# Want

The **Want** module provides the basic communication component of the system.

> **NOTE**
> 
> 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.

## Modules to Import

```
import Want from '@ohos.application.Want';
```

## Attributes

**System capability**: SystemCapability.Ability.AbilityBase

| Name       | Readable/Writable| Type                | Mandatory| Description                                                        |
| ----------- | -------- | -------------------- | ---- | ------------------------------------------------------------ |
| deviceId    | Read only    | string               | No  | ID of the device running the ability.                               |
| bundleName   | Read only    | string               | No  | Bundle name of the ability. If both **bundleName** and **abilityName** are specified in a **Want** object, the **Want** object can match a specific ability.|
| abilityName  | Read only    | string               | No  | Name of the ability. If both **bundleName** and **abilityName** are specified in a **Want** object, the **Want** object can match a specific ability. The value of **abilityName** must be unique in an application.|
| uri          | Read only    | string               | No  | URI information to match. If **uri** is specified in a **Want** object, the **Want** object will match the specified URI information, including **scheme**, **schemeSpecificPart**, **authority**, and **path**.|
| type         | Read only    | string               | No  | MIME type, that is, the type of the file to open, for example, **text/xml** and **image/***. For details about the MIME type definition, see https://www.iana.org/assignments/media-types/media-types.xhtml?utm_source=ld246.com.  |
| flags        | Read only    | number               | No  | How the **Want** object will be handled. For details, see [flags](js-apis-featureAbility.md#flags).|
| action      | Read only    | string               | No  | Action option.                          |
| parameters   | Read only    | {[key: string]: any} | No  | Want parameters in the form of custom key-value (KV) pairs. By default, the following keys are carried:<br>**ohos.aafwk.callerPid**: PID of the caller.<br>**ohos.aafwk.param.callerToken**: token of the caller.<br>**ohos.aafwk.param.callerUid**: UID of the caller. The **userId** parameter in the [Bundle](js-apis-Bundle.md) module can be used to obtain application and bundle information.                                      |
| entities    | Read only    | Array\<string>       | No  | List of entities.                                   |
| moduleName<sup>9+</sup> | Read only  | string | No   | Module to which the ability belongs.|

**Example**

- Basic usage

  ```  js
    var want = {
        "deviceId": "", // An empty deviceId indicates the local device.
        "bundleName": "com.extreme.test",
        "abilityName": "MainAbility",
        "moduleName": "entry" // moduleName is optional.
    };
    this.context.startAbility(want, (error) => {
        // Start an ability explicitly. The bundleName, abilityName, and moduleName parameters work together to uniquely identify an ability.
        console.log("error.code = " + error.code)
    })
  ```

- Passing a file descriptor (FD)

  ```  js
    import fileio from '@ohos.fileio';
    var fd;
    try {
        fd = fileio.openSync("/data/storage/el2/base/haps/pic.png");
    } catch(e) {
        console.log("openSync fail:" + JSON.stringify(e));
    }
    var want = {
        "deviceId": "", // An empty deviceId indicates the local device.
        "bundleName": "com.extreme.test",
        "abilityName": "MainAbility",
        "moduleName": "entry", // moduleName is optional.
        "parameters": {
            "keyFd":{"type":"FD", "value":fd}
        }
    };
    this.context.startAbility(want, (error) => {
        // Start an ability explicitly. The bundleName, abilityName, and moduleName parameters work together to uniquely identify an ability.
        console.log("error.code = " + error.code)
    })
  ```

- Passing **RemoteObject** data

  ```  js
    import rpc from '@ohos.rpc';
    import Ability from '@ohos.application.Ability'

    class Stub extends rpc.RemoteObject {
        constructor(des) {
            if (typeof des == 'string') {
                super(des);
            } else {
                return null;
            }
        }

        onRemoteRequest(code, data, reply, option) {
            if (code === 1) {
                console.log('onRemoteRequest called')
                let token = data.readInterfaceToken();
                let num = data.readInt();
                this.method();
                return true;
            }
            return false;
        }

        method() {
            console.log('method called');
        }
    }

    var remoteObject = new Stub('want-test');
    var want = {
        "deviceId": "", // An empty deviceId indicates the local device.
        "bundleName": "com.extreme.test",
        "abilityName": "MainAbility",
        "moduleName": "entry", // moduleName is optional.
        "parameters": {
            "keyRemoteObject":{"type":"RemoteObject", "value":remoteObject}
        }
    };

    this.context.startAbility(want, (error) => {
        // Start an ability explicitly. The bundleName, abilityName, and moduleName parameters work together to uniquely identify an ability.
        console.log("error.code = " + error.code)
    })

  ```
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