Actions Back

Definition

Actions are plain JavaScript objects. Actions must have a type property that indicates the type of action being performed.

const ADD_TODO = 'ADD_TODO';

let actions = {
    type: ADD_TODO,
    text: 'Add item to the todo list'
};

The structure of actions is up to you to define, and as a recommendation, we can see how a Flux Standard Actions is defined:

const ADD_TODO = 'ADD_TODO';

let actions = {
    type: ADD_TODO,
    payload: {
        text: 'Add item to the todo list'
    }
};

An action MUST:

• be a plain JavaScript object with notation {} to define.

• have a type property.

  The type of an action identifies to the consumer the nature of the action that has occurred. Two actions with the same type MUST be strictly equivalent (using ===). By convention, type is usually string constant or a Symbol.

An action MAY:

• have a error property.

  The optional error property MAY be set to true if the action represents an error.

  An action whose error is true is analogous to a rejected Promise. By convention, the payload SHOULD be an error object.

  If error has any other value besides true, including undefined and null, the action MUST NOT be interpreted as an error.

• have a payload property.

  The optional payload property MAY be any type of value. It represents the payload of the action. Any information about the action that is not the type or status of the action should be part of the payload field.

  By convention, if error is true, the payload SHOULD be an error object. This is akin to rejecting a promise with an error object.

• have a meta property.

  The optional meta property MAY be any type of value. It is intended for any extra information that is not part of the payload.

An action MUST NOT include properties other than type, error, payload, or meta.

Creators

Action Creators are exactly that functions that create actions.

In Redux, Action Creators simply return an action:

const ADD_TODO = 'ADD_TODO';

function addTodo(text) {
    return {
        type: ADD_TODO,
        payload: {
            text
        }
    };
}

And to actually initiate a dispatch by passing the result to the dispatch() function:

dispatch(addTodo(text));

The dispatch() function can be accessed directly from the store as store.dispatch(), but more likely you'll access it using a helper like react-redux's connect(). You can use bindActionCreators() to automatically bind many action creators to a dispatch() function:

const ADD_TODO = 'ADD_TODO';
const TOGGLE_TODO = 'TOGGLE_TODO'; 

function addTodo(text) {
    return {
        type: ADD_TODO,
        payload: {
            text
        }
    };
}

function toggleTodo(index) {
    return {
        type: TOGGLE_TODO,
        payload: {
            index
        }
    };
}

bindActionCreators({
    addTodo,
    toggleTodo
}, dispatch);

Note: Action Creators can also be asynchronous and have side-effects. You can read about async actions in the advanced tutorial to learn how to handle AJAX responses and compose action creators into async control flow. Don't skip ahead to async actions until you've completed the basics tutorial, as it covers other important concepts that are prerequisite for the advanced tutorial and async actions.

Sourc Code

/** action js */
export const ADD_TODO = 'ADD_TODO';
export const TOGGLE_TODO = 'TOGGLE_TODO';
export const SET_VISIBILITY_FILTER = 'SET_VISIBILITY_FILTER';

export const VisibilityFilters = {
    SHOW_ALL: 'SHOW_ALL',
    SHOW_COMPLETED: 'SHOW_COMPLETED',
    SHOW_ACTIVE: 'SHOW_ACTIVE'
};

/** Action Creators */
export function addTodo(text) {
    return {
        type: ADD_TODO,
        payload: {
            text
        }
    };
};

export function toggleTodo(index) {
    return {
        type: TOGGLE_TODO,
        payload: {
            index
        }
    };
};

export function setVisibilityFilter(filter) {
    return {
        type: SET_VISIBILITY_FILTER,
        payload: {
            filter
        }
    };
};

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