ReactJS デザイン パターン: 堅牢でスケーラブルなコンポーネントの作成

// Presentational Component: Displaying User List (UserList.js)
import React from 'react';

const UserList = ({ users }) => (
  <ul>
    {users.map((user) => (
      <li key={user.id}>{user.name}</li>
    ))}
  </ul>
);

export default UserList;

// Container Component: Fetching User Data (UserContainer.js)
import React, { useState, useEffect } from 'react';
import UserList from './UserList';

const UserContainer = () => {
  const [users, setUsers] = useState([]);

  useEffect(() => {
    const fetchUsers = async () => {
      const response = await fetch('https://jsonplaceholder.typicode.com/users');
      const data = await response.json();
      setUsers(data);
    };
    fetchUsers();
  }, []);

  return <UserList users={users} />;
};

export default UserContainer;

// withAuthorization.js (HOC for Authorization)
import React from 'react';

const withAuthorization = (WrappedComponent) => {
  return class extends React.Component {
    componentDidMount() {
      if (!localStorage.getItem('authToken')) {
        // Redirect to login if not authenticated
        window.location.href = '/login';
      }
    }

    render() {
      return <WrappedComponent {...this.props} />;
    }
  };
};

export default withAuthorization;

// Dashboard.js (Component Wrapped with HOC)
import React from 'react';
import withAuthorization from './withAuthorization';

const Dashboard = () => <h1>Welcome to the Dashboard</h1>;

export default withAuthorization(Dashboard);

// MouseTracker.js (Component with Render Props)
import React, { useState } from 'react';

const MouseTracker = ({ render }) => {
  const [position, setPosition] = useState({ x: 0, y: 0 });

  const handleMouseMove = (event) => {
    setPosition({ x: event.clientX, y: event.clientY });
  };

  return <div onMouseMove={handleMouseMove}>{render(position)}</div>;
};

export default MouseTracker;

// App.js (Using Render Props)
import React from 'react';
import MouseTracker from './MouseTracker';

const App = () => (
  <MouseTracker
    render={({ x, y }) => (
      <h1>
        Mouse position: ({x}, {y})
      </h1>
    )}
  />
);

export default App;

// useFetch.js (Custom Hook)
import { useState, useEffect } from 'react';

const useFetch = (url) => {
  const [data, setData] = useState(null);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    const fetchData = async () => {
      const response = await fetch(url);
      const result = await response.json();
      setData(result);
      setLoading(false);
    };
    fetchData();
  }, [url]);

  return { data, loading };
};

export default useFetch;

// App.js (Using the Custom Hook)
import React from 'react';
import useFetch from './useFetch';

const App = () => {
  const { data, loading } = useFetch('https://jsonplaceholder.typicode.com/posts');

  if (loading) return <div>Loading...</div>;

  return (
    <ul>
      {data.map((post) => (
        <li key={post.id}>{post.title}</li>
      ))}
    </ul>
  );
};

export default App;

// Tabs.js (Parent Component)
import React, { useState } from 'react';

const Tabs = ({ children }) => {
  const [activeIndex, setActiveIndex] = useState(0);

  return React.Children.map(children, (child, index) =>
    React.cloneElement(child, { isActive: index === activeIndex, setActiveIndex, index })
  );
};

const Tab = ({ children, isActive, setActiveIndex, index }) => (
  <button onClick={() => setActiveIndex(index)}>{children}</button>
);

const TabPanel = ({ children, isActive }) => (isActive ? <div>{children}</div> : null);

Tabs.Tab = Tab;
Tabs.TabPanel = TabPanel;

export default Tabs;

// App.js (Using Compound Components)
import React from 'react';
import Tabs from './Tabs';

const App = () => (
  <Tabs>
    <Tabs.Tab>Tab 1</Tabs.Tab>
    <Tabs.Tab>Tab 2</Tabs.Tab>
    <Tabs.TabPanel>Content for Tab 1</Tabs.TabPanel>
    <Tabs.TabPanel>Content for Tab 2</Tabs.TabPanel>
  </Tabs>
);

export default App;

// Controlled Component (TextInputControlled.js)
import React, { useState } from 'react';

const TextInputControlled = () => {
  const [value, setValue] = useState('');

  return (
    <input type="text" value={value} onChange={(e) => setValue(e.target.value)} />
  );
};

export default TextInputControlled;

// Uncontrolled Component (TextInputUncontrolled.js)
import React, { useRef } from 'react';

const TextInputUncontrolled = () => {
  const inputRef = useRef();

  const handleClick = () => {
    console.log(inputRef.current.value);
  };

  return (
    <>
      <input type="text" ref={inputRef} />
      <button onClick={handleClick}>Log Input Value</button>
    </>
  );
};

export default TextInputUncontrolled;

// useDynamicState.js (Hook Factory)
import { useState } from 'react';

const useDynamicState = (initialStates) => {
  const states = {};
  const setters = {};

  initialStates.forEach(([key, initialValue]) => {
    const [state, setState] = useState(initialValue);
    states[key] = state;
    setters[key] = setState;
  });

  return [states, setters];
};

export default useDynamicState;

// App.js (Using the Hooks Factory)
import React from 'react';
import useDynamicState from './useDynamicState';

const App = () => {
  const [states, setters] = useDynamicState([
    ['name', ''],
    ['age', 0],
  ]);

  return (
    <div>
      <input
        type="text"
        value={states.name}
        onChange={(e) => setters

.name(e.target.value)}
      />
      <input
        type="number"
        value={states.age}
        onChange={(e) => setters.age(parseInt(e.target.value))}
      />
      <p>Name: {states.name}</p>
      <p>Age: {states.age}</p>
    </div>
  );
};

export default App;