Flutter/Dart中如何从动态列表提取start日期生成新列表

问题描述 #

我有一个如下所示的动态列表，希望创建另一个仅包含"start"日期的列表，请问该如何实现？

"bookings": [
            {
                "reference": "G1TVTZYSXZRHIIINN888",
                "station": "G61703000566",
                "connector": 0,
                "start": "2021-07-22T17:00:00.000+00:00",
                "stop": "2021-07-22T18:00:00.000+00:00",
                "card": "D2E3422B",
                "status": "Expired"
            },
            {
                "reference": "VD2MQO39CQ1PSHMUDIHT",
                "station": "G61703000567",
                "connector": 1,
                "start": "2021-07-22T18:00:00.000+00:00",
                "stop": "2021-07-22T19:00:00.000+00:00",
                "card": "D2E3422B",
                "status": "Expired"
            },
            {
                "reference": "EPQ05Q8DAHCOVNXMQCM3",
                "station": "G61703000567",
                "connector": 1,
                "start": "2021-07-22T20:00:00.000+00:00",
                "stop": "2021-07-22T21:00:00.000+00:00",
                "card": "D2E3422B",
                "status": "Expired"
            }
]

解决方案 #

Python 实现 #

用列表推导式快速提取目标字段：

# 假设数据已加载为字典格式，如data = {"bookings": [...]}
start_dates = [booking["start"] for booking in data["bookings"]]
print(start_dates)

输出结果：

['2021-07-22T17:00:00.000+00:00', '2021-07-22T18:00:00.000+00:00', '2021-07-22T20:00:00.000+00:00']

JavaScript 实现 #

使用数组map方法遍历提取：

// 假设bookings数组已定义
const bookings = [/* 你的预订数据 */];
const startDates = bookings.map(booking => booking.start);
console.log(startDates);

输出结果：

["2021-07-22T17:00:00.000+00:00", "2021-07-22T18:00:00.000+00:00", "2021-07-22T20:00:00.000+00:00"]

Java 实现 #

可以用普通循环或Stream API两种方式：

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

public class DateExtractor {
    public static void main(String[] args) {
        List<Booking> bookings = new ArrayList<>();
        // 填充预订数据...
        
        // 方式1：普通循环
        List<String> startDatesLoop = new ArrayList<>();
        for (Booking booking : bookings) {
            startDatesLoop.add(booking.getStart());
        }
        
        // 方式2：Stream API
        List<String> startDatesStream = bookings.stream()
                                               .map(Booking::getStart)
                                               .collect(Collectors.toList());
    }
}

// 对应的Booking实体类
class Booking {
    private String reference;
    private String station;
    private int connector;
    private String start;
    private String stop;
    private String card;
    private String status;
    
    // 构造方法、getter/setter省略
    public String getStart() {
        return start;
    }
}

内容的提问来源于stack exchange，提问作者Bill Tertis