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  • Single Responsibility Principle vs Anemic Domain Model anti-pattern

    - by Niall Connaughton
    I'm in a project that takes the Single Responsibility Principle pretty seriously. We have a lot of small classes and things are quite simple. However, we have an anemic domain model - there is no behaviour in any of our model classes, they are just property bags. This isn't a complaint about our design - it actually seems to work quite well During design reviews, SRP is brought out whenever new behaviour is added to the system, and so new behaviour typically ends up in a new class. This keeps things very easily unit testable, but I am perplexed sometimes because it feels like pulling behaviour out of the place where it's relevant. I'm trying to improve my understanding of how to apply SRP properly. It seems to me that SRP is in opposition to adding business modelling behaviour that shares the same context to one object, because the object inevitably ends up either doing more than one related thing, or doing one thing but knowing multiple business rules that change the shape of its outputs. If that is so, then it feels like the end result is an Anemic Domain Model, which is certainly the case in our project. Yet the Anemic Domain Model is an anti-pattern. Can these two ideas coexist? EDIT: A couple of context related links: SRP - http://www.objectmentor.com/resources/articles/srp.pdf Anemic Domain Model - http://martinfowler.com/bliki/AnemicDomainModel.html I'm not the kind of developer who just likes to find a prophet and follow what they say as gospel. So I don't provide links to these as a way of stating "these are the rules", just as a source of definition of the two concepts.

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  • C headers: compiler specific vs library specific?

    - by leonbloy
    Is there some clear-cut distinction between standard C *.h header files that are provided by the C compiler, as oppossed to those which are provided by a standard C library? Is there some list, or some standard locations? Motivation: int this answer I got a while ago, regarding a missing unistd.h in the latest TinyC compiler, the author argued that unistd.h (contrarily to sys/unistd.h) should not be provided by the compiler but by your C library. I could not make much sense of that response (for one thing shouldn't that also apply to, say, stdio.h?) but I'm still wondering about it. Is that correct? Where is some authoritative reference for this? Looking in other compilers, I see that other "self contained" POSIX C compilers that are hosted in Windows (like the GCC toolchain that comes with MinGW, in several incarnations; or Digital Mars compiler), include all header files. And in a standard Linux distribution (say, Centos 5.10) I see that the gcc package provides a few header files (eg, stdbool.h, syslimits.h) in /usr/lib/gcc/i386-redhat-linux/4.1.1/include/, and the glibc-headers package provides the majority of the headers in /usr/include/ (including stdio.h, /usr/include/unistd.h and /usr/include/sys/unistd.h). So, in neither case I see support for the above claim.

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  • Clustered index - multi-part vs single-part index and effects of inserts/deletes

    - by Anssssss
    This question is about what happens with the reorganizing of data in a clustered index when an insert is done. I assume that it should be more expensive to do inserts on a table which has a clustered index than one that does not because reorganizing the data in a clustered index involves changing the physical layout of the data on the disk. I'm not sure how to phrase my question except through an example I came across at work. Assume there is a table (Junk) and there are two queries that are done on the table, the first query searches by Name and the second query searches by Name and Something. As I'm working on the database I discovered that the table has been created with two indexes, one to support each query, like so: --drop table Junk1 CREATE TABLE Junk1 ( Name char(5), Something char(5), WhoCares int ) CREATE CLUSTERED INDEX IX_Name ON Junk1 ( Name ) CREATE NONCLUSTERED INDEX IX_Name_Something ON Junk1 ( Name, Something ) Now when I looked at the two indexes, it seems that IX_Name is redundant since IX_Name_Something can be used by any query that desires to search by Name. So I would eliminate IX_Name and make IX_Name_Something the clustered index instead: --drop table Junk2 CREATE TABLE Junk2 ( Name char(5), Something char(5), WhoCares int ) CREATE CLUSTERED INDEX IX_Name_Something ON Junk2 ( Name, Something ) Someone suggested that the first indexing scheme should be kept since it would result in more efficient inserts/deletes (assume that there is no need to worry about updates for Name and Something). Would that make sense? I think the second indexing method would be better since it means one less index needs to be maintained. I would appreciate any insight into this specific example or directing me to more info on maintenance of clustered indexes.

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  • Creating many new instances vs reusing them?

    - by Hugo Riley
    I have multiple business entities in VB.NET Windows Forms application. Right now they are instanced on application startup and used when needed. They hold descriptions of business entities and methods for storing and retrieving data. To cut the long story short, they are somewhat heavy objects to construct (they have some internal dictionaries and references to other objects) created and held in one big global variable called "BLogic". Should I refactor this so that each object is created when needed and released when out of scope? Then every event on UI will probably create a few of this objects. Should I strive to minimize creation of new objects or to minimize number of static and global objects? Generally I am trying to minimize the scope of every variable but should I treat this business logic objects specially?

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  • measuring performance - using real clicks vs "ab" command

    - by shanyu
    I have a web site in closed beta, developed in Django, runs with Mysql on Debian. In the last few days, the main page has been showing a slowdown. For every ten clicks, one or two receives extremely slow response (10 secs or more), others are as fast as they used to be. When I was searching for the problem, I ran into this issue that I couldn't grasp: top command shows that when I request the main page, mysql shoots up to 90% - 100% cpu usage. I get the page just as the cpu use gets back to normal. So, I thought, it is db. Then I called ab with parameters -n 1000 -c 5, I got decent performance, about 100 pages per second, just as it was before the slowdown. I would imagine a worse performance as 10-20% of requests take 10 secs to load. Is this conflict between ab and "real" clicks normal, or am I using ab in a wrong configuration?

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  • Yet another Haskell vs. Scala question

    - by Travis Brown
    I've been using Haskell for several months, and I love it—it's gradually become my tool of choice for everything from one-off file renaming scripts to larger XML processing programs. I'm definitely still a beginner, but I'm starting to feel comfortable with the language and the basics of the theory behind it. I'm a lowly graduate student in the humanities, so I'm not under a lot of institutional or administrative pressure to use specific tools for my work. It would be convenient for me in many ways, however, to switch to Scala (or Clojure). Most of the NLP and machine learning libraries that I work with on a daily basis (and that I've written in the past) are Java-based, and the primary project I'm working for uses a Java application server. I've been mostly disappointed by my initial interactions with Scala. Many aspects of the syntax (partial application, for example) still feel clunky to me compared to Haskell, and I miss libraries like Parsec and HXT and QuickCheck. I'm familiar with the advantages of the JVM platform, so practical questions like this one don't really help me. What I'm looking for is a motivational argument for moving to Scala. What does it do (that Haskell doesn't) that's really cool? What makes it fun or challenging or life-changing? Why should I get excited about writing it?

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  • Ways to call Blocks within Magento: createBlock vs Layout xml file

    - by N. B.
    Context: I'm trying to include Adminhtml blocks in the frontend of the site to replace some of the user account blocks. The first thing I'm trying to do is simply display the block on the correct page. I can replace the entire page by setting the Body of the response inside the controller, but I'm having a hard time including the block in the layout xml file and then calling it within the template. Why would I be able to create an adminhtml/sales_order_grid from Mage_Sales_OrderController using createBlock: $this->getResponse()->setBody($this->getLayout()->createBlock('adminhtml/sales_order_grid')->toHtml()); But not from a frontend layout, using a declaration <block type="adminhtml/sales_order_grid" name="orders_widget"/> within app/design/frontend/default/default/layout/sales.xml The latter produces an error without a stack trace: Fatal error: Call to a member function toHtml() on a non-object in app/code/core/Mage/Core/Model/Layout.php on line 526 Thanks for any guidance!

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  • Mecurial vs Subversion

    - by Jeremy E
    I have a medium sized team of developers who moved to Subversion last December from VSS and I wanted to hear from people who have used both Mecurial and Subversion and get their feedback. What do they really like about Mecurial? What sucks? Is there a better open source tool? I didn't really want to put my devs through the whole source control migration thing again unless it is really worth it. Thanks in advance!

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  • Performance of fopen vs stat

    - by Alex Marshall
    Hello, I'm writing several C programs for an embedded system where every bit of performance we can squeeze out will matter. Part of that is accessing log files. When determining if a file exists, is there any performance difference between using open / fopen, and stat ? I've been using stat on the assumption that it only has to do a quick check against the file system, whereas fopen would have to actually gain access to a file and manipulate internal data structures before returning. Is there any merit to this ?

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  • id vs class selection benchmark

    - by zaf
    Has anybody bench marked selecting elements with id's and class's from CSS and javascript? It would make sense that an element with an id is faster to select than if it had a class even if it was the only element with that class. Do I really need to be concerned?

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  • SQL vs MySQL: Rules about aggregate operations and GROUP BY

    - by Phazyck
    In this book I'm currently reading while following a course on databases, the following example of an illegal query using an aggregate operator is given: Find the name and age of the oldest sailor. Consider the following attempt to answer this query: SELECT S.name, S.age FROM Sailors.S The intent is for this query to return not only the maximum age but also the name of the sailors having that age. However, this query is illegal in SQL--if the SELECT clause uses an aggregate operation, then it must use only aggregate operations unless the query contains a GROUP BY clause! Some time later while doing an exercise using MySQL, I faced a similar problem, and made a mistake similar to the one mentioned. However, MySQL didn't complain and just spit out some tables which later turned out not be what I needed. Is the query above really illegal in SQL, but legal in MySQL, and if so, why is that? In what situation would one need to make such a query?

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  • Advantages/Disadvantages of AIR vs Flex/Web

    - by Lizzan
    Hi all, I'm tasked with writing an application for placing and connecting objects (sort of like a room planner where you can place furniture). I've made a demo using Flash Builder 4 and built it for AIR as a desktop app. Now the client wants the full app, but they and I am unsure whether to continue building it as an AIR app or transform it to a web application using Flex. I tried making a simple conversion of the AIR app to a web app, and most things worked but not all. The things that don't work seem to be simple bugs, though, not complete lack of capability. The capabilities that I'm going to need (except for the modelling) are: Printing of the finished image + a list of the furniture that has been placed A way to save and retrieve finished plans A way to export the list of furniture to Excel format Handling a whole slew of data about the different objects Only the printing has been implemented so far, and seems to work in the web app as well. What advantages/disadvantages are there with the two approaches? Are any of the capabilities I need much worse (or even impossible) to implement in either approach?

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  • Advantages/disadvantages of browser-based interface vs. graphics

    - by Josh
    Hello everyone, I'm in the design phase for a desktop-based application. Because of the nature of this particular application, I believe it would benefit greatly from a web-based approach (i.e., allowing a user to interface with the application through a browser running in kiosk mode) in order to leverage the simplicity of HTML/CSS/JS and the availability of many great JS interface plugins. Does taking this approach (rather than coding in a native or cross-platform graphics library) come with any gotchas?

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  • Repository vs Data Access

    - by vdh_ant
    Hi guys In the context of the n-tier application, is there a difference between what you would consider your data access classes to be and your repositories? I tend to think yes but I just wanted to see what other thought. My thinking is that the job of the repository is just to contain and execute the raw query itself, where as the data access class would create the context, execute the repository (passing in the context), handle mapping the data model to the domain model and return the result back up... What do you guys think? Also do you see any of this changing in a Linq to XML scenario (assuming that you change the context for the relevant XDocument)? Cheers Anthony

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  • New to ASP.NET: Webforms vs MVC2

    - by Sahat
    I am new to ASP.NET Development and can't decide between developing with Webforms or MVC 2. Nevermind the pros and cons of each. I've seen mixed opinions of each. But which method would be the best for someone who has no prior experience in ASP.NET or C#? If your answer is: learn both, then which should I learn first? MVC 2 or Webforms?

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  • emacs-rails vs rinari??

    - by nimms
    Hi all, I'm just coming back to rails coding after a long hiatus. I was using rinari previously but noticed that there's a new version of emacs-rails. Is anyone using either?? Any preferences for one over the other?? What are people using for their rails projects within emacs these days??

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  • SelfReferenceProperty vs. ListProperty Google App Engine

    - by John
    Hi All, I am experimenting with the Google App Engine and have a question. For the sake of simplicity, let's say my app is modeling a computer network (a fairly large corporate network with 10,000 nodes). I am trying to model my Node class as follows: class Node(db.Model): name = db.StringProperty() neighbors = db.SelfReferenceProperty() Let's suppose, for a minute, that I cannot use a ListProperty(). Based on my experiments to date, I can assign only a single entity to 'neighbors' - and I cannot use the "virtual" collection (node_set) to access the list of Node neighbors. So... my questions are: Does SelfReferenceProperty limit you to a single entity that you can reference? If I instead use a ListProperty, I believe I am limited to 5,000 keys, which I need to exceed. Thoughts? Thanks, John

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  • java - POST vs JDBC

    - by Dan
    OK so here's the code: import java.io.BufferedReader; import java.io.InputStreamReader; import java.net.URL; public class Main { public static void main(String[] args) { try { URL my_url = new URL("http://www.viralpatel.net/blogs/"); BufferedReader br = new BufferedReader(new InputStreamReader(my_url.openStream())); String strTemp = ""; while(null != (strTemp = br.readLine())){ System.out.println(strTemp); } } catch (Exception ex) { ex.printStackTrace(); } } } Using this method I can use POST and GET methods using PHP scripts. I can then use the PHP scripts to the MySQL database which in turn outputs back to the java applet. Is this possible? (and safer?) Thanks.

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  • Spring 3.0 vs J2EE 6.0

    - by StudiousJoseph
    Hi everybody, I'm confronted with a situation... I've been asked to give an advise regarding which approach to take, in terms of J2EE development between Spring 3.0 and J2EE 6.0. I was, and still am, a promoter of Spring 2.5 over classic J2EE 5 development, specially with JBoss, I even migrated old apps to Spring and influenced the re-definition of the development policy here to include Spring specific APIs, and helped the development of a strategic plan to foster more lightweight solutions like Spring + Tomcat, instead of the heavier ones of JBoss, right now, we're using JBoss merely as a Web container, having what i call the "container inside the container paradox", that is, having Spring apps, with most of its APIs, running inside JBoss, So we're in the process of migrating to tomcat. However, with the coming of J2EE 6.0 many features, that made Spring attractive at that time, easy deployment, less-coupling, even some sort of D.I, etc, seems to have been mimicked, in one way or the other. JSF 2.0, JPA 2.0, WebBeans, WebProfiles, etc. So, the question goes... From your point of view, how save, and logical, it is to continue to invest in a non-standard J2EE development framework like Spring given the new perspectives offered by J2EE 6.0? Can we talk about maybe 3 or 4 more years of Spring development, or do you recommend early adoption of J2EE 6.0 APIs and it's practices? I'll appreciate any insights with this...

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  • LINQ-to-SQL vs stored procedures?

    - by scottmarlowe
    I took a look at the "Beginner's Guide to LINQ" post here on StackOverflow (http://stackoverflow.com/questions/8050/beginners-guide-to-linq), but had a follow-up question: We're about to ramp up a new project where nearly all of our database op's will be fairly simple data retrievals (there's another segment of the project which already writes the data). Most of our other projects up to this point make use of stored procedures for such things. However, I'd like to leverage LINQ-to-SQL if it makes more sense. So, the question is this: For simple data retrievals, which approach is better, LINQ-to-SQL or stored procs? Any specific pro's or con's? Thanks.

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  • Code Contracts Vs. Object Initializers (.net 4.0)

    - by Mystagogue
    At face value, it would seem that object initializers present a problem for .net 4.0 "code contracts", where normally the invariant should be established by the time the object constructor is finished. Presumably, however, object-initializers require properties to be set after construction is complete. My question is if the invariants of "code contracts" are able to handle object initializers, "as if" the properties were set before the constructor completes? That would be very nice indeed!!

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  • readObject() vs. readResolve() to restore transient fields

    - by Joonas Pulakka
    According to Serializable javadoc, readResolve() is intended for replacing an object read from the stream. But is it OK to use it for restoring transient fields, like so: private Object readResolve() { transientField = something; return this; } as opposed to using readObject(): private void readObject(ObjectInputStream s) { s.defaultReadObject(); transientField = something; } Is there any reason to choose one over other, when used to just restore transient fields?

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