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Visualizaçõesthis.setState() not changing value (not an asynchronous update issue)
Just a note, this question is NOT an asynchronous update problem (at least, I don't think it is).
I have a class component with the following content (heavily simplified to get right to the issue):
constructor(props) {
super(props);
this.state = {
aSelected: false;
bSelected: false
}
}
handleCheckboxChange = (e) => {
const { checked, value } = e.target;
console.log( 'checked: ', checked );
if(value=="a") {
this.setState( {aSelected: checked}, () => {
console.log('aSelected: ', this.state.aSelected);
console.log("---")
});
}
if(value=="b") {
this.setState( {bSelected: checked}, () => {
console.log('bSelected: ', this.state.bSelected);
console.log("---")
});
}
}
Somewhere inside the render return, I have this:
<input>
type="checkbox"
value="a"
onChange={this.handleCheckboxChange}
checked={this.state.aSelected}
disabled={ (this.state.aSelected || (!this.state.aSelected && !this.state.bSelected) ) ? false : true}
</input>
<input>
type="checkbox"
value="b"
onChange={this.handleCheckboxChange}
checked={this.state.bSelected}
disabled={ (this.state.bSelected || (!this.state.aSelected && !this.state.bSelected) ) ? false : true}
</input>
Here is the output logged in Chrome Developer Tools. As you can see, "checked" is toggled appropriately each time I selected and unselect the checkbox. However, the state of "selected" (should say "aSelected") is never changed and always has the initial state value of false. Anyone know why the value of "selected" (should say "aSelected") is never changed?
Edit: My goal is to create two checkbox items, where the user can only select ONE or select NONE. While one is selected, the other should be disabled.
1 Respostas
Responde à pergunta0
When you call setState to update the state, React re-renders the component, which resets the checkbox back to it's default (i.e. unchecked) state.
You'll need to use the current state to manage the checkbox as well. The JSX should look something like:
<input
type="checkbox"
checked={this.state.aSelected}
onChange={this.handleCheckboxChange}
/>
In React's terms, this is what's known as a "controlled component" because React is fully responsible for keeping up with the input's state. Read more in the docs here: https://reactjs.org/docs/forms.html#controlled-components vs https://reactjs.org/docs/uncontrolled-components.html
Edit to match the question's edits:
In your render function, be sure you're using this.state.aSlected. Note, you also still need the checked={this.state.aChecked} attribute as well, otherwise the checkbox will be unchecked on the next render.
Like:
<input
type="checkbox"
value="a"
onChange={this.handleCheckboxChange}
checked={this.state.aSelected}
// added for clarification *
disabled={this.state.aSelected || (!this.state.aSelected && !this.state.bSelected) ? false : true}
/>
Edit with Working Example Here's a working CodeSandbox example where checking one checkbox disables the other:
class CheckboxComponent extends React.Component {
constructor(props) {
super(props);
this.state = {
aSelected: false,
bSelected: false
};
}
handleCheckbox = (event) => {
if (event.target.name === "boxA") {
this.setState({ aSelected: event.target.checked });
} else if (event.target.name === "boxB") {
this.setState({ bSelected: event.target.checked });
}
};
render() {
let aDisabled = this.state.bSelected && !this.state.aSelected;
let bDisabled = this.state.aSelected && !this.state.bSelected;
return (
<div>
<label>
<input
type="checkbox"
name="boxA"
checked={this.state.aSelected}
onChange={this.handleCheckbox}
disabled={aDisabled}
/>
Checkbox A
</label>
<br />
<br />
<label>
<input
type="checkbox"
name="boxB"
checked={this.state.bSelected}
onChange={this.handleCheckbox}
disabled={bDisabled}
/>
Checkbox B
</label>
</div>
);
}
}