For tracking product impressions which Google Analytics hit type should I use?

Question

Currently for tracking product impressions, I am using below code:

    let tracker = GAI.sharedInstance().defaultTracker
    let builder = GAIDictionaryBuilder.createScreenView()
    let product = getProduct()
    let trackProduct = GAIEcommerceProduct()
    let impressionList = "test_prod"
    trackProduct.setId(product.ID)
    trackProduct.setName(product.name)
    trackProduct.setCategory(product.category)
    trackProduct.setBrand(product.brand)
    builder.addProductImpression(trackProduct, impressionList: impressionList, impressionSource: "")
 
}

if let screenName = screenName {
    tracker.set(kGAIScreenName, value: screenName)
}
tracker.add(customDimension: customDimensions)
tracker.send(builder.build() as [NSObject: AnyObject])

My problem is that every time screen view is being tracked. I am getting duplicate screen view's. I want to know how can I create GAIDictionaryBuilder other tha createScreenView. I know there are few other ways like
createEvent(withCategory: "ca", action: "search", label: nil, value: nil)

But is there a defined way which one to create for tracking impressions.