Inverse

Transaction-like rollback inside your code.

Use case

You have a program flow with many steps
Steps can fails
Previous successful steps must be cancelled

Usage examples

// It is a typical example of stream inverse function.
// Just define function which will be called if you will inverse your flow.
// See usage of InverseBeginTransaction in DoSomething function below.
func InverseBeginTransaction(tx *gorm.DB) inverse.Func {
	return func() error {
		return tx.Rollback().Error
	}
}

// It is another stream inverse function.
// For example, that function delete file from FileService if you will inverse your flow.
// See usage of InverseCreateFile in DoSomething function below.
func InverseCreateFile(fileSvc FileService, file File) inverse.Func {
	return func() error {
		return fileSvc.Delete(file)
	}
}

func DoSomething(db *gorm.DB, fileSvc FileService) error {
	tx := db.Begin()
	if tx.Error != nil {
		return tx.Error
	}

	// Create new stream and add InverseBeginTransaction Func.
	// If stream will be reversed, InverseBeginTransaction will be called.
	stream := inverse.NewStream(InverseBeginTransaction(tx))

	// ...

	// Create file in file service.
	file, err := fileSvc.Create("name", data)
	if err != nil {
		// There stream.Inverse() will call InverseCreateFile which rollback tx.
		return util.Err(stream.Inverse(), err)
	}

	// Add InverseCreateFile to stream.
	// If stream will be reversed, InverseBeginTransaction and InverseBeginTransaction will be called.
	stream.Add(InverseCreateFile(fileSvc, file))

	// ...

	// For example, buildSomeErr() will produce error.
	err = buildSomeErr()
	if err != nil {
		// There stream.Inverse() will call InverseBeginTransaction and after that InverseCreateFile.
		return util.Err(stream.Inverse(), err)
	}

	return nil
}

Testing

Install dependencies

Using dep you can install dependencies. It is necessary only for testing. In usual case of usage the library you no need to install any dependency.

make dep

Run tests

make test

Run benchmark

make bench

Performance

Benchmark results

BenchmarkInverseStream-4        1000000000               2.99 ns/op
BenchmarkInverseNative-4        1000000000               2.33 ns/op

Project is under development and is open for any proposals.

cv21/inverse