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
These are React Native-style/custom UI fragments: VStack/Input/Button, generated GraphQL hooks, schemas and navigation are project dependencies, not Formik exports. Web forms require DOM event/submit adapters. Client validation is UX only; validate/authenticate/authorize again on the server, redact mutation errors and never log passwords. enableReinitialize resets dirty edits when initial values change; prompt or merge deliberately before refreshing an edited record.
tsx
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="$4">
<Input
label="Email"
value={formik.values.email}
onChangeText={formik.handleChange('email')}
onBlur={formik.handleBlur('email')}
error={formik.touched.email ? formik.errors.email : undefined}
keyboardType="email-address"
autoCapitalize="none"
/>
<Input
label="Password"
value={formik.values.password}
onChangeText={formik.handleChange('password')}
onBlur={formik.handleBlur('password')}
error={formik.touched.password ? formik.errors.password : undefined}
secureTextEntry
/>
<Button
onPress={formik.handleSubmit}
isDisabled={!formik.isValid || formik.isSubmitting}
isLoading={formik.isSubmitting}
>
Login
</Button>
</VStack>
);
};
Validation Schemas
Common Patterns
typescript
import * as yup from 'yup';
// Email
email: yup.string()
.email('Invalid email address')
.required('Email is required')
// Password with requirements
password: yup.string()
.min(8, 'Must be at least 8 characters')
.matches(/[a-z]/, 'Must contain lowercase letter')
.matches(/[A-Z]/, 'Must contain uppercase letter')
.matches(/[0-9]/, 'Must contain number')
.required('Password is required')
// Confirm password
confirmPassword: yup.string()
.oneOf([yup.ref('password')], 'Passwords must match')
.required('Please confirm password')
// Phone number
phone: yup.string()
.matches(/^\+?[1-9]\d{1,14}$/, '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
typescript
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
tsx
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
tsx
<Select
label="Country"
value={formik.values.country}
onValueChange={(value) => formik.setFieldValue('country', value)}
error={formik.touched.country ? formik.errors.country : undefined}
options={countryOptions}
/>
Form Submission with GraphQL
tsx
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
onPress={formik.handleSubmit}
isDisabled={!formik.isValid || formik.isSubmitting}
isLoading={formik.isSubmitting}
>
Create
</Button>
</VStack>
);
};
Edit Form with Initial Values
tsx
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 ?? '',
},
enableReinitialize: true, // Update when item prop changes
validationSchema,
onSubmit: async (values) => {
await updateItem({
variables: { id: item.id, input: values },
});
},
});
// Track if form has changes
const hasChanges = formik.dirty;
return (
<VStack gap="$4">
{/* Form fields */}
<Button
onPress={formik.handleSubmit}
isDisabled={!hasChanges || !formik.isValid || formik.isSubmitting}
isLoading={formik.isSubmitting}
>
Save Changes
</Button>
</VStack>
);
};
Form State Helpers
tsx
const {
values, // Current form values
errors, // Validation errors
touched, // Fields that have been touched
isValid, // Form passes validation
isSubmitting, // Submit in progress
dirty, // Values differ from initial
handleSubmit, // Submit handler
handleChange, // Change handler
handleBlur, // Blur handler
setFieldValue, // Set single field
setFieldTouched, // Mark field touched
resetForm, // Reset to initial values
setSubmitting, // Control submitting state
} = formik;
Multi-Step Forms
tsx
const MultiStepForm = () => {
const [step, setStep] = useState(0);
const formik = useFormik({
initialValues: {
// Step 1
name: '',
email: '',
// Step 2
address: '',
city: '',
// Step 3
paymentMethodToken: '', // token from a payment provider’s hosted field; never raw card data
},
validationSchema: stepSchemas[step],
onSubmit: async (values) => {
if (step < steps.length - 1) {
setStep(step + 1);
} else {
// Validate the complete order schema here; step-only validation is insufficient.
await finalOrderSchema.validate(values, { abortEarly: false });
await submitOrder(values);
}
},
});
return (
<VStack>
{step ===
0 && <PersonalInfoStep formik={formik} />}
{step ===
1 && <AddressStep formik={formik} />}
{step ===
2 && <PaymentStep formik={formik} />}
<HStack gap="$4">
{step > 0 && (
<Button variant="outline" onPress={() => setStep(step - 1)}>
Back
</Button>
)}
<Button
onPress={formik.handleSubmit}
isDisabled={!formik.isValid || formik.isSubmitting}
isLoading={formik.isSubmitting}
>
{step < steps.length - 1 ? 'Next' : 'Submit'}
</Button>
</HStack>
</VStack>
);
};
Anti-Patterns
tsx
// WRONG - Not showing validation errors
<Input
value={formik.values.email}
onChangeText={formik.handleChange('email')}
/>
// CORRECT - Show errors when touched
<Input
value={formik.values.email}
onChangeText={formik.handleChange('email')}
onBlur={formik.handleBlur('email')}
error={formik.touched.email ? formik.errors.email : undefined}
/>
// WRONG - Submit button always enabled
<Button onPress={formik.handleSubmit}>Submit</Button>
// CORRECT - Disabled when invalid or submitting
<Button
onPress={formik.handleSubmit}
isDisabled={!formik.isValid || formik.isSubmitting}
isLoading={formik.isSubmitting}
>
Submit
</Button>
// WRONG - No error handling on mutation
onSubmit: async (values) => {
await createItem({ variables: { input: values } });
}
// CORRECT - Handle errors
onSubmit: async (values, { setSubmitting }) => {
try {
await createItem({ variables: { input: values } });
} catch (error) {
toast.error({ title: 'Failed to save' });
} finally {
setSubmitting(false);
}
}
Integration with Other Skills
- graphql-schema: Mutation submission patterns
- react-ui-patterns: Loading/error states
- testing-patterns: Test form validation and submission
Limitations
- Use this skill only when the task clearly matches its upstream source and local project context.
- Verify commands, generated code, dependencies, credentials, and external service behavior before applying changes.
- Do not treat examples as a substitute for environment-specific tests, security review, or user approval for destructive or costly actions.