Reduce redux-connect Typescript boilerplate

When you write React Redux connected component with Typescript, if you want a make sure your mapStatesToProps and mapDispatchToProps are typed-checked, often you need to write verbose code like below:

tsx
import * as React from 'react';
import { connect } from 'react-redux';
import { toggleTodo } from './actions';
import { selectTodoStatus, selectTodoDescription } from './selectors';
import { RootState } from './type';
interface ParentProps {
  id: string;
}
interface StoreProps {
  status: string;
  description: string;
}
interface DispatchProps {
  toggle: () => void;
}
const TodoItemView = (props: ParentProps & StoreProps & DispatchProps) => {
  return <div>...</div>;
};
const mapStatesToProps = (
  state: RootState,
  ownProps: ParentProps
): StoreProps => ({
  status: selectTodoStatus(state, ownProps.id),
  description: selectTodoDescription(state, ownProps.id),
});
const mapDispatchToProps = (
  dispatch: any,
  ownProps: ParentProps
): DispatchProps => ({
  toggle: () => dispatch(toggleTodo(ownProps.id)),
});
export const TodoItem = connect(
  mapStatesToProps,
  mapDispatchToProps
)(TodoItemView);

tsx
import * as React from 'react';
import { connect } from 'react-redux';
import { toggleTodo } from './actions';
import { selectTodoStatus, selectTodoDescription } from './selectors';
import { RootState } from './type';
interface ParentProps {
  id: string;
}
interface StoreProps {
  status: string;
  description: string;
}
interface DispatchProps {
  toggle: () => void;
}
const TodoItemView = (props: ParentProps & StoreProps & DispatchProps) => {
  return <div>...</div>;
};
const mapStatesToProps = (
  state: RootState,
  ownProps: ParentProps
): StoreProps => ({
  status: selectTodoStatus(state, ownProps.id),
  description: selectTodoDescription(state, ownProps.id),
});
const mapDispatchToProps = (
  dispatch: any,
  ownProps: ParentProps
): DispatchProps => ({
  toggle: () => dispatch(toggleTodo(ownProps.id)),
});
export const TodoItem = connect(
  mapStatesToProps,
  mapDispatchToProps
)(TodoItemView);

And that’s a pain-in-the-ass, as your selectors and actions are already properly typed, now you need to duplicate it. In addition, everytime you want to inject a new props/new actions, you need to update both the typing and the mapProps function.

Recently, I’ve stumble upon ReturnType in Typescript, and that’s the solution to fix the boiletplate:

tsx
import { connect } from 'react-redux';
import type { Dispatch } from 'redux';
 
type TodoStatus = 'not_started' | 'in_progress' | 'done';
 
type RootState = {
  todos: Record<string, { status: TodoStatus; description: string }>;
};
 
const toggleTodo = (id: string) => ({
  type: 'toggle',
  id,
});
 
const selectTodoStatus = (state: RootState, id: string) =>
  state.todos[id].status;
 
const selectTodoDescription = (state: RootState, id: string) =>
  state.todos[id].description;
 
interface ParentProps {
  id: string;
}
 
const TodoItemView = (
  props: ParentProps &
   
(parameter) props: ParentProps & {
    status: TodoStatus;
    description: string;
} & {
    toggle: () => {
        type: string;
        id: string;
    };
}
    ReturnType<typeof mapStatesToProps> &
    ReturnType<typeof mapDispatchToProps>
) => {
  return <div>...</div>;
};
 
const mapStatesToProps = (state: RootState, ownProps: ParentProps) => ({
  status: selectTodoStatus(state, ownProps.id),
  description: selectTodoDescription(state, ownProps.id),
});
 
const mapDispatchToProps = (dispatch: Dispatch, ownProps: ParentProps) => ({
  toggle: () => dispatch(toggleTodo(ownProps.id)),
});
 
export const TodoItem = connect(
  mapStatesToProps,
  mapDispatchToProps
)(TodoItemView);

tsx
import { connect } from 'react-redux';
import type { Dispatch } from 'redux';
 
type TodoStatus = 'not_started' | 'in_progress' | 'done';
 
type RootState = {
  todos: Record<string, { status: TodoStatus; description: string }>;
};
 
const toggleTodo = (id: string) => ({
  type: 'toggle',
  id,
});
 
const selectTodoStatus = (state: RootState, id: string) =>
  state.todos[id].status;
 
const selectTodoDescription = (state: RootState, id: string) =>
  state.todos[id].description;
 
interface ParentProps {
  id: string;
}
 
const TodoItemView = (
  props: ParentProps &
   
(parameter) props: ParentProps & {
    status: TodoStatus;
    description: string;
} & {
    toggle: () => {
        type: string;
        id: string;
    };
}
    ReturnType<typeof mapStatesToProps> &
    ReturnType<typeof mapDispatchToProps>
) => {
  return <div>...</div>;
};
 
const mapStatesToProps = (state: RootState, ownProps: ParentProps) => ({
  status: selectTodoStatus(state, ownProps.id),
  description: selectTodoDescription(state, ownProps.id),
});
 
const mapDispatchToProps = (dispatch: Dispatch, ownProps: ParentProps) => ({
  toggle: () => dispatch(toggleTodo(ownProps.id)),
});
 
export const TodoItem = connect(
  mapStatesToProps,
  mapDispatchToProps
)(TodoItemView);

Now you doesn’t need to type StoreProps and DispatchProps manually, Typescript will infer them from your selectors and actions.

Update on 26th Jan 2020

I’ve learnt recently that react-redux actually exports a ConnectedProps type utility that will infers the correct injected props for us.

Final version:

tsx
import { connect, ConnectedProps } from 'react-redux';
import type { Dispatch } from 'redux';
 
type TodoStatus = 'not_started' | 'in_progress' | 'done';
 
type RootState = {
  todos: Record<string, { status: TodoStatus; description: string }>;
};
 
const toggleTodo = (id: string) => ({
  type: 'toggle',
  id,
});
 
const selectTodoStatus = (state: RootState, id: string) =>
  state.todos[id].status;
 
const selectTodoDescription = (state: RootState, id: string) =>
  state.todos[id].description;
 
interface ParentProps {
  id: string;
}
 
const TodoItemView = (
  props: ParentProps &
   
(parameter) props: ParentProps & {
    status: TodoStatus;
    description: string;
} & {
    toggle: () => {
        type: string;
        id: string;
    };
}
    ConnectedProps<typeof connector>
) => {
  return <div>...</div>;
};
 
const mapStatesToProps = (state: RootState, ownProps: ParentProps) => ({
  status: selectTodoStatus(state, ownProps.id),
  description: selectTodoDescription(state, ownProps.id),
});
 
const mapDispatchToProps = (dispatch: Dispatch, ownProps: ParentProps) => ({
  toggle: () => dispatch(toggleTodo(ownProps.id)),
});
 
const connector = connect(mapStatesToProps, mapDispatchToProps);
 
export const TodoItem = connector(TodoItemView);

tsx
import { connect, ConnectedProps } from 'react-redux';
import type { Dispatch } from 'redux';
 
type TodoStatus = 'not_started' | 'in_progress' | 'done';
 
type RootState = {
  todos: Record<string, { status: TodoStatus; description: string }>;
};
 
const toggleTodo = (id: string) => ({
  type: 'toggle',
  id,
});
 
const selectTodoStatus = (state: RootState, id: string) =>
  state.todos[id].status;
 
const selectTodoDescription = (state: RootState, id: string) =>
  state.todos[id].description;
 
interface ParentProps {
  id: string;
}
 
const TodoItemView = (
  props: ParentProps &
   
(parameter) props: ParentProps & {
    status: TodoStatus;
    description: string;
} & {
    toggle: () => {
        type: string;
        id: string;
    };
}
    ConnectedProps<typeof connector>
) => {
  return <div>...</div>;
};
 
const mapStatesToProps = (state: RootState, ownProps: ParentProps) => ({
  status: selectTodoStatus(state, ownProps.id),
  description: selectTodoDescription(state, ownProps.id),
});
 
const mapDispatchToProps = (dispatch: Dispatch, ownProps: ParentProps) => ({
  toggle: () => dispatch(toggleTodo(ownProps.id)),
});
 
const connector = connect(mapStatesToProps, mapDispatchToProps);
 
export const TodoItem = connector(TodoItemView);