Can't set state in react

问题

So, I'm simply trying to set state in my react app. Simply get data from Axios, and then set state. But no matter what I do, the state will not set. I've tried putting it in a callback since it's async and putting it my component did mount and component did update alas nothing. any pointers?

class App extends Component {
  componentDidUpdate() {}

  constructor(props) {
    super(props);
    this.state = {
      Catogories: [
        "Business",
        "Entertainment",
        "General",
        "Health",
        "Science",
        "Sports",
        "Technology"
      ],
      CatPics: [],
      TopStories: [],
      Selection: [],
      Sources: [],
      selected: false
    };
  }
  GeneratePic = () => {
    this.state.Catogories.forEach(Catogory => {
      axios
        .get(
          "https://api.pexels.com/v1/search?query=" +
            Catogory +
            "&per_page=15&page=1",
          {
            Authorization:
              "563492ad6f91700001000001d33b5d31a9a145b78ee67e35c8e6c321"
          }
        )
        .then(res => {
          var object = { Catogory: res.photos[0].src.large2x };
          this.state.CatPics.push(object);
        });
    });
  };
  dump = x => {
    this.setState({ TopStories: x }, console.log(this.state.TopStories));
  };
  TopStories = () => {
    console.log("working");
    axios
      .get(
        "https://newsapi.org/v2/top-headlines?country=us&apiKey=91bec895cf8d45eaa46124fb19f6ad81"
      )
      .then(res => {
        console.log(res);
        const data = res.data.articles;
        console.log(data);
        this.dump(data);
      });
  };

回答1:

This should work.

Dont Mutate the state.

 GeneratePic = () => {
        this.state.Catogories.forEach(async Catogory => {
            await axios
                .get(
                    "https://api.pexels.com/v1/search?query=" +
                    Catogory +
                    "&per_page=15&page=1", {
                        Authorization: "563492ad6f91700001000001d33b5d31a9a145b78ee67e35c8e6c321"
                    }
                )
                .then(res => {
                    var object = { Catogory: res.data.photos[0].src.large2x };
                    const cPics = [...this.state.CatPics];
                    cPics.push(object);
                    this.setState({
                        CatPics: cPics
                    })
                });
        });
    };

回答2:

You are doing two things wrong.

Don't mutate the state
Don't do async actions inside loop and then use same loop variable inside async callback because at that point in time, loop variable will have some other value and not the respective iteration category.

  GeneratePic = async () => {
    const promises = this.state.Catogories.map(Catogory => {
      return axios
        .get(
          "https://api.pexels.com/v1/search?query=" +
            Catogory +
            "&per_page=15&page=1",
          {
            Authorization:
              "563492ad6f91700001000001d33b5d31a9a145b78ee67e35c8e6c321"
          }
        )
        .then(res => {
          return res.photos[0].src.large2x;
        });
    });

    let photos = await Promise.all(promises);
    photos = this.state.Catogories.map((cat, index) => ({ [cat]: photos[index] }));
    this.setState({ CatPics: photos });
  };

getPics = cat => {
      return axios
            .get(
              "https://api.pexels.com/v1/search?query=" +
                cat +
                "&per_page=15&page=1",
              {
                Authorization:
                  "563492ad6f91700001000001d33b5d31a9a145b78ee67e35c8e6c321"
              }
            )
            .then(res => {
              return { [cat]: res.photos[0].src.large2x };
            });

}

GeneratePic = async () => {
        const promises = this.state.Catogories.map(Catogory => {
          this.getPics(Catogory);
        });
        
        let photos = await Promise.all(promises);
        this.setState({ CatPics: photos });
      };

来源：https://stackoverflow.com/questions/59775699/cant-set-state-in-react

标签

javascript

reactjs

axios

es6-promise