Next.js 15 Fullstack (App Router + Server Actions) · Aula

Formulários básicos com Server Actions

Crie formulários interativos que enviem dados diretamente ao servidor usando Server Actions do Next.js.

Formulários básicos com Server Actions é uma aula grátis de Next.js 15 Fullstack (App Router + Server Actions) no CoddyKit. Esta é a aula 1 de 4. Você pode ler a aula completa abaixo gratuitamente — depois pratica ao vivo no navegador com um editor de código integrado e um tutor de IA 24/7. Faz parte do caminho de aprendizado de Next.js 15 Fullstack (App Router + Server Actions), e seu progresso é sincronizado entre a web e o app CoddyKit. O curso de Next.js 15 Fullstack (App Router + Server Actions) inclui 4 aulas no total.

Partes desta aula ainda não foram traduzidas e aparecem em inglês.

Intro to Server Actions

Welcome to Server Actions! This powerful Next.js 15 feature allows you to define functions that run directly on the server, callable from your client components.

Think of them as a way to send data to your server without needing to create a separate API route. They simplify data mutations and form submissions.

Why Use Server Actions?

Server Actions offer several key benefits for your Next.js applications:

Simplified Data Mutations: Directly call server-side code from your forms.
Reduced Client-Side JS: Less JavaScript needs to be sent to the browser.
Improved Performance: Actions run closer to your database, potentially reducing latency.
Automatic Revalidation: They can automatically update cached data after a successful mutation (more on this in a later lesson!).

Defining a Server Action

A Server Action is an async function marked with the "use server" directive. This directive tells Next.js to treat the function as server-only code.

You can define actions directly in your components or in a separate file (e.g., app/actions.js) and import them.

// app/actions.js
"use server";

export async function createItem(formData) {
  const itemName = formData.get("itemName");
  console.log(`Server received: ${itemName}`);
  // In a real app, you'd save 'itemName' to a database
}

Connecting Form to Action

To link an HTML <form> element to a Server Action, you simply pass the action function directly to the form's action prop. It's that easy!

When the form is submitted, Next.js automatically invokes the specified Server Action.

// app/page.js
import { createItem } from './actions';

export default function Page() {
  return (
    <form action={createItem}>
      <label htmlFor="item">New Item:</label>
      <input type="text" id="item" name="itemName" required />
      <button type="submit">Add Item</button>
    </form>
  );
}

Accessing Form Data

When a form submits to a Server Action, the action function automatically receives a FormData object as its first argument.

You can use formData.get('fieldName') to retrieve the value of an input based on its name attribute.

// app/actions.js
"use server";

export async function processForm(formData) {
  const username = formData.get("username");
  const email = formData.get("email");
  const age = formData.get("age");

  console.log(`User: ${username}, Email: ${email}, Age: ${age}`);
  // Perform server-side logic, e.g., save user to database
}

Full Form Example

Let's combine what we've learned into a simple guestbook entry form. The Server Action will log the guest's message.

Remember, this code is for a Next.js environment and isn't runnable as a standalone JS file.

// app/actions.js
"use server";

export async function addGuestbookEntry(formData) {
  const message = formData.get("message");
  console.log(`New guestbook entry: ${message}`);
  // In a real app, save to DB and revalidate cache
}

// app/page.js
import { addGuestbookEntry } from './actions';

export default function GuestbookPage() {
  return (
    <div>
      <h1>Guestbook</h1>
      <form action={addGuestbookEntry}>
        <textarea name="message" rows="4" cols="30" placeholder="Your message..." required></textarea>
        <button type="submit">Sign Guestbook</button>
      </form>
    </div>
  );
}

Handling Multiple Inputs

The FormData object efficiently captures all inputs within your form that have a name attribute. You can access them individually.

formData.get('inputName'): Gets the first value for a given name.
formData.getAll('inputName'): Returns an array of all values for inputs with the same name (useful for multiple checkboxes).
formData.entries(): Returns an iterator for all key/value pairs.

User Feedback: Loading States

When a form is submitting, it's good practice to provide visual feedback to the user. Next.js, along with React, provides the useFormStatus hook for this.

useFormStatus tells you if the parent <form> is currently submitting, allowing you to disable buttons or show a spinner.

// app/page.js (inside a component, e.g., SubmitButton.js)
import { useFormStatus } from "react-dom";

function SubmitButton() {
  const { pending } = useFormStatus(); // Gets status from parent <form>

  return (
    <button type="submit" disabled={pending}>
      {pending ? "Submitting..." : "Submit"}
    </button>
  );
}

// In your page.js:
// import { addGuestbookEntry } from './actions';
// export default function Page() {
//   return (
//     <form action={addGuestbookEntry}>
//       {/* ... other inputs */}
//       <SubmitButton />
//     </form>
//   );
// }

Quick Check

Which statements about basic Next.js Server Action forms are correct?

Recap & Next Steps

Great job! You've learned the fundamentals of creating basic forms with Next.js Server Actions:

Server Actions are server-side functions marked with "use server".
They simplify form submissions by allowing you to pass the action directly to a form's action prop.
Form data is accessed within the action via a FormData object.
The useFormStatus hook helps implement loading indicators.

Next, we'll dive into how Server Actions can mutate data and automatically revalidate your UI!

Perguntas Frequentes

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Sim — o texto completo de “Formulários básicos com Server Actions” é grátis para ler aqui na web. Para praticá-la interativamente (um editor de código integrado e um tutor de IA 24/7) e desbloquear o restante do curso de Next.js 15 Fullstack (App Router + Server Actions), atualize para CoddyKit PRO. O curso de Next.js 15 Fullstack (App Router + Server Actions) inclui 4 aulas no total.

O que vou aprender em “Formulários básicos com Server Actions”?

Crie formulários interativos que enviem dados diretamente ao servidor usando Server Actions do Next.js. Você pratica Next.js 15 Fullstack (App Router + Server Actions) com código prático que executa diretamente no navegador, e um tutor de IA 24/7 responde suas dúvidas enquanto trabalha na aula.

Preciso ter experiência prévia para começar Next.js 15 Fullstack (App Router + Server Actions)?

Nenhuma experiência prévia é necessária. Next.js 15 Fullstack (App Router + Server Actions) no CoddyKit é estruturado para alunos iniciantes até avançados, então você pode começar aqui ou desde o início e aprender no seu ritmo. Esta é a aula 1 de 4.

Quanto tempo leva a aula “Formulários básicos com Server Actions”?

A maioria das aulas CoddyKit leva cerca de 5–10 minutos. Cada uma é compacta e interativa, então você faz progresso constante e retoma exatamente de onde parou entre web e app.

Posso escrever e executar código nesta aula de Next.js 15 Fullstack (App Router + Server Actions)?

Sim. Cada aula de Next.js 15 Fullstack (App Router + Server Actions) inclui um editor de código integrado, então você escreve e executa código real direto no navegador e recebe feedback de IA instantaneamente — nenhuma configuração local necessária.

Todas as aulas deste curso

Formulários básicos com Server Actions
Mutação de dados e revalidação
Tratamento de erros em ações
Interface Otimista e Estados Pendentes com Ações de Servidor

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