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  • Why should a class be anything other than "abstract" or "final/sealed"

    - by Nicolas Repiquet
    After 10+ years of java/c# programming, I find myself creating either: abstract classes: contract not meant to be instantiated as-is. final/sealed classes: implementation not meant to serve as base class to something else. I can't think of any situation where a simple "class" (i.e. neither abstract nor final/sealed) would be "wise programming". Why should a class be anything other than "abstract" or "final/sealed" ? EDIT This great article explains my concerns far better than I can.

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  • Are python's cryptographic modules good enough?

    - by Aerovistae
    I mean, say you were writing professional grade software that would involve sensitive client information. (Take this in the context of me being an amateur programmer.) Would you use hlib and hmac? Are they good enough to secure data? Or would you write something fancier by hand? Edit: In context of those libraries containing more or less the best hashing algorithms in the world, I guess it's silly to ask if you'd "write something fancier." What I'm really asking here is whether it's enough on its own.

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  • ORM and component-based architecture

    - by EagleBeek
    I have joined an ongoing project, where the team calls their architecture "component-based". The lowest level is one big database. The data access (via ORM) and business layers are combined into various components, which are separated according to business logic. E.g., there's a component for handling bank accounts, one for generating invoices, etc. The higher levels of service contracts and presentation are irrelevant for the question, so I'll omit them here. From my point of view the separation of the data access layer into various components seems counterproductive, because it denies us the relational mapping capabilities of the ORM. E.g., when I want to query all invoices for one customer I have to identify the customer with the "customers" component and then make another call to the "invoices" component to get the invoices for this customer. My impression is that it would be better to leave the data access in one component and separate it from business logic, which may well be cut into various components. Does anybody have some advice? Have I overlooked something?

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  • How many developers actually have private offices?

    - by Morgan Herlocker
    So I know everyone here is all about private offices, how many developers actually have them. I am sort of half skeptical. I can believe that lead developers have them, but thats normally just one person in your average office. If it would not be to much to ask: Do you work in a totally awesome office or a nasty old cube? (or somewhere in between) What's your relative rank in the office? (junior, programmer II, senior, lead, etc.) are you doing internal software, or are you in a software-centric environment? (the general thought seems to be that internal developers get cubes while others live in "Joel-Spolsky-Programmer-Candyland")

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  • Proper way to implement Android XML onClick attribute in Activity

    - by Austyn Mahoney
    I have used the android:onClick attribute extensively in my XML layouts for my Android application. Example: <Button android:id="@+id/exampleButton" android:onClick="onButtonClick" /> Is it proper to create an Interface to enforce the implementation of those onClick methods in Activities that use that layout file? public interface MyButtonInterface { public onButtonClick(View v); }

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  • Is static universally "evil" for unit testing and if so why does resharper recommend it?

    - by Vaccano
    I have found that there are only 3 ways to unit test (mock/stub) dependencies that are static in C#.NET: Moles TypeMock JustMock Given that two of these are not free and one has not hit release 1.0, mocking static stuff is not too easy. Does that make static methods and such "evil" (in the unit testing sense)? And if so, why does resharper want me to make anything that can be static, static? (Assuming resharper is not also "evil".) Clarification: I am talking about the scenario when you want to unit test a method and that method calls a static method in a different unit/class. By most definitions of unit testing, if you just let the method under test call the static method in the other unit/class then you are not unit testing, you are integration testing. (Useful, but not a unit test.)

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  • Alternatives to Pessimistic Locking in Cluster Applications

    - by amphibient
    I am researching alternatives to database-level pessimistic locking to achieve transaction isolation in a cluster of Java applications going against the same database. Synchronizing concurrent access in the application tier is clearly not a solution in the present configuration because the same database transaction can be invoked from multiple JVMs concurrently. Currently, we are subject to occasional race conditions which, due to the optimistic locking we have in place via Hibernate, cause a StaleObjectStateException exception and data loss. I have a moderately large transaction within the scope of my refactoring project. Let's describe it as updating one top-level table row and then making various related inserts and/or updates to several of its child entities. I would like to insure exclusive access to the top-level table row and all of the children to be affected but I would like to stay away from pessimistic locking at the database level for performance reasons mostly. We use Hibernate for ORM. Does it make sense to start a single (perhaps synchronous) message queue application into which this method could be moved to insure synchronized access as opposed to each cluster node using its own, which is a clear race condition hazard? I am mentioning this approach even though I am not confident in it because both the top-level table row and its children could also be updated from other system calls, not just the mentioned transaction. So I am seeking to design a solution where the top-level table row and its children will all somehow be pseudo-locked (exclusive transaction isolation) but at the application and not the database level. I am open to ideas and suggestions, I understand this is not a very cut and dried challenge.

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  • Questions about software licensing

    - by iwayneo
    I've been having a discussion about licensing and open source software. Basically - the other guy is saying that licensing is easy, if you're going to build a product you can use an (any) open source project and make money by selling that code. My issue is that say I create a website or app with a project that uses a GPL license the restrictions aren't so straight forward - correct me if i'm wrong on each of these scenarios: 1 - i create an iPhone app using GPL code and put that app into the appstore - the code must be freely available to people buying that app. 2 - i create a website that my client hosts - they must have access to the code. 3 - i create a website as SaaS that my client "leases" but does not own - though it is hosted on their infrastructure - they must have access to that code Am i right on each of those assumptions? Are there any other issues i should be aware of under any other licensing terms for other licenses?

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  • how to call web method in java application?.

    - by user12344
    Hi, I have created java web application(Web Service). I want to call the setName() method in java application(GUI). how is call web method in application?. package sv; import javax.jws.WebMethod; import javax.jws.WebParam; import javax.jws.WebService; @WebService() public class MyService { @WebMethod(operationName = "setName") public String setName(@WebParam(name = "name") String name) { return "my string is "+ name; } }

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  • How do I learn algorithms and data structures?

    - by sushil bharwani
    this is in continuation to my previous question where i asked is it necessary to learn algorithm and datastructures. I feel yes it is. Now when i work in a enviornment where i wont ever get the chance to learn it by experimenting or practically or in any assignment. What is the right approach like the right books, right kind of problems, right kind of resources that i can go through to give six months or a year or two to learn it. And also mould my mind in a way that it can relate problems to datastructures and algos.

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  • Is encoding needed in this decryption?

    - by Lijo
    I have a Encryption – Decryption scenario as shown below. //[Clear text ID string as input] -- [(ASCII GetByte) + Encoding] -- [Encrption as byte array] -- [Database column is in VarBinary] -- [Pass byte[] as VarBinary parameter to SP for comparison] //[ID stored as VarBinary in Database] -- [Read as byte array] -- [(Decrypt as byte array) + Encoding + (ASCII Get String)] -- Show as string in the UI My question is in the decryption scenario. After decryption I get a byte array. I am doing an encoding (IBM037) after that. Is it correct? Is there something wrong in the flow shown above? private static byte[] GetEncryptedID(string id) { Interface_Request input = new Interface_Request(); input.RequestText = Encodeto64(id); input.RequestType = Encryption; ProgramInterface inputRequest = new ProgramInterface(); inputRequest.Test_Trial_Request = input; using (KTestService operation = new KTestService()) { return ((operation.KTrialOperation(inputRequest)).Test_Trial_Response.ResponseText); } } private static string GetDecryptedID(byte[] id) { Interface_Request input = new Interface_Request(); input.RequestText = id; input.RequestType = Decryption; ProgramInterface request = new ProgramInterface(); request.Test_Trial_Request = input; using (KTestService operationD = new KTestService()) { ProgramInterface1 response = operationD.KI014Operation(request); byte[] decryptedValue = response.ICSF_AES_Response.ResponseText; Encoding sourceByteFormat = Encoding.GetEncoding("IBM037"); Encoding destinationByteFormat = Encoding.ASCII; //Convert from one byte format to other (IBM to ASCII) byte[] ibmEncodedBytes = Encoding.Convert(sourceByteFormat, destinationByteFormat,decryptedValue); return System.Text.ASCIIEncoding.ASCII.GetString(ibmEncodedBytes); } } private static byte[] EncodeTo64(string toEncode) { byte[] dataInBytes = System.Text.ASCIIEncoding.ASCII.GetBytes(toEncode); Encoding destinationByteFormat = Encoding.GetEncoding("IBM037"); Encoding sourceByteFormat = Encoding.ASCII; //Convert from one byte format to other (ASCII to IBM) byte[] asciiBytes = Encoding.Convert(sourceByteFormat, destinationByteFormat, dataInBytes); return asciiBytes; }

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  • Caching factory design

    - by max
    I have a factory class XFactory that creates objects of class X. Instances of X are very large, so the main purpose of the factory is to cache them, as transparently to the client code as possible. Objects of class X are immutable, so the following code seems reasonable: # module xfactory.py import x class XFactory: _registry = {} def get_x(self, arg1, arg2, use_cache = True): if use_cache: hash_id = hash((arg1, arg2)) if hash_id in _registry: return _registry[hash_id] obj = x.X(arg1, arg2) _registry[hash_id] = obj return obj # module x.py class X: # ... Is it a good pattern? (I know it's not the actual Factory Pattern.) Is there anything I should change? Now, I find that sometimes I want to cache X objects to disk. I'll use pickle for that purpose, and store as values in the _registry the filenames of the pickled objects instead of references to the objects. Of course, _registry itself would have to be stored persistently (perhaps in a pickle file of its own, in a text file, in a database, or simply by giving pickle files the filenames that contain hash_id). Except now the validity of the cached object depends not only on the parameters passed to get_x(), but also on the version of the code that created these objects. Strictly speaking, even a memory-cached object could become invalid if someone modifies x.py or any of its dependencies, and reloads it while the program is running. So far I ignored this danger since it seems unlikely for my application. But I certainly cannot ignore it when my objects are cached to persistent storage. What can I do? I suppose I could make the hash_id more robust by calculating hash of a tuple that contains arguments arg1 and arg2, as well as the filename and last modified date for x.py and every module and data file that it (recursively) depends on. To help delete cache files that won't ever be useful again, I'd add to the _registry the unhashed representation of the modified dates for each record. But even this solution isn't 100% safe since theoretically someone might load a module dynamically, and I wouldn't know about it from statically analyzing the source code. If I go all out and assume every file in the project is a dependency, the mechanism will still break if some module grabs data from an external website, etc.). In addition, the frequency of changes in x.py and its dependencies is quite high, leading to heavy cache invalidation. Thus, I figured I might as well give up some safety, and only invalidate the cache only when there is an obvious mismatch. This means that class X would have a class-level cache validation identifier that should be changed whenever the developer believes a change happened that should invalidate the cache. (With multiple developers, a separate invalidation identifier is required for each.) This identifier is hashed along with arg1 and arg2 and becomes part of the hash keys stored in _registry. Since developers may forget to update the validation identifier or not realize that they invalidated existing cache, it would seem better to add another validation mechanism: class X can have a method that returns all the known "traits" of X. For instance, if X is a table, I might add the names of all the columns. The hash calculation will include the traits as well. I can write this code, but I am afraid that I'm missing something important; and I'm also wondering if perhaps there's a framework or package that can do all of this stuff already. Ideally, I'd like to combine in-memory and disk-based caching.

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  • Service Layer - how broad should it be, and should it be used also on the local application?

    - by BornToCode
    Background: I need to build a main application with some operations (CRUD and more) (-in winforms), I need to make another application which will re-use some of the functions of the main application (-in webforms). I understood that using service layer is the best approach here. If I understood correctly the service should be calling the function on the BL layer (correct me if I'm wrong) The dilemma: In my main winform UI - should I call the functions from the BL, or from the service? (please explain why) Should I create a service for every single function on the BL even if I need some of the functions only in one UI? for example - should I create services for all the CRUD operations, even though I need to re-use only update operation in the webform? YOUR HELP IS MUCH APPRECIATED

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  • My architecture has a problem with views that required information from different objects. How can I solve this?

    - by Oscar
    I am building an architecture like this: These are my SW layers ______________ | | | Views | |______________| ______________ | | |Business Logic| |______________| ______________ | | | Repository | |______________| My views are going to generate my HTML to be sent to the user Business logic is where all the business logics are Repository is a layer to access the DB My idea is that the repository uses entities (that are basically the representation of the tables, in order to perform DB queries. The layers communicate between themselves using Business Objects, that are objects that represent the real-world-object itself. They can contain business rules and methods. The views build/use DTOs, they are basically objects that have the information required to be shown on the screen. They expect also this kind of object on actions and, before calling the business logic, they create BO. First question: what is your overall feeling about this architecture? I've used similar architecture for some projects and I always got this problem: If my view has this list to show : Student1, age, course, Date Enrolled, Already paid? It has information from different BO. How do you think one should build the structure? These were the alternatives I could think of: The view layer could call the methods to get the student, then the course it studies, then the payment information. This would cause a lot of DB accesses and my view would have the knowledge about how to act to generate this information. This just seems wrong for me. I could have an "adapter object", that has the required information (a class that would have a properties Student, Course and Payment). But I would required one adapter object for each similar case, this may get very bad for big projects. I still don't like them. Would you have ideas? How would you change the architecture to avoid this kind of problems? @Rory: I read the CQRS and I don't think this suits my needs. As taken from a link references in your link Before describing the details of CQRS we need to understand the two main driving forces behind it: collaboration and staleness That means: many different actors using the same object (collaboration) and once data has been shown to a user, that same data may have been changed by another actor – it is stale (staleness). My problem is that I want to show to the user information from different BO, so I would need to receive them from the service layer. How can my service layer assemble and deliver this information? Edit to @AndrewM: Yes, you understood it correctly, the original idea was to have the view layer to build the BOs, but you have a very nice point about the creation of the BO inside the business layers. Assuming I follow your advice and move the creation logic inside the business layer, my business layer interface would contain the DTOs, for instance public void foo(MyDTO object) But as far as I understand, the DTO is tightly coupled to each view, so it would not be reusable by a second view. In order to use it, the second view would need to build a specific DTO from a specific view or I would have to duplicate the code in the business layer. Is this correct or am I missing something?

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  • Stuff you learned in school, that you have never used again?

    - by Mercfh
    Obviously we learn plenty of things in our University/College/Whatever that probably don't apply to everyday use, but is there anything that stands out particularly? Maybe something that was concentrated ALOT on? For me it was def. 2 things: OO Concepts and Pointers I still use OO, but not nearly to the amount people made it out to be, i can see where it'd be useful but in my line of work we don't have huge amounts of classes, maybe a couple at most. And there certainly isn't much OO reuse (i finally figured out what that means lol) Pointers are another thing, again I can see where they'd be useful...however I barely barely ever touch them, nor do the others I work with. I guess language choice has alot to do with that but still. What about you guys? edit: For those who are asking I work for a Large Printer company, and most of the Applications we work on are Java+XML and Actionscript for "Printer Apps". But we are moving towards other languages (think like webkits and stuff). So the Code amounts per parts are quite small. I never say OO wasn't useful I just said I personally havent seen it used in my workplace much.

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  • Liskov substitution principle with abstract parent class

    - by Songo
    Does Liskov substitution principle apply to inheritance hierarchies where the parent is an abstract class the same way if the parent is a concrete class? The Wikipedia page list several conditions that have to be met before a hierarchy is deemed to be correct. However, I have read in a blog post that one way to make things easier to conform to LSP is to use abstract parent instead of a concrete class. How does the choice of the parent type (abstract vs concrete) impacts the LSP? Is it better to have an abstract base class whenever possible?

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  • Are there any jobs for software developers with a BA and no previous employment? [closed]

    - by IDWMaster
    Are there any careers available for developers who have never been employed before in the industry, and who have a BA, rather than a BS in computer science? I'm currently pursuing a BS in computer science but realized that the math is too difficult for me. Someone suggested switching to a BA instead but I have not been able to find any jobs in my state (Minnesota) which take a BA. I was wondering if a BA is worth pursuing if I cannot get a BS.

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  • Using default parameters for 404 error (PHP with mvc design)?

    - by user1175327
    I have a custom made Framework (written in PHP). It all works very good, but i have some doubts about a certain thing. Right now when a user call this url for example: http://host.com/user/edit/12 Which would resolve to: user = userController edit = editAction() in userController 12 = treated as a param But suppose the controller 'userController' doesn't exist. Then i could throw a 404. But on the other hand, the url could also be used as params for the indexController (which is the default controller). So in that case: controller = indexController user = could be an action in indexController, otherwise treated as a param edit = treated as a param 12 = treated as a param That is actually how it works right now in my framework. So basically, i never throw a 404. I could ofcourse say that only params can be given if the controller name is explicitly named in the URL. So if i want the above url: http://host.com/user/edit/12 To be invoked by the indexController, in the indexAction. Then i specifically have to tell what controller and action it uses in the URL. So the URL should become: http://host.com/index/index/user/edit/12 index = indexController index (2nd one) = the action method user = treated as a param edit = treated as a param 12 = treated as a param That way, when a controller doesn't exist, i don't reroute everything as a param to the index controller and simply throw a 404 error. Now my question is, which one is more preffered? Should i allow both options to be configurable in a config file? Or should i always use one of them. Simply because that's the only and best way to do it?

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  • Database Driven Web Application, C# Front-End and F# Back-End meaning

    - by user1473053
    Hi I am an intern working with ASP.NET. My current task is to make a website which will incorporate some jquery viewing features. This project seems to me will be primarily dealing with reading data from a database and making graphs out of them. This will require me to make custom queries from whatever the client is looking at. I think it is going to be what this guy calls an Ad Hoc Query tool My plan for this is to make it a database-driven website. So I can utilize the jquery dynamic viewing capabilities. I stumbled upon the functional programming paradigm and found F#. I read that because of it's functional programming paradigm, it makes it a good language to do asynchronous functions. I read about how you can use this with LINQ to SQL and how easy it is to make queries without actually putting the query language in. I understand the concept of the MVC design pattern. But I don't understand what they mean about C# being the front-end and F# being the back-end. Can someone clarify this to me? Also what are your thoughts about doing this project in this way? Any comments and thoughts are greatly appreciated. I feel as if learning F# will be a great learning experience for me. My guess is that the F# back-end is like the part where it controls the calls to the database. F# is possibly the model part of the design pattern. And C# is the controller. So HTML, Javascript and Jquery stuff will be my View design pattern. Clarify please?

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  • Building general programming skills?

    - by toleero
    I currently am quite new to programming, I've had exposure to a few languages (C#, PHP, JavaScript, VB, and some others) and I'm quite new to OOP. I was just wondering what is the best way to build up general programming/problem solving skills without being language specific? I was thinking maybe of something like Project Euler but more geared towards newbies? Thanks! Edit: I am looking at getting into Game Scripting/Programming, I'm already in Games but in a different discipline :)

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  • Do you leverage the benefits of the open-closed principle?

    - by Kaleb Pederson
    The open-closed principle (OCP) states that an object should be open for extension but closed for modification. I believe I understand it and use it in conjunction with SRP to create classes that do only one thing. And, I try to create many small methods that make it possible to extract out all the behavior controls into methods that may be extended or overridden in some subclass. Thus, I end up with classes that have many extension points, be it through: dependency injection and composition, events, delegation, etc. Consider the following a simple, extendable class: class PaycheckCalculator { // ... protected decimal GetOvertimeFactor() { return 2.0M; } } Now say, for example, that the OvertimeFactor changes to 1.5. Since the above class was designed to be extended, I can easily subclass and return a different OvertimeFactor. But... despite the class being designed for extension and adhering to OCP, I'll modify the single method in question, rather than subclassing and overridding the method in question and then re-wiring my objects in my IoC container. As a result I've violated part of what OCP attempts to accomplish. It feels like I'm just being lazy because the above is a bit easier. Am I misunderstanding OCP? Should I really be doing something different? Do you leverage the benefits of OCP differently? Update: based on the answers it looks like this contrived example is a poor one for a number of different reasons. The main intent of the example was to demonstrate that the class was designed to be extended by providing methods that when overridden would alter the behavior of public methods without the need for changing internal or private code. Still, I definitely misunderstood OCP.

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  • What makes Instagram so valuable? [closed]

    - by ????
    If as in the FAQ, that topics about business (computer industry) is allowed here, I'd like to find out why Instagram can be so valuable, that it is acquired for $1 billion dollars (USD). To put it simply, isn't it just a photo enhancement app (such as making a photo vintage look), plus sharing those photos on Facebook? That's because in contrast, PlayFish had superb Facebook games, and many of them, and are so much more sophisticated (such as Restaurant City and Pet Society). And PlayFish was merely acquired for $400 million. Some companies such as RockYou, had the number one app on Facebook, but wasn't even acquired for a low price like $200 million. And now just a photo filter app and sharing photos, and it is a business considered to be worth a billion dollars. Why is that?

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  • CMS for coding blog

    - by OrgnlDave
    I've got a server with a LAMP stack and such. I'd like to host a blog-type site (or if there's a free place good for this, that would be cool!) that covers a variety of tutorials, interesting content, etc. There are tons of CMS's out there but if you search for tips on ones that do programming type things well, you get tons of hits about web development. I'd like to know if anyone here has recommendations from actually using a CMS for this type of thing or, short of that, can recommend one - not based on generalities like "Joomla! is great!" I'm looking for the least setup time possible. I'm proficient with CSS and I can design a color scheme, so that's not a big problem. As you can expect, attaching files, pictures, and syntax highlighting are musts (C/C++ ish is good). Ability to group posts, perhaps use tags, etc. would be cool too, but not necessary. As I'm writing this, it almost sounds like it'd be easier to custom-code a small PHP site myself.

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  • Writing Acceptance test cases

    - by HH_
    We are integrating a testing process in our SCRUM process. My new role is to write acceptance tests of our web applications in order to automate them later. I have read a lot about how tests cases should be written, but none gave me practical advices to write test cases for complex web applications, and instead they threw conflicting principles that I found hard to apply: Test cases should be short: Take the example of a CMS. Short test cases are easy to maintain and to identify the inputs and outputs. But what if I want to test a long series of operations (eg. adding a document, sending a notification to another user, the other user replies, the document changes state, the user gets a notice). It rather seems to me that test cases should represent complete scenarios. But I can see how this will produce overtly complex test documents. Tests should identify inputs and outputs:: What if I have a long form with many interacting fields, with different behaviors. Do I write one test for everything, or one for each? Test cases should be independent: But how can I apply that if testing the upload operation requires that the connect operation is successful? And how does it apply to writing test cases? Should I write a test for each operation, but each test declares its dependencies, or should I rewrite the whole scenario for each test? Test cases should be lightly-documented: This principles is specific to Agile projects. So do you have any advice on how to implement this principle? Although I thought that writing acceptance test cases was going to be simple, I found myself overwhelmed by every decision I had to make (FYI: I am a developer and not a professional tester). So my main question is: What steps or advices do you have in order to write maintainable acceptance test cases for complex applications. Thank you.

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  • How to implement child-parent aggregation link in C++?

    - by Giorgio
    Suppose that I have three classes P, C1, C2, composition (strong aggregation) relations between P <>- C1 and P <>- C2, i.e. every instance of P contains an instance of C1 and an instance of C2, which are destroyed when the parent P instance is destroyed. an association relation between instances of C1 and C2 (not necessarily between children of the same P). To implement this, in C++ I normally define three classes P, C1, C2, define two member variables of P of type boost::shared_ptr<C1>, boost::shared_ptr<C2>, and initialize them with newly created objects in P's constructor, implement the relation between C1 and C2 using a boost::weak_ptr<C2> member variable in C1 and a boost::weak_ptr<C1> member variable in C2 that can be set later via appropriate methods, when the relation is established. Now, I also would like to have a link from each C1 and C2 object to its P parent object. What is a good way to implement this? My current idea is to use a simple constant raw pointer (P * const) that is set from the constructor of P (which, in turn, calls the constructors of C1 and C2), i.e. something like: class C1 { public: C1(P * const p, ...) : paren(p) { ... } private: P * const parent; ... }; class P { public: P(...) : childC1(new C1(this, ...)) ... { ... } private: boost::shared_ptr<C1> childC1; ... }; Honestly I see no risk in using a private constant raw pointer in this way but I know that raw pointers are often frowned upon in C++ so I was wondering if there is an alternative solution.

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