首先我们用下面的目录结构来创建一个节点通知(node-notify)文件夹.
复制代码 代码如下:
.
|-- build/ # This is where our extension is built.
|-- demo/
| `-- demo.js # This is a demo Node.js script to test our extension.
|-- src/
| `-- node_gtknotify.cpp # This is the where we do the mapping from C++ to Javascript.
`-- wscript # This is our build configuration used by node-waf
这个看起来很漂亮的tree 用通用的 tree 生成.
现在让我来创建测试脚本demo.js 和决定我们扩展的API前期看起来应该像:
// This loads our extension on the notify variable. // It will only load a constructor function, notify.notification(). var notify = require("../build/default/gtknotify.node"); // path to our extension var notification = new notify.notification(); notification.title = "Notification title"; notification.icon = "emblem-default"; // see /usr/share/icons/gnome/16x16 notification.send("Notification message");
编写我们的Node.js扩展
Init方法
为了创建一个Node.js扩展，我们需要编写一个继承node::ObjectWrap的C++类。 ObjectWrap 实现了让我们更容易与Javascript交互的公共方法
我们先来编写类的基本框架：
#include <v8.h> // v8 is the Javascript engine used by QNode #include <node.h> // We will need the following libraries for our GTK+ notification #include <string> #include <gtkmm.h> #include <libnotifymm.h> using namespace v8; class Gtknotify : node::ObjectWrap { private: public: Gtknotify() {} ~Gtknotify() {} static void Init(Handle<Object> target) { // This is what Node will call when we load the extension through require(), see boilerplate code below. } }; /* * WARNING: Boilerplate code ahead. * * See https://www.cloudkick.com/blog/2010/aug/23/writing-nodejs-native-extensions/ & ?query=dlsym * * Thats it for actual interfacing with v8, finally we need to let Node.js know how to dynamically load our code. * Because a Node.js extension can be loaded at runtime from a shared object, we need a symbol that the dlsym function can find, * so we do the following: */ v8::Persistent<FunctionTemplate> Gtknotify::persistent_function_template; extern "C" { // Cause of name mangling in C++, we use extern C here static void init(Handle<Object> target) { Gtknotify::Init(target); } // @see #L101 NODE_MODULE(gtknotify, init); }
现在，我们必须把下面的代码编写到我们的Init()方法中：
声明构造函数，并将其绑定到我们的目标变量。var n = require("notification");将绑定notification() 到 n:n.notification().
// Wrap our C++ New() method so that it's accessible from Javascript // This will be called by the new operator in Javascript, for example: new notification(); v8::Local<FunctionTemplate> local_function_template = v8::FunctionTemplate::New(New); // Make it persistent and assign it to persistent_function_template which is a static attribute of our class. Gtknotify::persistent_function_template = v8::Persistent<FunctionTemplate>::New(local_function_template); // Each JavaScript object keeps a reference to the C++ object for which it is a wrapper with an internal field. Gtknotify::persistent_function_template->InstanceTemplate()->SetInternalFieldCount(1); // 1 since a constructor function only references 1 object // Set a "class" name for objects created with our constructor Gtknotify::persistent_function_template->SetClassName(v8::String::NewSymbol("Notification")); // Set the "notification" property of our target variable and assign it to our constructor function target->Set(String::NewSymbol("notification"), Gtknotify::persistent_function_template->GetFunction());
声明属性:n.title 和n.icon.
// Set property accessors // SetAccessor arguments: Javascript property name, C++ method that will act as the getter, C++ method that will act as the setter Gtknotify::persistent_function_template->InstanceTemplate()->SetAccessor(String::New("title"), GetTitle, SetTitle); Gtknotify::persistent_function_template->InstanceTemplate()->SetAccessor(String::New("icon"), GetIcon, SetIcon); // For instance, n.title = "foo" will now call SetTitle("foo"), n.title will now call GetTitle()
声明原型方法：n.send()