Al Newkirk > MongoDBI-0.0.12 > MongoDBI::Document

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Module Version: 0.0.12   Source   Latest Release: MongoDBI-0.02

NAME ^

MongoDBI::Document - Defines and Represents a MongoDB Collection and Document

VERSION ^

version 0.0.12

SYNOPSIS ^

    package CDDB::Album;

    use MongoDBI::Document;
    
    store 'albums';
    
    key 'title',    is_str,  is_req;
    key 'released', is_date, is_req;
    
    key 'rating', is_int, default => 1;
    
    has 'runtime', is_any; # will not be saved to the db
    
    embed 'tracks', class => 'CDDB::Track', type => 'multiple';
    
    has_one 'band', class => 'CDDB::Artist';
    
    1;

DESCRIPTION ^

MongoDBI::Document is thee class used to model objects that will be persisted in the MongoDB database. The representation of a Document in MongoDB is a BSON object that is very similar to a Perl hash or JSON object. Documents can be stored in their own collections in the database, or can be embedded in other Documents -n- levels deep.

There is one important (and probably noticeable) difference in how MongoDBI approaches document modeling, as opposed to other MongoDB frameworks, which is that a document class (a class that is modeled using MongoDBI::Document) has the same specifications whether its an embedded document, relational document or a standard document.

This is because MongoDB doesn't make that distinction so I don't see why we should be forced to. Instead, a document is a document with the only difference being how it is implemented ... also meaning that a single document class can be used in different contexts (relational document, embedded document, etc).

MongoDBI::Document subclasses MongoDBI::Document::Base, see that class also for additional information.

CONVENTIONS

It is important to take a moment to familiarize yourself with the conventions MongoDBI::Document uses, understanding these conventions will help you get up-to-speed faster and allow you to wield all available functionality.

A MongoDBI::Document has dual roles, the class role in which the class represents a MongoDB collection, and an object role in which the object represents a MongoDB document, as such there are methods that can be used on the the class (e.g. search, create, find_or_create, etc) and methods that can be used on the object (class instance) (e.g. save, update, remove, etc).

MongoDBI::Document is NOT a wrapper around MongoDB::Collection, although there are some methods with the same name their operations are different.

The vast majority of MongoDBI::Document method take hash key/value pairs as opposed to hash-references, ... this convention can be a gotcha for some developers so do remember.

Naming conventions are very important in a MongoDB database and MongoDBI document class. The following is merely an aid towards helping you name or databases, collections, fields and indexes properly.

Databases should not be named "admin, local, or test". Collections and/or MongoDBI document class names should not be named "system".

More importantly, Fields should never be named using terms that may collide or overwrite the functionality of existing Moose or MongoDBI reserved words or methods. Those terms include but are not limited to the following:

    package EggNoodle;
    
    use MongoDBI::Document ; # +Moose
    
    key 'has' ;     # BAD
    key 'can' ;     # BAD
    key 'extends' ; # BAD
    
    # ... and other Moose keywords
    
    key 'id' ;      # BAD
    key 'name' ;    # BAD
    key 'key' ;     # BAD
    key 'store' ;   # BAD
    key 'change' ;  # BAD
    key 'config' ;  # BAD
    key 'file' ;    # BAD
    
    # ... and other MongoDBI::Document::Sugar keywords
    
    index 'name' ;      # BAD
    index 'unique' ;    # BAD
    index 'drop_dups' ; # BAD
    index 'safe' ;      # BAD
    index 'background' ;# BAD
    
    # ... and other MongoDB indexing option keys
    
    1;

For now it is important for you to avoid using these names and others that might collide with some inherited functionality. As a rule, simply name things as specifically as possible. I apologize for any inconvenience. Please familiarize yourself with Moose's keywords as well as the keywords found in MongoDBI::Document::Sugar.

CONFIGURATION

Each MongoDBI::Document can have a completely different configuration including its database and host. It is not only possible, but easy as well, to have different classes operating on different machines.

    package CDDB::Album;
    use MongoDBI::Document;
    
    package main;
    
    my $config = CDDB::Album->config;
    $config->set_database(name => 'cddb');

DOCUMENT STORAGE

MongoDBI::Document by default generates its collection name by transforming the class name and pluralizing it thus storing the class Album in the collection albums, or CDDB::Album in the collection cddb_albums. This functionality can be averted by using the store() declaration or using the set_collection() config method. Read more on these methods in MongoDBI::Document::Config.

    # option A
    package CDDB::Album;
    use MongoDBI::Document;
    
    store 'my_albums'; # collection name literally
    
    # option B
    package CDDB::Album;
    use MongoDBI::Document;
    
    package main;
    CDDB::Album->config->set_collection(name => 'the_albums');
    
    # option C
    CDDB::Album->config->set_collection(
        naming => ['short', 'plural']
    );
    
    # valid option C naming keys are as follows:
    
        * same - as-is
        * short - only the final portion of the package name
        * plural - unintelligent 's' adder
        * decamel - MyApp becomes my_app
        * undercolon - :: becomes _
        * lower/lc - lowercase string
        * upper/uc - uppercase string
        * default - same as (decamel, undercolon, lower, plural)

FIELD DECLARATIONS

MongoDBI::Document exports Moose making your class a Moose class (technically) which means that Moose-base class declarations and rules apply however it is important to note that MongoDBI::Document exports its own sugary goodness for defining document classes, more-to-the-point, Moose attributes declared with the has() declaration will be ignored by MongoDBI::Document mechanisms. For more information on said sugary goodness, please review MongoDBI::Document::Sugar.

This blatant disregard is a feature, and allows us to have "protected" document class fields that are used (e.g. by user-defined methods, etc) within our application but never saved to the database.

When a class attribute needs to be declared as a database document key, the key() declaration should be used. The key() declaration can be passed any arguments which can be legally passed to Moose's has() method. Additionally, MongoDBI::Document::Sugar exports a few relevant attribute argument shorthands for your convenience such as (is_str, is_int, is_date, etc.).

Consider the follow simple class for modeling an album:

    package CDDB::Album;

    use MongoDBI::Document;
    
    key 'title',    is_str,  is_req;
    key 'released', is_date, is_req;
    key 'rating',   is_int,  default => 1;
    
    has 'active',   is_str; # never saved to the db
    
    # is_str  == (is => 'rw', isa => 'Str')
    # is_int  == (is => 'rw', isa => 'Int')
    # is_date == (is => 'rw', isa => 'DateTime')
    
    # etc.
    
    1;

If you do not specify the type of field with the declaration, MongoDBI::Document will treat it as a String as that is the most commonly used field type.

Once instantiated, you can/will update the object attributes in the same way as you would using a traditional Moose class.

PLEASE NOTE! There currently is NO mechanism in place to die or warn you if you define a field on your document that conflicts with a reserved word, attribute of method within the MongoDBI core, ... so please use caution and common sense naming. Although it may be pretty tempting to create a field on your class named 'name' but I would advise against it, .. instead try fullname or similar.

For a complete list of keywords and declarations, please see the MongoDBI::Document::Sugar documentation.

FIELD DIRTY TRACKING

MongoDBI::Document supports the tracking of changed or "dirty" fields by placing triggers on class attributes which retain a complete history of the changes to its field for the life of the parent object.

If a defined field has been modified by it will be marked as dirty and accessible as follows:

    use CDDB::Album;
    
    my $cd = CDDB::Album->new(title => 'LifeTime', released => DateTime->now);
    
    if ($cd->changed) {
        
        # okay, what changed?
        if ($cd->changed('title')) {
            
            print "You changed the title!";
            print "Title is now, ", $cd->change('title')->{new_value};
            
        }
        
    }
    
    # or, ... directly access the history
    $cd->_dirty->{title}->[2]->{new_value}; # 3rd title change
    $cd->_dirty->{title}->[2]->{old_value}; # value before 3rd title change

CLASS INHERITANCE

MongoDBI::Document, being a Moose class itself, supports inheritance much in the exact same way as Moose in both root and embedded documents. In scenarios where document classes are inherited from other document classes, their fields, indexes, declarations, etc, get copied up the chain into derived class.

    {
        package CDDB::Person;
        
        use MongoDBI::Document;
        
        key 'fullname', is_str, is_req, is_unique;
    }
    
    {
        package CDDB::Artist;
        
        use MongoDBI::Document;
        
        extends 'CDDB::Person';
        
        store 'artists';
        
        key 'handle', is_str;
    }

STANDARD OPERATIONS, QUERYING, ETC

MongoDBI::Document leverages the role MongoDBI::Document::Storage::Operation to provide a standard range of common methods you would expect to find in any other ORM, ODM, database framework.

    * CDDB::Album->count
    * CDDB::Album->create(...)
    * CDDB::Album->find(...)
    * CDDB::Album->find_one(...)
    * CDDB::Album->find_or_create(...)
    * CDDB::Album->find_or_new(...)
    * CDDB::Album->first
    * CDDB::Album->last
    * CDDB::Album->new(...)->save
    * CDDB::Album->create(...)->remove
    * CDDB::Album->create(...)->update
    * CDDB::Album->search
    
    ... etc

One of MongoDBI's greatest features is its querying abstraction layer handled by MongoDBI::Document::Storage::Criterion, please review that documentation for an in-depth look at MongoDBI's querying facilities. Most all queries in MongoDBI are wrapped around a MongoDBI::Document::Storage::Criterion object, which is a chainable object for building complex and dynamic queries. The querying object will never hit the database until you tell it to.

The following is an example of how MongoDBI's querying abstraction facilities can be used:

    * CDDB::Album->search->all_in(...)
    * CDDB::Album->search->all_of(...)
    * CDDB::Album->search->also_in(...)
    * CDDB::Album->search->any_in(...)
    * CDDB::Album->search->any_of(...)
    * CDDB::Album->search->asc_sort(...)
    * CDDB::Album->search->desc_sort(...)
    * CDDB::Album->search->select(...)
    
    ... etc
    
    my $search = CDDB::Album->search;
       $search = $search->where('released$lt' => DateTime->now->set(...));
       $search = $search->asc_sort('title')->limit(25);
       
    my $mongodb_cursor = $search->query;

While we're on the topic of serious querying, MongoDBI::Document also allows you to define "chains" on your classes as a convenience for generating complex query strings. Chains (chainable search objects) are declared on MongoDBI::Document classes using the chain() declaration. All class chains are chainable and might look as follows:

    package CDDB::Artist;
    
    use MongoDBI::Document;
    
    extends 'CDDB::Person';
    
    store 'artists';
    
    key 'handle', is_str;
    
    chain 'is_legal' => sub { shift->and_where('age$gt' => 21) }
    chain 'is_local' => sub { shift->and_where('state$in' => ['PA', 'NJ']) }
    
    package main;
    
    my $artists = CDDB::Artist;
    
    my $mongodb_cursor = $artists->is_legal->is_local->query; 

DOCUMENT CLASS RELATIONSHIPS

As previously stated, with MongoDBI::Document classes, the only difference between embedded, relational and standard documents are how they're declared to be applied to the database. All types of documents are designed as MongoDBI::Document classes. Declaring a document class to be applied to the database as an embedded or relational document simply means declaring a relationship between two document classes. The declarations used to declare such relationships are embed(), has_one(), and has_many(). These declarations are exported by and explained in further detail in the MongoDBI::Document::Sugar documentation.

Document class relationships are associations between one document and another. The embedded document relationship describes a child document(s) stored within a parent document. The relational (referenced) document relationship describes a document(s) referenced by separate document in separate collection.

MongoDBI::Document classes declared to be related to other document classes are wrapped by object-based proxies for the actual document class which provides functionality for accessing, replacing, appending and persisting.

Consider the following example which declares both an embedded and relational relationship:

    package CDDB::Album;

    use MongoDBI::Document;
    
    ...
    
    embed 'producer', class => 'CDDB::Person';
    embed 'tracks', class => 'CDDB::Track', type => 'multiple';
    
    has_one 'band', class => 'CDDB::Artist';
    has_many 'compilations', class => 'CDDB::Album';
    
    package main;
    
    my $albums = CDDB::Album;
    my $album  = $albums->new(...);
    
    $album->producer->add(name => 'Mike Nice');
    $album->tracks->add(title => 'Rainbow Bum');
    $album->tracks->add(title => 'Silver Gazelle');
    
    $album->band->add(name => 'Randy Watson', handle => 'Sexual Chocolate');
    
    $album->save;

For a more in-depth look at relationships, please review the documentation for MongoDBI::Document::Child and MongoDBI::Document::Relative.

AUTHOR ^

Al Newkirk <awncorp@cpan.org>

COPYRIGHT AND LICENSE ^

This software is copyright (c) 2011 by awncorp.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

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