反应：道具未在 map function 内部更新

Question

Edit:Codesandbox here

Here is a simplified version on my parent component:

export default function Parent() {
  // State
  const [status, setStatus] = useState(1);
  const [source, setSource] = useState('https://packagingeurope.com/downloads/7475/download/danone-05.03.20.jpg');
  const [steps, setSteps] = useState([
    {
      title: 'Prediction Initiated',
      value: 1,
      loading: false,
      completed: false,
      active: false,
    },
    {
      title: 'Prediction in Progress',
      value: 2,
      loading: false,
      completed: false,
      active: false,
    },
    {
      title: 'Prediction Finished',
      value: 3,
      loading: false,
      completed: false,
      active: false,
    },
  ]);

useEffect(() => {
    if (status) {
      const newSteps = steps;
      newSteps[status - 1].active = true;
      if (status > 1) {
        newSteps[status - 2].completed = true;
      }
      if (status === 3) {
        newSteps[status - 1].active = false;
        newSteps[status - 1].completed = true;
      }
      setSteps(newSteps);
    } else {
      // Do nothing
      console.log('No status match');
    }
  },
  [status]);

return (
<div className="container-fluid">
  <Timeline status={status} steps={steps} source={source} />
</div>
);
}

And here is my child component:

export default class Timeline extends React.Component {

  renderSteps() {
    const { steps } = this.props;

    return steps.map((step, index) => {
      console.log(step);
      console.log(steps);
      return (
        <div key={`test${index}`}>
          {step.title}
          {step.active && <span>is active</span>}
          {step.loading && <span>is loading</span>}
          {step.completed && <span>is completed</span>}
        </div>
      );
    });
  }

  render() {
    const { status, steps, source } = this.props;

    return (
        <div className="timeline">
          {this.renderSteps()}
        </div>
      </>
    );
  }
}

When i console.log steps props inside my child component, I see that they are correctly updated. (When status === 1, the first step active property is true )

But when i console.log step (inside my map function), none of the properties are updated. (When status === 1, the first step active property is false )

You can see on the capture below that something is not right (I already encountered this problem but unfortunately I can't remember how I solved it, and I am wondering if it's because of the useEffect hooks which I didn't use before this project.

Thank you for your help

Edit:Codesandbox here

Answer 1

Ok, I figured it out.

Since I got this code from another developer, I didn't understand everything that was implemented. I went to the React documentation to understand where the problem was coming from.

By passing a second parameter to the useEffect function, React can skip the effect and will not re-render the component for performance issues if there is not any change. As my status doesn't change (I change it manually for the moment), my component was not refreshing.

By adding [steps] width [status] inthe second parameter, everything works.

 useEffect(() => {
    if (status) {
      const newSteps = steps;
      newSteps[status - 1].active = true;
      if (status > 1) {
        newSteps[status - 2].completed = true;
      }
      if (status === 3) {
        newSteps[status - 1].active = false;
        newSteps[status - 1].completed = true;
      }
      setSteps(newSteps);
    } else {
      // Do nothing
      console.log('No status match');
    }
  }, [status, steps]);