hash

How do I find and replace 'nil' values of Ruby hash with “None” or 0?

由 你。 提交于 2019-12-23 18:52:13
问题 I'm trying to drill down to each value in an iteration of an array nested hash and replace all nil values with something like 'None' or 0. Please see my code that is clearly not working. I need to fix this before I pass it to my Views in Rails for iteration and rendering: My controller: def show results = Record.get_record(params[:trans_uuid]) if !results.empty? record = results.map { |res| res.attributes.symbolize_keys } @record = Record.replace_nil(record) # this calls method in Model else

java 8 Hashmap深入解析 —— put get 方法源码

由 主宰稳场 提交于 2019-12-23 18:30:53
本文为原创博文，转载请注明出处，侵权必究！ 每个java程序员都知道，HashMap是java中最重要的集合类之一，也是找工作面试中非常常见的考点，因为HashMap的实现本身确实蕴含了很多精妙的代码设计。 　　对于普通的程序员，可能仅仅能说出HashMap线程不安全，允许key、value为null，以及不要求线程安全时，效率上比HashTable要快一些。稍微好一些的，会对具体实现有过大概了解，能说出HashMap由数组+链表+RBT实现，并了解HashMap的扩容机制。但如果你真的有一个刨根问题的热情，那么你肯定会想知道具体是如何一步步实现的。HashMap的源码一共2000多行，很难在这里每一句都说明，但这篇文章会让你透彻的理解到我们平时常用的几个操作下，HashMap是如何工作的。 　 要先提一下的是，我看过很多讲解HashMap原理的文章，有一些讲的非常好，但这些文章习惯于把源代码和逻辑分析分开，导致出现了大段的文字讲解代码，阅读起来有些吃力和枯燥。所以我想尝试另一种风格，将更多的内容写进注释里，可能看起来有些啰嗦，但对于一些新手的理解，应该会有好的效果。 HashMap结构 　 首先是了解HashMap的几个核心成员变量（以下均为jdk源码）： 1 　　transient Node<K,V>[] table;　　　　　　　 //HashMap的哈希桶数组

Reproducing JS PBKDF2 Hash in C#

由 感情迁移 提交于 2019-12-23 17:27:02
问题 I had to implement some new security features for an Existing Database. They used to hash passwords on the side of the client with a salt from the DB. They used this code to hash the passwords before sending them to the server: var hash = CryptoJS.PBKDF2(password, USER_SALT, { keySize: 4, iterations: 1000 }); Now as you can already guess, this is highly insecure, cause an attacker gets the PW as if it was sent in plain text if the user gets the Salt from the server and the hasing is done

rails select maximum value from array of hash

由 独自空忆成欢 提交于 2019-12-23 14:58:01
问题 i have a array of hashes like this and i want to take the maximum value of that data = [{name: "abc", value: "10.0"}, {name: "def", value: "15.0"}, {name: "ghi", value: "20.0"}, {name: "jkl", value: "50.0"}, {name: "mno", value: "30.0"}] i want to select the maximum value of array of hashes, output i want is like data: "50.0" how possible i do that, i've try this but it is seem doesnt work and just give me an error data.select {|x| x.max['value'] } any help will be very appreciated 回答1: There

when add key-value pair to a hashMap, why Java makes hashMap's hashCode change?

由 好久不见. 提交于 2019-12-23 14:51:34
问题 If you look at java's hashCode method inside hashMap, you will find: public int hashCode() { int h = 0; Iterator<Entry<K,V>> i = entrySet().iterator(); while (i.hasNext()) h += i.next().hashCode(); return h; } So when you insert things into hashMap, hashMap's hashCode will change. Thus, if we insert an empty hashMap into hashSet, then insert something to this hashMap, then call hashSet.contains(hashMap) , it will return false . Why does Java allow such behavior? This will easily cause

when add key-value pair to a hashMap, why Java makes hashMap's hashCode change?

由 ♀尐吖头ヾ 提交于 2019-12-23 14:51:14
问题 If you look at java's hashCode method inside hashMap, you will find: public int hashCode() { int h = 0; Iterator<Entry<K,V>> i = entrySet().iterator(); while (i.hasNext()) h += i.next().hashCode(); return h; } So when you insert things into hashMap, hashMap's hashCode will change. Thus, if we insert an empty hashMap into hashSet, then insert something to this hashMap, then call hashSet.contains(hashMap) , it will return false . Why does Java allow such behavior? This will easily cause

Golang encode string UTF16 little endian and hash with MD5

由 眉间皱痕 提交于 2019-12-23 13:38:22
问题 I am a Go beginner and stuck with a problem. I want to encode a string with UTF16 little endian and then hash it with MD5 (hexadecimal). I have found a piece of Python code, which does exactly what I want. But I am not able to transfer it to Google Go. md5 = hashlib.md5() md5.update(challenge.encode('utf-16le')) response = md5.hexdigest() The challenge is a variable containing a string. 回答1: You can do it with less work (or at least more understandability, IMO) by using golang.org/x/text

How can I share Perl data structures through a socket?

由 ∥☆過路亽．° 提交于 2019-12-23 13:07:13
问题 In sockets I have written the client server program. First I tried to send the normal string among them it sends fine. After that I tried to send the hash and array values from client to server and server to client. When I print the values using Dumper, it gives me only the reference value. What should I do to get the actual values in client server? Server Program: use IO::Socket; use strict; use warnings; my %hash = ( "name" => "pavunkumar " , "age" => 20 ) ; my $new = \%hash ; #Turn on

Can I build a Perl Regex from a set of hash keys

由 自作多情 提交于 2019-12-23 13:01:09
问题 (related to previous question: Do I need to reset a Perl hash index?) I have a hash coming in from a file which is defined as follows: %project_keys = ( cd => "continuous_delivery", cm => "customer_management", dem => "demand", dis => "dis", do => "devops", sel => "selection", seo => "seo" ); I need to check whether a review title has the correct format, and if so, link to a separate URL. For instance, if a review title is "cm1234 - Do some CM work" then I want to link to the following URL:

using hash to determine whether 2 dataframes are identical (PART 01)

由 十年热恋 提交于 2019-12-23 12:16:11
问题 I have created a dataset using WHO ATC/DDD Index a few months before and I want to make sure if the database online remains unchanged today, so I downloaded it again and try to use the digest package in R to do the comparison. The two dataset (in txt format) can be downloaded here. (I am aware that you may think the files are unsafe and may have virus, but I don't know how to generate a dummy dataset to replicate the issue I have now, so I upload the dataset finally) And I have written a
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