Usage
Signature:
final class JoiningDataProvider<K, D extends BD, BD> implements DataProvider<K, D>
Generic Parameters
Parameter Description K Type of key D Type of returned data BD Type of base data
Typescript Import Format
//This class is exported directly as module. To import it
import JoiningDataProvider= require("ojs/ojjoiningdataprovider");
For additional information visit:
Final classes in JET
Classes in JET are generally final and do not support subclassing. At the moment, final is not enforced. However, this will likely change in an upcoming JET release.
Constructor
new JoiningDataProvider(baseDataProvider, options)
Parameters:
Name | Type | Description |
---|---|---|
baseDataProvider |
DataProvider.<K, BD> | The base data provider.
The metadata from this data provider will be the metadata for the JoiningDataProvider, and all data from this data provider will be part of the data for the JoiningDataProvider. The resulting data for the JoiningDataProvider will be the set of attributes from the base data provider, plus the set of attributes specified by the "joins" option. Data returned by each data provider specified in the "joins" options will be merged into the JoiningDataProvider as an object. |
options |
JoiningDataProvider.DataProviderOptions.<D, BD> | Options for the JoiningDataProvider. |
Example
let employee = [
{ id: 1001, departmentId: 2001, managerId: 1011, firstName: "Chris", lastName: "Black", title: "Software Engineer" },
{ id: 1011, departmentId: 2002, managerId: 1021, firstName: "Jenifer", lastName: "Cooper", title: "Manager" },
{ id: 1021, departmentId: 2003, managerId: 1031, firstName: "Kurt", lastName: "Jonhson", title: "VP" },
{ id: 1022, departmentId: 2003, managerId: 1031, firstName: "Mike", lastName: "Chrison", title: "VP", manager: { firstName: "Guangping", lastName: null } }
];
let department = [
{ id: 2001, locationId: 1, VPId: 1021, name: "JET" },
{ id: 2002, locationId: 1, VPId: 1022, name: "Visual Builder" }
];
let location = [
{ id: 1, city: "Redwood City", state: "California" }
];
// initialize basic DataProvider
let dpEmployee = new ArrayDataProvider(employee, { keyAttributes: 'id' });
let dpDepartment = new ArrayDataProvider(department, { keyAttributes: 'id' });
let dpLocation = new ArrayDataProvider(location, { keyAttributes: 'id' });
// join for department
let locJoin = { foreignKeyMapping: { foreignKey: 'locationId' }, joinedDataProvider: dpLocation };
let VPJoin = { foreignKeyMapping: { foreignKey: 'VPId' }, joinedDataProvider: dpEmployee };
let dpJoinDepartment = new JoiningDataProvider(dpDepartment,
{ joins: { location: locJoin, VP: VPJoin } });
let deptJoin = { foreignKeyMapping: { foreignKey: 'departmentId' }, joinedDataProvider: dpJoinDepartment };
let mgrJoin = { foreignKeyMapping: { foreignKey: 'managerId' }, joinedDataProvider: dpEmployee };
this.dpJoinEmployee = new JoiningDataProvider(dpEmployee,
{ joins: { manager: mgrJoin, department: deptJoin } });
// Using joined dataprovider attributes for fetch methods
// The returned fields will include all fields from base data provider and department plus title from manager.
this.dpJoinEmployee.fetchByOffset({ offset: 0, attributes: ['manager.title'] });
Methods
-
addEventListener(eventType: string, listener: EventListener): void
-
Add a callback function to listen for a specific event type.
Parameters:
Name Type Description eventType
string The event type to listen for. listener
EventListener The callback function that receives the event notification. -
containsKeys(parameters : FetchByKeysParameters<K>) : Promise<ContainsKeysResults<K>>
-
Check if there are rows containing the specified keys. The resulting key map will only contain keys which were actually found.
Parameters:
Name Type Description parameters
FetchByKeysParameters contains by key parameters - Since:
- 4.2.0
Returns:
Returns Promise which resolves to ContainsKeysResults.- Type
- Promise.<ContainsKeysResults>
Example
Check if keys 1001 and 556 are contained
let containsKeys = [1001, 556]; let value = await dataprovider.containsKeys({keys: containsKeys}); let results = value['results']; if (results.has(1001)) { console.log('Has key 1001'); } else if (results.has(556){ console.log('Has key 556'); }
-
createOptimizedKeyMap(initialMap?: Map<K, D>): Map<K, D>
-
Return an empty Map which is optimized to store key value pairs
Optionally provided by certain DataProvider implementations for storing key/value pairs from the DataProvider in a performant fashion. Sometimes components will need to temporarily store a Map of keys provided by the DataProvider, for example, in the case of maintaining a Map of selected keys. Only the DataProvider is aware of the internal structure of keys such as whether they are primitives, Strings, or objects and how to do identity comparisons. Therefore, the DataProvider can optionally provide a Map implementation which can performantly store key/value pairs surfaced by the DataProvider.
Parameters:
Name Type Argument Description initialMap
Map.<any> <optional>
Optionally specify an initial map of key/values for the Map. If not specified, then return an empty Map. - Since:
- 6.2.0
Returns:
Returns a Map optimized for handling keys from the DataProvider.- Type
- Map.<any>
Example
create empty key Map
// create optional parameter let initMap = new Map(); initMap.set('a', 'apple'); let keyMap = dataprovider.createOptimizedKeyMap(initMap);
-
createOptimizedKeySet(initialSet?: Set<K>): Set<K>
-
Return an empty Set which is optimized to store keys
Optionally provided by certain DataProvider implementations for storing keys from the DataProvider in a performant fashion. Sometimes components will need to temporarily store a Set of keys provided by the DataProvider, for example, in the case of maintaining a Set of selected keys. Only the DataProvider is aware of the internal structure of keys such as whether they are primitives, Strings, or objects and how to do identity comparisons. Therefore, the DataProvider can optionally provide a Set implementation which can performantly store keys surfaced by the DataProvider.
Parameters:
Name Type Argument Description initialSet
Set.<any> <optional>
Optionally specify an initial set of keys for the Set. If not specified, then return an empty Set. - Since:
- 6.2.0
Returns:
Returns a Set optimized for handling keys from the DataProvider.- Type
- Set.<any>
Example
create empty key Set
// create optional initial parameter let initSet = new Set(); initSet.add('a'); let keySet = dataprovider.createOptimizedKeySet(initSet);
-
dispatchEvent(evt: Event): boolean
-
Dispatch an event and invoke any registered listeners.
Parameters:
Name Type Description event
Event The event object to dispatch. Returns:
Return false if a registered listener has cancelled the event. Return true otherwise.- Type
- boolean
-
fetchByKeys(parameters : FetchByKeysParameters<K>) : Promise<FetchByKeysResults<K, D>>
-
Fetch rows by keys. The resulting key map will only contain keys which were actually found.
Parameters:
Name Type Description parameters
FetchByKeysParameters fetch by key parameters - Since:
- 4.2.0
Returns:
Returns Promise which resolves to FetchByKeysResults.- Type
- Promise.<FetchByKeysResults>
Example
Fetch for keys 1001 and 556
let fetchKeys = [1001, 556]; let value = await dataprovider.fetchByKeys({keys: fetchKeys}); // get the data for key 1001 console.log(value.results.get(1001).data);
-
fetchByOffset(parameters: FetchByOffsetParameters<D>): Promise<FetchByOffsetResults<K, D>>
-
Fetch rows by offset
A generic implementation of this method is available from FetchByOffsetMixin. It is for convenience and may not provide the most efficient implementation for your data provider. Classes that implement the DataProvider interface are encouraged to provide a more efficient implementation.
Parameters:
Name Type Description parameters
FetchByOffsetParameters fetch by offset parameters - Since:
- 4.2.0
Returns:
Returns Promise which resolves to FetchByOffsetResults.- Type
- Promise.<FetchByOffsetResults>
Example
Fetch by offset 5 rows starting at index 2
let result = await dataprovider.fetchByOffset({size: 5, offset: 2}); let results = result['results']; let data = results.map(function(value) { return value['data']; }); let keys = results.map(function(value) { return value['metadata']['key']; });
-
fetchFirst(parameters?: FetchListParameters<D>): AsyncIterable<FetchListResult<K, D>>
-
Get an asyncIterator which can be used to fetch a block of data.
Parameters:
Name Type Argument Description params
FetchListParameters <optional>
fetch parameters - Since:
- 4.2.0
- See:
-
- https://github.com/tc39/proposal-async-iteration for further information on AsyncIterable.
Returns:
AsyncIterable with FetchListResult- Type
- AsyncIterable.<FetchListResult>
Example
Get an asyncIterator and then fetch first block of data by executing next() on the iterator. Subsequent blocks can be fetched by executing next() again.
let asyncIterator = dataprovider.fetchFirst(options)[Symbol.asyncIterator](); let result = await asyncIterator.next(); let value = result.value; let data = value.data; let keys = value.metadata.map(function(val) { return val.key; }); // true or false for done let done = result.done;
-
getCapability(capabilityName: string): any
-
Determines whether this DataProvider defines a certain feature.
Parameters:
Name Type Description capabilityName
string capability name. Defined capability names are: "fetchByKeys", "fetchByOffset", "sort", "fetchCapability" and "filter". - Since:
- 4.2.0
Returns:
capability information or null if undefined- If capabilityName is "fetchByKeys", returns a FetchByKeysCapability object.
- If capabilityName is "fetchByOffset", returns a FetchByOffsetCapability object.
- If capabilityName is "sort", returns a SortCapability object.
- If capabilityName is "filter", returns a FilterCapability object.
- If capabilityName is "fetchCapability", returns a FetchCapability object.
- Type
- Object
Example
Check what kind of fetchByKeys is defined.
let capabilityInfo = dataprovider.getCapability('fetchByKeys'); if (capabilityInfo.implementation == 'iteration') { // the DataProvider supports iteration for fetchByKeys ...
-
getTotalSize : {Promise.<number>}
-
Return the total number of rows in this dataprovider
Returns:
Returns a Promise which resolves to the total number of rows. -1 is unknown row count.- Type
- Promise.<number>
Example
Get the total rows
let value = await dataprovider.getTotalSize(); if (value == -1) { // we don't know the total row count } else { // the total count console.log(value);
-
isEmpty(): 'yes' | 'no' | 'unknown'
-
Returns a string that indicates if this data provider is empty. Valid values are:
- "yes": this data provider is empty.
- "no": this data provider is not empty.
- "unknown": it is not known if this data provider is empty until a fetch is made.
- Since:
- 4.2.0
Returns:
string that indicates if this data provider is empty- Type
- "yes" | "no" | "unknown"
Example
Check if empty
let isEmpty = dataprovider.isEmpty(); console.log('DataProvider is empty: ' + isEmpty);
-
removeEventListener(eventType: string, listener: EventListener): void
-
Remove a listener previously registered with addEventListener.
Parameters:
Name Type Description eventType
string The event type that the listener was registered for. listener
EventListener The callback function that was registered.
Type Definitions
-
DataProviderOptions<D, BD>
-
Properties:
Name Type Description joins
Record<keyof Omit<D, keyof BD>, DataProviderJoinInfo<D, any, any>> A map of attribute name to information about DataProviders to join in.
The returned data for each row from the joined DataProvider will be merged as an object under the attribute name in the JoiningDataProvider.