NAME

GraphQL::Plugin::Convert::DBIC - convert DBIx::Class schema to GraphQL schema

SYNOPSIS

  use GraphQL::Plugin::Convert::DBIC;
  use Schema;
  my $converted = GraphQL::Plugin::Convert::DBIC->to_graphql(
    sub { Schema->connect }
  );
  print $converted->{schema}->to_doc;

DESCRIPTION

This module implements the GraphQL::Plugin::Convert API to convert a DBIx::Class::Schema to GraphQL::Schema etc.

Its Query type represents a guess at what fields are suitable, based on providing a lookup for each type (a DBIx::Class::ResultSource).

Example

Consider this minimal data model:

  blog:
    id # primary key
    articles # has_many
    title # non null
    language # nullable
  article:
    id # primary key
    blog # foreign key to Blog
    title # non null
    content # nullable

Generated Output Types

These GraphQL::Type::Object types will be generated:

  type Blog {
    id: Int!
    articles: [Article]
    title: String!
    language: String
  }

  type Article {
    id: Int!
    blog: Blog
    title: String!
    content: String
  }

  type Query {
    blog(id: [Int!]!): [Blog]
    article(id: [Int!]!): [Blog]
  }

Note that while the queries take a list, the return order is undefined. This also applies to the mutations. If this matters, request the primary key fields and use those to sort.

Generated Input Types

Different input types are needed for each of CRUD (Create, Read, Update, Delete).

The create one needs to have non-null fields be non-null, for idiomatic GraphQL-level error-catching. The read one needs all fields nullable, since this will be how searches are implemented, allowing fields to be left un-searched-for. Both need to omit primary key fields. The read one also needs to omit foreign key fields, since the idiomatic GraphQL way for this is to request the other object, with this as a field on it, then request any required fields of this.

Meanwhile, the update and delete ones need to include the primary key fields, to indicate what to mutate, and also all non-primary key fields as nullable, which for update will mean leaving them unchanged, and for delete is to be ignored.

Therefore, for the above, these input types (and an updated Query, and Mutation) are created:

  input BlogCreateInput {
    title: String!
    language: String
  }

  input BlogSearchInput {
    title: String
    language: String
  }

  input BlogMutateInput {
    id: Int!
    title: String
    language: String
  }

  input ArticleCreateInput {
    blog_id: Int!
    title: String!
    content: String
  }

  input ArticleSearchInput {
    title: String
    content: String
  }

  input ArticleMutateInput {
    id: Int!
    title: String!
    language: String
  }

  type Mutation {
    createBlog(input: [BlogCreateInput!]!): [Blog]
    createArticle(input: [ArticleCreateInput!]!): [Article]
    deleteBlog(input: [BlogMutateInput!]!): [Boolean]
    deleteArticle(input: [ArticleMutateInput!]!): [Boolean]
    updateBlog(input: [BlogMutateInput!]!): [Blog]
    updateArticle(input: [ArticleMutateInput!]!): [Article]
  }

  extends type Query {
    searchBlog(input: BlogSearchInput!): [Blog]
    searchArticle(input: ArticleSearchInput!): [Article]
  }

ARGUMENTS

To the to_graphql method: a code-ref returning a DBIx::Class::Schema object. This is so it can be called during the conversion process, but also during execution of a long-running process to e.g. execute database queries, when the database handle passed to this method as a simple value might have expired.

PACKAGE FUNCTIONS

field_resolver

This is available as \&GraphQL::Plugin::Convert::DBIC::field_resolver in case it is wanted for use outside of the "bundle" of the to_graphql method.

DEBUGGING

To debug, set environment variable GRAPHQL_DEBUG to a true value.

AUTHOR

Ed J, <etj at cpan.org>

LICENSE

Copyright (C) Ed J

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