// This is a Node macro to help bind C++ methods to Javascript methods (see https://github.com/joyent/node/blob/v0.2.0/src/node.h#L34) // Arguments: our constructor function, Javascript method name, C++ method name NODE_SET_PROTOTYPE_METHOD(Gtknotify::persistent_function_template, "send", Send);
现在我们的Init()方法看起来应该是这样的：
// Our constructor static v8::Persistent<FunctionTemplate> persistent_function_template; static void Init(Handle<Object> target) { v8::HandleScope scope; // used by v8 for garbage collection // Our constructor v8::Local<FunctionTemplate> local_function_template = v8::FunctionTemplate::New(New); Gtknotify::persistent_function_template = v8::Persistent<FunctionTemplate>::New(local_function_template); Gtknotify::persistent_function_template->InstanceTemplate()->SetInternalFieldCount(1); // 1 since this is a constructor function Gtknotify::persistent_function_template->SetClassName(v8::String::NewSymbol("Notification")); // Our getters and setters Gtknotify::persistent_function_template->InstanceTemplate()->SetAccessor(String::New("title"), GetTitle, SetTitle); Gtknotify::persistent_function_template->InstanceTemplate()->SetAccessor(String::New("icon"), GetIcon, SetIcon); // Our methods NODE_SET_PROTOTYPE_METHOD(Gtknotify::persistent_function_template, "send", Send); // Binding our constructor function to the target variable target->Set(String::NewSymbol("notification"), Gtknotify::persistent_function_template->GetFunction()); }
剩下要做的就是编写我们在Init方法中用的C++方法：New,GetTitle,SetTitle,GetIcon,SetIcon,Send
构造器方法: New()
New() 方法创建了我们自定义类的新实例(一个 Gtknotify 对象)，并设置一些初始值，然后返回该对象的 JavaScript 处理。这是 JavaScript 使用 new 操作符调用构造函数的期望行为。
std::string title; std::string icon; // new notification() static Handle<Value> New(const Arguments& args) { HandleScope scope; Gtknotify* gtknotify_instance = new Gtknotify(); // Set some default values gtknotify_instance->title = "Node.js"; gtknotify_instance->icon = "terminal"; // Wrap our C++ object as a Javascript object gtknotify_instance->Wrap(args.This()); return args.This(); } getters 和 setters: GetTitle(), SetTitle(), GetIcon(), SetIcon()
下面主要是一些样板代码，可以归结为 C++ 和 JavaScript (v8) 之间的值转换。
// this.title static v8::Handle<Value> GetTitle(v8::Local<v8::String> property, const v8::AccessorInfo& info) { // Extract the C++ request object from the JavaScript wrapper. Gtknotify* gtknotify_instance = node::ObjectWrap::Unwrap<Gtknotify>(info.Holder()); return v8::String::New(gtknotify_instance->title.c_str()); } // this.title= static void SetTitle(Local<String> property, Local<Value> value, const AccessorInfo& info) { Gtknotify* gtknotify_instance = node::ObjectWrap::Unwrap<Gtknotify>(info.Holder()); v8::String::Utf8Value v8str(value); gtknotify_instance->title = *v8str; } // this.icon static v8::Handle<Value> GetIcon(v8::Local<v8::String> property, const v8::AccessorInfo& info) { // Extract the C++ request object from the JavaScript wrapper. Gtknotify* gtknotify_instance = node::ObjectWrap::Unwrap<Gtknotify>(info.Holder()); return v8::String::New(gtknotify_instance->icon.c_str()); } // this.icon= static void SetIcon(Local<String> property, Local<Value> value, const AccessorInfo& info) { Gtknotify* gtknotify_instance = node::ObjectWrap::Unwrap<Gtknotify>(info.Holder()); v8::String::Utf8Value v8str(value); gtknotify_instance->icon = *v8str; }
原型方法: Send()
首先我们抽取 C++ 对象的 this 引用，然后使用对象的属性来构建通知并显示。
// this.send() static v8::Handle<Value> Send(const Arguments& args) { v8::HandleScope scope; // Extract C++ object reference from "this" Gtknotify* gtknotify_instance = node::ObjectWrap::Unwrap<Gtknotify>(args.This()); // Convert first argument to V8 String v8::String::Utf8Value v8str(args[0]); // For more info on the Notify library: Notify::init("Basic"); // Arguments: title, content, icon Notify::Notification n(gtknotify_instance->title.c_str(), *v8str, gtknotify_instance->icon.c_str()); // *v8str points to the C string it wraps // Display the notification n.show(); // Return value return v8::Boolean::New(true); }
编译扩展
node-waf 是一个构建工具，用来编译 Node 的扩展，这是 waf 的基本封装。构建过程可通过名为 wscript 的文件进行配置。
def set_options(opt): opt.tool_options("compiler_cxx") def configure(conf): conf.check_tool("compiler_cxx") conf.check_tool("node_addon") # This will tell the compiler to link our extension with the gtkmm and libnotifymm libraries. conf.check_cfg(package='gtkmm-2.4', args='--cflags --libs', uselib_store='LIBGTKMM') conf.check_cfg(package='libnotifymm-1.0', args='--cflags --libs', uselib_store='LIBNOTIFYMM') def build(bld): obj = bld.new_task_gen("cxx", "shlib", "node_addon") obj.cxxflags = ["-g", "-D_FILE_OFFSET_BITS=64", "-D_LARGEFILE_SOURCE", "-Wall"] # This is the name of our extension. obj.target = "gtknotify" obj.source = "src/node_gtknotify.cpp" obj.uselib = ['LIBGTKMM', 'LIBNOTIFYMM']
现在我们已经准备好要开始构建了，在顶级目录下运行如下命令：
node-waf configure && node-waf build
如果一切正常，我们将得到编译过的扩展，位于：./build/default/gtknotify.node ，来试试：
$ node > var notif = require('./build/default/gtknotify.node'); > n = new notif.notification(); { icon: 'terminal', title: 'Node.js' } > n.send("Hello World!"); true
上述的代码将在你的屏幕右上方显示一个通知信息。
打成npm包
这是非常酷的, 但是怎样与Node社区分享你的努力的成果呢? 这才是npm主要的用途: 使它更加容易扩展和分发.
打npm的扩展包是非常简单的. 你所要做的就是在你的顶级目录中创建一个包含你的扩展信息的文件package.json :