GoRecord 一个类似于ActiveRecord的Go ORM框架

GoRecord 一个类似于ActiveRecord的Go ORM框架

GoRecord

About

This is meant to be a Go ORM similar to ActiveRecord. There are a million Go ORMs, but none of them quite as good as ActiveRecord. sqlboiler comes close, but I don't like the reliance on separate config files, or its lack of a migrator. Looking for a more Go-ish solution.

Additionally, I want everything to be either (a) compiled in to the project, or (b) set via environment variable. This makes distribution and configuration across many different systems much easier.

This is a brand new project, so don't expect full magic. Also, currently this expects all models that have relationships with each other be in the same package.

For some of the thinking behind the way that this project is stuctured, see this short article on Automated Code Generation.

IMPORTANT

At the moment, go generate only works if there is at least one record in the database. So, when doing the examples, after the migration, add a record manually before running go generate. I hope to fix this shortly.

Installing

First, grab the generating command:

go get github.com/johnnyb/gorecord/...

This will get both the library and the command (if you just import the library, you won't get the gorec command).

Building an Example Program

In this section we are going to build a complete example GoRecord app from scratch. Create an empty directory called testprogram and go there. Now initialize the module:

go mod init example.com/testprogram

Now create a main.go file:

package mainimport ( "fmt")func main() { fmt.Println("Hello world")}

Now, go build and ./testprogram to make sure it works.

Creating the database

Create the database manually.

createdb -U postgres gotest

Set these two environment variables:

export DB_DRIVER=pgxexport DB_CONNECTION_STRING="user=postgres database=gotest password=REPLACE_WITH_YOUR_PWD"

Creating your first migration

Now, create a subdirectory called migrations to store your database migrations. Create your first migration with the gorec command. We are going to create a table called people:

gorec -action migration -directory migrations -named create_people

This will create a file called migrations/TIMESTAMP_create_people. Open the file. Replace the panic on the up migration with the following code:

_, err := conn.Exec("CREATE TABLE people (id serial PRIMARY KEY, name text, description text)")return err

Note that your migration can actually be any Go code that you want. However, I encourage you to mostly keep it to just Execing SQL commands. Note that since the id is serial the database will be responsible for generating primary keys.

Connecting your code to the database and migrations

Now, in your main.go file, add the following to your imports list:

"github.com/johnnyb/gorecord/gorec""github.com/johnnyb/gorecord/migrator"_ "github.com/jackc/pgx/v4/stdlib" // Load the database driver_ "example.com/testprogram/migrations" // Load your migrations

Now add the following code to your main() function:

db, err := gorec.AutoConnect()if err != nil { panic(err)}defer db.Close()err = migrator.MigrateRegisteredMigrations()if err != nil { panic(err)}

This will connect to the database, and auto-run any migrations that you have outstanding. Note that it keeps track of which migrations you have run, so if a migration has run it will not run again. The AutoConnect function connects to the database and sets the global variables gorec.GlobalConnection which will be implicitly used throughout GoRecord. If you need to connect to more than one database, that is supported, but is a little tricky.

Now, build a run your program: go build and ./testprogram. This will perform your migration for you!

Create your first model

Create the directory models. In that directory, create a file called person.go and put in the following code:

package models//go:generate gorec -model Persontype Person struct { PersonRecord}

Note that the LACK of a space between // and go:generate is EXTREMELY important in Go.

Now, while in the models directory, run go generate. This will make a file called person.impl.go which has all of the details of the model. This includes getters and setters for all of the fields, a PersonNew() function, a PersonFind() function, a PersonQuerySimple() function and a Save() method. gorec automagically discovers your table fields from the database itself. This is why you had to run migrations first. If you add more fields, to the table, you will need to re-run go generate here.

You may wonder how we went from a table named people to a model named Person. GoRecord adopts many of the ActiveRecord naming conventions. This means that the model name is an uppercase singular version of the word, and the table is an underscored plural version of the word. GoRecord contains an inflector which will singularize/pluralize words appropriately, though, at the current stage of development, its handling of special cases is limited. If you need to specify the table name, you can pass in a -table option to the gorec command.

Access your model from your code

In your main.go add the following import:

"example.com/testprogram/models"

Then, add the following code to the end of the main() function:

rec := models.PersonNew()rec.SetName("Bob")rec.SetDescription("Bob is a Great Guy")err = rec.Save()if(err != nil) { panic(err)}fmt.Printf("Bob's new record ID is %d\n", rec.Id())

If you want to get that same record again, you can add this code:

bobrec, err := models.PersonFind(rec.Id())fmt.Printf("Found record %d named %s\n", bobrec.Id(), bobrec.Name());

If you want to find Bob by his name, you can add this code:

bobrecs, err := models.PersonQuerySimple("where name = $1", rec.Name())fmt.Printf("Found %d records named Bob\n", len(bobrecs))

This will return a slice of Persons named Bob.

Creating a relationship

Let's say that we want to add a one-to-many relationship. We would do this using the HasMany relationship.

Let's start by creating a new migration, create_cars. From your main directory, do:

gorec -action migration -named create_cars -directory migrations

Put this in the migration:

_, err := conn.Exec("CREATE TABLE cars (id serial PRIMARY KEY, person_id int, make text, model text, year text)")return err

Build and run your program (./testprogram)to perform the migration. Now add the model. In models/car.go:

package models//go:generate gorec -model Car//go:generate gorec -model Car -action BelongsTo -relationship Persontype Car struct { CarRecord}

This will add a function .Person() to any car object to retrieve the related person object (also with an error result).

Note that this has an additional generator specifying the relationship between the Car and the Person, stating that a car "belongs to" that person. In person.go we need to add a similar relationship line. This has to come after the first go:generate command in the file:

//go:generate gorec -model Person -action HasMany -relationship Cars

This will add a function .Cars() to any person object to retrieve the related cars objects (as well as an error field). Additionally, you will get a .CarsBuild() function to create a new Car object that is already setup with the relationship.

Don't forget to run go generate in the models directory to make sure the files are implemented!

Testing

Most people have separate testing and primary databases. Therefore, you need to set the DB_TEST_CONNECTION_STRING to the connection you want to use for testing. The system will not use the main DB_CONNECTION_STRING for testing.

RDS

In addition to standard connection strings, this also supports RDS connection information through the standard RDS environment variables. Additionally, test info can be supplied through RDS_TEST_HOSTNAME, RDS_TEST_DB_NAME, etc.

Enjoy!

I hope you enjoy GoRecord. It is still in its early stages of development, but it is already pretty fun to play with.

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