Custom Events iOS - How to send an array of items on the properties object

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Hello,

I am sending custom events to Airship, along with properties on the properties object. I am able to access properties on the properties object when I send data along with a custom event like this:

let addToCartRetailTemplate = UARetailEventTemplate.addedToCart()
let addToCartRetailEvent = addToCartRetailTemplate.createEvent()
var propertyDictionary = Dictionary <String, Any>()
propertyDictionary["brand"] = "brand_value"
addToCartRetailEvent.properties = propertyDictionary
addToCartRetailEvent.track()

But I can't access properties sent as an array of objects. How do I send/access properties on the properties object when sending an array of objects? I want to send something like this to Airship

{
    "items": [
        {
          "brand": "brand_value"
        }
    ]
}

so I can access it like the example in your documentation: 

{{#each items}}
{{brand}}
{{/each}}