The distributed data objects allow data across devices to be processed like local variables by shielding complex data interaction between devices. For the devices that form a Super Device, when data in the distributed data object of an application is added, deleted, or modified on a device, the data for the same application is also updated on the other devices. The devices can listen for the data changes and online and offline states of other devices. The distributed data objects support basic data types, such as number, string, and Boolean, as well as complex data types, such as array and nested basic types.
The distributed data objects allow data across devices to be processed like local variables by shielding complex data interaction between devices. For the devices that form a Super Device, when data in the distributed data object of an application is added, deleted, or modified on a device, the data for the same application is also updated on the other devices. The devices can listen for the data changes and online and offline status of other devices. The distributed data objects support basic data types, such as number, string, and Boolean, as well as complex data types, such as array and nested basic types.
## Available APIs
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@@ -15,7 +15,7 @@ Call **createDistributedObject()** to create a distributed data object instance.
**Table 1** API for creating a distributed data object instance
| Package| API| Description|
| -------- | -------- | -------- |
| ohos.data.distributedDataObject| createDistributedObject(source: object): DistributedObject | Creates a distributed data object instance for data operations.<br>- **source**: attributes of the **distributedObject** set.<br>- **DistributedObject**: returns the distributed object created.|
| ohos.data.distributedDataObject| createDistributedObject(source: object): DistributedObject | Creates a distributed data object instance for data operations.<br>- **source**: attributes of the **distributedObject** set.<br>- **DistributedObject**: returns the distributed object created.|
### Generating a Session ID
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@@ -28,12 +28,12 @@ Call **genSessionId()** to generate a session ID randomly. The generated session
### Setting a SessionID for Distributed Data Objects
Call setSessionId() to set the session ID for a distributed data object. The session ID is a unique identifier for one collaboration across devices. The distributed data objects to be synchronized must be associated with the same session ID.
Call **setSessionId()** to set a session ID for a distributed data object. The session ID is a unique identifier for one collaboration across devices. The distributed data objects to be synchronized must be associated with the same session ID.
**Table 3** API for setting a session ID
| Class| API| Description|
| -------- | -------- | -------- |
| DistributedDataObject | setSessionId(sessionId?: string): boolean | Sets a session ID for distributed data objects.<br> **sessionId**: ID of a distributed object in a trusted network. To remove a distributed data object from the network, set this parameter to "" or leave it empty.|
| DistributedDataObject | setSessionId(sessionId?: string): boolean | Sets a session ID for distributed data objects.<br> **sessionId**: session ID of a distributed object in a trusted network. To remove a distributed data object from the network, set this parameter to "" or leave it empty.|
### Observing Data Changes
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@@ -43,7 +43,7 @@ Call **on()** to subscribe to data changes of a distributed data object. When th
| Class| API| Description|
| -------- | -------- | -------- |
| DistributedDataObject| on(type: 'change', callback: Callback<{sessionId:string,fields:Array<string>}>): void | Subscribes to data changes.|
| DistributedDataObject| off(type: 'change', callback?: Callback<{sessionId:string,fields:Array<string>}>): void | Unsubscribes from data changes. Callback used to return changes of the distributed object. If this parameter is not specified, all callbacks related to data changes will be unregistered.|
| DistributedDataObject| off(type: 'change', callback?: Callback<{sessionId:string,fields:Array<string>}>): void | Unsubscribes from data changes. **Callback**: specifies callback used to return changes of the distributed data object. If this parameter is not specified, all callbacks related to data changes will be unregistered.|
### Observing Online or Offline Status
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// After obtaining that the device status goes online, the remote object synchronizes data. That is, name changes to jack and age to 18.
// After learning that the device goes online, the remote object synchronizes data. That is, name changes to jack and age to 18.
```
4. Observe the data changes of the distributed data object. Subscribe to data changes of the remote end. When the data is the peer end changes, a callback will be called to return the data changes.
4. Observe the data changes of the distributed data object. You can subscribe to data changes of the peer object. When the data in the peer object changes, a callback will be called to return the data changes.
The sample code is as follows:
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}
}
// To refresh the page in changeCallback, correctly set this.changeCallback.bind(this) in
changeCallback.
// To refresh the page in changeCallback, correctly bind (this) to the changeCallback.
5. Modify object attributes. The object attributes support basic data types (such as number, Boolean, and string) and complex data types (array and nested basic types).
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> For the distributed data object of the complex type, only the root attribute can be modified. The subordinate attributes cannot be modified. Example:
```js
// Supported modification.
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The sample code is as follows:
```js
// Unsubscribe from changeCallback.
// Unsubscribe from the specified data change callback.
local_object.off("change",changeCallback);
// Unsubscribe from all data change callbacks.
local_object.off("change");
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@@ -156,16 +156,16 @@ The following example shows how to implement a distributed data object synchroni
local_object.on("status",this.statusCallback);
```
9. Unsubscribe from the status changes of the distributed data object. You can specify the callback to unsubscribe from. If you do not specify the callback, all status change callbacks will be unsubscribe from.
9. Unsubscribe from the status changes of the distributed data object. You can specify the callback to unsubscribe from. If you do not specify the callback, this API unsubscribes from all callbacks of this distributed data object.
The sample code is as follows:
```js
// Unsubscribe from the online status change callback.
// Unsubscribe from the specified status change callback.
local_object.off("status",statusCallback);
// Unsubscribe from all online status change callbacks.
// Unsubscribe from all status change callbacks.
local_object.off("status");
```
10. Remove a distributed data object from the synchronization network. After the distributed data object is removed from the network, the data changes on the local end will not be synchronized to the remote end.
10. Remove a distributed data object from the synchronization network. Data changes on the local object will not be synchronized to the removed distributed data object.
The sample code is as follows:
```js
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```
## Development Example
The following example is provided for you to better understand the development of distributed data object:
The following example is provided for you to better understand the development of distributed data objects:
When an event occurs on a device, such as a note is added, the tile or content of a note is changed, and the event list is cleared, the change will be synchronized to other devices in the trusted network by the Notepad app.
When an event of the Notepad app occurs on a device, such as a note is added, the tile or content of a note is changed, or the event list is cleared, the change will be synchronized to other devices in the trusted network.
> The initial APIs of this module are supported since API version 8. Newly added APIs will be marked with a superscript to indicate their earliest API version.
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| -------- | -------- | -------- | -------- |
| source | object | Yes| Attribute of the distributed data object to create.|
**Return Value**
**Return value**
| Type| Description|
| -------- | -------- |
| [DistributedObject](#distributedobject) | Distributed data object created.|
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@@ -78,7 +78,7 @@ Sets a session ID for synchronization. Automatic synchronization is performed fo
| -------- | -------- | -------- | -------- |
| sessionId | string | No| ID of a distributed data object on a trusted network. To remove a distributed data object from the network, set this parameter to "" or leave it empty.|
**Return Value**
**Return value**
| Type| Description|
| -------- | -------- |
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| type | string | Yes| Event type to subscribe to. The value is **change**, which indicates data change events.|
| callback | Callback<{sessionId:string,fields:Array<string>}> | Yes| Callback used to return the changes of the distributed data object.<br>**sessionId** indicates the session ID of the distributed data object.<br>**fields** indicates the attributes of the distributed data object changed.|
| type | string | Yes| Event type to subscribe to. The value is **change**, which indicates data changes.|
| callback | Callback<{sessionId:string,fields:Array<string>}> | Yes| Callback used to return the changes of the distributed data object.<br>**sessionId** indicates the session ID of the distributed data object.<br>**fields** indicates the changed attributes of the distributed data object.|
**Example**
```js
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| type | string | Yes| Event type to subscribe to. The value is **change**, which indicates data change events.|
| callback | Callback<{sessionId:string,fields:Array<string>}> | No| Callback used to return changes of the distributed data object. If this parameter is not specified, all callbacks related to data changes will be unregistered.<br>**sessionId** indicates the session ID of the distributed data object.<br>**fields** indicates the attributes of the distributed data object changed.|
| type | string | Yes| Event type to unsubscribe from. The value is **change**, which indicates data changes.|
| callback | Callback<{sessionId:string,fields:Array<string>}> | No| Callback used to return the changes of the distributed data object. If this parameter is not specified, this API unsubscribes from all callbacks for data changes of this distributed data object.<br>**sessionId** indicates the session ID of the distributed data object.<br>**fields** indicates the changed attributes of the distributed data object.|
**Example**
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| type | string | Yes| Event type to subscribe to. The value is "status", which indicates the status (online or offline) change events.|
| callback | Callback<{sessionId:string,networkId:string,status:'online'\|'offline'}> | Yes| Callback used to return the online or offline status.<br>**sessionId** indicates the session ID of the distributed data object.<br>**networkId** indicates the network ID of the device.<br>**status** indicates the status, which can be online or offline.|
| type | string | Yes| Event type to subscribe to. The value is **status**, which indicates the change in the status (online or offline) of the distributed data object.|
| callback | Callback<{sessionId:string,networkId:string,status:'online'\|'offline'}> | Yes| Callback used to return the status change.<br>**sessionId** indicates the session ID of the distributed data object.<br>**networkId** indicates the network ID of the device.<br>**status** indicates the status, which can be online or offline.|
**Example**
```js
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| type | string | Yes| Event type to subscribe to. The value is "status", which indicates the status (online or offline) change events.|
| callback | Callback<{sessionId:string,deviceId:string,status:'online'\|'offline'}> | No| Callback used to return the status changes. If this parameter is not specified, all the status change callbacks will be unregistered.<br>**sessionId** indicates the session ID of the distributed data object.<br>**deviceId** indicates the device ID of the distributed data object.<br>**status** indicates the status, which can be online or offline.|
| type | string | Yes| Event type to unsubscribe from. The value is **status**, which indicates the change in the status (online or offline) of the distributed data object.|
| callback | Callback<{sessionId:string,deviceId:string,status:'online'\|'offline'}> | No| Callback used to return the status change. If this parameter is not specified, this API unsubscribes from all callbacks of this distributed data object.<br>**sessionId** indicates the session ID of the distributed data object.<br>**deviceId** indicates the device ID of the distributed data object.<br>**status** indicates the status, which can be online or offline.|
**Example**
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