Passing this._id from a wrapped blaze component?

I’m using meteor uploads to handle some file uploads.

I want to get the _id of the current page. /uploads/:_id inside of a blaze template. Can flowrouter do this? Or how do I handle this? _id is undefined

UploaderJSX = React.createClass({
componentDidMount() {
  // Use Meteor Blaze to render login buttons
  this.view = Blaze.render(Template.uploader,
    React.findDOMNode(this.refs.container));
},
componentWillUnmount() {
  // Clean up Blaze view
  Blaze.remove(this.view);
},
render() {
  // Just render a placeholder container that will be filled in
  return <span ref="container" />;
}

});

Template.uploader.helpers({
FormData: function() {
  return {
    _id: this._id,
    userId: Meteor.userId(),
    username: Meteor.user().username
  }
}

});

Meteor.startup(function () {
		UploadServer.init({
		  tmpDir: process.env.PWD + '/upload/tmp',
		  uploadDir: process.env.PWD + '/upload/',
		  uploadUrl: '/upload/',
		  checkCreateDirectories: true,
		  getDirectory: function(fileInfo, formData) {
		    // create a sub-directory in the uploadDir based on the content type (e.g. 'images')
		    return formData.username + '/' +formData.contentType;
		  },
		  finished: function(fileInfo, formFields, formData) {
		    // perform a disk operation
		    console.log(formFields);
		    let name = fileInfo.name
		    console.log(name);
		    let url = fileInfo.url;
		    let userId = formFields.userId
		    console.log(userId)
		    let _id = formFields._id
		    console.log(_id)
		    console.log(url);
		      Purchases.update(_id, {
		        $set: {path: {name: name, url: url}}
		      });


		  },

I used passed the props to a session. And returned the session.get into the helper function. I guess this will work.