new DataService()
Provides data objects and manages changes to them.
Data service subclasses that implement their own constructor should call this
class' constructor at the beginning of their constructor implementation
with code like the following:
DataService.call(this);
Currently only one service tree with one
root services is supported, and every
instance of DataService or a DataService subclasses must either be that root
service or be set as a descendent of that root service.
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Extends
- external:Montage
Members
(static) mainService :DataService
A reference to the application's main service.
Applications typically have one and only one
root service to which all data requests
are sent, and this is called the application's main service. That service
can in turn delegate handling of different types of data to child
services specialized by type.
This property will be set automatically if the DataService
constructor is called and if the first service created is either the
main service or a descendent of the main service.
Type:
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addMappingForType
Adds a mapping to the service for the specified
type.
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authorization :Object
holds authorization object after a successfull authorization
Type:
- Object
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authorizationPanel :string
Module ID of the panel component used to gather necessary authorization information
Type:
- string
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authorizationPolicy :AuthorizationPolicyType
Returns the AuthorizationPolicyType used by this DataService.
Type:
- AuthorizationPolicyType
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authorizationServices :Array.<string>
Returns the list of moduleIds of DataServices a service accepts to provide
authorization on its behalf. If an array has multiple
authorizationServices, the final choice will be up to the App user
regarding which one to use. This array is expected to return moduleIds,
not objects, allowing the AuthorizationManager to manage unicity
Type:
- Array.<string>
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changedDataObjects :Set.<Object>
A set of the data objects managed by this service or any other descendent
of this service's root service that have
been changed since that root service's data was last saved, or since the
root service was created if that service's data hasn't been saved yet
Since root services are responsible for tracking data objects, subclasses
whose instances will not be root services should override this property
to return their root service's value for it.
Type:
- Set.<Object>
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childServices :Set.<DataService>
The child services of this service.
This value is modified by calls to
addChildService() and
removeChildService() and must not
be modified directly.
Type:
- Set.<DataService>
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createdDataObjects :Set.<Object>
A set of the data objects created by this service or any other descendent
of this service's root service since
that root service's data was last saved, or since the root service was
created if that service's data hasn't been saved yet.
Since root services are responsible for tracking data objects, subclasses
whose instances will not be root services should override this property
to return their root service's value for it.
Type:
- Set.<Object>
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dataMaxAge :Number
The maximum amount of time a DataService's data will be considered fresh.
ObjectDescriptor's maxAge should take precedence over this and a DataStream's dataMaxAge should
take precedence over a DataService's dataMaxAge global default value.
Type:
- Number
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emptyArrayPromise
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- To Do:
-
- Document.
eventLoopPromise :external:Promise
A possibly shared promise resolved in the next cycle of the event loop
or soon thereafter, at which point the current event handling will be
complete. This is useful for services that need to buffer up actions so
they're committed only once in a given event loop.
Type:
- external:Promise
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isOffline :boolean
Returns a value derived from and continuously updated with the value of
navigator.onLine.
Root services are responsible for tracking offline status, and subclasses
not designed to be root services should override this property to get
its value from their root service.
Type:
- boolean
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isRootService :Boolean
Convenience method to assess if a dataService is the rootService
Type:
- Boolean
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mappings :Array.<DataMapping>
The data mappings used by this service to convert objects to raw
data and vice-versa.
Type:
- Array.<DataMapping>
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mappingWithType
Return the mapping to use for the specified type.
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model
The model that this service supports. If the model is
defined the service supports all the object descriptors contained within the model.
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nullFunction :function
A function that does nothing but returns null, useful for terminating
a promise chain that needs to return null, as in the following code:
var self = this;
return this.fetchSomethingAsynchronously().then(function (data) {
return self.doSomethingAsynchronously(data.part);
}).then(this.nullFunction);
Type:
- function
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nullPromise :external:Promise
A shared promise resolved with a value of
`null`, useful for returning from methods like
fetchObjectProperty()
when the requested data is already there.
Type:
- external:Promise
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objectDescriptorForObject
Returns an object descriptor for the provided object. If this service
does not have an object descriptor for this object it will ask its
parent for one.
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(nullable) parentService :DataService
A read-only reference to the parent of this service.
This value is modified by calls to
addChildService() and
removeChildService() and cannot
be modified directly.
Data services that have no parents are called
root services.
Type:
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providesAuthorization :boolean
Indicates whether a service can provide user-level authorization to its
data. Defaults to false. Concrete services need to override this as
needed.
Type:
- boolean
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rootService :DataService
Convenience read-only reference to the root of the service tree
containing this service. Most applications have only one root service,
the application's main service.
Type:
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types :Array.<DataObjectDescriptor>
The types of data handled by this service. If this `undefined`, `null`,
or an empty array this service is assumed to handled all types of data.
The default implementation of this property returns the union of all
types handled by child services of this service. Subclasses without child
services should override this to directly return an array of the specific
types they handle.
Applications typically have one raw data service
service for each set of related data types and one
main service which is the parent of all
those other services and delegates work to them based on the type of data
to which the work applies. It is possible for child data services to have
children of their own and delegate some or all of their work to them.
A service's types must not be changed after it is added as a child of
another service.
Type:
- Array.<DataObjectDescriptor>
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Methods
addChildService(service, typesopt)
Adds a raw data service as a child of this data service and set it to
handle data of the types defined by its types
property.
Child services must have their types property
value or their model set before they are passed in to
this method, and that value cannot change after that. The model property takes
priority of the types property. If the model is defined the service will handle
all the object descriptors associated to the model.
Parameters:
Name | Type | Attributes | Description |
---|---|---|---|
service |
RawDataService | ||
types |
Array |
<optional> |
Types to use instead of the child's types. |
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authorize()
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Returns:
Promise
cancelDataStream(dataStreamopt, reasonopt)
To be called to indicates that the consumer has lost interest in the passed DataStream.
This will allow the RawDataService feeding the stream to take appropriate measures.
Parameters:
Name | Type | Attributes | Description |
---|---|---|---|
dataStream |
DataStream |
<optional> |
The DataStream to cancel |
reason |
Object |
<optional> |
An object indicating the reason to cancel. |
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createDataObject(type) → {Object}
Create a new data object of the specified type.
Since root services are responsible for tracking and creating data
objects, subclasses whose instances will not be root services should
override this method to call their root service's implementation of it.
Parameters:
Name | Type | Description |
---|---|---|
type |
DataObjectDescriptor | The type of object to create. |
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Returns:
- The created object.
- Type
- Object
dataIdentifierForObject(object) → {DataIdentifier}
Returns a unique object for a DataIdentifier
fetchObjectProperty() instead
of this method. That method will be called by this method when needed.
Parameters:
Name | Type | Description |
---|---|---|
object |
object | The object whose property values are being requested. |
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Returns:
- An object's DataIdentifier
- Type
- DataIdentifier
decacheObjectProperties()
Since root services are responsible for triggering data objects fetches,
subclasses whose instances will not be root services should override this
method to call their root service's implementation of it.
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- To Do:
-
- Rename and document API and implementation.
deleteDataObject(object) → {external:Promise}
Delete a data object.
Parameters:
Name | Type | Description |
---|---|---|
object |
Object | The object whose data should be deleted. |
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Returns:
- A promise fulfilled when the object has
been deleted.
- Type
- external:Promise
deleteOfflineOperations(operations) → {Promise}
Delete operations recorded while offline.
Services overriding the (plural)
performOfflineOperations()
method must invoke this method after each operation they perform is
successfully performed.
This method will be called automatically for services that perform
operations by implementing a
performOfflineOperation()
or `performFooOfflineOperation()` methods (where `foo` is an operation
data type).
Subclasses that provide offline operations support must override this
method to delete the specified offline operations from their records.
Parameters:
Name | Type | Description |
---|---|---|
operations |
Array.<Object> |
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Returns:
- A promise fulfilled with a null value when the
operations have been deleted.
- Type
- Promise
fetchData(queryOrType, optionalCriterianullable, optionalStreamnullable) → (nullable) {DataStream}
Fetch data from the service using its child services.
This method accept types as alternatives to
queries, and its [stream]{DataStream} argument is
optional, but when it calls its child services it will provide them with
a query, it provide them with a
[stream]{DataStream}, creating one if necessary, and the stream will
include a reference to the query. Also, if a child service's
implementation of this method return `undefined` or `null`, this method
will return the stream passed in to the call to that child.
The requested data may be fetched asynchronously, in which case the data
stream will be returned immediately but the stream's data will be added
to the stream at a later time.
Parameters:
Name | Type | Attributes | Description |
---|---|---|---|
queryOrType |
DataQuery | DataObjectDescriptor | ObjectDescriptor | function | String | If this argument's value is a query it will define what type of data should be returned and what criteria that data should satisfy. If the value is a type it will only define what type of data should be returned, and the criteria that data should satisfy can be defined using the `criteria` argument. A type is defined as either a DataObjectDesc- riptor, an Object Descriptor, a Construct- or the string module id. The method will convert the passed in type to a Data- ObjectDescriptor (deprecated) or an ObjectDescriptor. This is true whether passing in a DataQuery or a type. | |
optionalCriteria |
Object |
<nullable> |
If the first argument's value is a type this argument can optionally be provided to defines the criteria which the returned data should satisfy. If the first argument's value is a query this argument should be omitted and will be ignored if it is provided. |
optionalStream |
DataStream |
<nullable> |
The stream to which the provided data should be added. If no stream is provided a stream will be created and returned by this method. |
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Returns:
- The stream to which the fetched data objects
were or will be added, whether this stream was provided to or created by
this method.
- Type
- DataStream
fetchObjectProperty(object, name) → {external:Promise}
Fetch the value of a data object's property, possibly asynchronously.
The default implementation of this method delegates the fetching to a
child services, or does nothing but return a fulfilled promise for `null`
if no child service can be found to handle the specified object.
Raw data service subclasses should override
this method to perform any fetch or other operation required to get the
requested data. The subclass implementations of this method should use
only fetchData() calls to fetch data.
This method should never be called directly:
getObjectProperties() or
updateObjectProperties()
should be called instead as those methods handles some required caching,
fetch aggregation, and data trigger. Those methods
will call this method if and when that is necessary.
Like the promise returned by
getObjectProperties(), the
promise returned by this method should not pass the requested value to
its callback: That value must instead be set on the object passed in to
this method.
Parameters:
Name | Type | Description |
---|---|---|
object |
object | The object whose property value is being requested. |
name |
string | The name of the single property whose value is being requested. |
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Returns:
- A promise fulfilled when the requested
value has been received and set on the specified property of the passed
in object.
- Type
- external:Promise
getDataObject(type, data, context) → {Object}
Find an existing data object corresponding to the specified raw data, or
if no such object exists, create one.
Since root services are responsible for tracking and creating data
objects, subclasses whose instances will not be root services should
override this method to call their root service's implementation of it.
Parameters:
Name | Type | Description |
---|---|---|
type |
DataObjectDescriptor | The type of object to find or create. |
data |
Object | An object whose property values hold the object's raw data. That data will be used to determine the object's unique identifier. |
context |
? | A value, usually passed in to a raw data service's addRawData() method, that can help in getting or creating the object. |
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Returns:
- The existing object with the unique identifier
specified in the raw data, or if no such object exists a newly created
object of the specified type.
- Type
- Object
getObjectProperties(object, propertyNames) → {external:Promise}
Request possibly asynchronous values of a data object's properties. These
values will only be fetched if necessary and only the first time they are
requested.
To force an update of a value that was previously obtained or set, use
updateObjectProperties()
instead of this method.
Since root services are responsible for determining when to fetch or
update data objects values, subclasses whose instances will not be root
services should override this method to call their root service's
implementation of it.
Subclasses should define how property values are obtained by overriding
fetchObjectProperty() instead
of this method. That method will be called by this method when needed.
Although this method returns a promise, the requested data will not be
passed in to the promise's callback. Instead that callback will received
a `null` value and the requested values will be set on the specified
properties of the object passed in. Those values can be accessed there
when the returned promise is fulfilled, as in the following code:
myService.getObjectProperties(myObject, "x", "y").then(function () {
someFunction(myObject.x, myObject.y);
}
Parameters:
Name | Type | Description |
---|---|---|
object |
object | The object whose property values are being requested. |
propertyNames |
Array.<string> | The names of each of the properties whose values are being requested. These can be provided as an array of strings or as a list of string arguments following the object argument. |
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Returns:
- A promise fulfilled when all of the
requested data has been received and set on the specified properties of
the passed in object.
- Type
- external:Promise
logOut()
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Returns:
Promise
objectForDataIdentifier(object) → {DataIdentifier}
Returns a unique object for a DataIdentifier
fetchObjectProperty() instead
of this method. That method will be called by this method when needed.
Parameters:
Name | Type | Description |
---|---|---|
object |
object | object |
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Returns:
- object's DataIdentifier
- Type
- DataIdentifier
performOfflineOperation(operation) → {Promise}
Called from
performOfflineOperations()
to perform a particular operation when no more specific
`performFooOfflineOperation()` method is available for that operation,
where `Foo` is the operation's data type.
The default implementation does nothing.
Subclass overriding this method do not need to
delete the passed in
operation after it has successfully been performed: The method calling
this method will take care of that.
Parameters:
Name | Type | Description |
---|---|---|
operation |
DataOperation |
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Returns:
- A promise fulfilled with a null value when the
operation has been performed, or rejected if a problem occured that
should prevent following operations from being performed.
- Type
- Promise
performOfflineOperations() → {Promise}
Perform operations recorded while offline. This will be invoked when the
service comes online after being offline.
The default implementation delegates performance of each operation to
the child service responsible for that operation, as determined by
readOfflineOperations(). It
will batch operations if several consecutive operations belong to the
same child service.
For each operation not handled by a child service, the default
implementation calls a method named `performFooOfflineOperation()`, if
such a method exists in this service where `foo` is the operation's
data type. If no such method exists,
readOfflineOperation() is
called instead.
Subclasses that provide offline support should implement these
`performFooOfflineOperation()` methods or override the
`readOfflineOperation()` method to perform each operation, or they can
override this `performOfflineOperations()` method instead.
Subclass overriding this method are responsible for
deleting operations after
they have been performed. Subclasses implementing
`performFooOfflineOperation()` methods or overriding the
`readOfflineOperation()` method are not.
Parameters:
Type | Description |
---|---|
Array.<DataOperation> | operations |
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Returns:
- A promise fulfilled with a null value when the
operations have been performed, or rejected if a problem occured that
should prevent following operations from being performed.
- Type
- Promise
readOfflineOperations()
Reads all the offline operations recorded on behalf of this service.
The default implementation aggregates this service children's offline
operations, keeping track of which child service is responsible for each
operation.
Subclasses that provide offline support should override this method to
return the operations that have been performed while offline.
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recordDataIdentifierForObject(object, dataIdentifier)
Records an object's DataIdentifier
Parameters:
Name | Type | Description |
---|---|---|
object |
object | an Object. |
dataIdentifier |
DataIdentifier | The object whose property values are |
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recordObjectForDataIdentifier(dataIdentifier, object)
Records an object's DataIdentifier
Parameters:
Name | Type | Description |
---|---|---|
dataIdentifier |
DataIdentifier | DataIdentifier |
object |
object | object represented by dataIdentifier |
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registerChildService(child) → {Promise}
Alternative to addChildService().
While addChildService is synchronous, registerChildService is asynchronous
and may take a child whose types property is
a promise instead of an array.
This is useful for example if the child service does not know its types
immediately, e.g. if it must fetch them from a .mjson descriptors file.
If the child's types is an array, it is guaranteed to behave exactly
like addChildService.
Parameters:
Name | Type | Description |
---|---|---|
child |
DataService | service to add to this service. |
|
Promise | ObjectDescriptor | Array.<ObjectDescriptor> |
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Returns:
- Type
- Promise
removeChildService(service, typesopt)
Remove a raw data service as a child of this service and clear its parent
if that service is a child of this service.
The performance of this method is O(m) + O(n), where m is the number of
children of this service handling the same type as the child service to
remove and n is the number of types handled by all children of this
service.
Parameters:
Name | Type | Attributes | Description |
---|---|---|---|
service |
RawDataService | ||
types |
Array |
<optional> |
Types to use instead of the child's types. |
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removeDataIdentifierForObject(object)
Remove an object's DataIdentifier
Parameters:
Name | Type | Description |
---|---|---|
object |
object | an object |
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removeObjectForDataIdentifier(object)
Remove an object's DataIdentifier
Parameters:
Name | Type | Description |
---|---|---|
object |
object | an object |
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saveDataObject(object) → {external:Promise}
Save changes made to a data object.
Parameters:
Name | Type | Description |
---|---|---|
object |
Object | The object whose data should be saved. |
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Returns:
- A promise fulfilled when all of the data in
the changed object has been saved.
- Type
- external:Promise
spliceWithArray(array, insert, index, length)
Splice an array into another array.
Parameters:
Name | Type | Description |
---|---|---|
array |
Array | The array to modify. |
insert |
Array | The items to splice into that array. |
index |
number | The index at which to splice those items, by default `0`. |
length |
number | The number of items of the original array to replace with items from the spliced array, by default `array.length`. |
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unregisterChildService() → {Promise}
Alternative to removeChildService().
While removeChildService is synchronous, unregisterChildService is asynchronous
and may take a child whose types property is
a promise instead of an array.
This is useful for example if the child service does not know its types
immediately, e.g. if it must fetch them from a .mjson descriptors file.
If the child's types is an array, it is guaranteed to behave exactly
like removeChildService.
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Returns:
- Type
- Promise
updateObjectProperties(object, propertyNames) → {external:Promise}
Request possibly asynchronous values of a data object's properties,
forcing asynchronous values to be re-fetched and updated even if they
had previously been fetched or set.
Except for the forced update, this method behaves exactly like
getObjectProperties().
Since root services are responsible for determining when to fetch or
update data objects values, subclasses whose instances will not be root
services should override this method to call their root service's
implementation of it.
Subclasses should define how property values are obtained by overriding
fetchObjectProperty() instead
of this method. That method will be called by this method when needed.
Parameters:
Name | Type | Description |
---|---|---|
object |
object | The object whose property values are being requested. |
propertyNames |
Array.<string> | The names of each of the properties whose values are being requested. These can be provided as an array of strings or as a list of string arguments following the object argument. |
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Returns:
- A promise fulfilled when all of the
requested data has been received and set on the specified properties of
the passed in object.
- Type
- external:Promise