TAGDataLayer Class Reference

The data layer is a dictionary holding generic information about the application.

It uses a standard set of keys so it can be read by any party that understands the specification. The data layer state is updated through its API. For example, an app might start with the following dataLayer:

   {
     title: "Original screen title"
   }

As the state/data of an app can change, the app can update the dataLayer with a call such as:

   [dataLayer push:@{@"title": @"New screen title"}];

Now the data layer contains:

   {
     title: "New screen title"
   }

After another push happens:

   [dataLayer push:@{@"xyz": @3}];

The dataLayer contains:

   {
     "title": "New screen title",
     "xyz": 3
   }

The following example demonstrates how array and map merging works. If the original dataLayer contains:

   {
     "items": @[@"item1", [NSNull null], @"item2", @{@"a": @"aValue", @"b": @"bValue"}]
   }

After this push happens:

   [dataLayer push:@{@"items":
       @[[NSNull null], @"item6", kTAGDataLayerObjectNotPresent, @{@"a": [NSNull null]}]}

The dataLayer contains:

   {
     "items": @[[NSNull null], @"item6", @"item2", @{@"a": [NSNull null], @"b": @"bValue"}]}
   }

Pushes happen synchronously; after the push, changes have been reflected in the model.

When an event key is pushed to the data layer, rules for tags are evaluated and any tags matching this event will fire. For example, given a container with a tag whose firing rules is that "event" is equal to "openScreen", after this push:

   [dataLayer push:@{@"event", @"openScreen"}];

that tag will fire.