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  • Representing xml through a single class

    - by Charles
    I am trying to abstract away the difficulties of configuring an application that we use. This application takes a xml configuration file and it can be a bit bothersome to manually edit this file, especially when we are trying to setup some automatic testing scenarios. I am finding that reading xml is nice, pretty easy, you get a network of element nodes that you can just go through and build your structures quite nicely. However I am slowly finding that the reverse is not quite so nice. I want to be able to build a xml configuration file through a single easy to use interface and because xml is composed of a system of nodes I am having a lot of struggle trying to maintain the 'easy' part. Does anyone know of any examples or samples that easily and intuitively build xml files without declaring a bunch of element type classes and expect the user to build the network themselves? For example if my desired xml output is like so <cook version="1.1"> <recipe name="chocolate chip cookie"> <ingredients> <ingredient name="flour" amount="2" units="cups"/> <ingredient name="eggs" amount="2" units="" /> <ingredient name="cooking chocolate" amount="5" units="cups" /> </ingredients> <directions> <direction name="step 1">Preheat oven</direction> <direction name="step 2">Mix flour, egg, and chocolate</direction> <direction name="step 2">bake</direction> </directions> </recipe> <recipe name="hot dog"> ... How would I go about designing a class to build that network of elements and make one easy to use interface for creating recipes? Right now I have a recipe object, an ingredient object, and a direction object. The user must make each one, set the attributes in the class and attach them to the root object which assembles the xml elements and outputs the formatted xml. Its not very pretty and I just know there has to be a better way. I am using python so bonus points for pythonic solutions

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  • Searching for the right pattern to handle login data

    - by stevebot
    Hi all, I'm working on a controller that handles logins for a Web app. These logins will come from multiple clients but will all contain the same data. However, depending on the client, this data will be interpreted into common entities for our webapp differently. For instance, we have a user code that gets sent in, and in one case we may use the first four digits of the code, and in another case 12 digits of the code to map to a field on a User entity. Instead of handling this all in the controller and having big nasty if blocks of logic, I would like to use a pattern to handle how this information gets ingested into our application. What are your opinions?

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  • What is this Design Pattern?

    - by Can't Tell
    I read the Wikipedia articles on FactoryMethod and AbstractFactory but the following code doesn't seem to fit anywhere. Can someone explain to me what the following pattern is or if it is an anti-pattern? interace PaymentGateway{ void makePayment(); } class PaypalPaymentGateway implements PaymentGateway { public void makePayment() { //some implementation } } class AuthorizeNetPaymentGateway implements PaymentGateway { public void makePayment() { //some implementation } } class PaymentGatewayFacotry{ PaymentGateway createPaymentGateway(int gatewayId) { if(gatewayId == 1) return PaypalPaymentGateway(); else if(gatewayId == 2) return AuthorizeNetPaymentGateway(); } } Let's say the user selects the payment method using a radio button on an html page and the gatewayId is derived from the radio button value. I have seen code like this and thought it was the AbstractFactory pattern but after reading the Wikipedia article, I'm having doubts.

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  • Dependency Injection & Singleton Design pattern

    - by SysAdmin
    How do we identify when to use dependency injection or singleton pattern. I have read in lot of websites where they say "Use Dependency injection over singleton pattern". But I am not sure if I totally agree with them. For my small or medium scale projects I definitely see the use of singleton pattern straightforward. For example Logger. I could use Logger.GetInstance().Log(...) But, instead of this, why do I need to inject every class I create, with the logger's instance?.

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  • What is the best practice when coding math class/functions ?

    - by Isaac Clarke
    Introductory note : I voluntarily chose a wide subject. You know that quote about learning a cat to fish, that's it. I don't need an answer to my question, I need an explanation and advice. I know you guys are good at this ;) Hi guys, I'm currently implementing some algorithms into an existing program. Long story short, I created a new class, "Adder". An Adder is a member of another class representing the physical object actually doing the calculus , which calls adder.calc() with its parameters (merely a list of objects to do the maths on). To do these maths, I need some parameters, which do not exist outside of the class (but can be set, see below). They're neither config parameters nor members of other classes. These parameters are D1 and D2, distances, and three arrays of fixed size : alpha, beta, delta. I know some of you are more comfortable reading code than reading text so here you go : class Adder { public: Adder(); virtual Adder::~Adder(); void set( float d1, float d2 ); void set( float d1, float d2, int alpha[N_MAX], int beta[N_MAX], int delta[N_MAX] ); // Snipped prototypes float calc( List& ... ); // ... inline float get_d1() { return d1_ ;}; inline float get_d2() { return d2_ ;}; private: float d1_; float d2_; int alpha_[N_MAX]; // A #define N_MAX is done elsewhere int beta_[N_MAX]; int delta_[N_MAX]; }; Since this object is used as a member of another class, it is declared in a *.h : private: Adder adder_; By doing that, I couldn't initialize the arrays (alpha/beta/delta) directly in the constructor ( int T[3] = { 1, 2, 3 }; ), without having to iterate throughout the three arrays. I thought of putting them in static const, but I don't think that's the proper way of solving such problems. My second guess was to use the constructor to initialize the arrays Adder::Adder() { int alpha[N_MAX] = { 0, -60, -120, 180, 120, 60 }; int beta[N_MAX] = { 0, 0, 0, 0, 0, 0 }; int delta[N_MAX] = { 0, 0, 180, 180, 180, 0 }; set( 2.5, 0, alpha, beta, delta ); } void Adder::set( float d1, float d2 ) { if (d1 > 0) d1_ = d1; if (d2 > 0) d2_ = d2; } void Adder::set( float d1, float d2, int alpha[N_MAX], int beta[N_MAX], int delta[N_MAX] ) { set( d1, d2 ); for (int i = 0; i < N_MAX; ++i) { alpha_[i] = alpha[i]; beta_[i] = beta[i]; delta_[i] = delta[i]; } } My question is : Would it be better to use another function - init() - which would initialize arrays ? Or is there a better way of doing that ? My bonus question is : Did you see some mistakes or bad practice along the way ?

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  • small scale web site - global javascript file style/format/pattern - improving maintainability

    - by yaya3
    I frequently create (and inherit) small to medium websites where I have the following sort of code in a single file (normally named global.js or application.js or projectname.js). If functions get big, I normally put them in a seperate file, and call them at the bottom of the file below in the $(document).ready() section. If I have a few functions that are unique to certain pages, I normally have another switch statement for the body class inside the $(document).ready() section. How could I restructure this code to make it more maintainable? Note: I am less interested in the functions innards, more so the structure, and how different types of functions should be dealt with. I've also posted the code here - http://pastie.org/999932 in case it makes it any easier var ProjectNameEnvironment = {}; function someFunctionUniqueToTheHomepageNotWorthMakingConfigurable () { $('.foo').hide(); $('.bar').click(function(){ $('.foo').show(); }); } function functionThatIsWorthMakingConfigurable(config) { var foo = config.foo || 700; var bar = 200; return foo * bar; } function globallyRequiredJqueryPluginTrigger (tooltip_string) { var tooltipTrigger = $(tooltip_string); tooltipTrigger.tooltip({ showURL: false ... }); } function minorUtilityOneLiner (selector) { $(selector).find('li:even').not('li ul li').addClass('even'); } var Lightbox = {}; Lightbox.setup = function(){ $('li#foo a').attr('href','#alpha'); $('li#bar a').attr('href','#beta'); } Lightbox.init = function (config){ if (typeof $.fn.fancybox =='function') { Lightbox.setup(); var fade_in_speed = config.fade_in_speed || 1000; var frame_height = config.frame_height || 1700; $(config.selector).fancybox({ frameHeight : frame_height, callbackOnShow: function() { var content_to_load = config.content_to_load; ... }, callbackOnClose : function(){ $('body').height($('body').height()); } }); } else { if (ProjectNameEnvironment.debug) { alert('the fancybox plugin has not been loaded'); } } } // ---------- order of execution ----------- $(document).ready(function () { urls = urlConfig(); (function globalFunctions() { $('.tooltip-trigger').each(function(){ globallyRequiredJqueryPluginTrigger(this); }); minorUtilityOneLiner('ul.foo') Lightbox.init({ selector : 'a#a-lightbox-trigger-js', ... }); Lightbox.init({ selector : 'a#another-lightbox-trigger-js', ... }); })(); if ( $('body').attr('id') == 'home-page' ) { (function homeFunctions() { someFunctionUniqueToTheHomepageNotWorthMakingConfigurable (); })(); } });

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  • What design pattern to use for one big method calling many private methods

    - by Jeune
    I have a class that has a big method that calls on a lot of private methods. I think I want to extract those private methods into their own classes for one because they contain business logic and I think they should be public so they can be unit tested. Here's a sample of the code: public void handleRow(Object arg0) { if (continueRunning){ hashData=(HashMap<String, Object>)arg0; Long stdReportId = null; Date effDate=null; if (stdReportIds!=null){ stdReportId = stdReportIds[index]; } if (effDates!=null){ effDate = effDates[index]; } initAndPutPriceBrackets(hashData, stdReportId, effDate); putBrand(hashData,stdReportId,formHandlerFor==0?true:useLiveForFirst); putMultiLangDescriptions(hashData,stdReportId); index++; if (stdReportIds!=null && stdReportIds[0].equals(stdReportIds[1])){ continueRunning=false; } if (formHandlerFor==REPORTS){ putBeginDate(hashData,effDate,custId); } //handle logic that is related to pricemaps. lstOfData.add(hashData); } } What design pattern should I apply to this problem?

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  • Conceptually, how does replay work in a game?

    - by SnOrfus
    I was kind of curious as to how replay might be implemented in a game. Initially, I thought that there would be just a command list of every player/ai action that was taken in the game, and it then 're-plays' the game and lets the engine render as usual. However, I have looked at replays in FPS/RTS games, and upon careful inspection even things like the particles and graphical/audible glitches are consistent (and those glitches are generally *in*consistent). So How does this happen. In fixed camera angle games I though it might just write every frame of the whole scene to a stream that gets stored and then just replays the stream back, but that doesn't seem like enough for games that allow you to pause and move the camera around. You'd have to store the locations of everything in the scene at all points in time (No?). So for things like particles, that's a lot of data to push which seems like a significant draw on the game's performance whilst playing.

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  • Is there a more correct type for passing in the file path and file name to a method

    - by Rihan Meij
    Hi What I mean by this question is, when you need to store or pass a URL around, using a string is probably a bad practice, and a better approach would be to use a URI type. However it is so easy to make complex things more complex and bloated. So if I am going to be writing to a file on disk, do I pass it a string, as the file name and file path, or is there a better type that will be better suited to the requirement? This code seems to be clunky, and error prone? I would also need to do a whole bit of checking if it is a valid file name, if the string contains data and the list goes on. private void SaveFile(string fileNameAndPath) { //The normal stuff to save the file }

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  • Why are there magic attributes exposed in the Servlet spec?

    - by Brabster
    It's always seemed a little at odds with the principles of Java that the Java Servlet Spec (2.5 version here) includes a set of magic attributes containing info about included resources, namely: javax.servlet.include.request_uri javax.servlet.include.context_path javax.servlet.include.servlet_path javax.servlet.include.path_info javax.servlet.include.query_string It's not even specifically pointed out in the API documentation, only in the spec where it is a must for correct implementation. This approach feels very wrong, an exposed implementation detail that clients will use and depend on. Why is this information exposed in this way?

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  • How to refactor this Ruby on Rails code?

    - by yuval
    I want to fetch posts based on their status, so I have this code inside my PostsController index action. It seems to be cluttering the index action, though, and I'm not sure it belongs here. How could I make it more concise and where would I move it in my application so it doesn't clutter up my index action (if that is the correct thing to do)? if params[:status].empty? status = 'active' else status = ['active', 'deleted', 'commented'].include?(params[:status]) ? params[:status] : 'active' end case status when 'active' #active posts are not marked as deleted and have no comments is_deleted = false comments_count_sign = "=" when 'deleted' #deleted posts are marked as deleted and have no comments is_deleted = true comments_count_sign = "=" when 'commented' #commented posts are not marked as deleted and do have comments is_deleted = false comments_count_sign = ">" end @posts = Post.find(:all, :conditions => ["is_deleted = ? and comments_count_sign #{comments_count_sign} 0", is_deleted])

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  • Arranging VS2008 generated LinqToSql/EntityFramework data models/contexts in assemblies.

    - by JMSA
    What pattern should I use for data-access in case of VS2008 generated L2s or EF DataModels? Repository-pattern or what? As we know VS2008 generates Data-Models and DataContexts/ObjectContexts in the same file, then, how should I arrange my VS2008 assemblies in my VS2008 solution to achieve a layered design? If I use repository pattern, how should I arrange my assemblies in the VS2008 solution (as Data-Models and Data/Object-Contexts are stored in the same file...)? Any web/example link would be appreciated.

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  • How should my team decide between 3-tier and 2-tier architectures?

    - by j0rd4n
    My team is discussing the future direction we take our projects. Half the team believes in a pure 3-tier architecture while the other half favors a 2-tier architecture. Project Assumptions: Enterprise business applications Business logic needed between user and database Data validation necessary Service-oriented (prefer RESTful services) Multi-year maintenance plan Support hundreds of users 3-tier Team Favors: Persistant layer <== Domain layer <== UI layer Service boundary between at least persistant layer and domain layer. Domain layer might have service boundary between it. Translations between each layer (clean DTO separation) Hand roll persistance unless we can find creative yet elegant automation 2-tier Team Favors: Entity Framework + WCF Data Service layer <== UI layer Business logic kept in WCF Data Service interceptors Minimal translation between layers - favor faster coding So that's the high-level argument. What considerations should we take into account? What experiences have you had with either approach?

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  • How to expose a constructor variable(sic!) as read-only?

    - by Malax
    Hi StackOverflow! I have this rather simple question about Scala. Given that i have to following class definition: class Foo(var bar: Int) The code which is able to construct an instance of Foo must be able to pass the initial value for bar. But if I define bar as var the User is also able to change its value at runtime which is not what I want. The User should only be able to read bar. bar itself is modified internally so a val is not an option. I think I might be getting an answer very soon as this question is so simple. :-) Cheers, Malax

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  • In .NET which loop runs faster for or foreach

    - by Binoj Antony
    In c#/VB.NET/.NET which loop runs faster for or foreach? Ever since I read that for loop works faster than foreach a long time ago I assumed it stood true for all collections, generic collection all arrays etc. I scoured google and found few articles but most of them are inconclusive (read comments on the articles) and open ended. What would be ideal is to have each scenarios listed and the best solution for the same e.g: (just example of how it should be) for iterating an array of 1000+ strings - for is better than foreach for iterating over IList (non generic) strings - foreach is better than for Few references found on the web for the same: Original grand old article by Emmanuel Schanzer CodeProject FOREACH Vs. FOR Blog - To foreach or not to foreach that is the question asp.net forum - NET 1.1 C# for vs foreach [Edit] Apart from the readability aspect of it I am really interested in facts and figures, there are applications where the last mile of performance optimization squeezed do matter.

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  • Does it ever make sense to make a fundamental (non-pointer) parameter const?

    - by Scott Smith
    I recently had an exchange with another C++ developer about the following use of const: void Foo(const int bar); He felt that using const in this way was good practice. I argued that it does nothing for the caller of the function (since a copy of the argument was going to be passed, there is no additional guarantee of safety with regard to overwrite). In addition, doing this prevents the implementer of Foo from modifying their private copy of the argument. So, it both mandates and advertises an implementation detail. Not the end of the world, but certainly not something to be recommended as good practice. I'm curious as to what others think on this issue. Edit: OK, I didn't realize that const-ness of the arguments didn't factor into the signature of the function. So, it is possible to mark the arguments as const in the implementation (.cpp), and not in the header (.h) - and the compiler is fine with that. That being the case, I guess the policy should be the same for making local variables const. One could make the argument that having different looking signatures in the header and source file would confuse others (as it would have confused me). While I try to follow the Principle of Least Astonishment with whatever I write, I guess it's reasonable to expect developers to recognize this as legal and useful.

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  • Javascript clarity of purpose

    - by JesDaw
    Javascript usage has gotten remarkably more sophisticated and powerful in the past five years. One aspect of this sort of functional programming I struggle with, esp with Javascript’s peculiarities, is how to make clear either through comments or code just what is happening. Often this sort of code takes a while to decipher, even if you understand the prototypal, first-class functional Javascript way. Any thoughts or techniques for making perfectly clear what your code does and how in Javascript? I've asked this question elsewhere, but haven't gotten much response.

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  • Should I make sure arguments aren't null before using them in a function.

    - by Nathan W
    The title may not really explain what I'm really trying to get at, couldn't really think of a way to describe what I mean. I was wondering if it is good practice to check the arguments that a function accepts for nulls or empty before using them. I have this function which just wraps some hash creation like so. Public Shared Function GenerateHash(ByVal FilePath As IO.FileInfo) As String If (FilePath Is Nothing) Then Throw New ArgumentNullException("FilePath") End If Dim _sha As New Security.Cryptography.MD5CryptoServiceProvider Dim _Hash = Convert.ToBase64String(_sha.ComputeHash(New IO.FileStream(FilePath.FullName, IO.FileMode.Open, IO.FileAccess.Read))) Return _Hash End Function As you can see I just takes a IO.Fileinfo as an argument, at the start of the function I am checking to make sure that it is not nothing. I'm wondering is this good practice or should I just let it get to the actual hasher and then throw the exception because it is null.? Thanks.

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  • Learning Javascript in one weekend?

    - by dueyfinster
    Similiar to this question, I am wondering if experienced Javascript developers have any websites they use with examples to get the basics of Javascript down in 24/28 hours? I have looked at Douglas Crockford's Google Tech Talk and I bought the book "Javascript: the good parts" but I haven't had time to read it.

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  • Delphi: How to avoid EIntOverflow underflow when subtracting?

    - by Ian Boyd
    Microsoft already says, in the documentation for GetTickCount, that you could never compare tick counts to check if an interval has passed. e.g.: Incorrect (pseudo-code): DWORD endTime = GetTickCount + 10000; //10 s from now ... if (GetTickCount > endTime) break; The above code is bad because it is suceptable to rollover of the tick counter. For example, assume that the clock is near the end of it's range: endTime = 0xfffffe00 + 10000 = 0x00002510; //9,488 decimal Then you perform your check: if (GetTickCount > endTime) Which is satisfied immediatly, since GetTickCount is larger than endTime: if (0xfffffe01 > 0x00002510) The solution Instead you should always subtract the two time intervals: DWORD startTime = GetTickCount; ... if (GetTickCount - startTime) > 10000 //if it's been 10 seconds break; Looking at the same math: if (GetTickCount - startTime) > 10000 if (0xfffffe01 - 0xfffffe00) > 10000 if (1 > 10000) Which is all well and good in C/C++, where the compiler behaves a certain way. But what about Delphi? But when i perform the same math in Delphi, with overflow checking on ({Q+}, {$OVERFLOWCHECKS ON}), the subtraction of the two tick counts generates an EIntOverflow exception when the TickCount rolls over: if (0x00000100 - 0xffffff00) > 10000 0x00000100 - 0xffffff00 = 0x00000200 What is the intended solution for this problem? Edit: i've tried to temporarily turn off OVERFLOWCHECKS: {$OVERFLOWCHECKS OFF}] delta = GetTickCount - startTime; {$OVERFLOWCHECKS ON} But the subtraction still throws an EIntOverflow exception. Is there a better solution, involving casts and larger intermediate variable types?

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  • How to check for undefined or null variable in javascript

    - by Thomas Wanner
    We are frequently using the following code pattern in our javascript code if(typeof(some_variable) != 'undefined' && some_variable != null) { // do something with some_variable } and I'm wondering whether there is a less verbose way of checking that has the same effect. According to some forums and literature saying simply if(some_variable) { // do something with some_variable } should have the same effect. Unfortunately, Firebug evaluates such a statement as error on runtime when some_variable is undefined, whereas the first one is just fine for him. Is this only an (unwanted) behavior of Firebug or is there really some difference between those two ways ?

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  • Truth tables in code? How to structure state machine?

    - by HanClinto
    I have a (somewhat) large truth table / state machine that I need to implement in my code (embedded C). I anticipate the behavior specification of this state machine to change in the future, and so I'd like to keep this easily modifiable in the future. My truth table has 4 inputs and 4 outputs. I have it all in an Excel spreadsheet, and if I could just paste that into my code with a little formatting, that would be ideal. I was thinking I would like to access my truth table like so: u8 newState[] = decisionTable[input1][input2][input3][input4]; And then I could access the output values with: setOutputPin( LINE_0, newState[0] ); setOutputPin( LINE_1, newState[1] ); setOutputPin( LINE_2, newState[2] ); setOutputPin( LINE_3, newState[3] ); But in order to get that, it looks like I would have to do a fairly confusing table like so: static u8 decisionTable[][][][][] = {{{{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }}, {{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }}}, {{{ 0, 0, 1, 1 }, { 0, 1, 1, 1 }}, {{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}}}, {{{{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}, {{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}}, {{{ 0, 1, 1, 1 }, { 0, 1, 1, 1 }}, {{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}}}; Those nested brackets can be somewhat confusing -- does anyone have a better idea for how I can keep a pretty looking table in my code? Thanks! Edit based on HUAGHAGUAH's answer: Using an amalgamation of everyone's input (thanks -- I wish I could "accept" 3 or 4 of these answers), I think I'm going to try it as a two dimensional array. I'll index into my array using a small bit-shifting macro: #define SM_INPUTS( in0, in1, in2, in3 ) ((in0 << 0) | (in1 << 1) | (in2 << 2) | (in3 << 3)) And that will let my truth table array look like this: static u8 decisionTable[][] = { { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 1, 1 }, { 0, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }, { 0, 1, 1, 1 }, { 0, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }}; And I can then access my truth table like so: decisionTable[ SM_INPUTS( line1, line2, line3, line4 ) ] I'll give that a shot and see how it works out. I'll also be replacing the 0's and 1's with more helpful #defines that express what each state means, along with /**/ comments that explain the inputs for each line of outputs. Thanks for the help, everyone!

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  • Simple network gaming, client-server architecture planning.

    - by michal
    Hi, I'm coding simple game which I plan to make multiplayer (over the network) as my university project. I'm considering two scenarios for client-server communication: The physics (they're trivial! I should call it "collision tests" in fact :) ) are processed on server machine only. Therefore the communication looks like Client1->Server: Pressed "UP" Server->Clients: here you go, Client1 position is now [X,Y] Client2->Server: Pressed "fire" Server->Clients: Client1 hit Client2, make Client2 disappear! server receives the event and broadcasts it to all the other clients. Client1->Server: Pressed "UP" Server->Clients: Client1 pressed "UP", recalculate his position!! [Client1 receives this one as well!] Which one is better? Or maybe none of them? :)

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  • design decision between array or object save in database

    - by justjoe
    i code some configuration setting. And need those values to be load, everytime my webapp start. yes, it's somekind autoload setting. But, right now, i have to choose between save it as object or array. is there any different between them when we save them in database ? which one is faster or maintainable or other pro and cons thanks

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