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  • Why should I abstract my data layer?

    - by Gazillion
    OOP principles were difficult for me to grasp because for some reason I could never apply them to web development. As I developed more and more projects I started understanding how some parts of my code could use certain design patterns to make them easier to read, reuse, and maintain so I started to use it more and more. The one thing I still can't quite comprehend is why I should abstract my data layer. Basically if I need to print a list of items stored in my DB to the browser I do something along the lines of: $sql = 'SELECT * FROM table WHERE type = "type1"';' $result = mysql_query($sql); while($row = mysql_fetch_assoc($result)) { echo '<li>'.$row['name'].'</li>'; } I'm reading all these How-Tos or articles preaching about the greatness of PDO but I don't understand why. I don't seem to be saving any LoCs and I don't see how it would be more reusable because all the functions that I call above just seem to be encapsulated in a class but do the exact same thing. The only advantage I'm seeing to PDO are prepared statements. I'm not saying data abstraction is a bad thing, I'm asking these questions because I'm trying to design my current classes correctly and they need to connect to a DB so I figured I'd do this the right way. Maybe I'm just reading bad articles on the subject :) I would really appreciate any advice, links, or concrete real-life examples on the subject!

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  • Why is DivMod Limited to Words (<=65535)?

    - by Andreas Rejbrand
    In Delphi, the declaration of the DivMod function is procedure DivMod(Dividend: Cardinal; Divisor: Word; var Result, Remainder: Word); Thus, the divisor, result, and remainder cannot be grater than 65535, a rather severe limitation. Why is this? Why couldn't the delcaration be procedure DivMod(Dividend: Cardinal; Divisor: Cardinal; var Result, Remainder: Cardinal); The procedure is implemented using assembly, and is therefore probably extremely fast. Would it not be possible for the code PUSH EBX MOV EBX,EDX MOV EDX,EAX SHR EDX,16 DIV BX MOV EBX,Remainder MOV [ECX],AX MOV [EBX],DX POP EBX to be adapted to cardinals? How much slower is the naïve attempt procedure DivModInt(const Dividend: integer; const Divisor: integer; out result: integer; out remainder: integer); begin result := Dividend div Divisor; remainder := Dividend mod Divisor; end; that is not (?) limited to 16-bit integers?

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  • why it makes ie6 or ie8 compatible mode crash

    - by hylin
    Anybody can tell me why those code can make ie6 or ie8 compatible mode crash? PS:I know,there is so many ways to avoid this satuation, but I just want to know why. To avoid: Change class="wrapper"--class="wrapper2" or other != "wrapper" $('wrapper').style.overflow='visible'; -- setTimeout(function(){$('wrapper').style.overflow='visible';},10); Or remove any style , js operation... <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <style>.wrapper{width:975px;margin:60px auto 0}</style> </head> <body id="wrapper" style="overflow:hidden;"> <div id="overlay" style="position:absolute;"></div> <div class="wrapper"> <input type="text" id="input1"/> <a id="btn" href="javascript:;">test</a> </div> <script type="text/javascript"> $('btn').onclick = function(){ $('overlay').style.display='none'; $('wrapper').style.overflow='visible'; $("input1").focus(); } function $(s){ return document.getElementById(s); } </script> </body> </html>

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  • Why do you program? Why do you do what you do? [closed]

    - by Pirate for Profit
    To me, writing a new program is like a puzzle. Before you write any code for a large system, you have to carefully craft each piece in your mind and imagine how all the pieces will fit together. If you don't, your solution may end up being undefined. What I mean is, I often don't know what I'm doing so I'll come to this site and beg for a code snippet, and then somehow try to hack it into my projects. I started writing GW-Basic when I was around 8 years old. Then it progressed from there, went to california university and did some Python and C++, but really didn't learn anything(college = highsk00l++). I've mostly been self-taught, took awhile to break bad habits and I'd say only in recent years would I consider myself understanding of design patterns and all that stuff (no but honestly procedural dudes, I would not want to design and maintain a large system procedurally, yous crazy). And despite my username, money has NOT been a big motivator. I've gone from job to job, I can usually get the work done perfect very quickly, any delays on my part are understandable (well about as understandable as it gets in the industry). But I ain't gonna work for peanuts because I got mouths to feed. Why do you program? Why do you do what you do?

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  • Template neglects const (why?)

    - by Gabriel
    Does somebody know, why this compiles?? template< typename TBufferTypeFront, typename TBufferTypeBack = TBufferTypeFront> class FrontBackBuffer{ public: FrontBackBuffer( const TBufferTypeFront front, const TBufferTypeBack back): ////const reference assigned to reference??? m_Front(front), m_Back(back) { }; ~FrontBackBuffer() {}; TBufferTypeFront m_Front; ///< The front buffer TBufferTypeBack m_Back; ///< The back buffer }; int main(){ int b; int a; FrontBackBuffer<int&,int&> buffer(a,b); // buffer.m_Back = 33; buffer.m_Front = 55; } I compile with GCC 4.4. Why does it even let me compile this? Shouldn't there be an error that I cannot assign a const reference to a non-const reference?

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  • Why is Attributes.IsDefined() missing overloads?

    - by Hans Passant
    Inspired by an SO question. The Attribute class has several overloads for the IsDefined() method. Covered are attributes applied to Assembly, Module, MemberInfo, ParameterInfo. The MemberInfo overload covers PropertyInfo, FieldInfo, EventInfo, MethodInfo, ConstructorInfo. That takes care of most of the AttributeTargets. Except for one biggy: there is no overload for Attribute.IsDefined(Type, Type) so that you could check if an attribute is defined on a class. Or a struct, delegate or enum for that matter. Not that this is a real problem, Type.GetCustomAttributes() can fix that. But all of the BlahInfo types have this too. I wonder at the lack of symmetry. I can't put a finger on why this would be problem for Type. Guessing at an inheritance problem doesn't explain it to me. Having ValueType in the mix might be a lead, still doesn't make sense. I don't buy "they forgot", they never do. Why is this overload missing?

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  • Why extremely occasionally will one of bof/eof be true for a new non-empty recordset

    - by jjb
    set recordsetname = databasename.openrecordset(SQLString) if recordsetname.bof <> true and recordsetname.eof <> true then 'do something end if 2 questions : the above test can evaluate to false incorrectly but only extremely rarely (I've had one lurking in my code and it failed today, I believe for the first time in 5 years of daily use-that's how I found it). Why very occasionally will one of bof/eof be true for a non-empty recordset. It seems so rare that I wonder why it occurs at all. Is this a foolproof replacement: if recordsetname.bof <> true or recordsetname.eof <> true then Edit to add details of code : Customers have orders, each order begins with a BeginOrder item and end with an EndOrder item and in between are the items in the order. The SQL is: ' ids are autoincrement long integers ' SQLString = "select * from Orders where type = OrderBegin or type = OrderEnd" Dim OrderOpen as Boolean OrderOpen = False Set rs = db.Openrecordset(SQLString) If rs.bof <> True And rs.eof <> True Then myrec.movelast If rs.fields("type").value = BeginOrder Then OrderOpen = True End If End If If OrderOpen F False Then 'code here to add new BeginOrder Item to Orders table ' End If ShowOrderHistory 'displays the customer's Order history ' In this case which looks this this BeginOrder Item a Item b ... Item n EndOrder BeginOrder Item a Item b ... Item n EndOrder BeginOrder Item a item b ... Item m BeginOrder <----should not be there as previous order still open

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  • Why aren't Java's generics implicitly polymorphic?

    - by froadie
    I'm a bit confused about how Java generics handle inheritance / polymorphism. Assume the following hierarchy - Animal (Parent) Dog - Cat (Children) So suppose I have a method doSomething(List<Animal> animals). By all the rules of inheritance and polymorphism, I would assume that a List<Dog> is a List<Animal> and a List<Cat> is a List<Animal> - and so either one could be passed to this method. Not so. If I want to achieve this behavior, I have to explicitly tell the method to accept a list of any subset of Animal by saying doSomething(List<? extends Animal> animals). I understand that this is Java's behavior. My question is why? Why is polymorphism generally implicit, but when it comes to generics it must be specified?

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  • Why Is Java Missing Access Specifiers?

    - by Tom Tresansky
    Does anyone understand why Java is missing: An access specifier which allows access by the class and all subclasses, but NOT by other classes in the same package? (Protected-minus) An access specifier which allows access by the class, all classes in the same package, AND all classes in any sub-package? (Default-plus) An access specifier which adds classes in sub-packages to the entities currently allowed access by protected? (Protected-plus) I wish I had more choices than protected and default. In particular, I'm interested in the Protected-plus option. Say I want to use a Builder/Factory patterned class to produce an object with many links to other objects. The constructors on the objects are all default, because I want to force you to use the factory class to produce instances, in order to make sure the linking is done correctly. I want to group the factories in a sub-package to keep them all together and distinct from the objects they are instantiating---this just seems like a cleaner package structure to me. No can do, currently. I have to put the builders in the same package as the objects they are constructing, in order to gain the access to defaults. But separating project.area.objects from project.area.objects.builders would be so nice. So why is Java lacking these options? And, is there anyway to fake it?

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  • why is Active Record firing extra query when I use Includes method to fetch data

    - by riddhi_agrawal
    I have the following model structure: class Group < ActiveRecord::Base has_many :group_products, :dependent => :destroy has_many :products, :through => :group_products end class Product < ActiveRecord::Base has_many :group_products, :dependent => :destroy has_many :groups, :through => :group_products end class GroupProduct < ActiveRecord::Base belongs_to :group belongs_to :product end I wanted to minimize my database queries so I decided to use includes.In the console I tried something like, groups = Group.includes(:products) my development logs show the following calls, Group Load (403.0ms) SELECT `groups`.* FROM `groups` GroupProduct Load (60.0ms) SELECT `group_products`.* FROM `group_products` WHERE (`group_products`.group_id IN (1,3,14,15,16,18,19,20,21,22,23,24,25,26,27,28,29,30,33,42,49,51)) Product Load (22.0ms) SELECT `products`.* FROM `products` WHERE (`products`.`id` IN (382,304,353,12,63,103,104,105,262,377,263,264,265,283,284,285,286,287,302,306,307,308,328,335,336,337,340,355,59,60,61,247,309,311,66,30,274,294,324,350,140,176,177,178,64,240,327,332,338,380,383,252,254,255,256,257,325,326)) Product Load (10.0ms) SELECT `products`.* FROM `products` WHERE (`products`.`id` = 377) LIMIT 1 I could analyze the initial three calls were necessary but don't get the reason why the last database call is made, Product Load (10.0ms) SELECT `products`.* FROM `products` WHERE (`products`.`id` = 377) LIMIT 1 Any idea why this is happening? Thanks in advance. :)

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  • Why exactly is eval evil?

    - by Jay
    I know that Lisp and Scheme programmers usually say that eval should be avoided unless strictly necessary. I´ve seen the same recommendation for several programming languages, but I´ve not yet seen a list of clear arguments against the use of eval. Where can I find an account of the potential problems of using eval? For example, I know the problems of GOTO in procedural programming (makes programs unreadable and hard to maintain, makes security problems hard to find, etc), but I´ve never seen the arguments against eval. Interestingly, the same arguments against GOTO should be valid against continuations, but I see that Shemers, for example, won´t say that continuations are "evil" -- you should just be careful when using them. They´re much more likely to frown upon code using eval than upon code using continuations (as far as I can see -- I could be wrong).

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  • Why to store username and password in Keychain in iPhone app

    - by Suriya
    I have worked with NSUserDefault but this keychain concept is totally new for me. I have tried looking for similar Questions but couldn't find the exact reason to do so. What I have done: I already know how to store data in NSUserDefault. and also the reason why do we need to store it. Regarding Keychain I just know that storing in keychain stores the data with some extra security by encoding the original text while NSUserDefault stores the data as plain text. Is this the only reason for storing the data in keychain?

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  • Why my WCF Service returns xml serialized objects?

    - by user294554
    Hi, I'm new here and I hope anyonte can help me. I have WCF Service and Windows Forms working with this client written in VB.NET. The Service class started to return xml serialized objects, but all my classes on Service side are DataContract-s and the service class is DataContractFormat. I googled everywhere about serializations and I couldn't find reason why it started to do that. I checked my classes and service, app.config file, but I couldn't find anything. I checked Reference.vb class, and it's System.Xml.Serialization.XmlElementAttribute everywhere. The question may seem dummy, but I really don't know what to do. I just want to know what can cause the service to act like that. Thank you.

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  • Why self.view is not available

    - by amok
    I have this code in the main view controller and it is working just fine and as I wanted. loadingActionSheet = [[UIActionSheet alloc] initWithTitle:@"Posting To Twitter..." delegate:nil cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:nil]; [loadingActionSheet showInView:self.view]; I wanted that code to be reusable from different part of the project so I moved it in a separate file (UIView based). The poblem that I am facing is that self.view is not available there and I don't know why because I am learning and I don't know enough to understand what I am missing. What do I have to do/add/change to have the actionsheet shown in my current view even if that code lives somewhere else?

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  • Why is checking in files called a 'commit'?

    - by Kjetil Klaussen
    The act of checking in files in a source control repository like git, mercurial or svn, is called a commit. Does anyone know the reason behind calling it a commit instead of just check in? English is not my mother tongue, so it might be some linguistic I don't quite get her, but what I'm I actually commiting to? (Hopefully I'm not commiting a crime, but you'll never know.) Is it in the meaning of "to consign for preservation"? Is it related to transactions (commit at the end of a transaction)?

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  • Weblogic server: Why response sent prior to post completion

    - by markn
    When analyzing traffic with a packet sniffer, we are seeing an http response from a weblogic server prior to the completion of the http post to that server. In this case, the jsp page on the server is basically a static page, no logic to do anything with the contents of the post at this time. But why would the server send the response prior to completion of the post? I found Weblogic documentation about how to configure the server to ignore a denial-of-service attack using Http post. Maybe that is what is happening? No one I know has seen this behaviour before. Maybe some weblogic-savvy person will know what is going on. Thanks

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  • why are javascript functions like this

    - by Kajal
    I am a starter to javascript. I know to write JS userdefined functions. But recently I came across some thing that I can’t recognize. Can anyone explain to me what this is? (function( window, undefined ) { var jQuery = (function() { }); window.jQuery = window.$ = jQuery; })(window); What is the meaning of this? When I Google javascript functions I am getting only function foo(){ alert("This is an alert"); } I know to use these type of functions

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  • Why System.String's beahaves like a value type?

    - by Sorush Rabiee
    I want to write a 'Date' class that behaves like a Value Type. for example, Instead of writing a Clone method for setting properties safely, make the Date class to pass by value: public Date Birthday { get { return this.birthday; } set { this.birthday = value.Clone(); } //I want to write this.birthday = value; //without changing external value when this.Birthday changes } I know this is possible because System.String is a class and behaves like a value. for example: String s1 = "Hello"; String s2 = "Hi"; s1 = s2; s2="Hello"; Console.WriteLine(s1); //Prints 'Hi' First I thought writers of this class override '=' operator, but now I know that the '=' operator can not be overridden. so how they write String class?

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  • What do you need to know to be a world-class master software developer? [closed]

    - by glitch
    I wanted to bring up this question to you folks and see what you think, hopefully advise me on the matter: let's say you had 30 years of learning and practicing software development in front of you, how would you dedicate your time so that you'd get the biggest bang for your buck. What would you both learn and work on to be a world-class software developer that would make a large impact on the industry and leave behind a legacy? I think that most great developers end up being both broad generalists and specialists in one-two areas of interest. I'm thinking Bill Joy, John Carmack, Linus Torvalds, K&R and so on. I'm thinking that perhaps one approach would be to break things down by categories and establish a base minimum of "software development" greatness. I'm thinking: Operating Systems: completely internalize the core concepts of OS, perhaps gain a lot of familiarity with an OSS one such as Linux. Anything from memory management to device drivers has to be complete second nature. Programming Languages: this is one of those topics that imho has to be fully grokked even if it might take many years. I don't think there's quite anything like going through the process of developing your own compiler, understanding language design trade-offs and so on. Programming Language Pragmatics is one of my favorite books actually, I think you want to have that internalized back to back, and that's just the start. You could go significantly deeper, but I think it's time well spent, because it's such a crucial building block. As a subset of that, you want to really understand the different programming paradigms out there. Imperative, declarative, logic, functional and so on. Anything from assembly to LISP should be at the very least comfortable to write in. Contexts: I believe one should have experience working in different contexts to truly be able to appreciate the trade-offs that are being made every day. Embedded, web development, mobile development, UX development, distributed, cloud computing and so on. Hardware: I'm somewhat conflicted about this one. I think you want some understanding of computer architecture at a low level, but I feel like the concepts that will truly matter will be slightly higher level, such as CPU caching / memory hierarchy, ILP, and so on. Networking: we live in a completely network-dependent era. Having a good understanding of the OSI model, knowing how the Web works, how HTTP works and so on is pretty much a pre-requisite these days. Distributed systems: once again, everything's distributed these days, it's getting progressively harder to ignore this reality. Slightly related, perhaps add solid understanding of how browsers work to that, since the world seems to be moving so much to interfacing with everything through a browser. Tools: Have a really broad toolset that you're familiar with, one that continuously expands throughout the years. Communication: I think being a great writer, effective communicator and a phenomenal team player is pretty much a prerequisite for a lot of a software developer's greatness. It can't be overstated. Software engineering: understanding the process of building software, team dynamics, the requirements of the business-side, all the pitfalls. You want to deeply understand where what you're writing fits from the market perspective. The better you understand all of this, the more of your work will actually see the daylight. This is really just a starting list, I'm confident that there's a ton of other material that you need to master. As I mentioned, you most likely end up specializing in a bunch of these areas as you go along, but I was trying to come up with a baseline. Any thoughts, suggestions and words of wisdom from the grizzled veterans out there who would like to share their thoughts and experiences with this? I'd really love to know what you think!

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  • Why "no projects found to import"?

    - by Roman
    I am trying to "import existing project into workspace". As the "root directory" I select the directory where all my .java (and .class) files are located. Eclipse writes me that "no projects are found to import". Why?

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  • Why do many software projects fail today?

    - by TomTom
    As long as there are software projects, the world is wondering why they fail so often. I would like to know if there is a list or something equivalent which shows how many software projects fail today. Would be nice if there would be a comparison over the last 20 - 30 years. You can also add your top reason why a software project fails. Mine is "Requirements are poor or not even existing." which includes also "No (real) customer / user involved". EDIT: It is nearly impossible to clearly define the term "fail". Let's say that fail means: The project was more than 10% over budget and time. In my opinion the 10% + / - is a good range for an offer / tender. EDIT: Until now (Feb 11) it seems that most posters agree that a fail of the project is basically a failure of the project management (whatever fail means). But IMHO it comes out, that most developers are not happy with this situation. Perhaps because not the manager get penalized when a project was not successful, but the lazy, incompetent developer teams? When I read the posts I can also hear-out that there is a big "gap" between the developer side and the managment side. The expectations (perhaps also the requirements) seem to be so different, that a project cannot be successful in the end (over time / budget; users are not happy; not all first-prio features implemented; too many bugs because developers were forced to implement in too short timeframes ...) I',m asking myself: How can we improve it? Or do we have the possibility to improve it? Everybody seems to be unsatisfied with the way it goes now. Can we close the gap between these two worlds? Should we (the developers) go on strike and fight for "high quality reqiurements" and "realistic / iteration based time shedules"? EDIT: Ralph Westphal and Stefan Lieser have founded a new "community" called: Clean-Code-Developer. The aim of the group is to bring more professionalism into software engineering. Independently if a developer has a degree or tons of years of experience you can be part of this movement. Clean Code Developers live principles like SOLID every day. A professional developer is the biggest reviewer of his own work. And he has an internal value system which helps him to improve and become better. Check it out on: Clean Code Developer EDIT: Our company is doing at the moment a thing called "Application Development and Maintenance Benchmarking". This is a service offered by IBM to get a feedback from someone external on your software engineering process quality etc. When we get the results, I will tell you more about it.

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  • two's complement, why the name "two"

    - by lenatis
    i know unsigned,two's complement, ones' complement and sign magnitude, and the difference between these, but what i'm curious about is: why it's called two's(or ones') complement, so is there a more generalize N's complement? in which way did these genius deduce such a natural way to represent negative numbers?

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  • Why is a DataGridView so row-centric.

    - by Spike
    Why is there a DataGridViewRow.Cells property, but not a DataGridViewColumn.Cells property? What's so important about rows that I'll never want to iterate down a column? I'm not saying that it makes it particularly difficult to do or anything, it just strikes me as oddly asymmetrical. I'm implementing a "fill down" type behaviour, and it'd be handy is all.

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