This API is available on Firefox OS for internal applications only.
The DataStoreTask
interface of the Data Store API represents a record changed in the data store when a DataStoreCursor
is used to iterate through the data store's change history.
Note: The Data Store API is available in Web Workers, from Firefox 32 onwards (Firefox OS 2.0; see bug 949325.)
Properties
DataStoreTask.data
Read only- Returns the data stored in the changed record in the data store. Must return
null
if the operation isclear
ordone
. DataStoreTask.id
Read only- Returns the identifier of the changed record in the data store. Must return
null
if the operation isclear
ordone
. DataStoreTask.operation
Read only- Returns the type of operation that represents the current change that has been made to the data store.
DataStoreTask.revisionId
Read only- Returns the id of the current revision of the data store, i.e. the current change that has been made to a data record.
Example
In the following example, we use navigator.getDataStores
to return a list of DataStore
objects representing data stores on the device called contacts
. Since there is only one such data store, we can access it inside the outer promise using stores[0]
. The next promise uses DataStore.getLength
to return the number of records in the store. If the value is 0, we populate the data store with records contained in the contactsInit
object; if there is already data in the store, we run DataStore.sync
to create a DataStoreCursor
object allowing us to loop through any additions since the code last accessed the data store and update the data display as necessary.
The cursor is passed to the runNextTask()
function, which calls DataStoreCursor.next
to start the process of managing the next task — the resulting DataStoreTask
object is passed to the manageTask()
function to work out what to do with it. runNextTask()
is then called repeatedly by manageTask()
until the cursor has finished working through all the records.
navigator.getDataStores('contacts').then(function(stores) { stores[0].getLength().then(function(storeLength) { if(storeLength == 0) { for(i = 0; i < contactsInit.length; i++) { addContact(stores[0],contactsInit[i]); }; } else { var cursor = stores[0].sync(); runNextTask(cursor); } }); }); function runNextTask(cursor) { cursor.next().then(function(task) { manageTask(cursor, task); }); } function manageTask(cursor, task) { if (task.operation == 'done') { // Finished adding contacts! return; } if (task.operation == 'add') { // Add the contacts that are different to how it was before displayExisting(task.id, task.data); } runNextTask(cursor); }
Note: This code is taken from our Data Store Contacts Editor demo. Look through the code to help you understand better what is going on, and how the full code works.
Operation types
The different operation types used in DataStoreTask
are (see also the spec definitions):
Enumeration | Description |
---|---|
add |
The data record is added into the data store. |
update |
The data record is updated in the data store. |
remove |
The data record is deleted in the data store. |
clear |
All the records are deleted from the data store; a clear operation (plus a list of add operations) is also received when the revision ID is too old for the DataStore to be able to provide all the steps to bring you to the current ID. The DataStore Service has a list of about 100 operations in memory. |
done |
All changes are finished. |
Note: These are currently different to the operation types returned by DataStoreChangeEvent
. This discrepancy will be fixed soon at an appropriate time.
Specifications
Specification | Status | Comment |
---|---|---|
Data Store API The definition of 'DataStoreTask' in that specification. |
Draft |
The discussion concerning this API's creation happened in various Mozilla mailing lists and other places. A summary of the discussion and further pointers can be found on the Mozilla Wiki. For further feedback and questions, send mail to the dev-webapi mailing list.
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | No support | No support | No support | No support | No support |
Feature | Android | Chrome | Firefox Mobile (Gecko) | Firefox OS | IE Phone | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|---|
Basic support | No support | No support | No support | 1.0.1 | No support | No support | No support |
Available in web workers | No support | No support | No support | 2.0 | No support | No support | No support |