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• callback pattern

  - by robUK

  Hello, gcc 4.4.3 c89 I am creating a client server application and I will need to implement some callback functions. However, I am not too experienced in callbacks. And I am wondering if anyone knowns some good reference material to follow when designing callbacks. Is there any design patterns that are used for c. I did look at some patterns but there where all c++. Many thanks for any suggestions,

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• Does this singleton pattern make sense?

  - by dontWatchMyProfile

  @implementation MySingletonClass static MySingletonClass *sharedInstance = nil; + (MySingletonClass*)sharedInstance { @synchronized(self) { if (sharedInstance == nil) { sharedInstance = [[self alloc] init]; } } return sharedInstance; } + (id)alloc { @synchronized(self) { if (sharedInstance == nil) { sharedInstance = [super alloc]; return sharedInstance; } } return nil; } + (id)allocWithZone:(NSZone *)zone { @synchronized(self) { if (sharedInstance == nil) { sharedInstance = [super allocWithZone:zone]; return sharedInstance; } } return nil; } -(id)init { self = [super init]; if (self != nil) { // initialize stuff here } return self; } @end Not sure if it's ok to overwrite both alloc and allocWithZone: like this...?

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• MVC + Repository Pattern - Still depends on Data Model?

  - by Jack

  I've started a project for school in which I am using ASP.NET MVC 2 + LINQ2SQL, and a business layer so my UI doesnt interact with the DB directly. My question is this: In my MVC project, when bringing up views and passing around data, I still have to include my Data project for access to the classes in my Linq2Sql project. Is this correct? Example: Controller: ClassesRepository cr = new ClassesRepository(); // this is from my Business project Class classToEdit = cr.GetByClassId(id); // "Class" is from my data project I still have to reference the Class class in my linq2sql data project - shouldn't my UI be completely independent of my data layer? Or maybe I'm going about this all wrong.

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• Session vs singleton pattern

  - by chobo

  Hi, I have a web application where I would like to pull user settings from a database and store them for Global access. Would it make more sense to store the data in a Singleton, or a Session object? What's the difference between the two? Is it better to store the data as an object reference or break it up into value type objects (ints and strings)? Thanks!

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• autosave pattern

  - by Mark

  I'm using localstorage to do gmail-style autosave on a webpage. So I basically save every 30 seconds to local, OK. The problem is recovery. I can't detect whether or not a user has crashed or incorrectly exited. So let's say the user crashed and loads up the form again, I can't just continue saving and overwriting the previous autosaves. I need to restore the previous save. But let's say the user didn't crash. He did everything correctly, but then used a different browser to edit the same file, so no new data to the previous browser's localstorage. He then loads up the file in the previous browser. The localstorage should not be restored in that case. Assuming there's no way to compare timestamps, how can I solve this problem? Thanks.

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• Sed-replacing a pattern

  - by grails_enthu

  I have below code: <td nowrap="nowrap" width="74"> <p align="center">server1</p> </td> <td nowrap="nowrap" width="74"> <p align="center">server2</p> </td> and so on.I want to get output as: <td nowrap="nowrap" width="74">server1</td> <td nowrap="nowrap" width="74">server2</td> What should be my approach?Say for example the file is server.html I have done something like this: sed "s/<p align="center">*</p>/*/" -i server.html But its not working.

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• Replacing Text which does not match a pattern in Oracle

  - by kutekrish

  I have below text in a CLOB in a table Table Name: tbl1 Columns col1 - number (Primary Key) col2 - clob (as below) Row#1 ----- Col1 = 1 Col2 = 1331882981,ab123456,Some text here which can run multiple lines and have a lot of text... ~1331890329,pqr123223,Some more text... Row#2 ----- Col1 = 2 Col2 = 1331882981,abc333,Some text here which can run multiple lines and have a lot of text... ~1331890329,pqrs23,Some more text... Now I need to know how we can get below output Col1 Value ---- --------------------- 1 1331882981,ab123456 1 1331890329,pqr123223 2 1331882981,abc333 2 1331890329,pqrs23 ([0-9]{10},[a-z 0-9]+.), == This is the regular expression to match "1331890329,pqrs23" and I need to know how can replace which are not matching this regex and then split them into multiple rows

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• Replace String pattern in Java

  - by Hirantha

  I have the following string "value=\"\\d{4}((((0[1-9])|(1[0-2]))((0[1-9])|([12]\\d)|(3[01]))?)?|(\\-(((0[1-9])|(1[0-2]))(\\-((0[1-9])|([12]\\d)|(3[01])))?)?)?)d{4}" There I want to replace all the occurrences of "{" with NCHAR(0x7B) "}" with NCHAR(0x7D). An the content in-between "{ }" should remain unchanged: Ex: \\d{4} after replacing -> NCHAR(0x7B) 4 NCHAR(0x7D). Is there a way to do this using Regular Expressions in Java?. Anyway, this can be done processing the whole string using string operations.

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• design-pattern libraries ready-to-use?

  - by fayer

  symfony has released some of their components free to use outside the framework. i have used the event dispatcher and dependency injection...they are awesome! i wonder if there are other components/libraries (from other frameworks etc) that in the same way help you manage various design patterns? eg. decorator, facade, singleton, chain of commands etc. i think symfony is on the right path, abstracting away the design patterns. are there any other components out there doing the same? thanks

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• License key pattern detection?

  - by Ricket

  This is not a real situation; please ignore legal issues that you might think apply, because they don't. Let's say I have a set of 200 known valid license keys for a hypothetical piece of software's licensing algorithm, and a license key consists of 5 sets of 5 alphanumeric case-insensitive (all uppercase) characters. Example: HXDY6-R3DD7-Y8FRT-UNPVT-JSKON Is it possible (or likely) to extrapolate other possible keys for the system? What if the set was known to be consecutive; how do the methods change for this situation, and what kind of advantage does this give? I have heard of "keygens" before, but I believe they are probably made by decompiling the licensing software rather than examining known valid keys. In this case, I am only given the set of keys and I must determine the algorithm. I'm also told it is an industry standard algorithm, so it's probably not something basic, though the chance is always there I suppose. If you think this doesn't belong in Stack Overflow, please at least suggest an alternate place for me to look or ask the question. I honestly don't know where to begin with a problem like this. I don't even know the terminology for this kind of problem.

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• Regular Expression: Match untill pattern is found

  - by ZafarYousafi

  Hi, I want to extract the status from the string untill I found a timespan. My input is something like "Something in start but not with this keyword of sure. STATUS: My Status Is Here Which can be anything but timespan 23:59:01 and so on. I want to extract the string after STATUS: untill 23:59:01 is found. How can i achieve this through regex. this 23:59:01 is a timespan and it is always in this format hh:mm:ss

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• Repository Pattern : Add Item

  - by No Body

  Just need to clarify this one, If I have the below interface public interface IRepository<T> { T Add(T entity); } when implementing it, does checking for duplication if entity is already existing before persist it is still a job of the Repository, or it should handle some where else?

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• Does this pattern have a name?

  - by LK7jb

  Disclaimer: I'm trying to learn proper OO programming/design, so I'm pretty new to this stuff. I guess this is a general design patterns question, but I'll base my example on a game engine or something that renders objects to the display. Consider the following: How can this sort of separation between physical objects (e.g., cubes, spheres, etc.) and the rendering mechanism be achieved in an extensible manner? This design is not set in stone, and perhaps I've got something wrong from the start. I'm just curious as to how a problem like this is solved in real world code.

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• Templated derived class in CRTP (Curiously Recurring Template Pattern)

  - by Butterwaffle

  Hi, I have a use of the CRTP that doesn't compile with g++ 4.2.1, perhaps because the derived class is itself a template? Does anyone know why this doesn't work or, better yet, how to make it work? Sample code and the compiler error are below. Source: foo.C #include <iostream> using namespace std; template<typename X, typename D> struct foo; template<typename X> struct bar : foo<X,bar<X> > { X evaluate() { return static_cast<X>( 5.3 ); } }; template<typename X> struct baz : foo<X,baz<X> > { X evaluate() { return static_cast<X>( "elk" ); } }; template<typename X, typename D> struct foo : D { X operator() () { return static_cast<D*>(this)->evaluate(); } }; template<typename X, typename D> void print_foo( foo<X,D> xyzzx ) { cout << "Foo is " << xyzzx() << "\n"; } int main() { bar<double> br; baz<const char*> bz; print_foo( br ); print_foo( bz ); return 0; } Compiler errors foo.C: In instantiation of ‘foo<double, bar<double> >’: foo.C:8: instantiated from ‘bar<double>’ foo.C:30: instantiated from here foo.C:18: error: invalid use of incomplete type ‘struct bar<double>’ foo.C:8: error: declaration of ‘struct bar<double>’ foo.C: In instantiation of ‘foo<const char*, baz<const char*> >’: foo.C:13: instantiated from ‘baz<const char*>’ foo.C:31: instantiated from here foo.C:18: error: invalid use of incomplete type ‘struct baz<const char*>’ foo.C:13: error: declaration of ‘struct baz<const char*>’

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• jquery plugin pattern using jquery.data

  - by web_dev

  I have seen this piece of code in jquery plugin patterns and the notes section mention that we could attach the plugin to the DOM element using the jQuery.data function. What I don't understand is how do I make use of this piece of code. Can somebody provide examples of how to use this functionality and explain its significance? $.fn[pluginName] = function (options) { return $Extend(this).each(function () { if (!$.data(this, 'plugin_' + pluginName)) { $.data(this, 'plugin_' + pluginName, new Plugin( this, options )); } }); };

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• python copytree with negated ignore pattern

  - by Chris H

  I'm trying to use python to copy a tree of files/directories. is it possible to use copytree to copy everything that ends in foo? There is an ignore_patterns patterns function, can I give it a negated regular expression? Are they supported in python? eg. copytree(src, dest, False, ignore_pattern('!*.foo')) Where ! means NOT anything that ends in foo. thanks.

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• Another way to handle a common JQuery event handling pattern

  - by bradgonesurfing

  I have the following code for example $("a.foo").bind(function (e){ var t; if ( $(e.target).is("a") ){ t = $(e.target); }else{ t = $(e.target).parent("a"); } var data = t.attr("data-info"); }); In english. I might have a list of anchors within which there may be a number of spans. Each anchor is declared as <a class="foo" href="#" data-info="1"> <span> ... </span> <span> ... </span> </a> <a class="foo" href="#" data-info="2"> <span> ... </span> <span> ... </span> </a> ... ... I bind a handler to the click event of the anchor but the event object comes back with the anchor OR one of the spans depending on where I click. So to get my html5 "data-info" value into the callback I have to insert a bit of messy code. This is now appearing throughout my code to the point where I am guessing there might be an idiomatic JQuery way of handling this.

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• Good JDBC pattern

  - by Java Developer

  What is the good practice for database operation in Java application? Do you construct the DML syntax in the Java code and send the statements to DB engine for execution, or you just collect the parameters and then make a call to stored procedure with the parameters via java code? or neither because that's just not how to do it? can anyone give an example of a full database utility classes to do database operations in Java app? also what about the transaction manager? My assignment is to make database operation that is modular in Java. Thanks

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• how to use sed/awk to remove words with multiple pattern count

  - by user1461112

  I have a file of string records where one of the fields - delimited by "," - can contain one or more "-" inside it. The goal is to delete the field value if it contains more than two "-". i am trying to recoup my past knowledge of sed/awk but can't make much headway ========== info,whitepaper,Data-Centers,yes-the-6-top-problems-in-your-data-center-lane info,whitepaper,Data-Centers,the-evolution-center info,whitepaper,Data-Centers,the-evolution-of-lan-technology-lanner ========== expected outcome: info,whitepaper,Data-Centers info,whitepaper,Data-Centers,the-evolution-center info,whitepaper,Data-Centers thanks

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• Can i exclude a word in my pattern?

  - by acidzombie24

  I know i can do something like ab[^c]+def which should match ab_blah_hi_blah_def but is there a way to do something like ab(^hi)+def which will exclude the word hi causeing ab_blah_hi_blah_def to fail? but not ab_blah_h_i_blah_def

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• Time to start returning IQueryable<T> instead of IList<T> to my Web UI / Web API Layer?

  - by JohnnyO

  I've got a multi-layer application that starts with the repository pattern for all data access and it returns IQueryable to the Services layer. The Services layer, which includes all of the business logic, returns IList to the Controllers (note: I'm using ASP.NET MVC for the UI layer). The benefit of returning IQueryable in the data access layer is that it allows my repositories to be extremely simple and the database queries to be deferred. However, I'm triggering the database queries in my services layer so that my unit tests is more reliable and I don't give flexibility to the Controllers to reshape my queries. However, I've recently encountered several situations where deferring the execution of queries down to the Controllers would have been significantly more performant because the Controllers had to do some projections on the data that was UI specific. Additionally, with the emergence of things like oData, I was starting to wonder if end points (e.g. web UI or web apis) should be working directly with IQueryable. What are your thoughts? Is it time to start returning IQueryable from the services layer to the UI layer? Or stick with IList? This thread here: http://stackoverflow.com/questions/718624/to-return-iqueryablet-or-not-return-iqueryablet seems to vouch for returning IList to the UI layers, but I was wondering if things are changing because of new emerging technologies and techniques.

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• EntityFramework repository template- how to write GetByID lamba within a template class?

  - by FerretallicA

  I am trying to write a generic one-size-fits-most repository pattern template class for an Entity Framework-based project I'm currently working on. The (heavily simplified) interface is: internal interface IRepository<T> where T : class { T GetByID(int id); IEnumerable<T> GetAll(); IEnumerable<T> Query(Func<T, bool> filter); } GetByID is proving to be the killer. In the implementation: public class Repository<T> : IRepository<T>,IUnitOfWork<T> where T : class { // etc... public T GetByID(int id) { return this.ObjectSet.Single<T>(t=>t.ID == id); } t=t.ID == id is the particular bit I'm struggling with. Is it even possible to write lamba functions like that within template classes where no class-specific information is going to be available?

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• refactor LINQ TO SQL custom properties that instantiate datacontext

  - by Thiago Silva

  I am working on an existing ASP.NET MVC app that started small and has grown with time to require a good re-architecture and refactoring. One thing that I am struggling with is that we've got partial classes of the L2S entities so we could add some extra properties, but these props create a new data context and query the DB for a subset of data. This would be the equivalent to doing the following in SQL, which is not a very good way to write this query as oppsed to joins: SELECT tbl1.stuff, (SELECT nestedValue FROM tbl2 WHERE tbl2.Foo = tbl1.Bar), tbl1.moreStuff FROM tbl1 so in short here's what we've got in some of our partial entity classes: public partial class Ticket { public StatusUpdate LastStatusUpdate { get { //this static method call returns a new DataContext but needs to be refactored var ctx = OurDataContext.GetContext(); var su = Compiled_Query_GetLastUpdate(ctx, this.TicketId); return su; } } } We've got some functions that create a compiled query, but the issue is that we also have some DataLoadOptions defined in the DataContext, and because we instantiate a new datacontext for getting these nested property, we get an exception "Compiled Queries across DataContexts with different LoadOptions not supported" . The first DataContext is coming from a DataContextFactory that we implemented with the refactorings, but this second one is just hanging off the entity property getter. We're implementing the Repository pattern in the refactoring process, so we must stop doing stuff like the above. Does anyone know of a good way to address this issue?

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• "User Friendly" .net compatible Regex/Text matching tools?

  - by Binary Worrier

  Currently in our software we provide a hook where we call a DLL built by our clients to parse information out of documents we are processing (the DLL takes in some text (or a file) and returns a list of name/value pairs). e.g. We're given a Word doc or Text file to Archive. We do various things to the file, and call a DLL that will return "pertinent" information about the file. Among other things we store that "pertinent" data for posterity. What is considered "pertinent" depends on the client and the type of the document, we don't care, we get it and store it. I've been asked to develop a user friendly "something" that will allow a non-programmer user to "configure" how to get this data from a plain text document (<humor>The user story ends with the helpful suggestion/query "We could use regex for this?"</humor>) It's safe to assume that a list of regex's isn't going to cut this, I've written some of these parsers for customers, the regex's to do these would be hedious and some of them can't be done by regex's. Also one of the requirements above is "user friendly" which negates anything that has users seeing or editing regex expressions. As you can guess, I don't have a fortune of time to do this, and am wondering is there anything out there that I can plug in to our app that has a nice front end and does exactly what I need? :) No? Whadda mean no! . . . sigh Ok then failing that, anything out there that "visually" builds regex's and/or other pattern matching expressions, and then allows one to run those expressions against some text? The MS BRE will do what I want, but I need something prettier that looks less like code. Thanks guys,

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• Facade Design Patterns and Subclassing

  - by Code Sherpa

  Hi. I am using a facade design pattern for a C# program. The program basically looks like this... public class Api { #region Constants private const int version = 1; #endregion #region Private Data private XProfile _profile; private XMembership _membership; private XRoles _role; #endregion Private Data public Api() { _membership = new XMembership(); _profile = new XProfile(); _role = new XRoles(); } public int GetUserId(string name) { return _membership.GetIdByName(name); } } Now, as I would like subclass my methods into three categories: Role, Profile, and Member. This will be easier on the developers eye because both Profile and Membership expose a lot of methods that look similar (and a few by Role). For example, getting a user's ID would look like: int _id = Namespace.Api.Member.GetUserId("Henry222"); Can somebody "illustrate" how subclassing should work in this case to achieve the effect I am looking for? Thanks in advance.

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