dart | 易学教程

如何实现一次编码，到处运行？新一代云端一体化探索

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阿里妹导读：当前移动互联网业务研发运维模式，云与多端互相割裂，有些全栈的探索缺乏成功案例，行业对云端一体化研发这块仍是空白，我们要思考：如何能实现 1 个研发支撑云 + android + iOS 三端的业务快速落地？是否有新的研发运维模式，让程序员回归程序？“一次编码、到处运行”是我们的答案。我们在闲鱼项目验证，原本 60 天的项目时间减少了 20 天，提效 33% 。希望阿里高级技术专家孙棋的分析能够给大家带来收获。业务研发模式的演进效率是业务研发运维模式演进核心驱动力 PC 互联网时代，单体应用包含前后端是最初的研发模式（淘宝经历开发人员写 velocity 模板，以及更早的 jsp、asp 页面）其实质是中心化搭火车的研发模型。随着业务发展复杂性快速增加，赶火车的交付模式，极大的限制了业务发展，因此诞生了服务化的拆分，淘宝在 09 年的五彩石项目即基于这样的背景，微服务是一种软件架构，这背后更是一种研发模式的变革，从中心化研发模式到分布式的研发模式升级。在业务分布式研发模式升级的同时，前后端分离研发模式也在同步的演进，从 ajax 到专业前端独立完成业务闭环，职业分工细化提效。但对前端同学而言，服务端的运维始终是其痛苦的技术门槛，以及在阿里以 Java 语言为基础的中间件生态内，一直没有很好解决。进入移动互联网时代，客户端同样也经历同样的演进，阿里集团以

Flutter: How to update an Array within an Array in the firestore

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问题 banco firestore I need to update a status field in the index array [0] where time == 8:00, I need to pass this status to == "0", only that this array is inside a matrix that here in the image can be seen as a timer. How could I update this vector at index [0] by changing the status = 1 field to = 0? To update a status outside an array and passing the values by hand I am using an example like this for testing only: Firestore.instance.collection("area").document("alergia").collection("items")

Add nested data in Firestore by flutter

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问题 I'm from following issue. How to manage add and update data in Firebase Initially I can make data in firestore following code. However I would like to add car2 inside of cars after car1 . I have no idea of it. _firestore.collection('members').document(${loginUser.uid}).setData({ 'cars': { 'car1': { 'name': name, 'img_url': 'https://www.xxx.xxx/xxx.png', 'details': { 'type': carType, } } } Please give me advice. 回答1: To add cars2 , then do the following: _firestore.collection('members')

Get current date in Dart

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问题 How can I get the current date independent of system date and time in Dart? I have tried DateTime().now but it gives system date not the actual date (in case system date is altered). 回答1: If you don't trust the system to give the correct time you need to ask somewhere else to get the time. This can be done in multiply ways depending on which accuracy you need. E.g. the easiest way would be to just call a HTTP server with an API to get the time from the server. If accuracy are important you

Dart pass this as a parameter in a constructor

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问题 Lets say that I have an abstract class abstract class OnClickHandler { void doA(); void doB(); } I have a class class MyClass { OnClickHandler onClickHandler; MyClass({ this.onClickHandler }) void someFunction() { onClickHandler.doA(); } } And I have a class class Main implements onClickHandler { // This throws me an error MyClass _myClass = MyClass(onClickHandler = this); // <- Invalid reference to 'this' expression @override void doA() {} @override void doB() {} } How can I say that use the

Flutter rounded rectangle border with different colours for each side

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问题 I'm trying to re-create a button I made with React Native that had different colours for each side giving it a kind of chiseled effect, a bit like Photoshop bevel and emboss, but also with rounded corners. At the moment I have a container outside the button which has the border on it, and inside I'm using RawMaterialButton . The code for the container is like this: Container( BoxDecoration( border: Border( left: BorderSide( color: Colors.black, width: 1.0, ), top: BorderSide( color: Colors

Flutter The Function Color isn't defined or Undefined class Color

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问题 Okay I don't even know what to write. Everything was working fine few hours ago. Then I saw Flutter upgrade is available. So I tried to upgrade. That's when everything started to fall apart. Anyway, I used vpn to run terminal commands. I was successful. After that every single flutter project I am opening is showing this error. I tried with other projects. I can run and build apk but this errors are there. Here is output of run command: Launching lib\main.dart on POCOPHONE F1 in debug mode...

Flutter The Function Color isn't defined or Undefined class Color

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Why 2.0 (the number 2.0) is double and int at the same time?

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问题 I just started to learn Dart and came across the below code main(){ print(2.0 is int); print(2.0 is double); print(int is double); } It produces the below output true true false I am not sure why the above output is generated. The above output suggests that all integers can be treated as doubles. Am I missing something obvious here. Any pointers would help. Thanks. 回答1: You can only get this result if you run the code in the browser. The browser does not distinguish between int and double,

Why 2.0 (the number 2.0) is double and int at the same time?

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