ng2-redux-form

This library is a thin layer of connective tissue between Angular 2 forms and Redux. It provides unidirectional data binding between your Redux state and your forms elements. It builds on existing Angular functionality like NgModel and NgControl

For the simplest use-cases, the API is very straightforward. Your template would look something like this:

  <form connect="myForm">
    <input type="text" name="address" ngControl ngModel />
  </form>

The important bit to note here is the [connect] directive. This is the only thing you should have to add to your form template in order to bind it to your Redux state. The argument provided to connect is basically a path to form state inside of your overall app state. So for example if my Redux app state looks like this:

{
  "foo": "bar",
  "myForm": {
    "address": "1 Foo St."
  }
}

Then I would supply myForm as the argument to [connect]. If myForm were nested deeper inside of the app state, you could do something like this:

<form [connect]="['personalInfo', 'myForm']">
  ...
</form>

Note that ImmutableJS integration is provided seamlessly. If personalInfo is an immutable Map structure, the library will automatically use get() or getIn() to find the appropriate bits of state.

Then, in your application bootstrap code, you need to add a provider for the class that is responsible for connecting your forms to your Redux state. There are two ways of doing this: either using an Redux.Store<T> object or an NgRedux<T> object. There are no substantial differences between these approaches, but if you are already using ng2-redux or you wish to integrate it into your project, then you would do something like this:

@NgModule({
  imports: [
    BrowserModule,
    ReactiveFormsModule,
    FormsModule,
    NgReduxForms,
  ],
  providers: [
    NgRedux,
  ],
  bootstrap: [MyApplicationComponent]
})
export class ExampleModule {}

Or if you are using Redux without ng2-redux, then your bootstrap call would look more like this (substitute your own store creation code):

import {provideReduxForms} from 'ng2-redux-form';

const storeCreator = compose(applyMiddleware(logger))(createStore);
const store = create(reducers, <MyApplicationState> {});

@NgModule({
  imports: [
    BrowserModule,
    ReactiveFormsModule,
    FormsModule,
    NgReduxForms,
  ],
  providers: [
    provideReduxForms(store),
  ],
  bootstrap: [MyApplicationComponent]
})
export class ExampleModule {}

The essential bit of code in the above samples is the call to provideReduxForms(...). This configures ng2-form-redux and provides access to your Redux store or NgRedux instance. The shape of the object that provideReduxForms expects is very basic:

export interface AbstractStore<RootState> {
  /// Dispatch an action
  dispatch(action: Action & {payload?}): void;

  /// Retrieve the current application state
  getState(): RootState;

  /// Subscribe to changes in the store
  subscribe(fn: () => void): Redux.Unsubscribe;
}

Both NgRedux<T> and Redux.Store<T> conform to this shape. If you have a more complicated use-case that is not covered here, you could even create your own store shim as long as it conforms to the shape of AbstractStore<RootState>.

How the bindings work

The bindings work by inspecting the shape of your form and then binding to a Redux state object that has the same shape. The important element is NgControl::path. Each control in an Angular 2 form has a computed property called path which uses a very basic algorithm, ascending the tree from the leaf (control) to the root (the <form> element) and returning an array containing the name of each group or array in the path. So for example, let us take a look at this form that lets the user provide their full name and the names and types of their children:

<form connect="form1">
  <input ngControl ngModel name="fullname" type="text" />
  <template connectArray let-index connectArrayOf="dependents">
    <div [ngModelGroup]="index">
      <input ngControl ngModel name="fullname" type="text" />
      <select ngControl ngModel name="type">
        <option value="adopted">Adopted</option>
        <option value="biological">Biological child</option>
      </select>
    </div>
  </template>
</form>

Our root <form> element has a connect directive that points to the state element form1. This means that the children within your form will all be bound to some bit of state inside of the form1 object in your Redux state. Then we have a child input which is bound to a property called fullname. This is a basic text box. If you were to inspect it in the debugger, it would have a path value like this:

['form1', 'fullname']

And therefore it would bind to this piece of Redux state:

{
  "form1": {
    "fullname": "Chris Bond"
  }
}

So far so good. But look at the array element inside our form, in the <template> element. It is bound to an array property called dependents. The elements inside of the <template> tag contain the template that will be instantiated for each element inside of the dependents array. The ngModelGroup specifies that we should create a FormGroup element for each item in the array and the name of that group should be the value of index (the zero-based index of the element that is being rendered). This is important because it allows us to create a form structure that matches our Redux state. Let's say our state looks like this:

{
  "form1": {
    "fullname": "Chris Bond",
    "dependents": [
      {
        "fullname": "Christopher Bond Jr.",
        "type": "biological"
      }
    ]
  }
}

If you think about the 'path' to the first element of the dependents array, it would be this:

['form1', 'dependents', 0]

The last element, 0, is the index into the dependents array. This is our ngModelGroup element. This allows us to create a form structure that has the same structure as our Redux state. Therefore if we pause the debugger and look at the path property on our first <select> element, it would look like this:

['form1', 'dependents', 0, 'type']

From there, ng2-redux-form is able to take that path and extract the value for that element from the Redux state.

Troubleshooting

If you are having trouble getting data-binding to work for an element of your form, it is almost certainly because the path property on your control does not match the structure of your Redux state. Try pausing the debugger in Connect::resetState and check the value of path on the control that has failed to bind. Then make sure it is a valid path to the state in question.

Reducers

The library will automatically bind your state to value of your form inputs. This is the easy part and is unlikely to cause any problems for you. Slightly more difficult is updating your Redux state when the form values change. There are two approaches that you can take in order to do this.

The first, and by far the simplest, is to use the reducer that comes with ng2-redux-form and uses the value supplied in connect and the form input names in order to update your Redux state automatically. If you do not need to do any special processing on your data when the user updates form inputs, then you should use this default reducer. To use it, you need to combine it with your existing reducers like so:

import {composeReducers, defaultFormReducer} from 'ng2-redux-form';

const reducer = composeReducers(
  defaultFormReducer(),
  combineReducers({
    foo: fooReducer,
    bar: barReducer
  })
);

The important bits of code here are the calls to composeReducers and defaultFormReducer. The call to composeReducers essentially takes your existing reducer configuration and chains them together with defaultFormReducer. The default form reducer only handles one action, {FORM_CHANGED}. You can think of it like so:

function defaultFormReducer(state, action: Redux.Action & {payload?}) {
  switch (action.type) {
    case FORM_CHANGED:
      [return new state with form values from action.payload];
    default:
      break;
  }
  return state;
}

If you have a more complex use-case that the default form reducer is incompatible with, then you can very easily just handle the FORM_CHANGED actions in your existing reducers and manually update your state with the form values from action.payload.value, which has the shape of an object containing all of your raw form values:

{
  "address1": "129 Spadina Ave",
  "address2": "Toronto, Ontario M4Y 1F7",
  "otherGroup": {
    "foo": "bar",
    "biz": 1
  }
}

This would match a form that looks like this:

<form connect>
  <input name="address1" ngControl ngModel type="text" />
  <input name="address2" ngControl ngModel type="text" />
  <form name="otherGroup">
    <input name="foo" ngControl ngModel type="text" />
    <input name="biz" ngControl ngModel type="number" />
  </form>
</form>

Note: If you implement your own reducer instead of using the default one provided by ng2-form-redux, the state you return still needs to match the shape of your form, otherwise data-binding is not going to work. This is why it probably makes sense to just use the default reducer in almost every case - because your custom reducer would have to implement the same logic and produce a state object that is the same shape. But if you are having trouble with the default reducer, or if you find the fact that you have to use composeReducers distasteful, then this is another route available to you.

Examples

The examples directory contains some examples of how to use ng2-redux-form and how to connect it to your application. You may also find it useful to debug and step through the examples and the unit tests to get a better understanding of how the library works.

The unit tests in *.test.ts files also contain useful examples of how to build forms using ng2-redux-form.