How to refactor Handlebars template and helper code in Meteor when pass parameters?

Question

Any idea how to allow my BioPic Handlebars helper (I'm using Meteor) to allow different contexts for the param 'owner'. I'm calling showBioPic as a partial from another template i.e.

<template name="myMain">
    {{#each post}}
        {{> showBioPic}}
    {{/each}}
    Do a bunch of other stuff here too.
</template>

I want be able to pass in different 'owner' values depending on the calling template, i.e. Meteor.userId, post.owner, anotherUsersId. i.e. if I used {{#each user}} this doesn't have an owner field, it has a userId, so BioPic helper would not work.

<template name="showBioPic">        
    {{#with BioPic owner}}
        <img src="{{cfsFileUrl 'size48x48gm'}}" alt="Profile Picture: {{_id}}">
    {{else}}
        <img class="showShared" src="images/default-biopic-48x48.png" alt="Default Profile Picture">
    {{/with}}
</template>


Template.showBioPic.BioPic = function (IN_ownerId)    
   return BioPicsFS.findOne( { owner: IN_ownerId });
};

Answer 1

If using a Template helper is an option, then something like this should work:

Template.myMain.helpers({
  showBioPicWithContext: function (owner) {
    return Template.showBioPic(owner);
  }
});

<template name="myMain">
    {{#each post}}
        {{showBioPicWithContext id}}
    {{/each}}
    Do a bunch of other stuff here too.
</template>

<template name="showBioPic">
    {{#if _id}}
        <img src="{{cfsFileUrl 'size48x48gm'}}" alt="Profile Picture: {{_id}}">
    {{else}}
        <img class="showShared" src="images/default-biopic-48x48.png" alt="Default Profile Picture">
    {{/if}}
</template>

Answer 2

I'm not certain if I understand the details of your problem, but in one of my projects I do something like this:

Handlebars.registerHelper('BioPic', function(user) {
  if (_.isString(user)) {
    // assume user is an id
  } else {
    // assume user is an object like Meteor.user()
  }
});

Handlebars helpers are just functions, so you you can test the value of the parameter passed to them and act accordingly. In the above example, when user is a string we could assume it's an id and return something like Pictures.findOne({owner: user});. You can just add more clauses based on all possible variations of the user input.