Passing spacebar data context from parent template to child

Question

I am having a silly trouble with nested templates. I want to create a dropdown menu with 4 main categories and about 2-3 subcategories for each main category.

<template name="Warehouselist">
   <li class="dropdown">
    <a class="dropdown-toggle" data-toggle="dropdown" href="#"> {{warehouse}} <span class="caret"></span></a>
    <ul class="dropdown-menu">     
    {{#each Forms}}
      {{>Form}}  //Pass {{warehouse}} here
    {{/each}}                
    </ul>
  </li>
</template>
<template name="Form">
   <li id="EWPacking"><a href="#">{{FormName}}</a></li>
</template>

The problem is that I don't know how to pass the {{warehouse}} data to the child template's helper in order so I can do something like this.

  Template.bonus.helpers({
    Userform: function(){
      return UserForms.find({});
    },
    warehouse: function(){
      return Warehouse.find({});
    },
  });
  Template.Warehouselist.helpers({
    Forms: function(Warehouse){
      return Forms.find({Warehousename:Warehouse});
    }
  });

The point is that the helper of the child template has to return different data, depending on what is the Category of the parent element.

Answer 1

Use parent data context in the child template 'Form':

<template name="Warehouselist">
    <li class="dropdown">
          <a class="dropdown-toggle" data-toggle="dropdown" href="#">{{warehouse}}<span class="caret"></span>
          </a>
        <ul class="dropdown-menu">
            {{#each Forms}}
                {{>Form}}
            {{/each}}
        </ul>
    </li>
</template>
<template name="Form">
    <li id="EWPacking">
     <a href="#">{{FormName}} - {{../warehouse}}</a></li>
</template>

And change your javascript for the Warehouselist template helper. Get the warehouse from the data context with Template.currentData() and pass it in the Forms.find(). Like this:

Template.Warehouselist.helpers({
    Forms: function(){
        var warehouse = Template.currentData().warehouse;
        console.log('warehouse:', warehouse);
        return Forms.find({Warehousename: warehouse});
    }
});

If you want to pass warehouse to the child template like you asked use: (BUT: this is not needed if you follow the solution above!)

{{#each Forms}}
  {{>Form warehouse=warehouse}}
{{/each}}