This API is available on Firefox OS for internal applications 仅。
DataStoreCursor
接口在
Data Store API
represents a cursor that allows apps to iterate through a list of
DataStoreTask
objects representing the change history of the data store, for use when synchronizing the data.
注意 : The Data Store API is available in Web 工作者 , from Firefox 32 onwards (Firefox OS 2.0; see bug 949325 )。
DataStoreCursor.store
只读
Returns the name of the store that the cursor is iterating over.
DataStoreCursor.next()
Promise
类型
DataStoreTask
.
DataStoreCursor.close()
Makes a request to terminate the cursor.
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);
}
注意 : 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.
| 规范 | 状态 | 注释 |
|---|---|---|
|
Data Store API
The definition of 'DataStoreCursor' in that specification. |
草案 |
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.