Type Void is Not Assignable to Type Boolean (React/Typescript)

Question

I'm getting an error where I want to post a switch boolean value on Change. I'm using React/Typescript... What I want to do here send a post request of the boolean value in the handleChange() function, how would I do that?

The current error i'm getting is Type 'void' is not assignable to type '((event: ChangeEvent<HTMLInputElement>, checked: boolean) => void) | undefined'

interface IState {
  application?: Map<{}, {}>;
  hasChanged?: boolean;
  checkedA?: boolean;
}



 <div className={classes.switchContainer}>
                <FormGroup row>
                    <FormControlLabel
                      control={
                        <Switch
                          checked={this.state.checkedA}
                          onChange={this.handleChange()}
                          value="checkedA"
                        >Toggle</Switch>
                        }label="YES"
                        />
                  <Typography color="secondary" variant="body1" className={classes.toggleQuestions}>Is the Mentor information complete?</Typography>
                </FormGroup>
              </div>

 @autobind
  private handleChange() {
    console.log("checkedA")
  }

Just a minor sidenote, there is no need to use autobinding annotations (unless it's Angular...). In order to properly bind this you can just define your methods as follows private readonly handleChange = () => {/* do something */}; which will automatically bind this in the body of the lambda. — Christian Ivicevic
– Christian Ivicevic, Commented Jan 13, 2019 at 10:55

Leroy Stav · Accepted Answer · 2019-01-13 04:27:09Z

2

Try onChange={this.handleChange} instead Your way, you are calling handle change and setting its return value ("void") as the change handler. Under certain circumstances this might be appropriate, but not in yours.

answered Jan 13, 2019 at 4:27

Leroy Stav

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3 Comments

kjamp Over a year ago

got ya that makes perfect sense. how would i then: get the value of said state of the switch input, and send a post request?

Leroy Stav Over a year ago

dude its literally in the documentation.... handleChange(event) { console.log(event.target.value); } reactjs.org/docs/forms.html

kjamp Over a year ago

yeah i'm using typescript so it's a little different from the documentation. but thanks, i'll use this as a reference.

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