Nero

A library for generating the repository pattern.

Motivation

We heavily use the repository pattern in our codebases and we often write our queries manually. It becomes tedious and repetitive as we have more tables/models to maintain. So, we decided to experiment on creating this library to generate our repositories automatically.

Goals

• Decouple implementation from the Repository interface
• Easy integration with existing codebase
• Minimal API

Installation

$ go get github.com/stevenferrer/nero

Example

See the official example and integration test for a more complete demo.

import (
    "database/sql"

    // import the generated package
    "github.com/stevenferrer/nero-example/productrepo"
)

func main() {
    dsn := "postgres://postgres:postgres@localhost:5432/postgres?sslmode=disable"
    db, err := sql.Open("postgres", dsn)
    ...

    ctx := context.Background()


    // initialize the repository (and optionally enable debug)
    productRepo := productrepo.NewPostgresRepository(db).Debug()

    // create
    creator := productrepo.NewCreator().Name("Product 1")
    productID, err := productRepo.Create(ctx, creator)
    ...

    // query
    queryer := productrepo.NewQueryer().Where(productrepo.IDEq(product1ID))
    product, err := productRepo.QueryOne(ctx, queryer)
    ...

    // update
    now := time.Now()
    updater := productrepo.NewUpdater().Name("Updated Product 1").
        UpdatedAt(&now).Where(productrepo.IDEq(product1ID))
    _, err = productRepo.Update(ctx, updater)
    ...

    // delete
    deleter := productrepo.NewDeleter().Where(productrepo.IDEq(product1ID))
    _, err = productRepo.Delete(ctx, deleter)
    ...
}

Supported back-ends

Below is the list of supported back-ends.

Back-end	Library
PostgreSQL	lib/pq
SQLite	mattn/go-sqlite3
MySQL/MariaDB (soon)	go-sql-driver/mysql

If your your back-end is not yet supported, you can implement your own custom back-end.

Custom back-ends

Implementing a custom back-end is very easy. In fact, you don't have to use the official back-ends. You can implement custom back-ends (Oracle, MSSQL, BoltDB, MongoDB, etc.) by implementing the Template interface.

See official postgres template for reference.

Limitations

Currently, we only support basic CRUD and aggregate operations (i.e. count, sum). If you have more complex requirements other than that, we suggest that you just write your repositories manually, at least for now.

We're still in the process of brain-storming how to elegantly support other operations such as joins. If you have any ideas, we'd love to hear from you!

Standing on the shoulders of giants

This project wouldn't be possible without the amazing open-source projects it was built upon:

• Masterminds/squirrel - Fluent SQL generation in golang
• lib/pq - Pure Go Postgres driver for database/sql
• mattn/go-sqlite3 - sqlite3 driver conforming to the built-in database/sql interface
• pkg/errors - Simple error handling primitives
• hashicorp/multierror - A Go (golang) package for representing a list of errors as a single error.
• jinzhu/inflection - Pluralizes and singularizes English nouns
• stretchr/testify - A toolkit with common assertions and mocks that plays nicely with the standard library

Also, the following have a huge influence on this project and deserves most of the credits:

• ent - An entity framework for Go. Simple, yet powerful ORM for modeling and querying data.
• SQLBoiler - Generate a Go ORM tailored to your database schema.

What's in the name?

The project name is inspired by an anti-bird in an anime called Black Clover. The anti-bird, which the Black Bulls squad calls Nero is apparently a human named Secre Swallowtail. It's a really cool anime with lots of magic!

Contributing

Any suggestions and ideas are very much welcome, feel free to open an issue or make a pull request!

License

Apache-2.0