DataLayer

public class DataLayer

The data layer is a map 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(DataLayer.mapOf("title", "New screen title"));

Now the data layer contains:

   {
     title: "New screen title"
   }

After another push happens:

 dataLayer.push(DataLayer.mapOf("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", null, "item2", {"a": "aValue", "b": "bValue"}]
   }

After this push happens:

 dataLayer.push("items", DataLayer.listOf(null, "item6", DataLayer.OBJECT_NOT_PRESENT,
     DataLayer.mapOf("a", null)));

The dataLayer contains:

   {
     "items": [null, "item6", "item2", {"a": 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 rule is that "event" is equal to "openScreen", after this push:

 dataLayer.push("event", "openScreen");

that tag will fire.

Field Summary

public static final Object

OBJECT_NOT_PRESENT

Values of this type used in a List causes the List to be sparse when merging; it's as if there were no element at that index.

Public Method Summary

Object	get(String key)
static List<Object>	listOf(Object... objects)
static Map<Object, Object>	mapOf(Object... objects)
void	push(Map<Object, Object> update)
void	push(Object key, Object value)

Fields

public static final Object OBJECT_NOT_PRESENT

Values of this type used in a List causes the List to be sparse when merging; it's as if there were no element at that index.

Public Methods

public Object get (String key)

Returns the object in the model associated with the given key. If the key is not found, null is returned.

The key can can have embedded periods. For example: a key of "a.b.c" returns a map with key "c" in a map with key "b" in a map with key "a" in the model.

public static List<Object> listOf (Object... objects)

Utility method that creates a list.

For example, the following creates a list containing "object1" and "object2":

   List<Object> list = DataLayer.listOf("object1", "object2");
 

public static Map<Object, Object> mapOf (Object... objects)

Utility method that creates a map. The parameters should be pairs of key values.

For example, the following creates a map mapping "key1" to "value1" and "key2" to "value2":

   Map<Object, Object> map = DataLayer.mapOf("key1", "value1", "key2", "value2");
 

Throws

IllegalArgumentException

if there are an odd number of parameters

public void push (Map<Object, Object> update)

Merges the given update object into the existing data model, calling any listeners with the update (after the merge occurs).

If you want to represent a missing value (like an empty index in a List), use the OBJECT_NOT_PRESENT object.

If another thread is executing a push, this call blocks until that thread is finished.

This is normally a synchronous call. However, if, while the thread is executing the push, another push happens from the same thread, then that second push is asynchronous (the second push will return before changes have been made to the data layer). This second push from the same thread can occur, for example, if a data layer push is made in response to a tag firing.

If the update contains the key event, rules will be evaluated and matching tags will fire.

Parameters

update

the update object to process

public void push (Object key, Object value)

Pushes a key/value pair of data to the data layer. This is just a convenience method that calls push(DataLayer.mapOf(key, value)).