# README

Form Binding Example with Gin

This example demonstrates how to use Gin to bind and validate form data in a Go web application. The sample creates a simple booking API that accepts form submissions, validates the fields, and parses date values with custom formats.

Features

Binds form data from client requests into Go structs.
Validates form fields using Gin's binding and validation tags.
Handles date fields with custom format parsing.
Responds with JSON status and parsed data.

Prerequisites

Go 1.13+ installed
Gin web framework

Install Gin with:

go get -u github.com/gin-gonic/gin

How It Works

The main.go file defines a Booking struct with form tags and validators:

type Booking struct {
    Name     string     `form:"name" binding:"required"`
    CheckIn  *time.Time `form:"check_in" time_format:"2006-01-02" binding:"required"`
    CheckOut *time.Time `form:"check_out" time_format:"2006-01-02"`
}

form:"...": Maps incoming form field names to struct fields.
binding:"required": Marks a field as mandatory. If missing, binding fails and an error is returned.
time_format:"...": Tells Gin how to parse date strings into time.Time.

The /book endpoint receives POST requests, binds form data into a Booking struct, and responds with JSON.

Running the Example

Change into the form-binding directory:
```
cd form-binding
```
Run the application:
```
go run main.go
```
The server starts on http://localhost:8080.

Example Usage

Request

Send a POST request to /book with form data:

curl -X POST http://localhost:8080/book \
  -d "name=John Doe" \
  -d "check_in=2025-06-21" \
  -d "check_out=2025-06-25"

Successful Response

{
  "name": "John Doe",
  "check_in": "2025-06-21T00:00:00Z",
  "check_out": "2025-06-25T00:00:00Z"
}

Validation Error Example

If a required field (e.g., name or check_in) is missing:

{
  "error": "Key: 'Booking.Name' Error:Field validation for 'Name' failed on the 'required' tag"
}

Key Points

The ShouldBind method automatically performs validation based on struct tags.
If validation fails, the handler returns HTTP 400 with an error message.
Dates are parsed according to the time_format specified in struct tags (YYYY-MM-DD).