React-native搜索栏-错误:未定义不是函数(near '...this.state.books.filter...')

constructor(props) {
  super(props);
  this.state = {
    books: [], // 初始化books为空数组
  };
}

updateBooks = () => {
  // 获取新的书籍数据
  const newBooks = fetchBooks();

  // 更新state中的books
  this.setState({ books: newBooks });
}

render() {
  // 使用filter函数过滤books
  const filteredBooks = this.state.books.filter(book => book.title.includes(this.state.searchText));

  // 渲染搜索结果
  return (
    <View>
      <TextInput
        onChangeText={text => this.setState({ searchText: text })}
        value={this.state.searchText}
      />
      <Button title="Search" onPress={this.updateBooks} />
      <FlatList
        data={filteredBooks}
        renderItem={({ item }) => <Text>{item.title}</Text>}
        keyExtractor={item => item.id}
      />
    </View>
  );
}