1# @ohos.base (Public Callback Information) 2 3The **Base** module defines the public callback types of ArkTS APIs, including the common and error callbacks. 4 5> **NOTE** 6> 7> The initial APIs of this module are supported since API version 6. Newly added APIs will be marked with a superscript to indicate their earliest API version. 8 9## Modules to Import 10 11``` 12import base from '@ohos.base'; 13``` 14 15## Callback 16 17Callback\<T> { 18 19(data: T): void; 20 21} 22 23Defines a common callback. 24 25You can set **data** to customize the data type of the information returned by the callback. 26 27**System capability**: SystemCapability.Base 28 29| Name| Type| Mandatory| Description | 30| ---- | ---- | ---- | -------------------------- | 31| data | T | Yes | Common callback information.| 32 33## ErrorCallback 34 35ErrorCallback\<T extends Error = BusinessError> { 36 37(err: T): void; 38 39} 40 41Defines a common callback that carries an error parameter. 42 43The information returned by the callback is of the [BusinessError](#businesserror) type. 44 45**System capability**: SystemCapability.Base 46 47**Parameters** 48 49| Name| Type| Mandatory| Description | 50| ---- | ---- | ---- | ---------------------------- | 51| err | T | Yes | Common error information about the API invoking failure.| 52 53## AsyncCallback 54 55AsyncCallback\<T, E = void> { 56 57(err: BusinessError, data: T): void; 58 59} 60 61Defines a common callback that carries an error parameter and asynchronous return value. 62 63The error parameter is of the [BusinessError](#businesserror) type. 64 65The type of the asynchronous return value is defined by the developer. 66 67**System capability**: SystemCapability.Base 68 69| Name| Type | Mandatory| Description | 70| ---- | ------------------------------------------------------------ | ---- | ---------------------------- | 71| err | [BusinessError](#businesserror) | Yes | Common error information about the API invoking failure.| 72| data | T | Yes | Common callback information. | 73 74## BusinessError 75 76BusinessError\<T = void> extends Error { 77 78code: number; 79 80data?: T; 81} 82 83Defines the error parameter. 84 85**System capability**: SystemCapability.Base 86 87| Name| Type | Mandatory| Description | 88| ---- | ------ | ---- | ---------------------------------------------------------- | 89| code | number | Yes | Common error information about the API invoking failure. | 90| data | T | No | Common callback information. If this parameter is left empty, no related information is returned.| 91