Formik Patterns

Formik Patterns

When to Use

Use this skill when you need formik form handling with validation patterns. Use when building forms, implementing validation, or handling form submission.

Basic Form Setup

import { useFormik } from 'formik';
import * as yup from 'yup';

const validationSchema = yup.object({
  email: yup.string().email('Invalid email').required('Email is required'),
  password: yup.string().min(8, 'Min 8 characters').required('Password is required'),
});

const LoginForm = () => {
  const formik = useFormik({
    initialValues: {
      email: '',
      password: '',
    },
    validationSchema,
    onSubmit: async (values) => {
      await loginMutation({ variables: { input: values } });
    },
  });

  return (
    <VStack gap="$4">
      <Input
        label="Email"
        value={formik.values.email}
       
       
        error={formik.touched.email ? formik.errors.email : undefined}
        keyboardType="email-address"
        autoCapitalize="none"
      />

      <Input
        label="Password"
        value={formik.values.password}
       
       
        error={formik.touched.password ? formik.errors.password : undefined}
        secureTextEntry
      />

      <Button
       
        isDisabled={!formik.isValid || formik.isSubmitting}
        isLoading={formik.isSubmitting}
      >
        Login
      </Button>
    </VStack>
  );
};

Validation Schemas

Common Patterns

import * as yup from 'yup';

// Email
email: yup.string()
  .email('Invalid email address')
  .required('Email is required')

// Password with requirements
password: yup.string()
  .min(8, 'Must be at least 8 characters')
  .matches(/[a-z]/, 'Must contain lowercase letter')
  .matches(/[A-Z]/, 'Must contain uppercase letter')
  .matches(/[0-9]/, 'Must contain number')
  .required('Password is required')

// Confirm password
confirmPassword: yup.string()
  .oneOf([yup.ref('password')], 'Passwords must match')
  .required('Please confirm password')

// Phone number
phone: yup.string()
  .matches(/^\+?[1-9]\d{1,14}$/, 'Invalid phone number')
  .required('Phone is required')

// Optional field with validation when present
website: yup.string()
  .url('Must be a valid URL')
  .nullable()

// Number with range
quantity: yup.number()
  .min(1, 'Minimum 1')
  .max(100, 'Maximum 100')
  .required('Quantity required')

// Array with minimum items
tags: yup.array()
  .of(yup.string())
  .min(1, 'Select at least one tag')

Conditional Validation

const schema = yup.object({
  hasCompany: yup.boolean(),
  companyName: yup.string().when('hasCompany', {
    is: true,
    then: (schema) => schema.required('Company name required'),
    otherwise: (schema) => schema.nullable(),
  }),
});

Form Field Helpers

Input Helper

const getFieldProps = (name: keyof typeof formik.values) => ({
  value: formik.values[name],
  onChangeText: formik.handleChange(name),
  onBlur: formik.handleBlur(name),
  error: formik.touched[name] ? formik.errors[name] : undefined,
});

// Usage
<Input label="Email" {...getFieldProps('email')} />

Select/Picker Helper

<Select
  label="Country"
  value={formik.values.country}
  => formik.setFieldValue('country', value)}
  error={formik.touched.country ? formik.errors.country : undefined}
  options={countryOptions}
/>

Form Submission with GraphQL

const CreateItemForm = () => {
  const [createItem] = useCreateItemMutation({
    onCompleted: () => {
      toast.success({ title: 'Item created' });
      navigation.goBack();
    },
    onError: (error) => {
      console.error('createItem failed:', error);
      toast.error({ title: 'Failed to create item' });
    },
  });

  const formik = useFormik({
    initialValues: { name: '', description: '' },
    validationSchema,
    onSubmit: async (values, { setSubmitting }) => {
      try {
        await createItem({ variables: { input: values } });
      } finally {
        setSubmitting(false);
      }
    },
  });

  return (
    <VStack gap="$4">
      {/* Form fields */}
      <Button
       
        isDisabled={!formik.isValid || formik.isSubmitting}
        isLoading={formik.isSubmitting}
      >
        Create
      </Button>
    </VStack>
  );
};

Edit Form with Initial Values

const EditItemForm = ({ item }: { item: Item }) => {
  const [updateItem] = useUpdateItemMutation({
    onCompleted: () => toast.success({ title: 'Saved' }),
    onError: (error) => {
      console.error('updateItem failed:', error);
      toast.error({ title: 'Save failed' });
    },
  });

  const formik = useFormik({
    initialValues: {
      name: item.name,
      description: item.description ?? '',
    },
    enable