crudgen

README

crudgen

Generate CRUD operations for structs.

Install

go get github.com/pdk/crudgen

Currently depends on $GOPATH to find the template.

Example invocation

//go:generate crudgen -source $GOFILE -out sample1-crud.go -package $GOPACKAGE -bindstyle dollar -table stories
//go:generate gofmt -w sample1-crud.go

(gofmt added cuz default output is not yet canonical.)

Struct Composition

This system is not smart enough to understand complex structs with composition, but there is a command-line option to explicitly handle such cases.

For example:

-struct User -compose V:Version

This indicates that the User struct is the one we want to generate CRUD operations for, and it is composed on a Version struct, named V within User.

Only a single level of composition is handled, but multiple structs can be included like -compose S1:Struct1,S2:Struct2.

Also, the structs may exist in other files. Just list all the input .go files to the crudgen command.

Requirements

The struct fields must be of types suitable for use with database/sql, e.g. sql.NullInt64. There is nothing in the generation process to verify usable datatypes.

This will work for non-published fields. The generator is not using reflection, but parses of actual .go source, so non-published fields are included in crud operations.

On the other hand, composed structs are not handled. Only the fields directly listed in the struct definition are included in crud operations.

Hooks

There are Pre- and Post- hooks for insert, update and delete:

1. PreInsert(tx *sql.Tx, string) error and PostInsert(tx *sql.Tx, string) error
2. PreUpdate(tx *sql.Tx, string) error and PostUpdate(tx *sql.Tx, string) error
3. PreDelete(tx *sql.Tx, string) error and PostDelete(tx *sql.Tx, string) error

In all cases, the second arg, the string should be tableName. This is to support actions carried by via composition/inheritance.

The current transaction is passed to each hook, so that additional database operations may be performed.

To use any of these hooks, just define the methods on your struct type. The methods are detected dynamically via type assertions, so they do not necessarily need to be in the same source file as your struct. (I.e. the methods are not detected during code generation, but during execution via type assertions.)

Note that although the Insert() and Update() methods return new struct values, rather than mutating in place (for ID and timestamps) the hook methods may be mutating, and the mutations will be returned in the new struct values.

Also, note that the hooks take a transaction handle (*sql.Tx) rather than a database handle (*sql.DB). If you have the wrong signature on your hooks, they will not be found and not invoked.

Transaction Management

The insert, update and delete operations are each done within a single transaction, covering their Pre- and Post- hooks. If any error occurs, with the Pre- or Post- hook, or with the main operation itself, the transaction will be rolled back.

If the caller wants to include more operations in the transaction, then they InsertTx(), UpdateTx() and DeleteTx() methods are available. Rather than passing in a *sql.DB, the caller passes in an already active *sql.Tx.

The crudlib.InTransaction() function is available to wrap a set of operations in a single transaction.

Tests

Tests assume a local postgres database to talk to.

To setup test database, do this:

create database crud_test;
create user crud_test with password 'MudCrud';
grant all privileges on database crud_test to crud_test;