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Here are a few title options, focusing on the question aspect and ReactJS context:
1. **Controlled vs. Uncontrolled Inputs in React: How to Avoid the \'Switching State\' Warning?**
2. **Re
Here are a few title options, focusing on the question aspect and ReactJS context: 1. **Controlled vs. Uncontrolled Inputs in React: How to Avoid the \'Switching State\' Warning?** 2. **Re
Oct 27, 2024 am 03:06 AM
Controlled vs. Uncontrolled Input Error in ReactJS
When working with React components, it's important to understand the distinction between controlled and uncontrolled inputs. By default, inputs are uncontrolled, meaning their values are managed by the DOM. However, when we set the value attribute on an input, it becomes a controlled input, meaning its value is managed by React.
If a component initially renders an uncontrolled input as controlled without defining an initial value, React will raise a warning like the one you mentioned:
"A component is changing an uncontrolled input of type text to be controlled. Input elements should not switch from uncontrolled to controlled (or vice versa)".
In the provided code:
render() {
return(
<div className="form-group">
<input
value={this.state.fields["name"]}
onChange={this.onChange.bind(this, "name")}
className="form-control"
type="text"
refs="name"
placeholder="Name *"
/>
<span style={{color: "red"}}>{this.state.errors["name"]}</span>
</div>
)
}
The issue arises because in the constructor, fields is initialized as an empty object: fields: {}. This means that initially, this.state.fields.name will be undefined. As a result, the input field will be uncontrolled. However, when the user enters a value, the state updates, making the input a controlled component. This inconsistent behavior triggers the React warning.
Possible Solutions:
- Set an initial default value: Initialize fields in the constructor with a default value for name, such as "name": "". This ensures that the input field starts as a controlled component with a defined value.
- Use short-circuit evaluation: Set the value attribute of the input to the following: value={this.state.fields.name || ''}. This evaluates to an empty string if this.state.fields.name is undefined, ensuring the input field starts as controlled even without a defined default value.
The above is the detailed content of Here are a few title options, focusing on the question aspect and ReactJS context: 1. **Controlled vs. Uncontrolled Inputs in React: How to Avoid the \'Switching State\' Warning?** 2. **Re. For more information, please follow other related articles on the PHP Chinese website!
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