在单个页面中引入多个加载器：React JS

Question

I am trying to implement a dashboard where in I have couple of items that needs to be shown. In the following example I have 4 rectangular boxes(In actual those are 4 different graphs) and a table. I am using react-table for the data grid purposes and a semantic-ui-react table for the spinner purposes.

Now the issue is, these all are independent of each other. I have mocked the data using a settimeout as if it were coming from the back-end. All I need is individual loaders and it should be hidden whenever data arrives. I have extracted the loader as a separate component, so that it behaves as a common loader for all the items.

Usually the API would give me array of items if present, and if not an empty array. For mock purposes, I have used setTimeout

Could go for individual flags for each item, but that does not seems a good approach.

Mock Sandbox: https://codesandbox.io/s/react-table-row-table-vdnfh

App.tsx

import * as React from "react";
import { render } from "react-dom";
import "./styles.css";
import Card from "./Card";

interface IProps {}

interface IState {
  cardData1: any;
  cardData2: any;
  cardData3: any;
  cardData4: any;
}

class App extends React.Component<IProps, IState> {
  constructor(props: any) {
    super(props);
    this.state = {
      cardData1: undefined,
      cardData2: undefined,
      cardData3: undefined,
      cardData4: undefined
    };
  }

  componentDidMount() {
    this.getGraphData();
  }

  // the reason why I call this four times is because, in my case the API is same for all the graphs, only an attribute changes so just mocking it here
  getGraphData = () => {
    this.setGraphData("graph1");
    this.setGraphData("graph2");
    this.setGraphData("graph3");
    this.setGraphData("graph4");
  };

  setGraphData = (cardNumber: string) => {
    //based on the attribute I set the corresponding card data
    if (cardNumber === "graph1") {
      setTimeout(() => {
        this.setState({ cardData1: [1, 2, 3] });
      }, 1000);
    }
    if (cardNumber === "graph2") {
      setTimeout(() => {
        this.setState({ cardData2: [3, 4, 5] });
      }, 2000);
    }

    if (cardNumber === "graph3") {
      setTimeout(() => {
        this.setState({ cardData3: [6, 7, 8] });
      }, 3000);
    }
    if (cardNumber === "graph4") {
      setTimeout(() => {
        this.setState({ cardData4: [] });
      }, 4000);
    }
  };

  render() {
    let { cardData1, cardData2, cardData3, cardData4 } = this.state;
    return (
      <>
        <Card
          name="Card1"
          data={this.state.cardData1}
          spinnerFlag={cardData1 === undefined}
        />
        <Card
          name="Card3"
          data={this.state.cardData2}
          spinnerFlag={cardData2 === undefined}
        />
        <Card
          name="Card3"
          data={this.state.cardData3}
          spinnerFlag={cardData3 === undefined}
        />
        <Card
          name="Card3"
          data={this.state.cardData4}
          spinnerFlag={cardData4 === undefined}
        />
      </>
    );
  }
}

render(<App />, document.getElementById("root"));

Answer 1

I'm not entirely sure what the problem you're trying to solve is; your code sandbox shows the data arriving card-by-card, which I think is what you're going for. As each timeout resolves, the state changes, the component re-renders, and the newly arrived data appears.

However, I see that you're passing the same this.state.spinnerFlag into all the cards. Instead you can calculate the spinner state based on the availability of the data.

<Card
  name="Card1"
  data={this.state.cardData1}
  spinnerFlag={this.state.cardData1 === ""}
/>

Then the spinner will show exactly until the data for that card is available.

Answer 2

When using the absolutely positioned element import { Dimmer } from "semantic-ui-react" , and do not wish to have 4 overlapping elements over the whole page, you need to give them a relatively positions parent, eg:

.box {
  position: relative;
}

https://codesandbox.io/s/react-table-row-table-et7ie

---

If you need to distinguish between empty card and the API returns "" for an empty card, then the initial state needs to be different from that value, eg:

this.state = {
  cardData1: undefined,
  cardData2: undefined,
  cardData3: undefined,
  cardData4: undefined
};

and then check for that initial value:

<Card
  name="Card1"
  data={this.state.cardData1}
  spinnerFlag={this.state.cardData1 === undefined}
/>