更改对象属性以匹配给定数组中的值

Question

Heres my app structure

Codepen Example : https://codesandbox.io/s/awesome-blackwell-kd3nn

class MasterForm extends Component {
  constructor() {
    super();

    this.state = {
      userInput: "",
      available: "",
      silos: []
    };
  }

  handleFormSubmit = e => {
    e.preventDefault();
    this.silo_1Lookup();
  };

  handleInputChange = e => {
    let input = e.target;
    let name = e.target.name;
    let value = input.value;

    this.setState({
      [name]: value
    });
  };

  silo_1Lookup = () => {
    let silos = [...this.state.silos];

    silos.push({
      userInput: this.state.userInput,
      available: this.state.available
    });

    this.setState({
      silos,
      userInput: "",
      available: ""
    });

    const siloDepthFilling = {
      "0": "926",
      "0.5": "893",
      "1": "860",
      "1.5": "827",
      "2": "794",
      "2.5": "761",
      "3": "728",
      "3.5": "695",
      "4": "662",
      "4.5": "629",
      "5": "595"
    };
    console.log("function ran");
    return siloDepthFilling[silos[0].userInput];
  };
}

I'm trying to change the property of silos[0].available to match the content inside of my silo_1Lookup() function.

For example, if the user enters 5, silos[0].available should be set to "595"

if (silos[0].userInput === '5') {
 return silos[0].available = "595"
}

kinda like that but using the dictionary inside silo_1Lookup();

At the moment, the function runs, but silos[0].available is not being updated with a new value, and there is no error message

Answer 1

You are not updating the state after changing available value.

In your function, call setState() after making required changes.

You are using silos to display both userInput and available . So updating silos is what changes the view, not available .

silo_1Lookup = () => {

    const siloDepthFilling = {
      "0": "926",
      "0.5": "893",
      "1": "860",
      "1.5": "827",
      "2": "794",
      "2.5": "761",
      "3": "728",
      "3.5": "695",
      "4": "662",
      "4.5": "629",
      "5": "595"
    };
    console.log("function ran");

    let available = siloDepthFilling[this.state.userInput];

    let silos = [...this.state.silos];

    silos.push({
      userInput: this.state.userInput,
      available: available
    });

    this.setState(
      {
        silos: silos,
        available: available
      }
    );
  };

Also, you are not using key for your list items and it is throwing an error. Make following changes to your Table component.

{silos.map((silo, i) => {
     return (
        <tr key={i.toString()}>
           <td>{silo.userInput}</td>
           <td>{silo.available}</td>
        </tr>
      );
 })}

Live demo: https://codesandbox.io/s/vigorous-jennings-wlw8j

Answer 2

The root cause of your problem is, you need to update every time your array silos[] when you will get a new value for available . so the approach has given below.

  handleInputChange = e => {
    let input = e.target;
    let name = e.target.name;
    let value = input.value;

    this.setState({
      [name]: value
    });
  };

  silo_1Lookup = () => {
    let silosss = [...this.state.silos];
    const siloDepthFilling = {
      "0": "926",
      "0.5": "893",
      "1": "860",
      "1.5": "827",
      "2": "794",
      "2.5": "761",
      "3": "728",
      "3.5": "695",
      "4": "662",
      "4.5": "629",
      "5": "595"
    };

    // Push user input and available value in array
    silosss.push({
      userInput: this.state.userInput,
      available: siloDepthFilling[this.state.userInput]
    });

    // Finally update the state of both array and available value
    for(var item of silosss){
      this.setState({
        silos:silosss,
        available: item.available
      });
    }
  };

Finally, the output should be like that