如何查找是否有“儿童”文档。 在 MongoDBx::Class

Question

I am learning the Perl MongoDBX::Class and writing a blog app.

Bellow are Post and Comment model. If call this method:

my $comments = $a_post->comments;

it halt the application if there is no comment for this post. The question is how to check whether this post has comment?

Thanks.

package Model::Schema::Post;



use MongoDBx::Class::Moose;

use namespace::autoclean;



with 'MongoDBx::Class::Document';



has 'title' => (is => 'rw', isa => 'Str', required => 1,);

belongs_to 'author' => (is => 'ro', isa => 'Author', required => 1);

has 'post_date' => (is => 'ro', isa => 'DateTime', traits => ['Parsed'], required => 1);

has 'text' => (is => 'rw', isa => 'Str', required => 1);

joins_many 'comments' => (is => 'ro', isa => 'Comment', coll => 'comments', ref => 'post');

holds_many 'tags' => (is => 'rw', isa => 'Tag', predicate => 'has_tag');



__PACKAGE__->meta->make_immutable;


package Model::Schema::Comment;



use MongoDBx::Class::Moose;

use namespace::autoclean;



with 'MongoDBx::Class::Document';



belongs_to 'post' => (is => 'ro', isa => 'Post', required => 1);

has 'author' => (is => 'ro', isa => 'Author', required => 1);

has 'comment_date' => (is => 'ro', isa => 'DateTime', traits => ['Parsed'], required => 1);

has 'text' => (is => 'rw', isa => 'Str', required => 1);

has 'rateing' => (is => 'rw', isa => 'Int');



__PACKAGE__->meta->make_immutable;

Answer 1

I'm not sure why your application halts. Looking at your schema, running

my $comments = $a_post->comments;

Should return a MongoDBx::Class::Cursor object (which is really just a MongoDB::Cursor object). On this cursor, you can run:

my $num_comments = $comments->count;
if ($num_comments > 0) {
   my @comments = $comments->all;
   ...
}

If this doesn't help you, and your application still hangs, It'll help me if you send me a sample of your code so I can try to find out what's going on.

By the way I'm the author of MongoDBx::Class.

PS If you feel you've stumbled upon some bug in MongoDBx::Class, feel free to open a bug report as described on the MongoDBx::Class page on CPAN.