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  • C# Retrieving Data From XML File

    - by Christopher MacKinnon
    I seem to be having a problem with retrieving XML values with C#, which I know it is due to my very limited knowledge of C# and .XML. I was given the following XML file <PowerBuilderRunTimes> <PowerBuilderRunTime> <Version>12</Version> <Files> <File>EasySoap110.dll</File> <File>exPat110.dll</File> <File>pbacc110.dll</File> </File> </PowerBuilderRunTime> </PowerBuilderRunTimes> I am to process the XML file and make sure that each of the files in the exist in the folder (that's the easy part). It's the processing of the XML file that I have having a hard time with. Here is what I have done thus far: var runtimeXml = File.ReadAllText(string.Format("{0}\\{1}", configPath, Resource.PBRuntimes)); var doc = XDocument.Parse(runtimeXml); var topElement = doc.Element("PowerBuilderRunTimes"); var elements = topElement.Elements("PowerBuilderRunTime"); foreach (XElement section in elements) { //pbVersion is grabbed earlier. It is the version of PowerBuilder if( section.Element("Version").Value.Equals(string.Format("{0}", pbVersion ) ) ) { var files = section.Elements("Files"); var fileList = new List<string>(); foreach (XElement area in files) { fileList.Add(area.Element("File").Value); } } } My issue is that the String List is only ever populated with one value, "EasySoap110.dll", and everything else is ignored. Can someone please help me, as I am at a loss.

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  • Performance of Multiple Joins

    - by geeko
    Greetings Overflowers, I need to query against objects with many/complex spacial conditions. In relational databases that is translated to many joins (possibly 10+). I'm new to this business and wondering whether to go with MS SQL Server 2008 R2 or Oracle 11g or document-based solutions such as RavenDB or simply go with some spacial database (GIS)... Any thoughts ? Regards UPDATE: Thank you all for your answers. Would anybody opt for document/spatial databases ? My database would consist of tens of millions to few billion records. Mostly read-only. Almost no updates unless in case of mistakes in input. Overnight inserts and not that frequent. The join tables are predicted beforehand but the number of self joins (tables joining themselves multiple times) is not. Small pages of results from such queries are going to be viewed on an highly interactive website so response time is critical. Any predictions on how this can perform on MS SQL Server 2008 R2 or Oracle 11g ? I'm also concerned about boosting performance by adding more servers, which one scales better ? How about PostgresQL ?

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  • Generic validate input data via regex. Input error when match.count == 0

    - by Valamas
    Hi, I have a number of types of data fields on an input form, for example, a web page. Some fields are like, must be an email address, must be a number, must be a number between, must have certain characters. Basically, the list is undefinable. I wish to come up with a generic way of validating the data inputed. I thought I would use regex to validate the data. The fields which need validation would be related to a "regex expression" and a "regex error message" stating what the field should contain. My current mock up has that when the match count is zero, that would signify an error and to display the message. While still a white belt regex designer I have come to understand that in certain situations that it is difficult to write a regex which results in a match count of zero for every case. A complex regex case I looked for help on was Link Here. The forum post was a disaster because I confused people helping me. But one of the statements said that it was difficult to make a regex with a match count of zero meaning the input data was invalid; that the regex was very difficult to write that for. Does anyone have comments or suggestions on this generic validation system I am trying to create? thanks

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  • Partioning with Hibernate

    - by Alex
    Hello, We have a requirement to delete data in the range of 200K from database everyday. Our application is Java/JEE based using Oracle DB and Hibernate ORM tool. We explored various options like Hibernate batch processing Stored procedure Database partitioning Our DBA suggests database partitioning is the best way to go, so we can easily recreate and drop the partitioned table everyday. Now the issue is we have 2 kinds of data, one which we want to delete everyday and the other which we want to keep it. Suppose this data is stored in table "Trade". Now with partitioning, we have 2 tables "Trade". We have already existing Hibernate based DAO layer to fetch/store trades from/to DB. When we decide to partition the database, how can we control the trades to go in which of the two tables through hibernate. Basically I want , the trades need to be deleted by end of the day, to go in partitioned table and the trades I want to keep, in main table. Please suggest how can this be possible with Hibernate. We may add an additional column to identify the trades to be deleted but how can we ensure these trades should go to partitioned trade table using hibernate. I would appreciate if someone can suggest any better approach in case we are on wrong path.

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  • Safari Web Inspector is not updating when I update an element with ajax

    - by Ashley
    I have a checkout page http://www.oipolloi.com/oipolloi/shop/viewbasket.php with multiple ajax calls after certain items update (EG look up postage cost when country is changed, then update discount boxes etc). I've asked for help in the past about the best method of making sure ALL calls have returned before allowing the form to be submitted for payment processing: http://stackoverflow.com/questions/2290372/how-do-i-prevent-form-submission-until-multiple-ajax-calls-have-finished-jquery I was fairly happy that the logic in the finished solution was correct, but I have still been receiving reports that people using Safari are able to submit the form without the ajax calls returning properly. I have tried using the Safari Web Inspector to debug but it seems that when you Inspect Element, then update an element with an ajax call, the Inspector doesn't seem to update. I am updating hidden fields, so it's hard to be able to know whether the problem lies with the DOM not being updated properly, or the Inspector itself. I'm using Safari 4.0.5 on PC and you can reproduce the problem above by looking for a div id="countryFieldsBilling" with Web Inspector. It should contain three hidden fields that are initially empty. You can try to make it update (or not) by choosing a country from the select menu at the bottom of 'Shipping Address' box, and then clicking the 'click to use Shipping Address' link at the top of the 'Billing Address' just below. The behaviour I am seeing is that the country chosen in the shipping select gets copied correctly to the country in the billing select, but the hidden inputs in the Web Inspector do not get updated. When these hidden inputs do not get updated, this causes the problem that Mac Safari users report. If you can let me know either how to get Web Inspector to work properly, or something else I may have missed in the behaviour of Mac Safari that may cause these problems, that would be great. Thanks in advance

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  • SQL Server error handling: exceptions and the database-client contract

    - by gbn
    We’re a team of SQL Servers database developers. Our clients are a mixed bag of C#/ASP.NET, C# and Java web services, Java/Unix services and some Excel. Our client developers only use stored procedures that we provide and we expect that (where sensible, of course) they treat them like web service methods. Some our client developers don’t like SQL exceptions. They understand them in their languages but they don’t appreciate that the SQL is limited in how we can communicate issues. I don’t just mean SQL errors, such as trying to insert “bob” into a int column. I also mean exceptions such as telling them that a reference value is wrong, or that data has already changed, or they can’t do this because his aggregate is not zero. They’d don’t really have any concrete alternatives: they’ve mentioned that we should output parameters, but we assume an exception means “processing stopped/rolled back. How do folks here handle the database-client contract? Either generally or where there is separation between the DB and client code monkeys. Edits: we use SQL Server 2005 TRY/CATCH exclusively we log all errors after the rollback to an exception table already we're concerned that some of our clients won't check output paramaters and assume everything is OK. We need errors flagged up for support to look at. everything is an exception... the clients are expected to do some message parsing to separate information vs errors. To separate our exceptions from DB engine and calling errors, they should use the error number (ours are all 50,000 of course)

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  • Is there a programmatic way to transform a sequence of image files into a PDF?

    - by Salim Fadhley
    I have a sequence of JPG images. Each of the scans is already cropped to the exact size of one page. They are sequential pages of a valuable and out of print book. The publishing application requires that these pages be submitted as a single PDF file. I could take each of these images and just past them into a word-processor (e.g. OpenOffice) - unfortunately the problem here is that it's a very big book and I've got quite a few of these books to get through. It would obviously be time-consuming. This is volunteer work! My second idea was to use LaTeX - I could make a very simple document that consists of nothing more than a series of in-line image includes. I'm sure that this approach could be made to work, it's just a little on the complex side for something which seems like a very simple job. It occurred to me that there must be a simpler way - so any suggestions? I'm on Ubuntu 9.10, my primary programming language is Python, but if the solution is super-simple I'd happily adopt any technology that works.

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  • What is your personal approach/take on commenting?

    - by Trae
    Duplicate What are your hard rules about commenting? A Developer I work with had some things to say about commenting that were interesting to me (see below). What is your personal approach/take on commenting? "I don't add comments to code unless its a simple heading or there's a platform-bug or a necessary work-around that isn't obvious. Code can change and comments may become misleading. Code should be self-documenting in its use of descriptive names and its logical organization - and its solutions should be the cleanest/simplest way to perform a given task. If a programmer can't tell what a program does by only reading the code, then he's not ready to alter it. Commenting tends to be a crutch for writing something complex or non-obvious - my goal is to always write clean and simple code." "I think there a few camps when it comes to commenting, the enterprisey-type who think they're writing an API and some grand code-library that will be used for generations to come, the craftsman-like programmer that thinks code says what it does clearer than a comment could, and novices that write verbose/unclear code so as to need to leave notes to themselves as to why they did something."

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  • How do I update a webpage with the progress of a server-side task?

    - by Jim B
    Hi everyone, I'm working on a web project that takes the results from a survey type application, and runs them through a bunch of calculations to come up with some recommended suggestions for the user. Now, this calculation might take a minute or so, so I'd like to be able to give the user some update on it's progress. Obviously, the quick and dirty solution would be to put up a message along the lines of "Please wait while we calculate your recommendations" with a spinning gear type graphic. (or whatever, you get the point..). Once the task completes, I'd redirect to the results page. However, I'd like to do something a little more flashy. Maybe something along the lines of a progress bar, and even prompt the user with what's going on in the background. For example, give them a progress bar, with some text that says "Now processing suggestion 3 of 15; Multi-Vitamin" Any suggestions on how I could set this up? One way I'm thinking of doing it is to write the progress of the calculation method to the HttpContext, and slap up an update panel and timer that would show/refresh this info. I've also checked out maybe building a web service/method, and then poll that at some interval. Has anybody done something similar to this before? What worked for you? Thanks again! ~Jim

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  • Rewriting jQuery to plain old javascript - are the performance gains worth it?

    - by Swader
    Since jQuery is an incredibly easy and banal library, I've developed a rather complex project fairly quickly with it. The entire interface is jQuery based, and memory is cleaned regularly to maintain optimum performance. Everything works very well in Firefox, and exceptionally so in Chrome (other browsers are of no concern for me as this is not a commercial or publicly available product). What I'm wondering now is - since pure plain old javascript is really not a complicated language to master, would it be performance enhancing to rewrite the whole thing in plain old JS, and if so, how much of a boost would you expect to get from it? If the answers prove positive enough, I'll go ahead and do it, run a benchmark and report back with the precise findings. Cheers Edit: Thanks guys, valuable insight. The purpose was not to "re-invent the wheel" - it was just for experience and personal improvement. Just because something exists, doesn't mean you shouldn't explore it into greater detail, know how it works or try to recreate it. This is the same reason I seldom use frameworks, I would much rather use my own code and iron it out and gain massive experience doing it, than start off by using someone else's code, regardless of how ironed out it is. Anyway, won't be doing it, thanks for saving me the effort :)

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  • NSInvocation object not getting allocated iphone sdk

    - by neha
    Hi all, I'm doing NSString *_type_ = @"report"; NSNumber *_id_ = [NSNumber numberWithInt:report.reportId]; NSDictionary *paramObj = [NSDictionary dictionaryWithObjectsAndKeys: _id_, @"bla1", _type_, @"bla2",nil]; _operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(initParsersetId:) object:paramObj]; But my _operation object is nil even after processing this line. The selector here is actually a function I'm writing which is like: -(void)initParsersetId:(NSInteger)_id_ type:(NSString *)_type_ { NSString *urlStr = [NSString stringWithFormat:@"apimediadetails?id=624&type=report"]; NSString *finalURLstr = [urlStr stringByAppendingString:URL]; NSURL *url = [[NSURL alloc] initWithString:finalURLstr]; NSXMLParser *xmlParser = [[NSXMLParser alloc] initWithContentsOfURL:url]; //Initialize the delegate. DetailedViewObject *parser = [[DetailedViewObject alloc] initDetailedViewObject]; //Set delegate [xmlParser setDelegate:parser]; //Start parsing the XML file. BOOL success = [xmlParser parse]; if(success) NSLog(@"No Errors"); else NSLog(@"Error Error Error!!!"); } Can anybody please point out wheather where I'm going wrong. Thanx in advance.

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  • C++ Builder 2010 Exception Dead Lock ???

    - by James
    Hello Is this some kind of exception dead lock i am facing? How to avoid it ? Have a look at below line where i have TIdContext objects of connected clients stored in an objlist and at times i need to process it. But if one user is disconnected while another thread is processing the list, then for that freed TIdContext-Data object I am getting Access voilation, Ok its fine i am using try/catch but problem is that at below line there is some kind of dead lock and process hangs , if i attach a debuger it show Access voilation Again and Again and Again, and cpu coonsumption goes up because of that exception dead lock. AnsiString UserID = ((Tmyobject*) ((TIdContext*) ObjList->Objects[i])->Data)->UserID; i know i can check before accessing the object, if object is not Null, It works.. But my question is what if once in a blue moon the Data object is freed at the point when NULL check is performed and on next line when again i am accessing the object i get same dead lock ??? So how to avoid/handle this dead lock exception ? Here is the call stack... :005F07C0 System::AnsiStringBase::AnsiStringBase(this=:0285FCE0, src=????) :0040223F System::AnsiStringT<0>::AnsiStringT<0>(this=:0285FCE0, src=:00000008) :00457996 TSomeClass::SomeFunction(this=:009D8230, UserID={ }, DataSize={ }, ) :0047BFF1 __linkproc__ ThreadProc(Thread=:009561C0) :004AD00E __linkproc__ ThreadWrapper(Parameter=:009EAA30) :7c80b729 ; C:\WINDOWS\system32\kernel32.dll Please helppppppppppppppppppppp Thanks

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  • Implementing a bitfield using java enums

    - by soappatrol
    Hello, I maintain a large document archive and I often use bit fields to record the status of my documents during processing or when validating them. My legacy code simply uses static int constants such as: static int DOCUMENT_STATUS_NO_STATE = 0 static int DOCUMENT_STATUS_OK = 1 static int DOCUMENT_STATUS_NO_TIF_FILE = 2 static int DOCUMENT_STATUS_NO_PDF_FILE = 4 This makes it pretty easy to indicate the state a document is in, by setting the appropriate flags. For example: status = DOCUMENT_STATUS_NO_TIF_FILE | DOCUMENT_STATUS_NO_PDF_FILE; Since the approach of using static constants is bad practice and because I would like to improve the code, I was looking to use Enums to achieve the same. There are a few requirements, one of them being the need to save the status into a database as a numeric type. So there is a need to transform the enumeration constants to a numeric value. Below is my first approach and I wonder if this is the correct way to go about this? class DocumentStatus{ public enum StatusFlag { DOCUMENT_STATUS_NOT_DEFINED(1<<0), DOCUMENT_STATUS_OK(1<<1), DOCUMENT_STATUS_MISSING_TID_DIR(1<<2), DOCUMENT_STATUS_MISSING_TIF_FILE(1<<3), DOCUMENT_STATUS_MISSING_PDF_FILE(1<<4), DOCUMENT_STATUS_MISSING_OCR_FILE(1<<5), DOCUMENT_STATUS_PAGE_COUNT_TIF(1<<6), DOCUMENT_STATUS_PAGE_COUNT_PDF(1<<7), DOCUMENT_STATUS_UNAVAILABLE(1<<8), private final long statusFlagValue; StatusFlag(long statusFlagValue) { this.statusFlagValue = statusFlagValue } public long getStatusFlagValue(){ return statusFlagValue } } /** * Translates a numeric status code into a Set of StatusFlag enums * @param numeric statusValue * @return EnumSet representing a documents status */ public EnumSet<StatusFlag> getStatusFlags(long statusValue) { EnumSet statusFlags = EnumSet.noneOf(StatusFlag.class) StatusFlag.each { statusFlag -> long flagValue = statusFlag.statusFlagValue if ( (flagValue&statusValue ) == flagValue ) { statusFlags.add(statusFlag) } } return statusFlags } /** * Translates a set of StatusFlag enums into a numeric status code * @param Set if statusFlags * @return numeric representation of the document status */ public long getStatusValue(Set<StatusFlag> flags) { long value=0 flags.each { statusFlag -> value|=statusFlag.getStatusFlagValue() } return value } public static void main(String[] args) { DocumentStatus ds = new DocumentStatus(); Set statusFlags = EnumSet.of( StatusFlag.DOCUMENT_STATUS_OK, StatusFlag.DOCUMENT_STATUS_UNAVAILABLE) assert ds.getStatusValue( statusFlags )==258 // 0000.0001|0000.0010 long numericStatusCode = 56 statusFlags = ds.getStatusFlags(numericStatusCode) assert !statusFlags.contains(StatusFlag.DOCUMENT_STATUS_OK) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_TIF_FILE) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_PDF_FILE) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_OCR_FILE) } }

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  • Building static (but complicated) lookup table using templates.

    - by MarkD
    I am currently in the process of optimizing a numerical analysis code. Within the code, there is a 200x150 element lookup table (currently a static std::vector < std::vector < double ) that is constructed at the beginning of every run. The construction of the lookup table is actually quite complex- the values in the lookup table are constructed using an iterative secant method on a complicated set of equations. Currently, for a simulation, the construction of the lookup table is 20% of the run time (run times are on the order of 25 second, lookup table construction takes 5 seconds). While 5-seconds might not seem to be a lot, when running our MC simulations, where we are running 50k+ simulations, it suddenly becomes a big chunk of time. Along with some other ideas, one thing that has been floated- can we construct this lookup table using templates at compile time? The table itself never changes. Hard-coding a large array isn't a maintainable solution (the equations that go into generating the table are constantly being tweaked), but it seems that if the table can be generated at compile time, it would give us the best of both worlds (easily maintainable, no overhead during runtime). So, I propose the following (much simplified) scenario. Lets say you wanted to generate a static array (use whatever container suits you best- 2D c array, vector of vectors, etc..) at compile time. You have a function defined- double f(int row, int col); where the return value is the entry in the table, row is the lookup table row, and col is the lookup table column. Is it possible to generate this static array at compile time using templates, and how?

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  • How to map combinations of things to a relational database?

    - by Space_C0wb0y
    I have a table whose records represent certain objects. For the sake of simplicity I am going to assume that the table only has one row, and that is the unique ObjectId. Now I need a way to store combinations of objects from that table. The combinations have to be unique, but can be of arbitrary length. For example, if I have the ObjectIds 1,2,3,4 I want to store the following combinations: {1,2}, {1,3,4}, {2,4}, {1,2,3,4} The ordering is not necessary. My current implementation is to have a table Combinations that maps ObjectIds to CombinationIds. So every combination receives a unique Id: ObjectId | CombinationId ------------------------ 1 | 1 2 | 1 1 | 2 3 | 2 4 | 2 This is the mapping for the first two combinations of the example above. The problem is, that the query for finding the CombinationId of a specific Combination seems to be very complex. The two main usage scenarios for this table will be to iterate over all combinations, and the retrieve a specific combination. The table will be created once and never be updated. I am using SQLite through JDBC. Is there any simpler way or a best practice to implement such a mapping?

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  • Patterns / Solutions to complicated Feature Management

    - by yclian
    Hi all, My company develops CDN / Web-Hosting solution. We have a middleware that's served as a business logic layer and exposes web service for the front-end. I would like to seek for a clean solution to feature management - there're uncertainties and ugly workarounds/solutions in the software that the dev would say "when it happens or is broken, we will fix it". For example, here're the following features that a web publisher can have: Sites limit Bandwidth limit SSL feature + SSL configuration per site If we downgrade a web publisher, when he's having 10 sites, down to 5 sites, we can choose not to suspend the rest of the 5 sites, or we shall prompt for suspension before the downgrade. For the case of bandwidth limit, the downgrade is easy, when the bandwidth check happens, if the publisher has it exceeded, then we will suspend his account. For the case of SSL feature. Every SSL configuration is tied to a site, what shall happen to these configuration object when the SSL feature is downgraded from enabled to disabled? So as you can see, there're many different situations and there are different ways of handling it. I can make a system that examines the impacts and prompts the user to make changes before the downgrade/upgrade. Or a system that ignores the impacts and just upgrade/downgrade. Bad. Or a system designed in a way that the client code need to be aware of the complex feature matrix (or I can expose a helper to the client code to check if a feature is not DEFUNCT) There can be many ways that I am still thinking but puzzled. I am wondering, how would you tackle this issue and is there any recommended patterns or books or software that you think I can refer to? Appreciate your help.

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  • I can learn either C or Java, which one should I choose first? Should I take them concurrently?

    - by GR1000
    I realize this is a subject of hot debate, but I'm interested in opinions that relate to my specific situation. I want to learn the basics and fundamentals of programming, so I'm already taking a college course in general programming concepts. It isn't covering a specific language, but it's giving me a solid foundation that I can build upon when I move on to a class that teaches a specific language. My two options for a specific language are Java and C because those are the two languages taught at the college I want to take classes from. What I want to do is learn a complex language so that I can apply that knowledge to languages that I use, or will eventually use, in my current job building web pages: XHTML, CSS, JavaScript, PHP, XML, ActionScript. I'm not necessariy interested in becoming a Java developer or a C developer in the immediate future, but I do have aspirations of developing web applications and iPod/iPhone applications. So, basically, I'm looking for answers to these questions and the reasoning behind them: Do I take the introductory course in Java first, and then take the intro course in C, or Do I take C first and then take Java? Is there any reason not to take them concurrently? Should I skip C altogether as Java covers everything I need to know? EDIT: Thanks everyone for your thoughtful and insightful responses.

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  • EF4 Code-First CTP5 Many-to-one

    - by Kevin McKelvin
    I've been trying to get EF4 CTP5 to play nice with an existing database, but struggling with some basic mapping issues. I have two model classes so far: public class Job { [Key, Column(Order = 0)] public int JobNumber { get; set; } [Key, Column(Order = 1)] public int VersionNumber { get; set; } public virtual User OwnedBy { get; set; } } and [Table("Usernames")] public class User { [Key] public string Username { get; set; } public string EmailAddress { get; set; } public bool IsAdministrator { get; set; } } And I have my DbContext class exposing those as IDbSet I can query my users, but as soon as I added the OwnedBy field to the Job class I began getting this error in all my tests for the Jobs: Invalid column name 'UserUsername'. I want this to behave like NHibernate's many-to-one, whereas I think EF4 is treating it as a complex type. How should this be done?

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  • Need a better way to execute console commands from python and log the results

    - by Wim Coenen
    I have a python script which needs to execute several command line utilities. The stdout output is sometimes used for further processing. In all cases, I want to log the results and raise an exception if an error is detected. I use the following function to achieve this: def execute(cmd, logsink): logsink.log("executing: %s\n" % cmd) popen_obj = subprocess.Popen(\ cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE) (stdout, stderr) = popen_obj.communicate() returncode = popen_obj.returncode if (returncode <> 0): logsink.log(" RETURN CODE: %s\n" % str(returncode)) if (len(stdout.strip()) > 0): logsink.log(" STDOUT:\n%s\n" % stdout) if (len(stderr.strip()) > 0): logsink.log(" STDERR:\n%s\n" % stderr) if (returncode <> 0): raise Exception, "execute failed with error output:\n%s" % stderr return stdout "logsink" can be any python object with a log method. I typically use this to forward the logging data to a specific file, or echo it to the console, or both, or something else... This works pretty good, except for three problems where I need more fine-grained control than the communicate() method provides: stdout and stderr output can be interleaved on the console, but the above function logs them separately. This can complicate the interpretation of the log. How do I log stdout and stderr lines interleaved, in the same order as they were output? The above function will only log the command output once the command has completed. This complicates diagnosis of issues when commands get stuck in an infinite loop or take a very long time for some other reason. How do I get the log in real-time, while the command is still executing? If the logs are large, it can get hard to interpret which command generated which output. Is there a way to prefix each line with something (e.g. the first word of the cmd string followed by :).

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  • Game logic dynamically extendable architecture implementation patterns

    - by Vlad
    When coding games there are a lot of cases when you need to inject your logic into existing class dynamically and without making unnecessary dependencies. For an example I have a Rabbit which can be affected by freeze ability so it can't jump. It could be implemented like this: class Rabbit { public bool CanJump { get; set; } void Jump() { if (!CanJump) return; ... } } But If I have more than one ability that can prevent it from jumping? I can't just set one property because some circumstances can be activated simultanously. Another solution? class Rabbit { public bool Frozen { get; set; } public bool InWater { get; set; } bool CanJump { get { return !Frozen && !InWater; } } } Bad. The Rabbit class can't know all the circumstances it can run into. Who knows what else will game designer want to add: may be an ability that changes gravity on an area? May be make a stack of bool values for CanJump property? No, because abilities can be deactivated not in that order in which they were activated. I need a way to seperate ability logic that prevent the Rabbit from jumping from the Rabbit itself. One possible solution for this is making special checking event: class Rabbit { class CheckJumpEventArgs : EventArgs { public bool Veto { get; set; } } public event EventHandler<CheckJumpEvent> OnCheckJump; void Jump() { var args = new CheckJumpEventArgs(); if (OnCheckJump != null) OnCheckJump(this, args); if (!args.Veto) return; ... } } But it's a lot of code! A real Rabbit class would have a lot of properties like this (health and speed attributes, etc). I'm thinking of borrowing something from MVVM pattern where you have all the properties and methods of an object implemented in a way where they can be easily extended from outside. Then I want to use it like this: class FreezeAbility { void ActivateAbility() { _rabbit.CanJump.Push(ReturnFalse); } void DeactivateAbility() { _rabbit.CanJump.Remove(ReturnFalse); } // should be implemented as instance member // so it can be "unsubscribed" bool ReturnFalse(bool previousValue) { return false; } } Is this approach good? What also should I consider? What are other suitable options and patterns? Any ready to use solutions? UPDATE The question is not about how to add different behaviors to an object dynamically but how its (or its behavior) implementation can be extended with external logic. I don't need to add a different behavior but I need a way to modify an exitsing one and I also need a possibiliity to undo changes.

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  • A good data model for finding a user's favorite stories

    - by wings
    Original Design Here's how I originally had my Models set up: class UserData(db.Model): user = db.UserProperty() favorites = db.ListProperty(db.Key) # list of story keys # ... class Story(db.Model): title = db.StringProperty() # ... On every page that displayed a story I would query UserData for the current user: user_data = UserData.all().filter('user =' users.get_current_user()).get() story_is_favorited = (story in user_data.favorites) New Design After watching this talk: Google I/O 2009 - Scalable, Complex Apps on App Engine, I wondered if I could set things up more efficiently. class FavoriteIndex(db.Model): favorited_by = db.StringListProperty() The Story Model is the same, but I got rid of the UserData Model. Each instance of the new FavoriteIndex Model has a Story instance as a parent. And each FavoriteIndex stores a list of user id's in it's favorited_by property. If I want to find all of the stories that have been favorited by a certain user: index_keys = FavoriteIndex.all(keys_only=True).filter('favorited_by =', users.get_current_user().user_id()) story_keys = [k.parent() for k in index_keys] stories = db.get(story_keys) This approach avoids the serialization/deserialization that's otherwise associated with the ListProperty. Efficiency vs Simplicity I'm not sure how efficient the new design is, especially after a user decides to favorite 300 stories, but here's why I like it: A favorited story is associated with a user, not with her user data On a page where I display a story, it's pretty easy to ask the story if it's been favorited (without calling up a separate entity filled with user data). fav_index = FavoriteIndex.all().ancestor(story).get() fav_of_current_user = users.get_current_user().user_id() in fav_index.favorited_by It's also easy to get a list of all the users who have favorited a story (using the method in #2) Is there an easier way? Please help. How is this kind of thing normally done?

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  • Retrieve class name hierarchy as string

    - by Jeff Wain
    Our system complexity has risen to the point that we need to make permission names tied to the client from the database more specific. In the client, permissions are referenced from a static class since a lot of client functionality is dependent on the permissions each user has and the roles have a ton of variety. I've referenced this post as an example, but I'm looking for a more specific use case. Take for instance this reference, where PermissionAlpha would be a const string: return HasPermission(PermissionNames.PermissionAlpha); Which is great, except now that things are growing more complex the classes are being structured like this: public static class PermissionNames { public static class PermissionAlpha { public const string SubPermission; } } I'm trying to find an easy way to reference PermissionAlpha in this new setup that will act similar to the first declaration above. Would the only way to do this be to resort to pulling the value of the class name like in the example below? I'm trying to keep all the names in one place that can be reference anywhere in the application. public static class PermissionAlpha { public static string Name { get { return typeof(PermissionAlpha).Name; } } }

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  • Anyone NOT using a Web Framework? Why?

    - by tom
    I'm well aware of the many reasons to use a web framework. I'm just wondering whether anyone out there is using absolutely no web framework whatsoever to develop their web projects. I would really love to know the reason(s) why you're not using a web framework. For the sake of this discussion, your programming language of choice does not matter. Some possibilities for discussion: You don't hide behind an ORM. You don't rely on any sort of templating system. You think MVC is a really nice TLA but lacks an essential vowel or two. No need for any additional javascript framework tomfoolery. You just write as much code as possible in your native programming language(s). Summary of reasons thus far: Language learning opportunities. Specific performance reasons (write-intensive transaction processing). Seeking more nuanced control over your data and applications (less abstraction). You're building your own framework! Prove to yourself that you can succeed (or fail) just like the big framework-building gurus. Integration issues with unpopular/legacy technologies (exotic databases or protocols come to mind). Big company, lots of code, no talent nor buy-in present to move to a web framework. Some frameworks really lock you in and cannot perpetually grow along with your needs. These few black sheep don't make it easy to jump outside of the framework, write some custom code, and easily jump back in. When you finally escape the asylum, you'll never look back.

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  • Host WCF in MVC2 Site

    - by Basiclife
    Hi, We've got a very large, complex MVC2 website. We want to add an API for some internal tools and decided to use WCF. Ideally, we want MVC itself to host the WCF service. Reasons include: Although there's multiple tiers to the application, some functionality we'd like in the API requires the website itself (e.g. formatting emails). We use TFS to auto-build (continuous integration) and deploy - The less we need to modify the build and release mechanism the better We use the Unity container and Inversion of Control throughout the application. Being part of the Website would allow us to re-use configuration classes and other helper methods. I've written a custom ServiceBehavior which in turn has a custom InstanceProvider - This allows me to instantiate and configure a container which is then used to service all requests for class instances from WCF. So my question is; Is it possible to host a WCF service from within MVC itself? I've only had experience in Services / Standard Asp.Net websites before and didn't realise MVC2 might be different until I actually tried to wire it into the config and nothing happened. After some googling, there don't seem to be many references to doing this - so thought I'd ask here.

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  • How to deal with seniors' bad coding style/practices?

    - by KaluSingh Gabbar
    I am new to work but the company I work in hires a lot of non-comp-science people who are smart enough to get the work done (complex) but lack the style and practices that should help other people read their code. For example they adopt C++ but still use C-like 3 page functions which drives new folks nuts when they try to read that. Also we feel very risky changing it as it's never easy to be sure we are not breaking something. Now, I am involved in the project with these guys and I can't change the entire code base myself or design so that code looks good, what can I do in this situation? PS we actually have 3 page functions & because we do not have a concept of design, all we can do is assume what they might have thought as there is no way to know why is it designed the way it is. I am not complaining.I am asking for suggestion,already reading some books to solve the issues Pragmatic Programmer; Design portion from B.Stroustrup; Programming and principles by B.Stroustrup;

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