# shadcn/ui - Forms and Validation

## Installation

```bash
npx shadcn@latest add form input textarea select checkbox
npm install react-hook-form @hookform/resolvers zod
```

## Basic Form with Zod Validation

```tsx
"use client"

import { zodResolver } from "@hookform/resolvers/zod"
import { useForm } from "react-hook-form"
import * as z from "zod"
import { Button } from "@/components/ui/button"
import {
  Form,
  FormControl,
  FormDescription,
  FormField,
  FormItem,
  FormLabel,
  FormMessage,
} from "@/components/ui/form"
import { Input } from "@/components/ui/input"

const formSchema = z.object({
  username: z.string().min(2, { message: "Username must be at least 2 characters." }),
  email: z.string().email({ message: "Please enter a valid email address." }),
})

export function ProfileForm() {
  const form = useForm<z.infer<typeof formSchema>>({
    resolver: zodResolver(formSchema),
    defaultValues: { username: "", email: "" },
  })

  function onSubmit(values: z.infer<typeof formSchema>) {
    console.log(values)
  }

  return (
    <Form {...form}>
      <form onSubmit={form.handleSubmit(onSubmit)} className="space-y-8">
        <FormField
          control={form.control}
          name="username"
          render={({ field }) => (
            <FormItem>
              <FormLabel>Username</FormLabel>
              <FormControl>
                <Input placeholder="shadcn" {...field} />
              </FormControl>
              <FormDescription>This is your public display name.</FormDescription>
              <FormMessage />
            </FormItem>
          )}
        />
        <FormField
          control={form.control}
          name="email"
          render={({ field }) => (
            <FormItem>
              <FormLabel>Email</FormLabel>
              <FormControl>
                <Input type="email" placeholder="you@example.com" {...field} />
              </FormControl>
              <FormMessage />
            </FormItem>
          )}
        />
        <Button type="submit">Submit</Button>
      </form>
    </Form>
  )
}
```

## Advanced Form with Multiple Field Types

```tsx
const formSchema = z.object({
  username: z.string().min(2).max(50),
  email: z.string().email(),
  bio: z.string().max(160).min(4),
  role: z.enum(["admin", "user", "guest"]),
  notifications: z.boolean().default(false),
})

export function AdvancedForm() {
  const form = useForm<z.infer<typeof formSchema>>({
    resolver: zodResolver(formSchema),
    defaultValues: {
      username: "",
      email: "",
      bio: "",
      role: "user",
      notifications: false,
    },
  })

  return (
    <Form {...form}>
      <form onSubmit={form.handleSubmit(console.log)} className="space-y-8">
        {/* Text input */}
        <FormField
          control={form.control}
          name="username"
          render={({ field }) => (
            <FormItem>
              <FormLabel>Username</FormLabel>
              <FormControl><Input placeholder="johndoe" {...field} /></FormControl>
              <FormMessage />
            </FormItem>
          )}
        />

        {/* Textarea */}
        <FormField
          control={form.control}
          name="bio"
          render={({ field }) => (
            <FormItem>
              <FormLabel>Bio</FormLabel>
              <FormControl>
                <Textarea placeholder="Tell us about yourself" className="resize-none" {...field} />
              </FormControl>
              <FormMessage />
            </FormItem>
          )}
        />

        {/* Select */}
        <FormField
          control={form.control}
          name="role"
          render={({ field }) => (
            <FormItem>
              <FormLabel>Role</FormLabel>
              <Select onValueChange={field.onChange} defaultValue={field.value}>
                <FormControl>
                  <SelectTrigger>
                    <SelectValue placeholder="Select a role" />
                  </SelectTrigger>
                </FormControl>
                <SelectContent>
                  <SelectItem value="admin">Admin</SelectItem>
                  <SelectItem value="user">User</SelectItem>
                  <SelectItem value="guest">Guest</SelectItem>
                </SelectContent>
              </Select>
              <FormMessage />
            </FormItem>
          )}
        />

        {/* Checkbox */}
        <FormField
          control={form.control}
          name="notifications"
          render={({ field }) => (
            <FormItem className="flex flex-row items-start space-x-3 space-y-0">
              <FormControl>
                <Checkbox checked={field.value} onCheckedChange={field.onChange} />
              </FormControl>
              <div className="space-y-1 leading-none">
                <FormLabel>Email notifications</FormLabel>
                <FormDescription>Receive emails about your account activity.</FormDescription>
              </div>
            </FormItem>
          )}
        />

        <Button type="submit">Submit</Button>
      </form>
    </Form>
  )
}
```

## Login Form Pattern (Card + Form)

```tsx
<Card className="w-[350px]">
  <CardHeader>
    <CardTitle>Login</CardTitle>
    <CardDescription>Enter your credentials to continue</CardDescription>
  </CardHeader>
  <CardContent>
    <Form {...form}>
      <form onSubmit={form.handleSubmit(onSubmit)} className="space-y-4">
        <FormField
          control={form.control}
          name="email"
          render={({ field }) => (
            <FormItem>
              <FormLabel>Email</FormLabel>
              <FormControl>
                <Input type="email" placeholder="you@example.com" {...field} />
              </FormControl>
              <FormMessage />
            </FormItem>
          )}
        />
        <FormField
          control={form.control}
          name="password"
          render={({ field }) => (
            <FormItem>
              <FormLabel>Password</FormLabel>
              <FormControl>
                <Input type="password" {...field} />
              </FormControl>
              <FormMessage />
            </FormItem>
          )}
        />
        <Button type="submit" className="w-full">Login</Button>
      </form>
    </Form>
  </CardContent>
</Card>
```

## Contact Form with API Submission

```tsx
"use client"

import { zodResolver } from "@hookform/resolvers/zod"
import { useForm } from "react-hook-form"
import * as z from "zod"
import { Button } from "@/components/ui/button"
import { Form, FormControl, FormField, FormItem, FormLabel, FormMessage } from "@/components/ui/form"
import { Input } from "@/components/ui/input"
import { Textarea } from "@/components/ui/textarea"
import { toast } from "@/components/ui/use-toast"

const formSchema = z.object({
  name: z.string().min(2),
  email: z.string().email(),
  message: z.string().min(10),
})

async function onSubmit(values: z.infer<typeof formSchema>) {
  try {
    const response = await fetch("/api/contact", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify(values),
    })
    if (!response.ok) throw new Error("Failed to submit")
    toast({ title: "Success!", description: "Your message has been sent." })
  } catch {
    toast({ variant: "destructive", title: "Error", description: "Failed to send message." })
  }
}

export default function ContactPage() {
  const form = useForm<z.infer<typeof formSchema>>({
    resolver: zodResolver(formSchema),
  })

  return (
    <div className="container mx-auto max-w-2xl py-8">
      <Form {...form}>
        <form onSubmit={form.handleSubmit(onSubmit)} className="space-y-6">
          <FormField control={form.control} name="name"
            render={({ field }) => (
              <FormItem>
                <FormLabel>Name</FormLabel>
                <FormControl><Input placeholder="Your name" {...field} /></FormControl>
                <FormMessage />
              </FormItem>
            )}
          />
          <FormField control={form.control} name="email"
            render={({ field }) => (
              <FormItem>
                <FormLabel>Email</FormLabel>
                <FormControl><Input type="email" placeholder="your@email.com" {...field} /></FormControl>
                <FormMessage />
              </FormItem>
            )}
          />
          <FormField control={form.control} name="message"
            render={({ field }) => (
              <FormItem>
                <FormLabel>Message</FormLabel>
                <FormControl>
                  <Textarea placeholder="Your message..." className="resize-none" {...field} />
                </FormControl>
                <FormMessage />
              </FormItem>
            )}
          />
          <Button type="submit" className="w-full">Send Message</Button>
        </form>
      </Form>
    </div>
  )
}
```

## Route Handler for Form Validation (API)

```ts
// app/api/contact/route.ts
import { NextRequest, NextResponse } from "next/server"
import { z } from "zod"

const contactSchema = z.object({
  name: z.string().min(2),
  email: z.string().email(),
  message: z.string().min(10),
})

export async function POST(request: NextRequest) {
  try {
    const body = await request.json()
    const validated = contactSchema.parse(body)
    console.log("Form submission:", validated)
    return NextResponse.json({ success: true })
  } catch (error) {
    if (error instanceof z.ZodError) {
      return NextResponse.json({ errors: error.errors }, { status: 400 })
    }
    return NextResponse.json({ error: "Internal server error" }, { status: 500 })
  }
}
```