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doc: don't use using namespace v8
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Wholesale importing an entire namespace with `using namespace` is a bad
practice.  Remove it from the addons documentation and replace it with
proper `using` directives.  Wrap code in a namespace while we are here.

PR-URL: #1125
Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
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@bnoordhuis
bnoordhuis committed Mar 21, 2015
1 parent c4e1b82 commit 55abf34
Showing 1 changed file with 145 additions and 11 deletions.
156 changes: 145 additions & 11 deletions doc/api/addons.markdown
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Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,15 @@ First we create a file `hello.cc`:
// hello.cc
#include <node.h>

using namespace v8;
namespace demo {

using v8::FunctionCallbackInfo;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::Object;
using v8::String;
using v8::Value;

void Method(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = args.GetIsolate();
Expand All @@ -54,6 +62,8 @@ First we create a file `hello.cc`:

NODE_MODULE(addon, init)

} // namespace demo

Note that all io.js addons must export an initialization function:

void Initialize(Local<Object> exports);
Expand Down Expand Up @@ -141,7 +151,17 @@ function calls and return a result. This is the main and only needed source
// addon.cc
#include <node.h>

using namespace v8;
namespace demo {

using v8::Exception;
using v8::FunctionCallbackInfo;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::Number;
using v8::Object;
using v8::String;
using v8::Value;

void Add(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = args.GetIsolate();
Expand Down Expand Up @@ -170,6 +190,8 @@ function calls and return a result. This is the main and only needed source

NODE_MODULE(addon, Init)

} // namespace demo

You can test it with the following JavaScript snippet:

// test.js
Expand All @@ -186,7 +208,16 @@ there. Here's `addon.cc`:
// addon.cc
#include <node.h>

using namespace v8;
namespace demo {

using v8::Function;
using v8::FunctionCallbackInfo;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::Object;
using v8::String;
using v8::Value;

void RunCallback(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = args.GetIsolate();
Expand All @@ -202,6 +233,8 @@ there. Here's `addon.cc`:

NODE_MODULE(addon, Init)

} // namespace demo

Note that this example uses a two-argument form of `Init()` that receives
the full `module` object as the second argument. This allows the addon
to completely overwrite `exports` with a single function instead of
Expand All @@ -226,7 +259,15 @@ the string passed to `createObject()`:
// addon.cc
#include <node.h>

using namespace v8;
namespace demo {

using v8::FunctionCallbackInfo;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::Object;
using v8::String;
using v8::Value;

void CreateObject(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = args.GetIsolate();
Expand All @@ -243,6 +284,8 @@ the string passed to `createObject()`:

NODE_MODULE(addon, Init)

} // namespace demo

To test it in JavaScript:

// test.js
Expand All @@ -261,7 +304,17 @@ wraps a C++ function:
// addon.cc
#include <node.h>

using namespace v8;
namespace demo {

using v8::Function;
using v8::FunctionCallbackInfo;
using v8::FunctionTemplate;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::Object;
using v8::String;
using v8::Value;

void MyFunction(const FunctionCallbackInfo<Value>& args) {
Isolate* isolate = args.GetIsolate();
Expand All @@ -286,6 +339,8 @@ wraps a C++ function:

NODE_MODULE(addon, Init)

} // namespace demo

To test:

// test.js
Expand All @@ -305,14 +360,19 @@ module `addon.cc`:
#include <node.h>
#include "myobject.h"

using namespace v8;
namespace demo {

using v8::Local;
using v8::Object;

void InitAll(Local<Object> exports) {
MyObject::Init(exports);
}

NODE_MODULE(addon, InitAll)

} // namespace demo

Then in `myobject.h` make your wrapper inherit from `node::ObjectWrap`:

// myobject.h
Expand All @@ -322,6 +382,8 @@ Then in `myobject.h` make your wrapper inherit from `node::ObjectWrap`:
#include <node.h>
#include <node_object_wrap.h>

namespace demo {

class MyObject : public node::ObjectWrap {
public:
static void Init(v8::Local<v8::Object> exports);
Expand All @@ -336,6 +398,8 @@ Then in `myobject.h` make your wrapper inherit from `node::ObjectWrap`:
double value_;
};

} // namespace demo

#endif

And in `myobject.cc` implement the various methods that you want to expose.
Expand All @@ -345,7 +409,19 @@ prototype:
// myobject.cc
#include "myobject.h"

using namespace v8;
namespace demo {

using v8::Function;
using v8::FunctionCallbackInfo;
using v8::FunctionTemplate;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::Number;
using v8::Object;
using v8::Persistent;
using v8::String;
using v8::Value;

Persistent<Function> MyObject::constructor;

Expand Down Expand Up @@ -398,6 +474,8 @@ prototype:
args.GetReturnValue().Set(Number::New(isolate, obj->value_));
}

} // namespace demo

Test it with:

// test.js
Expand All @@ -423,7 +501,15 @@ Let's register our `createObject` method in `addon.cc`:
#include <node.h>
#include "myobject.h"

using namespace v8;
namespace demo {

using v8::FunctionCallbackInfo;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::Object;
using v8::String;
using v8::Value;

void CreateObject(const FunctionCallbackInfo<Value>& args) {
MyObject::NewInstance(args);
Expand All @@ -437,6 +523,8 @@ Let's register our `createObject` method in `addon.cc`:

NODE_MODULE(addon, InitAll)

} // namespace demo

In `myobject.h` we now introduce the static method `NewInstance` that takes
care of instantiating the object (i.e. it does the job of `new` in JavaScript):

Expand All @@ -447,6 +535,8 @@ care of instantiating the object (i.e. it does the job of `new` in JavaScript):
#include <node.h>
#include <node_object_wrap.h>

namespace demo {

class MyObject : public node::ObjectWrap {
public:
static void Init(v8::Isolate* isolate);
Expand All @@ -462,6 +552,8 @@ care of instantiating the object (i.e. it does the job of `new` in JavaScript):
double value_;
};

} // namespace demo

#endif

The implementation is similar to the above in `myobject.cc`:
Expand All @@ -470,7 +562,19 @@ The implementation is similar to the above in `myobject.cc`:
#include <node.h>
#include "myobject.h"

using namespace v8;
namespace demo {

using v8::Function;
using v8::FunctionCallbackInfo;
using v8::FunctionTemplate;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::Number;
using v8::Object;
using v8::Persistent;
using v8::String;
using v8::Value;

Persistent<Function> MyObject::constructor;

Expand Down Expand Up @@ -530,6 +634,8 @@ The implementation is similar to the above in `myobject.cc`:
args.GetReturnValue().Set(Number::New(isolate, obj->value_));
}

} // namespace demo

Test it with:

// test.js
Expand Down Expand Up @@ -558,7 +664,16 @@ In the following `addon.cc` we introduce a function `add()` that can take on two
#include <node_object_wrap.h>
#include "myobject.h"

using namespace v8;
namespace demo {

using v8::FunctionCallbackInfo;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::Number;
using v8::Object;
using v8::String;
using v8::Value;

void CreateObject(const FunctionCallbackInfo<Value>& args) {
MyObject::NewInstance(args);
Expand All @@ -585,6 +700,8 @@ In the following `addon.cc` we introduce a function `add()` that can take on two

NODE_MODULE(addon, InitAll)

} // namespace demo

To make things interesting we introduce a public method in `myobject.h` so we
can probe private values after unwrapping the object:

Expand All @@ -595,6 +712,8 @@ can probe private values after unwrapping the object:
#include <node.h>
#include <node_object_wrap.h>

namespace demo {

class MyObject : public node::ObjectWrap {
public:
static void Init(v8::Isolate* isolate);
Expand All @@ -610,6 +729,8 @@ can probe private values after unwrapping the object:
double value_;
};

} // namespace demo

#endif

The implementation of `myobject.cc` is similar as before:
Expand All @@ -618,7 +739,18 @@ The implementation of `myobject.cc` is similar as before:
#include <node.h>
#include "myobject.h"

using namespace v8;
namespace demo {

using v8::Function;
using v8::FunctionCallbackInfo;
using v8::FunctionTemplate;
using v8::HandleScope;
using v8::Isolate;
using v8::Local;
using v8::Object;
using v8::Persistent;
using v8::String;
using v8::Value;

Persistent<Function> MyObject::constructor;

Expand Down Expand Up @@ -666,6 +798,8 @@ The implementation of `myobject.cc` is similar as before:
args.GetReturnValue().Set(instance);
}

} // namespace demo

Test it with:

// test.js
Expand Down

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