Attribute Class
Attribute provides configurable attribute support along with attribute change events. It is designed to be augmented on to a host class, and provides the host with the ability to configure attributes to store and retrieve state, along with attribute change events.
For example, attributes added to the host can be configured:
- As read only.
- As write once.
- With a setter function, which can be used to manipulate values passed to Attribute's set method, before they are stored.
- With a getter function, which can be used to manipulate stored values, before they are returned by Attribute's get method.
- With a validator function, to validate values before they are stored.
See the addAttr method, for the complete set of configuration options available for attributes.
NOTE: Most implementations will be better off extending the Base class, instead of augmenting Attribute directly. Base augments Attribute and will handle the initial configuration of attributes for derived classes, accounting for values passed into the constructor.
Item Index
Methods
- _addAttrs
- _addLazyAttr
- _defAttrChangeFn
- _fireAttrChange
- _getAttr
- _getAttrCfg
- _getAttrInitVal
- _getAttrs
- _getStateVal
- _getType
- _initAttrHost
- _initAttrs
- _isLazyAttr
- _monitor
- _normAttrVals
- _parseType
- _protectAttrs deprecated
- _set
- _setAttr
- _setAttrs
- _setAttrVal
- _setStateVal
- addAttr
- addAttrs
- addTarget
- after
- attrAdded
- before
- bubble
- detach
- detachAll
- fire
- get
- getAttrs
- getEvent
- getTargets
- modifyAttr
- on
- once
- onceAfter
- parseType
- protectAttrs static
- publish
- removeAttr
- removeTarget
- reset
- set
- setAttrs
- subscribe deprecated
- unsubscribe deprecated
- unsubscribeAll deprecated
Properties
- _ATTR_CFG static
- INVALID_VALUE static
Methods
_addAttrs
-
cfgs -
values -
lazy
Implementation behind the public addAttrs method.
This method is invoked directly by get if it encounters a scenario in which an attribute's valueFn attempts to obtain the value an attribute in the same group of attributes, which has not yet been added (on demand initialization).
Parameters:
-
cfgsObjectAn object with attribute name/configuration pairs.
-
valuesObjectAn object with attribute name/value pairs, defining the initial values to apply. Values defined in the cfgs argument will be over-written by values in this argument unless defined as read only.
-
lazyBooleanWhether or not to delay the intialization of these attributes until the first call to get/set. Individual attributes can over-ride this behavior by defining a lazyAdd configuration property in their configuration. See addAttr.
_addLazyAttr
-
name
Finishes initializing an attribute which has been lazily added.
Parameters:
-
nameObjectThe name of the attribute
_defAttrChangeFn
-
e
Default function for attribute change events.
Parameters:
-
eEventFacadeThe event object for attribute change events.
_fireAttrChange
-
attrName -
subAttrName -
currVal -
newVal -
opts
Utility method to help setup the event payload and fire the attribute change event.
Parameters:
-
attrNameStringThe name of the attribute
-
subAttrNameStringThe full path of the property being changed, if this is a sub-attribute value being change. Otherwise null.
-
currValAnyThe current value of the attribute
-
newValAnyThe new value of the attribute
-
optsObjectAny additional event data to mix into the attribute change event's event facade.
_getAttr
-
name
Provides the common implementation for the public get method, allowing Attribute hosts to over-ride either method.
See get for argument details.
Parameters:
-
nameStringThe name of the attribute.
Returns:
_getAttrCfg
-
name
Returns an object with the configuration properties (and value) for the given attribute. If attrName is not provided, returns the configuration properties for all attributes.
Parameters:
-
nameStringOptional. The attribute name. If not provided, the method will return the configuration for all attributes.
Returns:
_getAttrInitVal
-
attr -
cfg -
initValues
Returns the initial value of the given attribute from either the default configuration provided, or the over-ridden value if it exists in the set of initValues provided and the attribute is not read-only.
Parameters:
Returns:
_getAttrs
-
attrs
Implementation behind the public getAttrs method, to get multiple attribute values.
Parameters:
-
attrsArray | booleanOptional. An array of attribute names. If omitted, all attribute values are returned. If set to true, all attributes modified from their initial values are returned.
Returns:
_getStateVal
-
name
Gets the stored value for the attribute, from either the internal state object, or the state proxy if it exits
Parameters:
-
nameStringThe name of the attribute
Returns:
_getType
()
private
If the instance has a prefix attribute and the event type is not prefixed, the instance prefix is applied to the supplied type.
_initAttrHost
-
attrs -
values -
lazy
Constructor logic for attributes. Initializes the host state, and sets up the inital attributes passed to the constructor.
Parameters:
-
attrsObjectThe attributes to add during construction (passed through to addAttrs). These can also be defined on the constructor being augmented with Attribute by defining the ATTRS property on the constructor.
-
valuesObjectThe initial attribute values to apply (passed through to addAttrs). These are not merged/cloned. The caller is responsible for isolating user provided values if required.
-
lazyBooleanWhether or not to add attributes lazily (passed through to addAttrs).
_initAttrs
-
attrs -
values -
lazy
Utility method to set up initial attributes defined during construction, either through the constructor.ATTRS property, or explicitly passed in.
Parameters:
-
attrsObjectThe attributes to add during construction (passed through to addAttrs). These can also be defined on the constructor being augmented with Attribute by defining the ATTRS property on the constructor.
-
valuesObjectThe initial attribute values to apply (passed through to addAttrs). These are not merged/cloned. The caller is responsible for isolating user provided values if required.
-
lazyBooleanWhether or not to add attributes lazily (passed through to addAttrs).
_isLazyAttr
-
name
Checks whether or not the attribute is one which has been added lazily and still requires initialization.
Parameters:
-
nameStringThe name of the attribute
Returns:
_monitor
-
what -
eventType -
o
This is the entry point for the event monitoring system. You can monitor 'attach', 'detach', 'fire', and 'publish'. When configured, these events generate an event. click -> clickattach, clickdetach, click_publish -- these can be subscribed to like other events to monitor the event system. Inividual published events can have monitoring turned on or off (publish can't be turned off before it it published) by setting the events 'monitor' config.
Parameters:
-
whatString'attach', 'detach', 'fire', or 'publish'
-
eventTypeString | CustomEventThe prefixed name of the event being monitored, or the CustomEvent object.
-
oObjectInformation about the event interaction, such as fire() args, subscription category, publish config
_normAttrVals
-
valueHash
Utility method to split out simple attribute name/value pairs ("x") from complex attribute name/value pairs ("x.y.z"), so that complex attributes can be keyed by the top level attribute name.
Parameters:
-
valueHashObjectAn object with attribute name/value pairs
Returns:
_parseType
()
private
Returns an array with the detach key (if provided), and the prefixed event name from _getType Y.on('detachcategory| menu:click', fn)
_protectAttrs
-
attrs
Utility method to protect an attribute configuration hash, by merging the entire object and the individual attr config objects.
Parameters:
-
attrsObjectA hash of attribute to configuration object pairs.
Returns:
_set
-
name -
val
Allows setting of readOnly/writeOnce attributes. See set for argument details.
Parameters:
-
nameStringThe name of the attribute.
-
valAnyThe value to set the attribute to.
Returns:
_setAttr
-
name -
value -
opts -
force
Provides the common implementation for the public set and protected _set methods.
See set for argument details.
Parameters:
-
nameStringThe name of the attribute.
-
valueAnyThe value to set the attribute to.
-
optsObject(Optional) Optional event data to be mixed into the event facade passed to subscribers of the attribute's change event. This is currently a hack. There's no real need for the AttributeCore implementation to support this parameter, but breaking it out into AttributeObservable, results in additional function hops for the critical path.
-
forceBooleanIf true, allows the caller to set values for readOnly or writeOnce attributes which have already been set.
Returns:
_setAttrs
-
attrs
Implementation behind the public setAttrs method, to set multiple attribute values.
Parameters:
-
attrsObjectAn object with attributes name/value pairs.
Returns:
_setAttrVal
-
attrName -
subAttrName -
prevVal -
newVal
Updates the stored value of the attribute in the privately held State object, if validation and setter passes.
Parameters:
Returns:
_setStateVal
-
name -
value
Sets the stored value for the attribute, in either the internal state object, or the state proxy if it exits
Parameters:
-
nameStringThe name of the attribute
-
valueAnyThe value of the attribute
addAttr
-
name -
config -
lazy
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.
Parameters:
-
nameStringThe name of the attribute.
-
configObjectAn object with attribute configuration property/value pairs, specifying the configuration for the attribute.
NOTE: The configuration object is modified when adding an attribute, so if you need to protect the original values, you will need to merge the object.
-
lazyBoolean(optional) Whether or not to add this attribute lazily (on the first call to get/set).
Returns:
addAttrs
-
cfgs -
values -
lazy
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.
Parameters:
-
cfgsObjectAn object with attribute name/configuration pairs.
-
valuesObjectAn object with attribute name/value pairs, defining the initial values to apply. Values defined in the cfgs argument will be over-written by values in this argument unless defined as read only.
-
lazyBooleanWhether or not to delay the intialization of these attributes until the first call to get/set. Individual attributes can over-ride this behavior by defining a lazyAdd configuration property in their configuration. See addAttr.
Returns:
addTarget
-
o
Registers another EventTarget as a bubble target. Bubble order is determined by the order registered. Multiple targets can be specified.
Events can only bubble if emitFacade is true.
Included in the event-custom-complex submodule.
Parameters:
-
oEventTargetthe target to add
after
-
type -
fn -
[context] -
[arg*]
Subscribe to a custom event hosted by this object. The supplied callback will execute after any listeners add via the subscribe method, and after the default function, if configured for the event, has executed.
Parameters:
Returns:
attrAdded
-
name
Checks if the given attribute has been added to the host
Parameters:
-
nameStringThe name of the attribute to check.
Returns:
before
()
Executes the callback before a DOM event, custom event or method. If the first argument is a function, it is assumed the target is a method. For DOM and custom events, this is an alias for Y.on.
For DOM and custom events: type, callback, context, 0-n arguments
For methods: callback, object (method host), methodName, context, 0-n arguments
Returns:
bubble
-
evt
Propagate an event. Requires the event-custom-complex module.
Parameters:
-
evtCustomEventthe custom event to propagate
Returns:
detach
-
type -
fn -
context
Detach one or more listeners the from the specified event
Parameters:
-
typeString | ObjectEither the handle to the subscriber or the type of event. If the type is not specified, it will attempt to remove the listener from all hosted events.
-
fnFunctionThe subscribed function to unsubscribe, if not supplied, all subscribers will be removed.
-
contextObjectThe custom object passed to subscribe. This is optional, but if supplied will be used to disambiguate multiple listeners that are the same (e.g., you subscribe many object using a function that lives on the prototype)
Returns:
detachAll
-
type
Removes all listeners from the specified event. If the event type is not specified, all listeners from all hosted custom events will be removed.
Parameters:
-
typeStringThe type, or name of the event
fire
-
type -
arguments
Fire a custom event by name. The callback functions will be executed from the context specified when the event was created, and with the following parameters.
If the custom event object hasn't been created, then the event hasn't been published and it has no subscribers. For performance sake, we immediate exit in this case. This means the event won't bubble, so if the intention is that a bubble target be notified, the event must be published on this object first.
The first argument is the event type, and any additional arguments are passed to the listeners as parameters. If the first of these is an object literal, and the event is configured to emit an event facade, that object is mixed into the event facade and the facade is provided in place of the original object.
Parameters:
-
typeString | ObjectThe type of the event, or an object that contains a 'type' property.
-
argumentsObject*an arbitrary set of parameters to pass to the handler. If the first of these is an object literal and the event is configured to emit an event facade, the event facade will replace that parameter after the properties the object literal contains are copied to the event facade.
Returns:
get
-
name
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.
Parameters:
-
nameStringThe name of the attribute. If the value of the attribute is an Object, dot notation can be used to obtain the value of a property of the object (e.g.
get("x.y.z"))
Returns:
getAttrs
-
attrs
Gets multiple attribute values.
Parameters:
-
attrsArray | booleanOptional. An array of attribute names. If omitted, all attribute values are returned. If set to true, all attributes modified from their initial values are returned.
Returns:
getEvent
-
type -
prefixed
Returns the custom event of the provided type has been created, a falsy value otherwise
Parameters:
Returns:
getTargets
()
Returns an array of bubble targets for this object.
Returns:
modifyAttr
-
name -
config
Updates the configuration of an attribute which has already been added.
The properties which can be modified through this interface are limited to the following subset of attributes, which can be safely modified after a value has already been set on the attribute: readOnly, writeOnce, broadcast and getter.
on
-
type -
fn -
[context] -
[arg*]
Subscribe a callback function to a custom event fired by this object or from an object that bubbles its events to this object.
Callback functions for events published with emitFacade = true will
receive an EventFacade as the first argument (typically named "e").
These callbacks can then call e.preventDefault() to disable the
behavior published to that event's defaultFn. See the EventFacade
API for all available properties and methods. Subscribers to
non-emitFacade events will receive the arguments passed to fire()
after the event name.
To subscribe to multiple events at once, pass an object as the first argument, where the key:value pairs correspond to the eventName:callback, or pass an array of event names as the first argument to subscribe to all listed events with the same callback.
Returning false from a callback is supported as an alternative to
calling e.preventDefault(); e.stopPropagation();. However, it is
recommended to use the event methods whenever possible.
Parameters:
Returns:
once
-
type -
fn -
[context] -
[arg*]
Listen to a custom event hosted by this object one time.
This is the equivalent to on except the
listener is immediatelly detached when it is executed.
Parameters:
Returns:
onceAfter
-
type -
fn -
[context] -
[arg*]
Listen to a custom event hosted by this object one time.
This is the equivalent to after except the
listener is immediatelly detached when it is executed.
Parameters:
Returns:
parseType
-
type -
[pre=this._yuievt.config.prefix]
Takes the type parameter passed to 'on' and parses out the various pieces that could be included in the type. If the event type is passed without a prefix, it will be expanded to include the prefix one is supplied or the event target is configured with a default prefix.
Returns:
protectAttrs
-
attrs
Utility method to protect an attribute configuration hash, by merging the entire object and the individual attr config objects.
Parameters:
-
attrsObjectA hash of attribute to configuration object pairs.
Returns:
attrs argument.
publish
-
type -
opts
Creates a new custom event of the specified type. If a custom event by that name already exists, it will not be re-created. In either case the custom event is returned.
Parameters:
-
typeStringthe type, or name of the event
-
optsObjectoptional config params. Valid properties are:
- 'broadcast': whether or not the YUI instance and YUI global are notified when the event is fired (false)
- 'bubbles': whether or not this event bubbles (true) Events can only bubble if emitFacade is true.
- 'context': the default execution context for the listeners (this)
- 'defaultFn': the default function to execute when this event fires if preventDefault was not called
- 'emitFacade': whether or not this event emits a facade (false)
- 'prefix': the prefix for this targets events, e.g., 'menu' in 'menu:click'
- 'fireOnce': if an event is configured to fire once, new subscribers after the fire will be notified immediately.
- 'async': fireOnce event listeners will fire synchronously if the event has already fired unless async is true.
- 'preventable': whether or not preventDefault() has an effect (true)
- 'preventedFn': a function that is executed when preventDefault is called
- 'queuable': whether or not this event can be queued during bubbling (false)
- 'silent': if silent is true, debug messages are not provided for this event.
- 'stoppedFn': a function that is executed when stopPropagation is called
- 'monitored': specifies whether or not this event should send notifications about when the event has been attached, detached, or published.
- 'type': the event type (valid option if not provided as the first parameter to publish)
Returns:
removeAttr
-
name
Removes an attribute from the host object
Parameters:
-
nameStringThe name of the attribute to be removed.
reset
-
name
Resets the attribute (or all attributes) to its initial value, as long as the attribute is not readOnly, or writeOnce.
Parameters:
-
nameStringOptional. The name of the attribute to reset. If omitted, all attributes are reset.
Returns:
set
-
name -
value
Sets the value of an attribute.
Parameters:
-
nameStringThe name of the attribute. If the current value of the attribute is an Object, dot notation can be used to set the value of a property within the object (e.g.
set("x.y.z", 5)). -
valueAnyThe value to set the attribute to.
Returns:
setAttrs
-
attrs
Sets multiple attribute values.
Parameters:
-
attrsObjectAn object with attributes name/value pairs.
Returns:
subscribe
()
deprecated
subscribe to an event
unsubscribe
()
deprecated
detach a listener
unsubscribeAll
-
type
Removes all listeners from the specified event. If the event type is not specified, all listeners from all hosted custom events will be removed.
Parameters:
-
typeStringThe type, or name of the event
Properties
_ATTR_CFG
Array
protected
static
The list of properties which can be configured for each attribute (e.g. setter, getter, writeOnce etc.).
This property is used internally as a whitelist for faster Y.mix operations.
INVALID_VALUE
Object
final
static
The value to return from an attribute setter in order to prevent the set from going through.
You can return this value from your setter if you wish to combine validator and setter functionality into a single setter function, which either returns the massaged value to be stored or AttributeCore.INVALID_VALUE to prevent invalid values from being stored.