crud

Package crud is meant to create REST API HTTP endpoint for simple data management.

HTTP endpoint can be set to allow creating, updating, removing new object, along with returning its details, or list of objects. All requests and responses are in the JSON format.

Example usage

TL;DR

Check code in the *_test.go files, starting with main_test.go to get examples.

Defining structs (models)

Models are defined with structs as follows (take a closer look at the tags):

type User struct {
	ID                 int    `json:"user_id"`
	Flags              int    `json:"flags"`
	Name               string `json:"name" crud:"req lenmin:2 lenmax:50"`
	Email              string `json:"email" crud:"req"`
	Password           string `json:"password"`
	EmailActivationKey string `json:"email_activation_key" crud:""`
	CreatedAt          int    `json:"created_at"`
	CreatedByUserID    int    `json:"created_by_user_id"`
}

type Session struct {
	ID                 int    `json:"session_id"`
	Flags              int    `json:"flags"`
	Key                string `json:"key" crud:"uniq lenmin:32 lenmax:50"`
	ExpiresAt          int    `json:"expires_at"`
	UserID             int    `json:"user_id" crud:"req"`
}

type Something struct {
	ID                 int    `json:"something_id"`
	Flags              int    `json:"flags"`
	Email              string `json:"email" crud:"req"`
	Age                int    `json:"age" crud:"req valmin:18 valmax:130 val:18"`
	Price              int    `json:"price" crud:"req valmin:0 valmax:9900 val:100"`
	CurrencyRate       int    `json:"currency_rate" crud:"req valmin:40000 valmax:61234 val:10000"`
	PostCode           string `json:"post_code" crud:"req val:32-600"`
}

Field tags

Struct tags define ORM behaviour. crud parses tags such as crud, http and various tags starting with crud_. Apart from the last one, a tag define many properties which are separated with space char, and if they contain a value other than bool (true, false), it is added after semicolon char. See below list of all the tags with examples.

Tag	Example	Explanation
crud	crud:"req valmin:0 valmax:130 val:18"	Struct field properties defining its valid value for model. See RESTAPI Field Properties for more info
crud_val	crud_val:"Default value"	Struct field default value
crud_regexp	crud_regexp:"^[0-9]{2}\\-[0-9]{3}$"	Regular expression that struct field must match
crud_testvalpattern	crud_testvalpattern:DD-DDD	Very simple pattern for generating valid test value (used for tests). In the string, D is replaced with a digit

CRUD Field Properties

Property	Explanation
req	Field is required
uniq	Field has to be unique (like UNIQUE on the database column)
valmin	If field is numeric, this is minimal value for the field
valmax	If field is numeric, this is maximal value for the field
val	Default value for the field. If the value is not a simple, short alphanumeric, use the crud_val tag for it
lenmin	If field is string, this is a minimal length of the field value
lenmax	If field is string, this is a maximal length of the field value
password	Field is a password, and a function that generates it can be attached (see ControllerConfig)
hidden	Field's value will not be shown when listing item(s)

Database storage

Currently, crud supports only PostgreSQL as a storage for objects.

Controller

To perform model database actions, a Controller object must be created. See below example that modify object(s) in the database.

import (
	crud "github.com/go-phings/crud"
)

// Create connection with sql
conn, _ := sql.Open("postgres", fmt.Sprintf("host=%s port=%s user=%s password=%s dbname=%s sslmode=disable", dbHost, dbPort, dbUser, dbPass, dbName))
defer conn.Close()

// Create RESTAPI controller and an instance of a struct
c := crud.NewController(conn, "app1_", nil)
user := &User{}

// Database tables have to be created. This could be done using some ORM like struct-db-postgres or it can be done manually.

ControllerConfig

crud.&ControllerConfig{} can be passed to a constructor. It contains the following fields:

• TagName can be used to change the name of the tag in struct (by the default it is crud)
• PasswordGenerator - when a field is a password (see field tags above), a function can be attached, that generates the value to be put in the database

HTTP Endpoints

With crud, HTTP endpoints can be created to manage objects stored in the database.

If User struct is used for HTTP endpoint, fields such as Password will be present when listing users. Therefore, it's necessary to create new structs to define CRUD endpoints' input and/or output. These structs unfortunately need validation tags (which can be different than the ones from "main" struct).

In below example, User_Create defines input fields when creating a User, User_Update defines fields that are meant to change when permorming update, User_UpdatePassword is an additional struct just for updating User password, and finally - fields in User_List will be visible when listing users or reading one user. (You can define these as you like).

type User_Create struct {
	ID       int    `json:"user_id"`
	Name     string `json:"name" crud:"req lenmin:2 lenmax:50"`
	Email    string `json:"email" crud:"req"`
	Password string `json:"password"`
}
type User_Update struct {
	ID       int    `json:"user_id"`
	Name     string `json:"name" crud:"req lenmin:2 lenmax:50"`
	Email    string `json:"email" crud:"req"`
}
type User_UpdatePassword struct {
	ID       int `json:"user_id"`
	Password string `json:"password"`
}
type User_List struct {
	ID       int    `json:"user_id"`
	Name     string `json:"name"`
}

var parentFunc = func() interface{} { return &User{}; }
var createFunc = func() interface{} { return &User_Create{}; }
var readFunc   = func() interface{} { return &User_List{}; }
var updateFunc = func() interface{} { return &User_Update{}; }
var listFunc   = func() interface{} { return &User_List{}; }

var updatePasswordFunc = func() interface{} { return &User_UpdatePassword{}; }

http.Handle("/users/", c.Handler("/users/", parentFunc, HandlerOptions{
	CreateConstructor: createFunc, // input fields (and JSON payload) for creating
	ReadConstructor: readFunc,     // output fields (and JSON output) for reading
	UpdateConstructor: updateFunc, // input fields (and JSON payload) for updating
	ListConstructor: listFunc,     // fields to appear when listing items (and JSON output)
}))
http.Handle("/users/password/", c.Handler("/users/password/", parentFunc, HandlerOptions{
	UpdateConstructor: updatePasswordFunc, // input fields for that one updating endpoint
	Operations: OpUpdate, // only updating will be allowed
}))
log.Fatal(http.ListenAndServe(":9001", nil))

In the example, /users/ CRUDL endpoint is created and it allows to:

• create new User by sending JSON payload using PUT method
• update existing User by sending JSON payload to /users/:id with PUT method
• get existing User details with making GET request to /users/:id
• delete existing User with DELETE request to /users/:id
• get list of Users with making GET request to /users/ with optional query parameters such as limit, offset to slice the returned list and filter_ params (eg. filter_email) to filter out records with by specific fields

When creating or updating an object, JSON payload with object details is required. It should match the struct used for Create and Update operations. In this case, User_Create and User_Update.

{
	"email": "[email protected]",
	"name": "Jane Doe",
	...
}

Output from the endpoint is in JSON format as well and it follows below structure:

{
	"ok": 1,
	"err_text": "...",
	"data": {
		...
	}
}