ReactJs

Question

我有一个找不到解决办法的困境。我想导入许多产品，但它们可能属于同一类别，所以当我单击“+”时，显示会添加类似图片的行我在互联网上看到了很多教程并按照它们进行了操作，但它们都失败了。我不知道该怎么做。请帮我！非常感谢

state = {
  listItems: [],
  userInput: this.need,
}

need = {
  category: "",
  name: "",
  quantity: ""
}
    handleChange = (event) => {
        const target = event.target;
        const value = target.value;
        const name = target.name;
        let userInput = { ...this.state.userInput };
        userInput[name] = value;
        this.setState({ userInput });
    }
    submitHandler = e => {
        e.preventDefault()
        this.setState({
            listItems: [...this.state.listItems, this.state.userInput],
        })
    }
<Form>
<Form.Group id="need">
    <Row>
     <Col md="3">
       <label>Category</label>
       <select name="category" className="form-control" onChange={this.handleChange}>
         <option value="1">Water</option>
         <option value="2">Food</option>
       </select>
    </Col>
    <Col md="4">
      <label>Name</label>
        <Input
           name="name"
           className="form-control-alternative"
           onChange={this.handleChange}
           type="text"
         />
    </Col>
    <Col md="4">
      <label>Quantity</label>
      <Input
        name="quantity"
        className="form-control-alternative"
        type="text"
        onChange={this.handleChange}
      />
   </Col>
   <Col>
<i style={{ marginTop: 45 }} onClick={submitHandler} >Add more</i>
   </Col>
</Row>
</Form.Group>
</Form>

CodeSandbox!

Answer 1

对于这种形式，我更喜欢使用formik而不是this.setState。

解决方案 1. this.setState

我会这样设计状态

this.state = {
  form: [
    {
      category: "",
      name: "",
      quantity: 0,
    },
  ],
};

以及添加更多项目的方法，编辑它们的内容

handleAdd = () => {
  this.setState({
    form: [
      ...this.state.form,
      {
        category: "",
        name: "",
        quantity: 0,
      },
    ]
  });
};

handleEditFieldOfItem = (event, itemIndex, fieldName) => {
  const value = event.target.value;
  this.setState({
    form: this.state.form.map((item, index) => {
      if (index === itemIndex) {
        return { ...item, [fieldName]: value };
      }
      return item;
    })
  });
};

我会将这些项目呈现如下：

render() {
  return (
    <div>
      {this.state.form.map((item, index) => {
        return (
          <div key={index}>
            <div>
              <select value={item.category} onChange={(event) => { this.handleEditFieldOfItem(event, index, 'category'); }}>
                <option value="water">Water</option>
                <option value="food">Food</option>
              </select>
            </div>
            <div>
              <input type="text" value={item.name} onChange={(event) => { this.handleEditFieldOfItem(event, index, 'name'); }} />
            </div>
            <div>
              <input type="text" value={item.quantity} onChange={(event) => { this.handleEditFieldOfItem(event, index, 'quantity'); }} />
            </div>
          </div>
        );
      })}
      <button onClick={this.handleAdd}>Add</button>
    </div>
  );
}

解决方案 2. 使用 Formik（带有 FieldArray 组件）

Formik 具有验证、处理嵌套值的能力，...

您应该先查看 Formik documentation。

import { Formik, Field, FieldArray } from "formik";

// ...

<Formik
  initialValues={{
    form: [
      {
        category: "",
        name: "",
        quantity: 0
      }
    ]
  }}
  onSubmit={(values, helpers) => {
    // 
  }}
>
  {(formikProps) => {
    const { values, handleSubmit } = formikProps;
    return (
      <>
        <FieldArray name="form">
          {(arrayHelpers) => {
            return (
              <div>
                {values.form.map((item, index) => {
                  return (
                    <div key={index}>
                      <Field as="select" name={`form.${index}.category`}>
                        <option value="water">Water</option>
                        <option value="food">Food</option>
                      </Field>
                      <Field name={`form.${index}.name`} />
                      <Field name={`form.${index}.quantity`} />
                    </div>
                  );
                })}
                <div>
                  <button onClick={() => arrayHelpers.push({ category: '', name: '', quantity: 0 })}>Add</button>
                </div>
              </div>
            )}}
        </FieldArray>
        <button type="submit">Submit</button>
      </>
    );
  }}
</Formik>

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