createModel

The primary way to create a form model instance.

Signature

function createModel<T>(args: FormModelArgs<T>): FormModel<T>

Parameters

FormModelArgs<T>

Property	Type	Required	Description
descriptors	Partial<Descriptors<T>>	Yes	Field definitions with validation rules
initialState	Partial<T>	No	Initial values for the fields
options	{ throwIfMissingField?: boolean }	No	If true (default), throws when updateFrom encounters unknown keys

Returns

A FormModel<T> instance with typed fields, validation methods, and data serialization.

Usage

Basic

import { createModel } from 'mobx-form';

const form = createModel({
  descriptors: {
    name: { required: 'Name is required' },
    email: { required: 'Email is required' },
  },
  initialState: {
    name: '',
    email: '',
  },
});

With TypeScript Generics

type ProfileForm = {
  name: string;
  bio: string;
  age: number;
};

const form = createModel<ProfileForm>({
  descriptors: {
    name: { required: 'Required' },
    bio: {},
    age: {
      validator: ({ value }) => {
        if (value < 0) return { error: 'Age must be positive' };
      },
    },
  },
  initialState: { name: '', bio: '', age: 0 },
});

// TypeScript knows:
form.fields.name;  // Field<string, ProfileForm>
form.fields.age;   // Field<number, ProfileForm>
form.serializedData; // ProfileForm

Without Initial State

Provide value in individual descriptors instead:

const form = createModel({
  descriptors: {
    name: { value: '', required: 'Required' },
    terms: { value: false },
  },
});

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createModelFromState

A convenience function for quickly creating a model from a plain state object.

Signature

function createModelFromState<T>(
  initialState?: Partial<T>,
  validators?: Descriptors<T>,
  options?: { throwIfMissingField?: boolean },
): FormModel<T>

Usage

import { createModelFromState } from 'mobx-form';

// No validation — just reactive fields
const form = createModelFromState({
  name: 'John',
  email: 'john@example.com',
});

// With partial validation
const form2 = createModelFromState(
  { name: '', email: '' },
  { name: { required: 'Name is required' } },
);

This merges the keys from initialState and validators to create complete descriptors, then delegates to createModel.