Adds an attribute with the provided configuration to the host object.

The config argument object supports the following properties:

value <Any>

The initial value to set on the attribute

valueFn <Function | String>

A function, which will return the initial value to set on the attribute. This is useful for cases where the attribute configuration is defined statically, but needs to reference the host instance ("this") to obtain an initial value. If both the value and valueFn properties are defined, the value returned by the valueFn has precedence over the value property, unless it returns undefined, in which case the value property is used.

valueFn can also be set to a string, representing the name of the instance method to be used to retrieve the value.

readOnly <boolean>

Whether or not the attribute is read only. Attributes having readOnly set to true cannot be modified by invoking the set method.

writeOnce <boolean> or <string>

Whether or not the attribute is "write once". Attributes having writeOnce set to true, can only have their values set once, be it through the default configuration, constructor configuration arguments, or by invoking set.

The writeOnce attribute can also be set to the string "initOnly", in which case the attribute can only be set during initialization (when used with Base, this means it can only be set during construction)

setter <Function | String>

The setter function used to massage or normalize the value passed to the set method for the attribute. The value returned by the setter will be the final stored value. Returning Attribute.INVALID_VALUE, from the setter will prevent the value from being stored.

setter can also be set to a string, representing the name of the instance method to be used as the setter function.

getter <Function | String>

The getter function used to massage or normalize the value returned by the get method for the attribute. The value returned by the getter function is the value which will be returned to the user when they invoke get.

getter can also be set to a string, representing the name of the instance method to be used as the getter function.

validator <Function | String>

The validator function invoked prior to setting the stored value. Returning false from the validator function will prevent the value from being stored.

validator can also be set to a string, representing the name of the instance method to be used as the validator function.

lazyAdd <boolean>

Whether or not to delay initialization of the attribute until the first call to get/set it. This flag can be used to over-ride lazy initialization on a per attribute basis, when adding multiple attributes through the addAttrs method.

The setter, getter and validator are invoked with the value and name passed in as the first and second arguments, and with the context ("this") set to the host object.

Configuration properties outside of the list mentioned above are considered private properties used internally by attribute, and are not intended for public use.

Configures a group of attributes, and sets initial values.

NOTE: This method does not isolate the configuration object by merging/cloning. The caller is responsible for merging/cloning the configuration object if required.

Checks if the given attribute has been added to the host

Returns the current value of the attribute. If the attribute has been configured with a 'getter' function, this method will delegate to the 'getter' to obtain the value of the attribute.

Gets multiple attribute values.

Sets the value of an attribute.

Sets multiple attribute values.