在 React Hooks 中使用带有“Set”状态的动态变量？

Question

This is a pretty common pattern in React components:

handleTextFieldChange(event)
{
    const name = event.currentTarget.name;
    this.setState({[name]: event.currentTarget.value})
}

What Javascript syntax could be used to do the same with React hooks?

ie something possibly along the lines of:

handleTextFieldChange(event)
{
    const name = event.currentTarget.name;
    this.set[name](event.currentTarget.value);
}

Answer 1

You could use a single useState with a default value of an object that contains all your input values and update that like you are used to with class components.

Example

 const { useState } = React; function App() { const [state, setState] = useState({ email: "", password: "" }); function onChange(event) { const { name, value } = event.target; setState(prevState => ({ ...prevState, [name]: value })); } return ( <div> <input value={state.email} name="email" onChange={onChange} /> <input value={state.password} name="password" onChange={onChange} /> </div> ); } ReactDOM.render(<App />, document.getElementById("root"));

 <script src="https://unpkg.com/react@16/umd/react.development.js"></script> <script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script> <div id="root"></div>

Answer 2

How about something like this?

function handleTextFieldChange(mySetFunction, event) {
    const value = event.currentTarget.value;
    mySetFunction(value);
}

<TextField
    placeholder="Email"
    name="passwordResetEmailAddress"
    onChange={(e) => handleTextFieldChange(setPasswordResetEmailAddress, e)}
>
    {passwordResetEmailAddress}
</TextField>

I've tested it and it works.

Answer 3

class Yup extends React.Component {
  state = {
    first: "",
    second: ""
  };

  handleTextFieldChange = ({ target: { name, value } }) =>
    this.setState({ [name]: value });

  render() {
    const { first, second } = this.state;
    return (
      <div>
        <p>{first}</p>
        <p>{second}</p>
        <input type="text" name="first" onChange={this.handleTextFieldChange} />
        <input
          type="text"
          name="second"
          onChange={this.handleTextFieldChange}
        />
      </div>
    );
  }
}

same with hook

function Yup() {
  const [{ first, second }, setState] = useState({ first: "", second: "" });

  function handleTextFieldChange({ target: { name, value } }) {
    setState(prevState => ({ ...prevState, [name]: value }));
  }

  return (
    <div>
      <p>{first}</p>
      <p>{second}</p>
      <input type="text" name="first" onChange={handleTextFieldChange} />
      <input type="text" name="second" onChange={handleTextFieldChange} />
    </div>
  );
}

Answer 4

You can dynamically update a state for the target field by receiving an update state function as an argument in onChange function.

Example

import React, { useState } from "react";

const App = () => {
  const [email, setEmail] = useState("");
  const [password, setPassword] = useState("");

  const onChangeHandler = (setIdentifierState, event) => {
    setIdentifierState(event.target.value);
  };

  return (
    <div>
      <p>{"Email: " + email}</p>
      <p>{"Password: " + password}</p>
      <input
        type="text"
        placeholder="email"
        onChange={onChangeHandler.bind(this, setEmail)}
      />
      <input
        type="text"
        placeholder="password"
        onChange={onChangeHandler.bind(this, setPassword)}
      />
    </div>
  );
};

export default App;

Answer 5

I recently tackled this same problem while converting my components from classes to functions. I ended up creating an object that could then point to the separate state hooks:

const textStates = {};
const setTextStates= {};
for (var name of names) {
  let [textState, setTextState] = useState("");
  textStates[name] = textState;
  setTextStates[name] = setTextState;
}

Answer 6

I solved it this way (a slightly more dynamic solution than what @VikR offered)

const [title, setTitle] = useState("");
const [desc, setDesc] = useState("");
const [video, setVideo] = useState("");

const handleChange = setter => event => {
    const value = event.target.value;
    //special cases
    if (setter === setVideo) {
        setInvalidVideo(!ReactPlayer.canPlay(value))
    }

    setter(value)
}

Then in my code:

        <TextField fullWidth value={title} type="date"
                   label={t('service.ticket.add.title')}
                   placeholder={t('service.ticket.add.titlePh')}
                   onChange={handleChange(setTitle)} variant="outlined"/>