Golang HTTP CRUD+L: The Create Part

CRUD+L: Create, Read, Update, Delete, List

CRUDL is very common needed feature for relational database, so I created a Repo for it. This post will introduce the http wrapper in that Repo and the Create part

How do we achieve the automatically create db record from object and http handler for creation in Golang? The answer is SQLX, reflection, wrapper http handler

The CRUD Structure

You need to specify 5 things:

• Database object (DB mandatory ), crud doesn’t connect db for you (you can use this Source for MySQL wrapper).
• Table name (TableName mandatory ) where we inserting rows.
• Object generator (Object mandatory ) the object of corresponding struct that reflect the table model
• Enable http handler for Create part (C optional ).
• List of validators to validate input parameters (Validators Optional ).

The Object generator interface

The Object interface only has one method Get which is use for getting new object from the struct which is corresponding for the table we inserting rows. This apply the Prototype Design Pattern where we has a way to generate a prototype to reuse. This Object has type interface but the underlying type must be a pointer to struct which is use for getting the field and the crud tag for building the rest of CRUD structure.

The CRUD Tag

CRUD uses Golang custom tag “db”, this tag also use by SQLX

The custom tag use for setting up the options for each field. Example:

db:"field_name,pk,create,select,update,list,validator=name"

• field_name: the actual field name in database.
• pk: this field is primary key.
• create: this field is allowed for creation.
• select: this field is allowed for selection(read).
• update: this field is allowed for updating.
• list: this field is allowed for listing.
• validator: name of validator which is the key in Validators map, value of validator name is the right operand of validator.

The Input Validator Type

CRUD+L allows for validating input parameters when creating or updating data, it’s very generic when validator is a function type:

Validator function inputs:

• method: current running method (create, update)
• obj: the input object which is the interface returned from Get function of Object interface

Validator must assert obj to corresponding object structure then it can validate input freely

The Create Handler

We need a http handler for creation and a SQL template for creating row from data object, inside RegisterC function:

It will build the SQL create template which is have all the allowed creation fields and create a ServerRoute object for http handler

The Create Part

Finally create function will insert new row by using the Named Query of SQLX:

Specially if the primary key of object struct is int64 type and Table has Auto Increment key, it will set the primary key with the inserted value

Full working code can be found at https://github.com/hauxe/GoM/tree/master/crudl

Tips#1: Next Topic will be about The Read Part

Tips#2: We will have a topic about HTTP Wrapper which is designed for simplicity and Decorator design pattern