Connecting to MongoDB

    use Mongoose;
    Mongoose->db('mydb'); # looks for a localhost connection

    # or, for more control:

    Mongoose->db(
        host    => 'mongodb://mongodb.server:4000',
        db_name => 'mydb'
    );

This is done globally here for simplicity sake, but multiple connections and databases are also supported.

Connecting to more than one database

    # No class, this will be default db
    Mongoose->db( db_name => 'mydbone', ... );

    # A db for one class
    Mongoose->db( class => 'Person', db_name => 'mydbone', ... );

    # A db/host for several classes
    Mongoose->db( class => ['Address', 'Telephone'], db_name => 'mydbtwo', host => 'mongodb://host:27017' );

Loading a Schema

    package main;
    Mongoose->load_schema( search_path => 'MyApp::Schema', shorten => 1 );

Use it only once in your program. Your modules will be "require"d and may be used from anywhere else.

If set to 1, the "shorten" option will alias "MyApp::Schema::MyClass" into "MyClass" for convenience. Be careful not to shadow other classes by using this option.

Preventing attributes from being stored

    package Person;
    use Moose;
    with 'Mongoose::Document';

    has name   => ( is => 'rw', isa => 'Str', required => 1 );
    has age    => ( is => 'rw', isa => 'Int', default  => 40 );
    has salary => ( is => 'rw', isa => 'Int', traits => ['DoNotMongoSerialize'] );

One-to-many Relationships

ArrayRef

Use the "ArrayRef" Moose type.

    package Person;
    use Moose;
    with 'Mongoose::Document';

    has name     => ( is => 'rw', isa => 'Str', required => 1 );
    has accounts => ( is => 'rw', isa => 'ArrayRef[Account]' );

Then, define the Account class, either as a document or embedded document, depending on how you want it stored.

    package Account;
    use Moose;
    with Mongoose::EmbeddedDocument;

    has amount => ( is => 'rw', isa => 'Int', required => 1 );

But this has a memory and performance cost, since all related rows will be loaded in memory during object expansion.

To avoid loading related rows, use a Mongoose::Join parameterized type.

Mongoose::Join

Establishing a Mongoose::Join relationship will load relationships lazily:

    package Person;
    use Moose; with 'Mongoose::Document';

    has name     => ( is => 'rw', isa => 'Str', required => 1 );
    has accounts => ( is => 'rw', isa => 'Mongoose::Join[Account]' );

Then retrieve data with a cursor:

    my $large_acc = $person->accounts->find({ amount => { '$gt' => 100000 } });
    while( my $account = $large_acc->next ) {
        ...
    }

Sugar for Defining Relationships

    package Article;
    use Mongoose::Class; with 'Mongoose::Document';

    has        title    => ( is => 'rw', isa => 'Str', required => 1 );
    has_one    author   => 'Author';
    has_many   comments => 'Comment';
    belongs_to acc      => 'Account';

Normalizing a Relationship

Sometimes it may just be more adequate than storing relationships directly in objects:

    package Authorship;
    use Mongoose::Class; with 'Mongoose::Document';

    has_one  author   => 'Author';
    has_many articles => 'Article';

    # or even:
    #  has_one article => 'Article';

    package main;

    # create

    my $authorship = Authorship->new;
    $authorship->author( Author->new );
    $authorship->articles->add( Article->new );
    $authorship->articles->add( Article->new );

    # find

    my $articles = Authorship->find_one({ author => $author->_id });
    while( my $article = $articles->next ) {
        ...
    }

Package aliasing

    package My::Mumbo::Jumbo::Class;
    with 'Mongoose::Document' => { -as => 'Mumbo' };

    # then in your code

    my $obj = Mumbo->find_one({ flavor=>'gum' })

    print ref $obj;
    # prints 'My::Mumbo::Jumbo::Class'

    print $obj->isa('Mumbo')
    # prints 1

Method aliasing

    package BankAccount;
    with 'Mongoose::Document' => {
        -alias    => { 'find_one' => '_find_one' },
        -excludes => { 'find_one' },
    };

Raw Storage of Attribute Values

But there are special types of objects that the Perl MongoDB driver may expect to receive blessed, such as a "MongoDB::Code" object.

To skip the Mongoose Engine collapsing process altogether, use the "Raw" trait. That way, the MongoDB driver will receive the attribute as is.

    has code => ( is => 'rw', isa => 'MongoDB::Code', traits => ['Raw'] );

DateTime Handling

This attribute:

    has date => (
        is      => 'rw',
        isa     => 'DateTime',
        default => sub{ DateTime->now }
    );

Is collapsed exactly the same as:

    has date => (
        is      => 'rw',
        isa     => 'DateTime',
        traits  => ['Raw'],
        default => sub{ DateTime->now }
    );

Which in turn is stored as:

    {
        "_id" : ObjectId("4c750574a74100a588000000"),
        "date" : ISODate("2012-12-20T05:00:49Z")
    }

Either way the object will be expanded back from the database into a "BSON::TIme" object. If you want to have it back as a DateTime object as in the old versions, you should not use the Raw trait and make sure your attribute 'isa' DateTime:

    has date => (
        is      => 'rw',
        isa     => 'DateTime',
        default => sub{ DateTime->now }
    );

Paging and Sorting

    # sorting

    Person->find->sort({ name => 1 })->each(sub{
        my $person = shift;
        print $person->name;
    });

    # paging

    Person->find->sort({ name => 1 })->skip(20)->limit(20)->each(sub{
        my $person = shift;
        print $person->name;
    });

FileHandle

    package Thing;
    use Mongoose::Class; with 'Mongoose::Document';
    has 'file' => ( is=>'rw', isa=>'FileHandle' );

Then store it using a "FileHandle" type object:

    require IO::File;
    my $fh = new IO::File "myfile.txt", "r";
    my $t = Thing->new( file=>$fh );
    $t->save;

The file is stored in Mongo's GridFS using the field name and "_id" as filename. A special reference is created in your document to point to the GridFS file. The "thing" collection BSON may look like this:

    { "file":
        { "$ref": "FileHandle",
          "$id": ObjectId("4c7619d02f2e70d7a4140000") }
    }

When expanding the doc, the file attibute becomes a Mongoose::File, a wrapper of MongoDB::GridFSBucket::DownloadStream, which can be easily slurped or streamed.

    my $file = Thing->find_one->file;
    print $file->slurp;

This is asymmetric, which means it's probably best if you check the attribute if it isa "Mongoose::File" before using it as such, specially in your class methods.

    package Thing;
    # ...
    sub my_file_method {
        my $self = shift;
        if( $self->file->isa('Mongoose::File') ) {
            my $data = $file->slurp;
            # do stuff
        } else {
            # probably an IO::File filehandle still
        }
    }

This less-than-optimal asymmetric behavior may change in the future.

Direct access to MongoDB Calls

    # finds and expands documents into objects

    my $cur = Person->find;

    # or just get the plain documents (hashrefs)

    my $cur = Person->collection->find;

    # get the MongoDB::Database object for your class

    my $db = Person->db;
    $db->run_command({ shutdown => 1 });

This can be useful for performance reasons, when you don't need to expand objects, or need to access MongoDB functionality not available in Mongoose. It's also useful for testing, to compare if some set of query results returned by Mongoose are identical to the straight MongoDB driver's results.

Finding by string _id

The MongoDB way of retrieving an "_id" from a string is a little annoying to type:

    $author_id = "4dd77f4ebf4342d711000000";
    $author = Author->find_one( BSON::OID->new( oid => pack("H*",$author_id) ) );

So, there is a shorthand variation of "find_one" to help you on this:

    $author = Author->find_one('4dd77f4ebf4342d711000000');

Will automatically search by "_id" on the given value by first turning it into a "BSON::OID".