node.js – req.busboy.on(‘file’)没有触发

form(method='post', action='/encoder_post', enctype='multipart/form-data')
    .form-group
        label(for='name') Name
        input.form-control(type='text', id='name', name='name')
    .form-group
        label(for='message') Message
        input.form-control(type='text', id='message', name='message')
    .form-group
        label(for='file') Audio File (*.wav)
        input.form-control(type='file', id='file')
    button.btn.btn-cicada.btn-block(type='submit') Submit

在encoder_post里面,我有以下函数来处理post请求：

router.post('/', function(req, res){
    req.busboy.on('file', function(fieldname, file, filename, encoding, mimetype) {
        console.log("this is in file");
    });
    req.busboy.on('field', function(key, value, keyTruncated, valueTruncated) {
        console.log("The value is: " + value);
    });
    req.pipe(req.busboy);
});

但是,每当我提交表单时,“字段”处理程序都会触发,但“文件”不会触发.

在app.js里面我有：

var busboy = require('connect-busboy');
app.use(busboy());

有任何想法吗？