For up-to-date product documentation, see the IBM MobileFirst Foundation Developer Center.

Querying data

After you create an index, we can query the data in your database.

For more details, see CDTDatastore Query documentation.

For more details, see Cloudant® Sync Query documentation.

For query operations on a remote store, see the Cloudant Query API.

Procedure

• Create and run a query on iOS.

  BEFORE (with IMFData/CloudantToolkit):

  // Use an existing store
  CDTStore *store = existingStore;
  
  NSPredicate *queryPredicate = [NSPredicate predicateWithFormat:@"(year = 2006)"];
  CDTCloudantQuery *query = [[CDTCloudantQuery alloc] initDataType:[store.mapper dataTypeForClassName:NSStringFromClass([Automobile class])] withPredicate:queryPredicate];
  
  [store performQuery:query completionHandler:^(NSArray *results, NSError *error) {
      if(error){
          // Handle error
      }else{
          // Use result of query.  Result will be Automobile objects.
      }
  }];

  // Use an existing store
  let store:CDTStore = existingStore
  
  let queryPredicate:NSPredicate = NSPredicate(format:"(year = 2006)")
  let query:CDTCloudantQuery = CDTCloudantQuery(dataType: "Automobile", withPredicate: queryPredicate)
  
  store.performQuery(query, completionHandler: { (results:[AnyObject]!, error:NSError!) -> Void in
      if nil != error {
          // Handle error
      } else {
          // Use result of query.  Result will be Automobile objects.
      }
  })

  AFTER (with Cloudant Sync):

  // Use an existing store
  CDTDatastore *datastore = existingDatastore;
  
  CDTQResultSet *results = [datastore find:@{@"@datatype" : @"Automobile", @"year" : @2006}];
  if(results){
      // Use results
  }

  // Use an existing store
  let datastore:CDTDatastore = existingDatastore
  
  let results:CDTQResultSet? = datastore.find(["@datatype" : "Automobile", "year" : 2006])
  if(results == nil){
      // Handle error
  }

• Create and run a query for objects on Android.

  To run a query for objects, create a Cloudant query with the query filters on data type. Run the query against a Store object.

  BEFORE (with IMFData/CloudantToolkit):

  // Use an existing store
  Store store = existingStore;
  
  // Create data type predicate
  Map<String, Object> dataTypeEqualityOpMap = new HashMap<String, Object>();
  dataTypeEqualityOpMap.put("$eq", "Automobile");
  
  Map<String, Object> dataTypeSelectorMap = new HashMap<String, Object>();
  dataTypeSelectorMap.put("@datatype", dataTypeEqualityOpMap);
  
  // Create year predicate
  Map<String, Object> yearEqualityOpMap = new HashMap<String, Object>();
  yearEqualityOpMap.put("$eq", 2006);
  
  Map<String, Object> yearSelectorMap = new HashMap<String, Object>();
  yearSelectorMap.put("year", yearEqualityOpMap);
  
  // Add predicates to AND compound predicate
  List<Map<String, Object>> andPredicates = new ArrayList<Map<String, Object>>();
  andPredicates.add(dataTypeSelectorMap);
  andPredicates.add(yearSelectorMap);
  
  Map<String, Object> andOpMap = new HashMap<String, Object>();
  andOpMap.put("$and", andPredicates);
  
  Map<String, Object> cloudantQueryMap = new HashMap<String, Object>();
  cloudantQueryMap.put("selector", andOpMap);
  
  // Create a Cloudant Query Object
  CloudantQuery query = new CloudantQuery(cloudantQueryMap);
  
  // Run the Cloudant Query against a Store
  Task<List> queryTask = store.performQuery(query);
  queryTask.continueWith(new Continuation<List, Object>() {
      @Override
      public Object then(Task<List> task) throws Exception {
          if(task.isFaulted()){
              // Handle Error
          }else{
              List queryResult = task.getResult();
              // Use queryResult to do something
          }
          return null;
      }
  });

  AFTER (with Cloudant Sync):

  // Use an existing store
  Datastore datastore = existingStore;
  IndexManager indexManager = existingIndexManager;
  
  // Create data type predicate
  Map<String, Object> dataTypeEqualityOpMap = new HashMap<String, Object>();
  dataTypeEqualityOpMap.put("$eq", "Automobile");
  
  Map<String, Object> dataTypeSelectorMap = new HashMap<String, Object>();
  dataTypeSelectorMap.put("@datatype", dataTypeEqualityOpMap);
  
  // Create year predicate
  Map<String, Object> yearEqualityOpMap = new HashMap<String, Object>();
  yearEqualityOpMap.put("$eq", 2006);
  
  Map<String, Object> yearSelectorMap = new HashMap<String, Object>();
  yearSelectorMap.put("year", yearEqualityOpMap);
  
  // Add predicates to AND compound predicate
  List<Map<String, Object>> andPredicates = new ArrayList<Map<String, Object>>();
  andPredicates.add(dataTypeSelectorMap);
  andPredicates.add(yearSelectorMap);
  
  Map<String, Object> selectorMap = new HashMap<String, Object>();
  selectorMap.put("$and", andPredicates);
  
  // Run the query against a Store
  QueryResult result = indexManager.find(selectorMap);

Parent topic: Migrating apps storing mobile data in Cloudant with IMFData or Cloudant SDK