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ActiveRecord-Simple-0.51
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/ ActiveRecord::Simple::Tutorial

NAME

ActiveRecord::Simple::Tutorial

DESCRIPTION

Information how to use ActiveRecord::Simple as an ORMapper in your project.

INTRO

Before we start, you should to know a few issues about ActiveRecord::Simple

-There is no database handler's

ARSimple doesn't handle your database connection, just keeps a handler that you have already created.

-ARSimpe doesn't try to cover all your sql-requests by object-related code

It's simple, so if you need to do something very sophisticated, just do it by yourself.

-ARSimple doesn't check types

Perl doesn't check types. ARSimple is like perl.

PROJECT's FILE SYSTEM

Filesystem of the future project looks like that.

-sql

Directory with sql-code.

-lib

Directory with perl-classes

-t

Tests.

DATABASE DESIGN

We're going to make yet another blog engine and create a simple model: authors, articles and comments.

CREATE TABLE authors (
    id   INTEGER PRIMARY KEY,
    name TEXT
);

CREATE TABLE articles (
    id        INTEGER PRIMARY KEY,
    title     TEXT NOT NULL,
    content   TEXT NOT NULL,
    author_id INTEGER NOT NULL REFERENCES authors(id)
);

CREATE TABLE comments (
    id              INTEGER PRIMARY KEY,
    create_date     TIMESTAMP NOT NULL DEFAULT NOW,
    comments_author TEXT NOT NULL,
    comment         TEXT,
    article_id      INTEGER NOT NULL REFERENCES articles(id)
);

Save this SQL-code in "sql/myschema.sql" and create the sqlite database:

$ sqlite3 blog.db < sql/myschema.sql

CLASSES

To generate classes, run "mars" script:

$ cd lib && mars -perl -dir ../sql -driver SQLite

The script will read recursively directory, find the .sql files and create perl-classes from sql. Now we have three files: Articles.pm, Authors.pm and Comments.pm. Let's start the test.

BASIC SYNTAX

In first test we have to create authors. Let's go to t/ and create test-file authors.t:

$ touch authors.t

You have to create database handler and insert it into Authors->dbh():

use DBI;
use Authors;

Authors->dbh(DBI->connect("dbi:SQLite:sql/blog.db"));

So, we are ready to write our first bunch of tests. First, let's create authors John Doe and Jack Black:

ok Authors->new({ name => 'John Doe' })->save;
ok Authors->new({ name => 'Jack Black' })->save;

Second, check each author has been saved in the database:

ok my $john = Authors->find({ name => 'John Doe' })->fetch;
ok $john->is_defined;
is $john->name, 'John Doe';
is $john->id, 1;

ok my $jack = Authors->find({ name => 'Jack Black' })->fetch;
ok $jack->is_defined;
is $jack->name, 'Jack Black';
is $jack->id, 2;

We have done with authors. Let's create articles.

RELATIONS

As you can see, table "articles" belongs to "authors", this is relation one-to-many: one author can have many articles, but only one article belongs to one author. We have to reflect it in the code. In Authors.pm (one-to-many):

    __PACKAGE__->relations({
	    articles => {
	        class => 'Articles',
	        type  => 'many',
	        key   => 'author_id'
	    }
    });

In Articles.pm (one-to-one):

    __PACKAGE__->relations({
	    author => {
	        class => 'Authors',
	        type => 'one',
	        key  => 'author_id'
	    }
    });

The foreign key is "author_id".

So we are ready to create articles. Let's do it:

ok my $john = Authors->find({ name => 'John Doe' })->fetch;
ok my $article = Artices->new({
    title     => 'My first article',
    content   => '...',
    author_id => $john->id
});
ok $article->save;

Now check the article has been saved and linked to the author:

ok my @articles = $john->articles->fetch;
my $first_article = shift @articles;
is $first_article->title, 'My first article';

Also we can change article's author. Just put new object into accessor "author":

ok $first_article->author(Authors->find({ name => 'Jack Black' })->fetch)->save;
is $first_article->author->name, 'Jack Black';

SQL-MODIFIERS

ARSimple provides a few sql-modifiers: order_by, asc, desc, limit, offset. All this modifiers you can use before call "fetch". Let's create test "comments" and take a look a bit closer to that functions. Of course, we need to add new relations to Articles and Comments classes to use it in our tests. I think, you already know how to do it ;-)

my $article = Articles->get(1); ### it's the same as Articles->find(1)->fetch;
my $comment1 = Comments->new({
    id => 1,
    comments_author => 'Batman',
    comment => 'Hello from Batman!',
    article_id => $article_id
});
my $comment2 = Comments->new({
    id => 2,
    comments_author => 'Superman',
    comment => 'Yahoo!',
    article_id => $article_id
});
ok $comment1->save;
ok $comment2->save;

So we have two commets. Let's see what methods of sampling, we can use:

my @comments;
# by date (desc):
@comments = Comments->find->order_by('create_date')->desc->fetch;
is scalar @comments, 2;

# by author (desc):
@comments = Comments->find->order_by('comments_author')->asc->fetch;
is $comments[0]->comments_author, 'Batman';

# only one comment from database:
@comments = Comments->find->limit(1)->fetch;
is scalar @comments, 1;

# only one, second comment:
@comments = Comments->find->limit(1)->offset(1)->fetch;
is scalar @comments, 1;

# first comment:
@comments = Comments->find->order_by('id')->limit(1)->fetch; # or:
@comments = Comments->first->fetch;
ok $comments[0]->id, 1;

# last comment:
@comments = Comments->find->order_by('id')->desc->limit(1)->fetch; # or:
@comments = Comments->last->fetch;
ok $comments[0]->id, 2;

What if we have to know only creation date of last comments? We have to use another one cool feature: method only. It tells what fields we want to get:

my $last_comment = Comments->last->only('create_date')->fetch;
ok $last_comment->create_date;
ok !$last_comment->comments_author;

It works everywhere before you fetch it:

Comments->find('id > ?', 1)->only('comments_author', 'article_id')->fetch;

FETCHING

First of all, fetching is not limiting. If you'll write this:

my @articles = Articles->find->fetch(1);

Will be fetched *ALL* records from the table "articles", but you'll get only one. Why? We need it ;-) For example, to do something like that:

my $articles_res = Articles->find;
while (my $article = $articles_res->fetch) {
    say $article->title;
}
### or even that:
while (my @articles = $articles_res->fetch(3)) {
    say $_->title for @articles;
    say 'Next 3 Articles:';
}

So, if you want to get only 10 records from database, use limit ;-)

my @articles = Articles->find->limit(10)->fetch;

MANY-TO-MANY

In this tutorial we don't need to use many-to-many relations. But in real life we have to. To read documantation how "many-to-many" relations does work, please, wisit our wiki on github: Relationship Tutorial

HOW TO REPORT ABOUT A PROBLEM

Please, make an issue on my github page. Or you can write an e-mail: mailto:shootnix@cpan.org