gt;GetFunction());
}
Handle&lt;Value&gt; MyObject::New(const Arguments&amp; args) {
HandleScope scope;
if (args.IsConstructCall()) {
// Invoked as constructor: `new MyObject(...)`
double value = args[0]-&gt;IsUndefined() ? 0 : args[0]-&gt;NumberValue();
MyObject* obj = new MyObject(value);
obj-&gt;Wrap(args.This());
return args.This();
} else {
// Invoked as plain function `MyObject(...)`, turn into construct call.
const int argc = 1;
Local&lt;Value&gt; argv[argc] = { args[0] };
return scope.Close(constructor-&gt;NewInstance(argc, argv));
}
}
Handle&lt;Value&gt; MyObject::NewInstance(const Arguments&amp; args) {
HandleScope scope;
const unsigned argc = 1;
Handle&lt;Value&gt; argv[argc] = { args[0] };
Local&lt;Object&gt; instance = constructor-&gt;NewInstance(argc, argv);
return scope.Close(instance);
}
Handle&lt;Value&gt; MyObject::PlusOne(const Arguments&amp; args) {
HandleScope scope;
MyObject* obj = ObjectWrap::Unwrap&lt;MyObject&gt;(args.This());
obj-&gt;value_ += 1;
return scope.Close(Number::New(obj-&gt;value_));
}</code></pre>
<p>Test it with:
</p>
<pre><code>var createObject = require(&#39;./build/Release/addon&#39;);
var obj = createObject(10);
console.log( obj.plusOne() ); // 11
console.log( obj.plusOne() ); // 12
console.log( obj.plusOne() ); // 13
var obj2 = createObject(20);
console.log( obj2.plusOne() ); // 21
console.log( obj2.plusOne() ); // 22
console.log( obj2.plusOne() ); // 23</code></pre>
<h3>Passing wrapped objects around<span><a class="mark" href="#addons_passing_wrapped_objects_around" id="addons_passing_wrapped_objects_around">#</a></span></h3>
<p>In addition to wrapping and returning C++ objects, you can pass them around
by unwrapping them with Node&#39;s <code>node::ObjectWrap::Unwrap</code> helper function.
In the following <code>addon.cc</code> we introduce a function <code>add()</code> that can take on two
<code>MyObject</code> objects:
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#include &lt;node.h&gt;
#include &quot;myobject.h&quot;
using namespace v8;
Handle&lt;Value&gt; CreateObject(const Arguments&amp; args) {
HandleScope scope;
return scope.Close(MyObject::NewInstance(args));
}
Handle&lt;Value&gt; Add(const Arguments&amp; args) {
HandleScope scope;
MyObject* obj1 = node::ObjectWrap::Unwrap&lt;MyObject&gt;(
args[0]-&gt;ToObject());
MyObject* obj2 = node::ObjectWrap::Unwrap&lt;MyObject&gt;(
args[1]-&gt;ToObject());
double sum = obj1-&gt;Value() + obj2-&gt;Value();
return scope.Close(Number::New(sum));
}
void InitAll(Handle&lt;Object&gt; exports) {
MyObject::Init();
exports-&gt;Set(String::NewSymbol(&quot;createObject&quot;),
FunctionTemplate::New(CreateObject)-&gt;GetFunction());
exports-&gt;Set(String::NewSymbol(&quot;add&quot;),
FunctionTemplate::New(Add)-&gt;GetFunction());
}
NODE_MODULE(addon, InitAll)</code></pre>
<p>To make things interesting we introduce a public method in <code>myobject.h</code> so we
can probe private values after unwrapping the object:
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#ifndef MYOBJECT_H
#define MYOBJECT_H
#include &lt;node.h&gt;
class MyObject : public node::ObjectWrap {
public:
static void Init();
static v8::Handle&lt;v8::Value&gt; NewInstance(const v8::Arguments&amp; args);
double Value() const { return value_; }
private:
explicit MyObject(double value = 0);
~MyObject();
static v8::Handle&lt;v8::Value&gt; New(const v8::Arguments&amp; args);
static v8::Persistent&lt;v8::Function&gt; constructor;
double value_;
};
#endif</code></pre>
<p>The implementation of <code>myobject.cc</code> is similar as before:
</p>
<pre><code>#define BUILDING_NODE_EXTENSION
#include &lt;node.h&gt;
#include &quot;myobject.h&quot;
using namespace v8;
Persistent&lt;Function&gt; MyObject::constructor;
MyObject::MyObject(double value) : value_(value) {
}
MyObject::~MyObject() {
}
void MyObject::Init() {
// Prepare constructor template
Local&lt;FunctionTemplate&gt; tpl = FunctionTemplate::New(New);
tpl-&gt;SetClassName(String::NewSymbol(&quot;MyObject&quot;));
tpl-&gt;InstanceTemplate()-&gt;SetInternalFieldCount(1);
constructor = Persistent&lt;Function&gt;::New(tpl-&gt;GetFunction());
}
Handle&lt;Value&gt; MyObject::New(const Arguments&amp; args) {
HandleScope scope;
if (args.IsConstructCall()) {
// Invoked as constructor: `new MyObject(...)`
double value = args[0]-&gt;IsUndefined() ? 0 : args[0]-&gt;NumberValue();
MyObject* obj = new MyObject(value);
obj-&gt;Wrap(args.This());
return args.This();
} else {
// Invoked as plain function `MyObject(...)`, turn into construct call.
const int argc = 1;
Local&lt;Value&gt; argv[argc] = { args[0] };
return scope.Close(constructor-&gt;NewInstance(argc, argv));
}
}
Handle&lt;Value&gt; MyObject::NewInstance(const Arguments&amp; args) {
HandleScope scope;
const unsigned argc = 1;
Handle&lt;Value&gt; argv[argc] = { args[0] };
Local&lt;Object&gt; instance = constructor-&gt;NewInstance(argc, argv);
return scope.Close(instance);
}</code></pre>
<p>Test it with:
</p>
<pre><code>var addon = require(&#39;./build/Release/addon&#39;);
var obj1 = addon.createObject(10);
var obj2 = addon.createObject(20);
var result = addon.add(obj1, obj2);
console.log(result); // 30</code></pre>
</div>
</div>
</div>
<div id="footer">
<a href="http://joyent.com" class="joyent-logo">Joyent</a>
<ul class="clearfix">
<li><a href="/">Node.js</a></li>
<li><a href="/download/">Download</a></li>
<li><a href="/about/">About</a></li>
<li><a href="http://npmjs.org/">npm Registry</a></li>
<li><a href="http://nodejs.org/api/">Docs</a></li>
<li><a href="http://blog.nodejs.org">Blog</a></li>
<li><a href="/community/">Community</a></li>
<li><a href="/logos/">Logos</a></li>
<li><a href="http://jobs.nodejs.org/">Jobs</a></li>
<li><a href="http://twitter.com/nodejs" class="twitter">@nodejs</a></li>
</ul>
<p>Copyright <a href="http://joyent.com/">Joyent, Inc</a>, Node.js is a <a href="/trademark-policy.pdf">trademark</a> of Joyent, Inc. View <a href="https://raw.github.com/joyent/node/v0.10.24/LICENSE">license</a>.</p>
</div>
<script src="../sh_main.js"></script>
<script src="../sh_javascript.min.js"></script>
<script>highlight(undefined, undefined, 'pre');</script>
<script>
window._gaq = [['_setAccount', 'UA-10874194-2'], ['_trackPageview']];
(function(d, t) {
var g = d.createElement(t),
s = d.getElementsByTagName(t)[0];
g.src = '//www.google-analytics.com/ga.js';
s.parentNode.insertBefore(g, s);
}(document, 'script'));
</script>
</body>
</html>