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• Where to put a piece of code in Ruby on Rails?

  - by yuval

  I have a post controller that has many comments. The post model has a field called has_comments which is a boolean (so I can quickly select from the database only posts that have comments). To create a new comment for a post, I use the create action of my comments controller. After I create the comment I need to update my post's has_comments field and set it to true. I can update this field from the create action of my comments controller, but that doesn't seem right - I feel that I should really be using the post's update action, but I'm not sure if it's right to call it (via send?) from the create action of the comments controller. Where should the code for updating the post be? Thank you!

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• On Mac OS X, do you use the shipped python or your own?

  - by The MYYN

  On Tiger, I used a custom python installation to evaluate newer versions and I did not have any problems with that*. Now Snow Leopard is a little more up-to-date and by default ships with $ ls /System/Library/Frameworks/Python.framework/Versions/ 2.3 2.5 2.6 @Current What could be considered best practice? Using the python shipped with Mac OS X or a custom compiled version in, say $HOME. Are there any advantages/disadvantages using the one option over the other? My setup was fairly simple so far and looked like this: Custom compiled Python in $HOME and a $PATH that would look into $HOME/bin first, and subsequently would use my private Python version. Also $PYTHONPATH pointed to this local installation. This way, I did not need to sudo–install packages - virtualenv took care of the rest.

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• Lock thread using somthing other than a object

  - by Scott Chamberlain

  when using a lock does the thing you are locking on have to be a object. For example is this legal static DateTime NextCleanup = DateTime.Now; const TimeSpan CleanupInterval = new TimeSpan(1, 0, 0); private static void DoCleanup() { lock ((object)NextCleanup) { if (NextCleanup < DateTime.Now) { NextCleanup = DateTime.Now.Add(CleanupInterval); System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(cleanupThread)); } } return; } EDIT-- From reading SLaks' responce I know the above code would be not valid but would this be? static MyClass myClass = new MyClass(); private static void DoCleanup() { lock (myClass) { // } return; }

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• SQL programming interface to external storage application

  - by Gopala

  My application is a non-relational database application with a tcl interface to retrieve data. I would like to add SQL programming interface to my application. Is there any library that converts SQL/PLSQL statements to API calls? It should also support stored procedures. SQLite(Embedded) has 'virtual table' mechanism that suits my requirement but it lacks stored procedure feature. -Gopala

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• Null and blank values

  - by Jonathan D

  What's the best way of writing robust code so that a variable can be checked for null and blank. e.g. string a; if((a != null) && (a.Length() > 0)) { //do some thing with a }

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• Is it ok to throw NotImplemented exception in virtual methods?

  - by Axarydax

  I have a base class for some plugin-style stuff, and there are some methods that are absolutely required to be implemented. I currently declare those in the base class as virtual, for example public virtual void Save { throw new NotImplementedException(); } and in the descendand I have a public override void Save() { //do stuff } Is it a good practice to throw a NotImplementedException there? The descendand classes could for example be the modules for handling different file formats. Thanks

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• How to avoid nested functions when using AJAX?

  - by Fletcher Moore

  Sequential Asynchronous calls are gross. Is there a more readable solution? The problem is this is hard to follow: ajaxOne(function() { // do something ajaxTwo(function() { // do something ajaxThree() }); }); where the anonymous functions are callbacks that are called on server response. I'm using a third party API to make the AJAX calls, so I need a generic solution.

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• How to pass non-fatal warnings from a library

  - by wRAR

  A library function parses a file and returns an object. If a parser encounters unknown data, missing values etc., it shouldn't throw an exception and stop parsing (because this is not fatal), but there should be a way to pass information about these things to a caller (so that warnings can be displayed in the UI, for example). How can these warning be returned? I'm thinking of passing a callback function/object into the library, are there any other possible solutions?

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• Finding relative libraries when using symlinks to ruby executables

  - by dgtized

  Imagine you have an executable foo.rb, with libraries bar.rb layed out in the following manner: <root>/bin/foo.rb <root>/lib/bar.rb In the header of foo.rb you place the following require to bring in functionality in bar.rb: require File.dirname(__FILE__)+"../lib/bar.rb" This works fine so long as all calls to foo.rb are direct. If you put as say $HOME/project, and symlink foo.rb into $HOME/usr/bin, then __FILE__ resolves to $HOME/usr/bin/foo.rb, and is thus unable to locate bar.rb in relation to the dirname for foo.rb. I realize that packaging systems such as rubygems fix this by creating a namespace to search for the library, and that it is also possible to adjust the load_path using $: to include $HOME/project/lib, but it seems as if a more simple solution should exist. Has anyone had experience with this problem and found a useful solution or recipe?

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• Securing input of private / protected methods?

  - by ts

  Hello, normally, all sane developers are trying to secure input of all public methods (casting to proper types, validating, sanitizing etc.) My question is: are you in your code validating also parameters passed to protected / private methods? In my opinion it is not necessary, if you securize properly parameters of public methods and return values from outside (other classes, db, user input etc...). But I am constantly facing frameworks and apps (ie. prestashop to name one) where validation is often repeated in method call, in method body and once again for securize returned value - which, I think, is creating performace overhead and is also a sign of bad design.

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• using ref to view error

  - by Avram

  Hello. I working now on firm that using ref in every function. The reason, is to catch errors. There example : //return true if the read is success //otherwise writing to the error ,the problem bool ReadFile(ref string error) Question: How do you catching errors? Using ref,exceptions or other way?

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• Best practice for near reuse of model components?

  - by Chris Knight

  I have a requirement to use a Fund model in my code. It will contain a fund name and fund code. In the interest of reuse I've poked around the package containing the other models used and found an existing Fund model. However the issue here is that, in addition to fund name and code, it also contains an amount. Amount isn't directly relevant in my context. So, do I: 1) Use the existing Fund model as is, ignoring the setters/getters for fund amount. 2) Put a FundDescription interface onto the existing Fund model for accessing only the information I'm interested in. 3) Make a FundDescription base class from which the existing Fund model could now extend 4) Create a whole new seperate model since the two are slightly contextually different

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• Why doesn't String's hashCode() cache 0?

  - by polygenelubricants

  I noticed in the Java 6 source code for String that hashCode only caches values other than 0. The difference in performance is exhibited by the following snippet: public class Main{ static void test(String s) { long start = System.currentTimeMillis(); for (int i = 0; i < 10000000; i++) { s.hashCode(); } System.out.format("Took %d ms.%n", System.currentTimeMillis() - start); } public static void main(String[] args) { String z = "Allocator redistricts; strict allocator redistricts strictly."; test(z); test(z.toUpperCase()); } } Running this in ideone.com gives the following output: Took 1470 ms. Took 58 ms. So my questions are: Why doesn't String's hashCode() cache 0? What is the probability that a Java string hashes to 0? What's the best way to avoid the performance penalty of recomputing the hash value every time for strings that hash to 0? Is this the best-practice way of caching values? (i.e. cache all except one?) For your amusement, each line here is a string that hash to 0: pollinating sandboxes amusement & hemophilias schoolworks = perversive electrolysissweeteners.net constitutionalunstableness.net grinnerslaphappier.org BLEACHINGFEMININELY.NET WWW.BUMRACEGOERS.ORG WWW.RACCOONPRUDENTIALS.NET Microcomputers: the unredeemed lollipop... Incentively, my dear, I don't tessellate a derangement. A person who never yodelled an apology, never preened vocalizing transsexuals.

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• Is it a good idea to define a variable in a local block for a case of a switch statement?

  - by Paperflyer

  I have a rather long switch-case statement. Some of the cases are really short and trivial. A few are longer and need some variables that are never used anywhere else, like this: switch (action) { case kSimpleAction: // Do something simple break; case kComplexAction: { int specialVariable = 5; // Do something complex with specialVariable } break; } The alternative would be to declare that variable before going into the switch like this: int specialVariable = 5; switch (action) { case kSimpleAction: // Do something simple break; case kComplexAction: // Do something complex with specialVariable break; } This can get rather confusing since it is not clear to which case the variable belongs and it uses some unnecessary memory. However, I have never seen this usage anywhere else. Do you think it is a good idea to declare variables locally in a block for a single case?

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• Why cast null before checking if object is equal to null?

  - by jacerhea

  I was looking through the "Domain Oriented N-Layered .NET 4.0 Sample App" project and ran across some code that I do not understand. In this project they often use syntax like the following to check arguments for null: public GenericRepository(IQueryableContext context,ITraceManager traceManager) { if (context == (IQueryableContext)null) throw new ArgumentNullException("context", Resources.Messages.exception_ContainerCannotBeNull); Why would you cast null to the type of the object you are checking for null?

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• Comparing objects and inheritance

  - by ereOn

  Hi, In my program I have the following class hierarchy: class Base // Base is an abstract class { }; class A : public Base { }; class B : public Base { }; I would like to do the following: foo(const Base& one, const Base& two) { if (one == two) { // Do something } else { // Do something else } } I have issues regarding the operator==() here. Of course comparing an instance A and an instance of B makes no sense but comparing two instances of Base should be possible. (You can't compare a Dog and a Cat however you can compare two Animals) I would like the following results: A == B = false A == A = true or false, depending on the effective value of the two instances B == B = true or false, depending on the effective value of the two instances My question is: is this a good design/idea ? Is this even possible ? What functions should I write/overload ? My apologies if the question is obviously stupid or easy, I have some serious fever right now and my thinking abilities are somewhat limited :/ Thank you.

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• Should I use block identifiers ("end;") in my code?

  - by JosephStyons

  Code Complete says it is good practice to always use block identifiers, both for clarity and as a defensive measure. Since reading that book, I've been doing that religiously. Sometimes it seems excessive though, as in the case below. Is Steve McConnell right to insist on always using block identifiers? Which of these would you use? //naughty and brief with myGrid do for currRow := FixedRows to RowCount - 1 do if RowChanged(currRow) then if not(RecordExists(currRow)) then InsertNewRecord(currRow) else UpdateExistingRecord(currRow); //well behaved and verbose with myGrid do begin for currRow := FixedRows to RowCount - 1 do begin if RowChanged(currRow) then begin if not(RecordExists(currRow)) then begin InsertNewRecord(currRow); end //if it didn't exist, so insert it else begin UpdateExistingRecord(currRow); end; //else it existed, so update it end; //if any change end; //for each row in the grid end; //with myGrid

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• Which options do I have for Java process communication?

  - by Dmitriy Matveev

  We have a place in a code of such form: void processParam(Object param) { wrapperForComplexNativeObject result = jniCallWhichMayCrash(param); processResult(result); } processParam - method which is called with many different arguments. jniCallWhichMayCrash - a native method which is intended to do some complex processing of it's parameter and to create some complex object. It can crash in some cases. wrapperForComplexNativeObject - wrapper type generated by SWIG processResult - a method written in pure Java which processes it's parameter by creation of several kinds (by the kinds I'm not meaning classes, maybe some like hierarchies) of objects: 1 - Some non-unique objects which are referencing each other (from the same hierarchy), these objects can have duplicates created from the invocations of processParam() method with different parameter values. Since it's costly to keep all the duplicates it's necessary to cache them. 2 - Some unique objects which are referencing each other (from the same hierarchy) and some of the objects of 1st kind. After processParam is executed for each of the arguments from some set the data created in processResult will be processed together. The problem is in fact that jniCallWhichMayCrash method may crash the entire JVM and this will be very bad. The reason of crash may be such that it can happen for one argument value and not for the other. We've decided that it's better to ignore crashes inside of JVM and just skip some chunks of data when such crashes occur. In order to do this we should run processParam function inside of separate process and pass the result somehow (HOW? HOW?! This is a question) to the main process and in case of any crashes we will only lose some part of data (It's ok) without lose of everything else. So for now the main problem is implementation of transport between different processes. Which options do I have? I can think about serialization and transmitting of binary data by the streams, but serialization may be not very fast due to object complexity. Maybe I have some other options of implementing this?

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• Should you always write code for else cases that "can never happen"?

  - by johnswamps

  Take some code like if (person.IsMale()) { doGuyStuff(); } else { doGirlOtherStuff(); } (Yes, I realize this is bad OO code, it's an example) Should this be written so that to explicitly check if person.isFemale(), and then add a new else that throws an exception? Or maybe you're checking values in an enum, or something like that. You think that no one will add new elements to the enum, but who knows? "Can never happen" sounds like famous last words.

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• Python-based password tracker (or dictionary)

  - by Arrieta

  Hello: Where we work we need to remember about 10 long passwords which need to change every so often. I would like to create a utility which can potentially save these passwords in an encrypted file so that we can keep track of them. I can think of some sort of dictionary passwd = {'host1':'pass1', 'host2':'pass2'}, etc, but I don't know what to do about encryption (absolutely zero experience in the topic). So, my question is really two questions: Is there a Linux-based utility which lets you do that? If you were to program it in Python, how would you go about it? A perk of approach two, would be for the software to update the ssh public keys after the password has been changed (you know the pain of updating ~15 tokens once you change your password). As it can be expected, I have zero control over the actual network configuration and the management of scp keys. I can only hope to provide a simple utility to me an my very few coworkers so that, if we need to, we can retrieve a password on demand. Cheers.

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• Why do people keep parsing HTML using regex? [closed]

  - by polygenelubricants

  As much as I love regular expressions, it's obvious to me that it's not the best tool for parsing HTML, especially given the numerous good HTML parsers out there. And yet there are numerous questions on stackoverflow that attempts to parse HTML using regex. And people would always point out what a bad idea that is in the comments. And the accepted answer would often have a disclaimer how this isn't really the ideal way of doing things. But based on the constant flow of questions, it still seems that people keep parsing HTML using regex, despite the perceived difficulty in reading and maintaining it (and that's putting correctness aside for now). So my question is: why? Is it because it's easy to learn? Is it because it's faster? Is it because it's the industry standard? Is it because there are already so many reusable regexes to build from? Is it because 100% correctness is never really the objective? (90% good enough?) etc... I'd also like to hear from the downvoters why they did so. Is it because: There's absolutely nothing wrong with using regex to parse HTML and asking "Why?" is just dumb? The premise of the question is flawed because the people who are using regex to parse HTML is such a small minority?

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• Does knowing a Natural Language well help with Programming?

  - by Earlz

  We all hear that math at least helps a little bit with programming. My question though, does English or other natural language skills help with programming? I know it has to help with technical documentation, but what about actual programming? Are certain constructs in a programming language also there in natural languages? Does knowing how to write a 20 page research paper help with writing a 20k loc programming project?

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• One class per file rule in .NET?

  - by Joan Venge

  I follow this rule but some of my colleagues disagree with it and argue that if a class is smaller it can be left in the same file with other class(es). Another argument I hear all the time is "Even Microsoft don't do this, so why should we?" What's the general consensus on this? Are there cases where this should be avoided?

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• Are upper bounds of indexed ranges always assumed to be exclusive?

  - by polygenelubricants

  So in Java, whenever an indexed range is given, the upper bound is almost always exclusive. From java.lang.String: substring(int beginIndex, int endIndex) Returns a new string that is a substring of this string. The substring begins at the specified beginIndex and extends to the character at index endIndex - 1 From java.util.Arrays: copyOfRange(T[] original, int from, int to) from - the initial index of the range to be copied, inclusive to - the final index of the range to be copied, exclusive. From java.util.BitSet: set(int fromIndex, int toIndex) fromIndex - index of the first bit to be set. toIndex - index after the last bit to be set. As you can see, it does look like Java tries to make it a consistent convention that upper bounds are exclusive. My questions are: Is this the official authoritative recommendation? Are there notable violations that we should be wary of? Is there a name for this system? (ala "0-based" vs "1-based")

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• Building a life-critical System using Agile

  - by Ben Breen

  Looking at the general trend of comments in my question about Building an Aircraft using Agile, the biggest problem other than cost appears to be safety. Do people feel that it is not possible to build a safe system (or prove it is safe) using agile? Doesn’t all the iterative testing mitigate this? Is it likely that a piece of software developed using agile will never be as reliable as counterparts such as waterfall?

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