Show: Object Pascal C++
Display Preferences

FireDAC.Phys.MongoDBWrapper.TMongoCollection

From Appmethod Libraries
Jump to: navigation, search

FireDAC.Phys.MongoDBWrapper.TMongoObjectSystem.TObjectTMongoCollection

Object Pascal

TMongoCollection = class(TMongoObject)

C++

class PASCALIMPLEMENTATION TMongoCollection : public TMongoObject

Properties

Type Visibility Source Unit Parent
class public
FireDAC.Phys.MongoDBWrapper.pas
FireDAC.Phys.MongoDBWrapper.hpp
FireDAC.Phys.MongoDBWrapper FireDAC.Phys.MongoDBWrapper

Description

Represents a MongoDB collection.

TMongoCollection encapsulates the mongoc_collection_t structure of MongoDB.

You cannot create an instance of TMongoCollection directly. Instead, you must use one of the following members of TMongoConnection and TMongoDatabase:

TMongoCollection provides read-only properties to access basic data about the collection:

  • DB is the name of the database that contains the collection.
  • Name is the name of the collection.
  • NS is the namespace of the collection.

Use the following members to query data from the collection:

To edit the data of the collection, you can use the following members:

Each call to Insert, Remove, or Update, TMongoCollection submits the changes to the database. To perform several changes and submit them to the database all at once:

  1. Call BeginBulk to start a bulk operation.
  2. Call Insert, Remove, or Update as many times as you need to perform your changes locally.
  3. Call EndBulk to submit your bulk operation.

You can call CancelBulk if you want to abort a bulk operation that you started with BeginBulk. You can read the value of IsBulk to determine whether you are in the middle of a bulk operation (True) or not (False).

TMongoCollection provides properties that indicate the number of documents inserted (DocsInserted), matched (DocsMatched), modified (DocsModified), removed (DocsRemoved), or inserted as part of an update operation (DocsUpserted). TMongoCollection updates the values of these properties after each submission of data to the database.

To run database commands on the collection, use any of the following methods:

To configure the replica set read and write semantics use the following properties:

Some Methods Support Two Different Coding Styles

Some methods of TMongoCollection support two different coding styles: a regular coding style and a fluent coding style. Those methods are: Aggregate, Count, Find, Insert, Remove, Update.

Using a Regular Coding Style

If you use a regular coding style you can reuse builder objects, such as instances of TMongoPipeline or TMongoQuery.

You must pass the the target method a builder object that you have previously created and configured. The method submits a request to the MongoDB server based on the specified builder object.

The following example shows how to submit a query using a regular coding style:

Object Pascal:

MyQuery := TMongoQuery.Create(MyConnection.Env);
try
  MyQuery.Match
    .Add('cuisine', 'Italian')
    .Add('address.zipcode', '10075');
  MyQuery.Sort
    .Ascending(['name']);
  MyQuery.Limit(3);
  MyCursor := MyCollection.Find(MyQuery);
  // …
finally
  MyQuery.Free;

C++:

TMongoQuery* MyQuery = new TMongoQuery(MyConnection->Env);
try {
  MyQuery->Match()
    ->Add("cuisine", String("Italian"))
    ->Add("address.zipcode", String("10075"));
  MyQuery->Sort()
    ->Ascending(OPENARRAY((String("name"))));
  MyQuery->Limit(3);
  _di_IMongoCursor MyCursor = MyCollection->Find(MyQuery);
  // …
} __finally {
  delete MyQuery;
}

Using a Fluent Coding Style

If you use a fluent coding style you can make your code more readable.

The target method returns a builder object. You can fill the returned builder object with data and submit your request to the MongoDB server using method chaining.

The method that you use to submit your request depends on the method that you use to obtain a builder object:

TMongoCollection Method Builder Object Method
Aggregate TMongoPipeline.Open
Count TMongoQuery.Value
Find TMongoQuery.Open
Insert TMongoInsert.Exec
Remove TMongoSelector.Exec
Update TMongoUpdate.Exec
Note: In Object Pascal you can omit the call to TMongoPipeline.Open orTMongoQuery.Open, you can cast your builder object to IMongoCursor instead. See the example below.

The following example shows how to submit a query using a fluent coding style:

Object Pascal:

MyCursor := MyCollection.Find
  .Match
    .Add('cuisine', 'Italian')
    .Add('address.zipcode', '10075')
  .&End
  .Sort
    .Ascending(['name'])
  .&End
  .Limit(3);

C++:

_di_IMongoCursor MyCursor = MyCollection->Find()
  ->Match()
    ->Add("cuisine", String("Italian"))
    ->Add("address.zipcode", String("10075"))
  ->End()
  ->Sort()
    ->Ascending(OPENARRAY((String("name"))))
  ->End()
  ->Limit(3)
  ->Open();
Personal tools
Translations