node.js - Nodejs - 如何让功能只发生一次？

Question

我得到了一个使用 socket.io 和 express 框架的简单聊天应用程序，下面是部分代码:

var app = express.createServer();
var socket = io.listen(app);

var store = new express.session.MemoryStore;
app.use(express.cookieParser());
app.use(express.session({ 
    secret: 'something', 
    store: store, 
    cookie: { 
        maxAge: 60*60*24*30*1000
    }
}));

app.get('/', function(req, res){
    socket.on('connection', function(client) {
        req.session.ioid = client.sessionId;
        req.session.channel = req.param('channel');
        req.session.username = req.param('username');
        //I want the code below happen just once                
        res.header('Content-Type', 'text/plain');
        res.header('Access-Control-Allow-Origin', '*');
        res.send({sid:req.session.id});
    });
});

您可以在 socket.on 闭包中看到 res.header 和 res.send。那些“res”将不断执行，并导致错误“发送后无法设置 header ”。

我正在寻找制作方 block 的方法-

res.header('Content-Type', 'text/plain');

res.header('Access-Control-Allow-Origin', '*');

res.send({sid:req.session.id});

-只发生一次。

Answer 1

app.get('/', function(req, res){
    socket.on("connection", function(client) {
        req.session.ioid = client.sessionId;
        req.session.channel = req.param('channel');
        req.session.username = req.param('username');
    });

    socket.once('connection', function(client) {
        //I want the code below happen just once                
        res.header('Content-Type', 'text/plain');
        res.header('Access-Control-Allow-Origin', '*');
        res.send({sid:req.session.id});
    });
});

使用.once