使用Shadcn+Zod+Next.js表单时出现受控/非受控输入警告

问题原因 #

你遇到的警告是因为username字段在useForm初始化时未设置初始值，导致Input组件的value一开始为undefined（非受控状态），用户输入内容后value变为字符串（受控状态），React检测到这种状态切换后抛出警告。

解决方案 #

无需额外使用useState，直接在useForm的配置项中添加defaultValues，给username设置初始空字符串，让组件从一开始就处于受控状态：

const form = useForm<z.infer<typeof FormSchema>>({
  resolver: zodResolver(FormSchema),
  defaultValues: { // 新增默认值配置
    email: undefined,
    username: ""
  }
})

修改后的完整代码 #

'use client'
import {
    Form,
    FormControl,
    FormDescription,
    FormField,
    FormItem,
    FormLabel,
    FormMessage,
  } from "@/components/ui/form"
import { useForm } from 'react-hook-form'
import { zodResolver } from "@hookform/resolvers/zod"
import * as z from "zod"
import {
  Select,
  SelectContent,
  SelectItem,
  SelectTrigger,
  SelectValue,
} from "@/components/ui/select"
import { toast } from "@/components/ui/use-toast"
import Link from "next/link"
import { Input } from "@/components/ui/input"
import { ReactNode } from "react"

const FormSchema = z.object({
  email: z
    .string({
      required_error: "Please select an email to display.",
    })
    .email(),
    username: z.string(),
 
})

const ZodForm = () => {

  const form = useForm<z.infer<typeof FormSchema>>({
    resolver: zodResolver(FormSchema),
    defaultValues: {
      email: undefined,
      username: ""
    }
  })
  
  function onSubmit(data: z.infer<typeof FormSchema>) {
    console.log(data);
    
    toast({
      title: "You submitted the following values:",
      description: (
        <pre className="mt-2 w-[340px] rounded-md bg-slate-950 p-4">
          <code className="text-white">{JSON.stringify(data, null, 2)}</code>
        </pre>
      ),
    })
  }


  return (
    <Form {...form}>
      <form onSubmit={form.handleSubmit(onSubmit)} className="w-2/3 space-y-6">
        <FormField
          control={form.control}
          name="email"
          render={({ field }) => (
            <FormItem>
              <FormLabel>Email</FormLabel>
              <Select onValueChange={field.onChange} defaultValue={field.value}>
                <FormControl>
                  <SelectTrigger>
                    <SelectValue placeholder="Select a verified email to display" />
                  </SelectTrigger>
                </FormControl>
                <SelectContent>
                  <SelectItem value="m@example.com">m@example.com</SelectItem>
                  <SelectItem value="m@google.com">m@google.com</SelectItem>
                  <SelectItem value="m@support.com">m@support.com</SelectItem>
                </SelectContent>
              </Select>
              <FormDescription>
                You can manage email addresses in your{" "}
                <Link href="/examples/forms">email settings</Link>.
              </FormDescription>
              <FormMessage />
            </FormItem>
          )}
        />
        <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>
          )}
        />
        <button type="submit">Submit</button>
      </form>
    </Form>
  )
}

export default ZodForm

为什么之前的尝试失败 #

你之前用useState手动设置value或defaultValue，覆盖了React Hook Form提供的field.value，导致表单状态脱离了RHF的控制，提交时无法获取正确的字段值。

内容的提问来源于stack exchange，提问作者IdoBa