callback | 易学教程

Android的架构主体演变

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Android的架构主体演变在过去Android一直在MVC、MVP中探索。在2019基本没有谁再去纠结这两个架构了，因为Android的Jetpack提供了MVVM架构，说到MVVM架构我第一时间想到刚刚毕业的时候，在WPF的window开发中使用到MVVM的数据绑定。如果你是一个初学者我的建议是直接忽略MVP架构，直接入门MVC，开发MVVM。最佳架构对于MVVM，google提供了Jetpack组件。成为Android最佳架构实践。可以通过以下网址学习和探索：https://developer.android.com/jetpack 。Jetpack组件已经植入了Android的SDK，从这一点可以看出最佳架构不是徒有空名的，那些还在观念意识上不接受的就快点转换思维吧。学习Jetpack中的设计思想公司的主体Android架构已经切换到了MVVM结构了，而且App运行良好，优势也渐渐凸显。在这里我和大家分享一下我眼中的Jetpack组件值得学习的切入点主要有两点：构建对象管理器、数据绑定。构建对象管理器对于对象的生成和销毁的管理一直以来都是各大架构的一个主题功能。归根结底就是一个工厂模式，在Jetpack中我们也看到这个设计模式的应用，在ViewModelProviders和RepositoryProviders。先不看这个两个类的实现

Accessing Parameters and Events in function from jQuery Event

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问题 This is a follow-up question to a different question I asked not too long ago. Typically, you can access an event in a function call from a jQuery event like this: $item.live("click", functionToCall); and in the function: function functionToCall(ev) { // do something with ev here, like check 'ev.target' } But what if I wanted to send a parameter to functionToCall() and access the event? So something like this, maybe? : $item.live("click", functionToCall($(this)); // send over parameter this

Rails accepts_nested_attributes_for callbacks

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问题 I have two models Ticket and TicketComment , the TicketComment is a child of Ticket. ticket.rb class Ticket < ActiveRecord::Base has_many :ticket_comments, :dependent => :destroy, :order => 'created_at DESC' # allow the ticket comments to be created from within a ticket form accepts_nested_attributes_for :ticket_comments, :reject_if => proc { |attributes| attributes['comment'].blank? } end ticket_comment.rb class TicketComment < ActiveRecord::Base belongs_to :ticket validates_presence_of

Rails accepts_nested_attributes_for callbacks

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KVO differentiating between willChangeValueForKey and didChangeValueForKey - are both necessary?

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问题 In line with Apple's own recommendations, when setting KVC/KVO compliant accessors manually, one should include BOTH KVO methods willChange and didChange . This is what I have done in all my manual accessor methods. However, observeValueForKeyPath:ofObject:change:context gets called for each half of the KVC methods (will and did) with exactly the same dictionary contents. When registering an observer using the option: NSKeyValueObservingOptionPrior the observer still gets called twice - once

How to write a simple callback function?

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问题 Python 2.7.10 I wrote the following code to test a simple callback function. def callback(a, b): print('Sum = {0}'.format(a+b)) def main(callback=None): print('Add any two digits.') if callback != None: callback main(callback(1, 2)) I receive this when I execute it: Sum = 3 Add any two digits. Why Add any two digits is after Sum = 3 ? I guess it is because the callback function executes first. How to execute the callback function after all other code in main() executed? 回答1: callback on its

scrapy框架结合项目使用，超级合适新手

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一、流程步骤 HelloWorld Scrapy 创建一个工程 scrapy startproject XXX 创建一个爬虫 scrapy genspider YYY domain domain 爬取主站地址运行爬虫 scrapy crawl YYY 完善爬虫定向获取内容 parse函数参数 response response xpath 写规则就可以会返回提取好的内容 Selector get 获取内容 extract extract_all re css 二、代码操作： 1下载： pip install scrapy 2.终端创建项目ZhouWu scrapy startproject ZhouWu 3.pycharm打开项目，配置虚拟环境，生成爬虫文件；爬取http://lab.scrapyd.cn/这个网站，执行命令后会生成lab.py文件； scrapy genspider lab lab.scrapyd.cn 4.运行此蜘蛛文件 scrapy crawl lab 5.scrapy项目架构原理解析：爬取流程：在Spiders中编写爬虫，把开始的地址配置好，会交给Scheduler调度器，Scheduler从请求队列中拿出调度器，把Requests发出去，Requests对应互联网资源，给Downloader下载器把资源变成Response，回到Spiders中

3.6.2 RabbitMQ教程一

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Introduction RabbitMQ is a message broker: it accepts and forwards messages. You can think about it as a post office: when you put the mail that you want posting in a post box, you can be sure that Mr. or Ms. Mailperson will eventually deliver the mail to your recipient. In this analogy, RabbitMQ is a post box, a post office and a postman. RabbitMQ是一个消息中转器，它接收并转发消息。你可以把它看成是一个邮局：当你放了一封你要寄出的信到邮箱里时，你可以肯定邮递员先生或女士最终会把信交给你的收件人。在这个类比中，RabbitMQ充当了邮箱，邮局以及邮递员的角色。 The major difference between RabbitMQ and the post office is that it doesn't deal with paper, instead it accepts, stores and forwards binary

glfwSetCursorPosCallback to function in another class

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问题 I'm really stuck: I have the mainWindow and in the main game loop I do: // poll for input glfwPollEvents(); this->controls->handleInput(window, world->getPlayer()); glfwSetCursorPosCallback(window, controls->handleMouse); What I want to do is to have one class responsible for the controls and to have this class also handle the mouse. I always get: 'Controls::handleMouse': function call missing argument list; use '&Controls::handleMouse' to create a pointer to member Now when I try this I get:

setTimeout - callback argument must be a function

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问题 My code was working until i updated node.js to version 8.11.3 Now i always get error "callback argument must be a function" when trying to call a function with setTimeout. function testFunction(itemid, price) { var url = 'https://example.com'; var options = { method: 'get', url: url } request(options, function (err, res, body) { var response = JSON.parse(body); if(response.status == 'fail'){ setTimeout(testFunction(itemid, price), 100); } }) } 回答1: Callback argument for setTimeout must be a