Dynamic routing with iron:router

Hi there. I’m trying to make unique page for each posts from my collection ising iron:router. I’m using this code:

Router.route(’/items/:_id’, function () {
var item = Items.findOne({ _id: this.params._id});
this.render(‘ShowItem’, {data: item});

I’m getting this error:

TypeError: fn is not a function
Can anyone explain me what I’m doing wrong?

It would be helpful if you could post the whole stack trace for the error, with line numbers etc.