# CallbackProperty

#### new Cesium.CallbackProperty(callback, isConstant)
DataSources/CallbackProperty.js 23

  A `Property` whose value is lazily evaluated by a callback function.

  Name | Type | Description
  --- | --- | ---
  `callback` | CallbackProperty~Callback | The function to be called when the property is evaluated.
  `isConstant` | Boolean | `true` when the callback function returns the same value every time, `false` if the value will change.

### Members

#### readonlydefinitionChanged : Event
DataSources/CallbackProperty.js 51

  Gets the event that is raised whenever the definition of this property changes. The definition is changed whenever setCallback is called.

#### readonlyisConstant : Boolean
DataSources/CallbackProperty.js 38

  Gets a value indicating if this property is constant.

### Methods

#### equals(other) → Boolean
DataSources/CallbackProperty.js 102

  Compares this property to the provided property and returns `true` if they are equal, `false` otherwise.

  Name | Type | Description
  --- | --- | ---
  `other` | Property | optional The other property.

  ##### Returns:

  `true` if left and right are equal, `false` otherwise.

#### getValue(time, result) → Object
DataSources/CallbackProperty.js 65

  Gets the value of the property.

  Name | Type | Description
  --- | --- | ---
  `time` | JulianDate | optional The time for which to retrieve the value. This parameter is unused since the value does not change with respect to time.
  `result` | Object | optional The object to store the value into, if omitted, a new instance is created and returned.

  ##### Returns:

  The modified result parameter or a new instance if the result parameter was not supplied or is unsupported.

#### setCallback(callback, isConstant)
DataSources/CallbackProperty.js 75

  Sets the callback to be used.

  Name | Type | Description
  --- | --- | ---
  `callback` | CallbackProperty~Callback | The function to be called when the property is evaluated.
  `isConstant` | Boolean | `true` when the callback function returns the same value every time, `false` if the value will change.

### Type Definitions

#### Callback(time, result) → Object
DataSources/CallbackProperty.js 106

  A function that returns the value of the property.

  Name | Type | Description
  --- | --- | ---
  `time` | JulianDate | optional The time for which to retrieve the value.
  `result` | Object | optional The object to store the value into, if omitted, a new instance is created and returned.

  ##### Returns:

  The modified result parameter or a new instance if the result parameter was not supplied or is unsupported.