block | 易学教程

浅谈Ruby中的block, proc, lambda, method object的区别

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 前言当大家在百度中搜索“block proc lambda”的时候，会出来很多关于这几个概念之间区别的介绍，既然搜索结果中已经有了这些介绍，那为什么还要写这篇文章？相信看过百度搜索结果中排名靠前的几篇文章的同学，都会发现其实这些文章并没有很好的说明他们之间区别是什么，大多只是介绍各自的用法，加上些许的区别，即使个别介绍了一些区别，也不够系统，不够深入。正是基于上述原因，才酝酿了本文。本文以简单示例的方式，详细的介绍了它们之间的区别。相信您阅读完本文，一定会豁然开朗，并在今后的开发中准确并优雅的使用它们。由于时间，个人能力水平等有限，本文难免有错误或缺失之处，欢迎不吝指出。 block & proc 在介绍它们的区别之前，我们先来看一段有关block的简单使用方法： def use_yield yield end use_yield do puts 'use yield' end def use_block_call(&block) block.call end use_block do puts 'use block call' end 以上介绍了两种在函数中使用block的方式，第一种是通过yield来使用block，另外一种则是通过block.call来使用block。

Java AES cipher text size

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问题 I'm using a very standard way of Java AES encryption / decryption. byte[] key = hexStringToByteArray("C0C1C2C3C4C5C6C7C8C9CACBCCCDCECF"); byte[] message = hexStringToByteArray("01A0A1A2A3A4A5A6A703020100060001"); SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES"); // Instantiate the cipher Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec); byte[] encrypted = cipher.doFinal(message); cipher.init(Cipher.DECRYPT_MODE, secretKeySpec); byte[]

(java) variable scope inside try { } when accessing from finally { }?

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问题 I noticed that when the following variables when in try { }, I couldn't use methods on them from finally for example: import java.io.*; public class Main { public static void main()throws FileNotFoundException { Try{ File src = new File("src.txt"); File des = new File("des.txt"); /*code*/ } finally{ try{ /*closing code*/ System.out.print("After closing files:Size of src.txt:"+src.length()+" Bytes\t"); System.out.println("Size of des.txt:"+des.length()+" Bytes"); } catch (IOException io){

(java) variable scope inside try { } when accessing from finally { }?

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Magento- How can i add a new custom block in product details page using module

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问题 I am doing a magento customaization site, I need to add the products addtional attributes like it's type,version etc .I am new to magento , How can i add the new custom block to product details page. I have created a module , and i am using below coding. app\code\local\SmartGrowth\CompatibleWith\Block\compatible.php class SmartGrowth_CompatibleWith_Block_CompatibleWith extends Mage_Catalog_Block_Product_View { protected function _prepareLayout() { //$this->getProduct()->setName($this-

Java code hangs at Scanner hasNextLine

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问题 First off, I'm new to java and trying to complete an assignment from school on creating a vending machine. My program is taking in 2 files as cli arguments, one for products, and the other for money. For the life of me I cannot figure out why the code is hanging on line 42 (while (moneyTemp.hasNextLine());) I tried to debug on eclipse using breakpoints and noticed the code never goes past this line. Putting a print statement inside the while loop, i don't get the output so i know it is not

Returning a variable value outside a block - Objective-C, iOS

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问题 I have the code below that a an connection to an URL and fetches some header responses like http code response and final URL (for redirection case): - (NSString *)test { __block NSString *cod = @"x"; NSString *urlString = @" http://www.google.com "; NSURL *url = [NSURL URLWithString:urlString]; NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:15.0f]; [request setHTTPMethod:@"HEAD"]; [NSURLConnection

How do I change the CSS property “display” in javascript

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问题 How do I change the CSS property display , in JavaScript, from display:none to display:normal for these divs? #hide_0 { display:none } #hide_1 { display:none } #hide_2 { display:none } #hide_3 { display:none } #hide_4 { display:none } #hide_5 { display:none } Only one at a time. I need to display one and hide the rest. What I used: var persistent_element='hide_1'; function link_update(link_display) { var local_element; local_element=document.getElementById(persistent_element); local_element

CSS的inline、block与inline-block

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基本知识点行内元素一般是内容的容器，而块级元素一般是其他容器的容器，行内元素适合显示具体内容，而块级元素适合做布局。块级元素(block)：独占一行，对宽高的属性值生效；如果不给宽度，块级元素就默认为浏览器的宽度，即就是100%宽。行内元素(inline)：可以多个标签存在一行，对宽高属性值不生效，完全靠内容撑开宽高。行内块元素(inline-block)：结合的行内和块级的优点，既可以设置长宽，可以让padding和margin生效，又可以和其他行内元素并排。其中 img和input为行内块元素。行内元素与块状元素之间的转换: float: 当把行内元素设置完float:left/right后，该行内元素的display属性会被赋予block值，且拥有浮动特性。行内元素去除了之间的莫名空白。 <head> <meta charset="UTF-8"> <title>测试</title> <style type="text/css"> p{ background-color: red; height: 500px; width: 30%; padding: 20px; margin: 20px; float: left;} div{ background-color: green; height: 50px; width: 40%; padding: 20px;

RSpec — test if method called its block parameter

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问题 I have a method that takes block of code as an argument. The problem is: how to test using RSpec if this method called the block? The block may be evaluated in any scope the method needs, not necessarily using a yield or block.call . It be passed to another class, or evaluated it in an anonymous class object or somewhere else. For the test to pass it is enough to evaluate the block somewhere as a result of the method call. Is there a way to test something like this using RSpec? See also this