将函数作为道具传递给功能组件时，React - “不是函数”错误

Question

我对React比较陌生，而且我正在开发一个待办事项列表样式Recipe app。我问a previous question here有关重构功能组件的问题，以便配方成分出现在单独的行上，而不是全部显示为单行段落。

我实现了建议的更改，并使用第二个.map函数迭代成分并成功使它们出现在单独的行上。但是，在实施更改后，当用户单击编辑按钮并尝试编辑配方成分时，我会收到错误。

处理显示配方名称和成分的功能组件（Item.js）如下所示：

import React from 'react';
import Button from 'react-bootstrap/lib/Button';


const Item = (props) => (
  <div>
    <div className="Recipe-Item-Container" key={props.text}>
      {props.items.map((item, index) => {
        return (
        <div className="Recipe-Item" key={index}>
          <h3>{item}</h3>

        // This p and the map function within it were the changes I made
        <p className="ingredients-list">
          {props.ingredients[index].map((ingredient, ingredientIndex) => {
            return (
              <div className="ingredient" key={ingredient}>
                {ingredient}
              </div>
            )
          })}
        </p>

        <div className="buttons-container">
          <Button className="edit-button" onClick={() => props.edit(item, index)}>Edit</Button>
          <Button className="delete-button" onClick={() => props.delete(item, index)}>Delete</Button>
          </div>
        </div>
      );
    }
  )}
  </div>
</div>
)

export default Item;

现在，当我单击编辑按钮并尝试编辑成分列表时，我收到此错误：

这是我的App.js组件，它存储状态并将数据传递给Item.js：

import React, { Component } from 'react';
import Item from './Item';
import './App.css';
import ModalComponent from './Modal.js';
import Button from 'react-bootstrap/lib/Button';
import EditModalComponent from './EditModal.js';

export default class App extends Component {
  constructor(props) {
    super(props);

    this.state = {
      items: ["Pumpkin Pie", "Spaghetti", "Onion Pie"],
      ingredients:[
        ["Pumpkin Puree ", "Sweetened Condensed Milk ", "Eggs ", "Pumpkin Pie Spice ", "Pie Crust "],
        ["Noodles ", "Tomato Sauce ", "(Optional) Meatballs "],
        ["Onion ", "Pie Crust "]
      ],

      // Recipe name and ingredients
      inputVal: '',
      ingredientVal: '',
      // Recipe name and ingredients when user is editing existing recipe
      inputValEdit: '',
      ingredientValEdit: '',
      // Controls whether forms are displayed or hidden
      showRecipeForm: false,
      showRecipeEditForm: false,
      // Index to select which recipe item is being edited
      editingIndex: ''
    };

  }

  // Get text user inputs for recipes
  handleChange = (event) => {
    this.setState({ [event.target.name]: event.target.value });
  };


  // When user submits recipe this adds it to the list
  onSubmit = (event) => {
    event.preventDefault()
    this.setState({
      items: [...this.state.items, this.state.inputVal],
      ingredients: [...this.state.ingredients, this.state.ingredientVal],
      showRecipeForm: false
    });
  }

  onEditSubmit = (event) => {
    event.preventDefault();
    const {items, ingredients, inputValEdit, ingredientValEdit, editingIndex} = this.state;

    // Selects proper recipe item to edit
    items[editingIndex] = inputValEdit;
    ingredients[editingIndex] = ingredientValEdit;

    this.setState({
      items: items,
      ingredients: ingredients,
      inputVal: '',
      ingredientVal: '',
      showRecipeEditForm: false
    });
  }

  closeRecipeForm = () => {
    this.setState({
      showRecipeForm: false,
      showRecipeEditForm: false
    });
  }

  // Shows recipe
  AddRecipe = (bool) => {
    this.setState({
      showRecipeForm: bool
    });
  }

  // Is called when one of the edit recipe buttons is clicked, shows RecipeEditForm
  edit = (item, index) => {
    this.setState({
      showRecipeEditForm: !this.state.showRecipeEditForm,
      editingIndex: index
    });
  }

  // Deletes recipe item from the list
  delete = (item, index) => {
     this.setState({
      ingredients : this.state.ingredients.filter((_, i) => i !== index),
      items: this.state.items.filter((_, i) => i !== index)
    });
  }


  render() {
    return (
      <div className="container">
        <h1>Recipe List</h1>


        <ModalComponent
          inputVal={this.state.inputVal}
          handleChange={this.handleChange}
          ingredientVal={this.state.ingredientVal}
          onSubmit={this.onSubmit}
          addRecipe={this.addRecipe}
          showRecipeForm={this.state.showRecipeForm}
          closeRecipeForm={this.closeRecipeForm}
        />

        <EditModalComponent
          inputValEdit={this.state.inputValEdit}
          handleChange={this.handleChange}
          ingredientValEdit={this.state.ingredientValEdit}
          onEditSubmit={this.onEditSubmit}
          closeRecipeForm={this.closeRecipeForm}
          addRecipe={this.addRecipe}
          showRecipeEditForm={this.state.showRecipeEditForm}
        />


        <Item
          items={this.state.items}
          ingredients={this.state.ingredients}
          edit={this.edit}
          delete={this.delete}
        />

      <Button className="add-recipe-button" onClick={this.AddRecipe}>Add New Recipe</Button>

      </div>
    );
  }

}

当用户尝试编辑成分列表时，为什么我在Item.js中收到此错误？我认为它涉及onEditSubmit功能，但我不确定。

Answer 1

所以，我在你的onEditSubmit看到你这样做：

ingredients[editingIndex] = ingredientValEdit; // line 57

你在状态中的成分实际上是一个阵列阵列（多维）。就像这样：

ingredients:[
        ["Pumpkin Puree ", "Sweetened Condensed Milk ", "Eggs ", "Pumpkin Pie Spice ", "Pie Crust "],
        ["Noodles ", "Tomato Sauce ", "(Optional) Meatballs "],
        ["Onion ", "Pie Crust "]
      ],

但是在那行代码之后，你的数组变成了这样的东西：我已经输入'Chicken Lollipop'作为例如的成分。

ingredients:[
        "Chicken Lollipop",
        ["Noodles ", "Tomato Sauce ", "(Optional) Meatballs "],
        ["Onion ", "Pie Crust "]
      ],

因此，所选索引处的值将变为字符串而不是数组。在这种情况下，索引0处的值现在是一个字符串。

因此，你在Item.js中的渲染函数会破坏，因为它试图映射它不能的字符串。

要解决此问题，您可以将第57行更改为：

ingredients[editingIndex] = [ingredientValEdit];

现在，每个条目都将正确存储为数组，您的代码应该可以正常工作。更新后的数组如下所示：

ingredients:[
        ["Chicken Lollipop"],
        ["Noodles ", "Tomato Sauce ", "(Optional) Meatballs "],
        ["Onion ", "Pie Crust "]
      ]

其他内容（此答案不需要）：

但是，由于您始终需要将成分作为数组，因此您还可以使用分隔符分割输入值，例如：

用户输入的成分为：'Lollipop，Candy，Something'

在你的第57行你也可以这样做：

ingredients[editingIndex] = ingredientValEdit.split(',');