Struggling to update state data with response data in React, despite the response not being empty

Question

Struggling to update state data with response data in React, despite the response not being empty

I'm currently working on my first React API application and I am facing an issue where the state data appears to be empty even after assigning res.data, which is not empty. Additionally, I am struggling with rendering all of this content inside a div.

When I console.log res.data, here is what it returns:

(2) [{…}, {…}]
0: {user: {…}, available_amount: 4324324}
1: {user: {…}, available_amount: 43243243}
length: 2
__proto__: Array(0)

Below is a snippet of my code:

  class App extends Component{
        constructor(props) {
        super(props);
        let data;
        this.state = {
          data: [],
          loaded: false,
          placeholder: "Loading"
        };
      }
    

    async componentDidMount(){
        let data;
        axios
            .get('http://127.0.0.1:8000/api/',{
                headers:{
                'Authorization': 'Token 8651a2b6c28ecd5cd25c0e67dfd7f3642a3d0029'
                }
            })
            .then(res => {
                this.setState(() => {
                    return {
                    data: res,
                    loaded: true
                };
                });
            })
            .then(console.log(this.state.data))

    }

json reactjs api django-rest-framework

Answer 1

Answer №1

Added new state to the existing state instead of replacing it, the code could look something like this.

class App extends Component {
  constructor(props) {
    super(props);
    let data;
    this.state = {
      data: [],
      loaded: false,
      placeholder: "Loading",
    };
  }

  async componentDidMount() {
    let data;
    axios
      .get("http://127.0.0.1:8000/api/", {
        headers: {
          Authorization: "Token 8651a2b6c28ecd5cd25c0e67dfd7f3642a3d0029",
        },
      })
      .then((res) => {
-        this.setState(() => {
-          return {
-            data: res,
-            loaded: true,
-          };
-        });
+        this.setState((prev) => {
+          return {
+            data: prev.data.concat(res),
+            loaded: true,
+          };
+        });
      })
      .then(console.log(this.state.data));
  }
}

Answer 2

Added new state to the existing state instead of replacing it, the code could look something like this.

class App extends Component {
  constructor(props) {
    super(props);
    let data;
    this.state = {
      data: [],
      loaded: false,
      placeholder: "Loading",
    };
  }

  async componentDidMount() {
    let data;
    axios
      .get("http://127.0.0.1:8000/api/", {
        headers: {
          Authorization: "Token 8651a2b6c28ecd5cd25c0e67dfd7f3642a3d0029",
        },
      })
      .then((res) => {
-        this.setState(() => {
-          return {
-            data: res,
-            loaded: true,
-          };
-        });
+        this.setState((prev) => {
+          return {
+            data: prev.data.concat(res),
+            loaded: true,
+          };
+        });
      })
      .then(console.log(this.state.data));
  }
}

Answer 3

Answer №2

setState operates asynchronously, meaning that the state may not be updated by the time you check it with console.log inside the then callback. One way to handle this is to provide a second argument to setState, which is a callback function where you can access the updated state:

this.setState(() => {...}, () => { console.log(this.state.data) })

If your new state does not rely on the previous state, you can simply pass an object to setState instead of a function like so:

this.setState(
    {
        data: res,
        ...
    },
    () => {
        console.log(this.state.data)
    }
)

Answer 4

setState operates asynchronously, meaning that the state may not be updated by the time you check it with console.log inside the then callback. One way to handle this is to provide a second argument to setState, which is a callback function where you can access the updated state:

this.setState(() => {...}, () => { console.log(this.state.data) })

If your new state does not rely on the previous state, you can simply pass an object to setState instead of a function like so:

this.setState(
    {
        data: res,
        ...
    },
    () => {
        console.log(this.state.data)
    }
)

Answer 5

Answer №3

Here are some recommendations to improve your code: Update setState method with setState({...}) and make sure to include the loading property in your state

import React, { Component } from "react";

const arrayOne = [
  {
    id: 1,
    name: "John Doe"
  },
  {
    id: 2,
    name: "Jane Smith"
  },
  {
    id: 3,
    name: "Michael Brown"
  }
];

export default class App extends Component {
  constructor(props) {
    super(props);
    this.state = {
      data: [],
      loading: true
    };
  }

  async componentDidMount() {
    setTimeout(() => {
      this.setState({ data: arrayOne, loading: false });
    }, 1000)
  }

  render() {
    return (
      <div>
        {this.state.loading ? (
          <h1>Loading...</h1>
        ) : (
          <div>
            {this.state.data.map((item) => {
              return <h1>{item.name}</h1>;
            })}
          </div>
        )}
      </div>
    );
  }
}

Answer 6

Here are some recommendations to improve your code: Update setState method with setState({...}) and make sure to include the loading property in your state

import React, { Component } from "react";

const arrayOne = [
  {
    id: 1,
    name: "John Doe"
  },
  {
    id: 2,
    name: "Jane Smith"
  },
  {
    id: 3,
    name: "Michael Brown"
  }
];

export default class App extends Component {
  constructor(props) {
    super(props);
    this.state = {
      data: [],
      loading: true
    };
  }

  async componentDidMount() {
    setTimeout(() => {
      this.setState({ data: arrayOne, loading: false });
    }, 1000)
  }

  render() {
    return (
      <div>
        {this.state.loading ? (
          <h1>Loading...</h1>
        ) : (
          <div>
            {this.state.data.map((item) => {
              return <h1>{item.name}</h1>;
            })}
          </div>
        )}
      </div>
    );
  }
}

Struggling to update state data with response data in React, despite the response not being empty

Answer №1

Answer №2

Answer №3

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