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• Design Pattern for Changing Object

  - by user210757

  Is there a Design Pattern for supporting different permutations object? Version 1 public class myOjbect { public string field1 { get; set; } /* requirements: max length 20 */ public int field2 { get; set; } . . . public decimal field200 { get; set; } } Version 2 public class myObject { public string field1 { get; set; } /* requirements: max length 40 */ public int field2 { get; set; } . . . public double field200 { get; set; } /* changed data types */ . . ./* 10 new properties */ public double field210 { get; set; } } of course I could just have separate objects, but thought there might be a good pattern for this sort of thing.

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• Design pattern for loading multiple message types

  - by lukem00

  As I was looking through SO I came across a question about handling multiple message types. My concern is - how do I load such a message in a neat way? I decided to have a separate class with a method which loads one message each time it's invoked. This method should create a new instance of a concrete message type (say AlphaMessage, BetaMessage, GammaMessage, etc.) and return it as a Message. class MessageLoader { public Message Load() { // ... } } The code inside the method is something which looks really awful to me and I would very much like to refactor it/get rid of it: Message msg = Message.Load(...); // load yourself from whatever source if (msg.Type == MessageType.Alpha) return new AlphaMessage(msg); if (msg.Type == MessageType.Beta) return new BetaMessage(msg); // ... In fact, if the whole design looks just too messy and you guys have a better solution, I'm ready to restructure the whole thing. If my description is too chaotic, please let me know what it's missing and I shall edit the question. Thank you all.

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• Design Advice Needed For Synonyms Database

  - by James J

  I'm planning to put together a database that can be used to query synonyms of words. The database will end up huge, so the idea is to keep things running fast. I've been thinking about how to do this, but my database design skills are not up to scratch these days. My initial idea was to have each word stored in one table, and then another table with a 1 to many relationship where each word can be linked to another word and that table can be queried. The application I'm developing allows users to highlight a word, and then type in, or select some synonyms from the database for that word. The application learns from the user input so if someone highlights "car" and types in "motor" the database would be updated to link the relationship if it don't exist already. What I don't want to happen is for a user to type in the word "shop" and link it to the word car. So I'm thinking I will need to add some sort of weight to each relationship. Eventually the synonyms the users enter will be used so they can auto select common synonyms used with a certain word. The lower weight words will not be displayed so shop could never be a synonym of car unless it had a very high weight, and chances are nobody is going to do that. Does the above sound right? Can you offer any suggestions or improvements?

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• Objective-C wrapper API design methodology

  - by Wade Williams

  I know there's no one answer to this question, but I'd like to get people's thoughts on how they would approach the situation. I'm writing an Objective-C wrapper to a C library. My goals are: 1) The wrapper use Objective-C objects. For example, if the C API defines a parameter such as char *name, the Objective-C API should use name:(NSString *). 2) The client using the Objective-C wrapper should not have to have knowledge of the inner-workings of the C library. Speed is not really any issue. That's all easy with simple parameters. It's certainly no problem to take in an NSString and convert it to a C string to pass it to the C library. My indecision comes in when complex structures are involved. Let's say you have: struct flow { long direction; long speed; long disruption; long start; long stop; } flow_t; And then your C API call is: void setFlows(flow_t inFlows[4]); So, some of the choices are: 1) expose the flow_t structure to the client and have the Objective-C API take an array of those structures 2) build an NSArray of four NSDictionaries containing the properties and pass that as a parameter 3) create an NSArray of four "Flow" objects containing the structure's properties and pass that as a parameter My analysis of the approaches: Approach 1: Easiest. However, it doesn't meet the design goals Approach 2: For some reason, this seems to me to be the most "Objective-C" way of doing it. However, each element of the NSDictionary would have to be wrapped in an NSNumber. Now it seems like we're doing an awful lot just to pass the equivalent of a struct. Approach 3: Seems the cleanest to me from an object-oriented standpoint and the extra encapsulation could come in handy later. However, like #2, it now seems like we're doing an awful lot (creating an array, creating and initializing objects) just to pass a struct. So, the question is, how would you approach this situation? Are there other choices I'm not considering? Are there additional advantages or disadvantages to the approaches I've presented that I'm not considering?

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• C# Design Questions

  - by guazz

  How to approach unit testing of private methods? I have a class that loads Employee data into a database. Here is a sample: public class EmployeeFacade { public Employees EmployeeRepository = new Employees(); public TaxDatas TaxRepository = new TaxDatas(); public Accounts AccountRepository = new Accounts(); //and so on for about 20 more repositories etc. public bool LoadAllEmployeeData(Employee employee) { if (employee == null) throw new Exception("..."); EmployeeRepository emps = new EmployeeRepository(); bool exists = emps.FetchExisting(emps.Id); if (!exists) { emps.AddNew(); } try { emps.Id = employee.Id; emps.Name = employee.EmployeeDetails.PersonalDetails.Active.Names.FirstName; emps.SomeOtherAttribute; } catch() {} try { emps.Save(); } catch(){} try { LoadorUpdateTaxData(employee.TaxData); } catch() {} try { LoadorUpdateAccountData(employee.AccountData); } catch() {} ... etc. for about 20 more other employee objects } private bool LoadorUpdateTaxData(employeeId, TaxData taxData) { if (taxData == null) throw new Exception("..."); ...same format as above but using AccountRepository } private bool LoadorUpdateAccountData(employee.TaxData) { ...same format as above but using TaxRepository } } I am writing an application to take serialised objects(e.g. Employee above) and load the data to the database. I have a few design question that I would like opinions on: A - I am calling this class "EmployeeFacade" because I am (attempting?) to use the facade pattern. Is it good practace to name the pattern on the class name? B - Is it good to call the concrete entities of my DAL layer classes "Repositories" e.g. "EmployeeRepository" ? C - Is using the repositories in this way sensible or should I create a method on the repository itself to take, say, the Employee and then load the data from there e.g. EmployeeRepository.LoadAllEmployeeData(Employee employee)? I am aim for cohesive class and but this will requrie the repository to have knowledge of the Employee object which may not be good? D - Is there any nice way around of not having to check if an object is null at the begining of each method? E - I have a EmployeeRepository, TaxRepository, AccountRepository declared as public for unit testing purpose. These are really private enities but I need to be able to substitute these with stubs so that the won't write to my database(I overload the save() method to do nothing). Is there anyway around this or do I have to expose them? F - How can I test the private methods - or is this done (something tells me it's not)? G- "emps.Name = employee.EmployeeDetails.PersonalDetails.Active.Names.FirstName;" this breaks the Law of Demeter but how do I adjust my objects to abide by the law?

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• Design question for WinForms (C#) app, using Entity Framework

  - by cdotlister

  I am planning on writing a small home budget application for myself, as a learning excercise. I have built my database (SQL Server), and written a small console application to interact with it, and test out scenarios on my database. Once I am happy, my next step would be to start building the application - but I am already wondering what the best/standard design would be. I am palnning on using Entity Framework for handling my database entities... then linq to sql/objects for getting the data, all running under a WinForms (for now) application. My plan (I've never used EF... and most of my development background is Web apps) is to have my database... with Entity Framework in it's own project.. which has the connection to the database. This project would expose methods such as 'GetAccount()', 'GetAccount(int accountId)' etc. I'd then have a service project that references my EF project. And on top of that, my GUI project, which makes the calls to my service project. But I am stuck. Lets say I have a screen that displays a list of Account types (Debit, Credit, Loan...). Once I have selected one, the next drop down shows a list of accounts I have that suite that account type. So, my OnChange event on my DropDown on the account type control will make a call to the serviceLayer project, 'GetAccountTypes()', and I would expect back a List< of Account Types. However, the AccountType object ... what is that? That can't be the AccountType object from my EF project, as my GUI project doesn't have reference to it. Would I have to have some sort of Shared Library, shared between my GUI and my Service project, with a custom built AccountType object? The GUI can then expect back a list of these. So my service layer would have a method: public List<AccountType> GetAccountTypes() That would then make a call to a custom method in my EF project, which would probably be the same as the above method, except, it returns an list of EF.Data.AccountType (The Entity Framework generated Account Type object). The method would then have the linq code to get the data as I want it. Then my service layer will get that object, and transform it unto my custom AccountType object, and return it to the GUI. Does that sound at all like a good plan?

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• Design pattern question: encapsulation or inheritance

  - by Matt

  Hey all, I have a question I have been toiling over for quite a while. I am building a templating engine with two main classes Template.php and Tag.php, with a bunch of extension classes like Img.php and String.php. The program works like this: A Template object creates a Tag objects. Each tag object determines which extension class (img, string, etc.) to implement. The point of the Tag class is to provide helper functions for each extension class such as wrap('div'), addClass('slideshow'), etc. Each Img or String class is used to render code specific to what is required, so $Img->render() would give something like <img src='blah.jpg' /> My Question is: Should I encapsulate all extension functionality within the Tag object like so: Tag.php function __construct($namespace, $args) { // Sort out namespace to determine which extension to call $this->extension = new $namespace($this); // Pass in Tag object so it can be used within extension return $this; // Tag object } function render() { return $this->extension->render(); } Img.php function __construct(Tag $T) { $args = $T->getArgs(); $T->addClass('img'); } function render() { return '<img src="blah.jpg" />'; } Usage: $T = new Tag("img", array(...); $T->render(); .... or should I create more of an inheritance structure because "Img is a Tag" Tag.php public static create($namespace, $args) { // Sort out namespace to determine which extension to call return new $namespace($args); } Img.php class Img extends Tag { function __construct($args) { // Determine namespace then call create tag $T = parent::__construct($namespace, $args); } function render() { return '<img src="blah.jpg" />'; } } Usage: $Img = Tag::create('img', array(...)); $Img->render(); One thing I do need is a common interface for creating custom tags, ie I can instantiate Img(...) then instantiate String(...), I do need to instantiate each extension using Tag. I know this is somewhat vague of a question, I'm hoping some of you have dealt with this in the past and can foresee certain issues with choosing each design pattern. If you have any other suggestions I would love to hear them. Thanks! Matt Mueller

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• JavaScript Resource Management Design Pattern

  - by Adam

  As a web developer, a common problem I find myself tackling is waiting for something to load before doing something else. In particular, I often hide (using either display: none; or visibility: hidden; depending on the situation) elements while waiting for a background image or a CSS file to load. Consider this example from Last.FM. They overlay a semi-transparant PNG over each album art image so that it looks like it's inside a jewel-case. They let it load when it loads, so depending on your internet speed, you may see the art image by itself (without the overlay) temporarily. In this case, the album art looks fine without the jewel-case effect. But in similar situations, I have found that I don't want the user to see the site's design mangled as resources incrementally load. So, in rare cases I have hidden everything from the user until the whole kit and kaboodle has loaded. But this is often a pain to write out, and may force the user to wait for a pretty long time to see anything (besides "loading..." text). I can think of (and have used on occasion) some obvious solutions/compromises: Use some inline CSS so that as certain parts of the DOM load and render, they will immediately have the correct size/position/etc. Immediately render the navigation part of the site, so that if the user wanted to use the current page purely to get somewhere else, they don't have to wait for the rest to load. Load pixelated images first as placeholders for layout while lazy-loading higher quality images as replacements. Something quirky like using a cute animated gif to distract the user during a "loading..." phase. Show useful information as a reference while loading the full UI. (Something akin to Gmail Inbox Preview, etc.) (Sorry if my question was basically just asked and answered...) Despite all of these ideas, I still find myself hoping there are better ways of doing some of these things. So I guess what I'm looking for is some inspiration and/or any creative ways of dealing with this problem that you guys may have seen out in the wild.

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• SQLAlchemy unsupported type error - and table design issues?

  - by Az

  Hi there, back again with some more SQLAlchemy shenanigans. Let me step through this. My table is now set up as so: engine = create_engine('sqlite:///:memory:', echo=False) metadata = MetaData() students_table = Table('studs', metadata, Column('sid', Integer, primary_key=True), Column('name', String), Column('preferences', Integer), Column('allocated_rank', Integer), Column('allocated_project', Integer) ) metadata.create_all(engine) mapper(Student, students_table) Fairly simple, and for the most part I've been enjoying the ability to query almost any bit of information I want provided I avoid the error cases below. The class it is mapped from is: class Student(object): def __init__(self, sid, name): self.sid = sid self.name = name self.preferences = collections.defaultdict(set) self.allocated_project = None self.allocated_rank = 0 def __repr__(self): return str(self) def __str__(self): return "%s %s" %(self.sid, self.name) Explanation: preferences is basically a set of all the projects the student would prefer to be assigned. When the allocation algorithm kicks in, a student's allocated_project emerges from this preference set. Now if I try to do this: for student in students.itervalues(): session.add(student) session.commit() It throws two errors, one for the allocated_project column (seen below) and a similar error for the preferences column: sqlalchemy.exc.InterfaceError: (InterfaceError) Error binding parameter 4 - probably unsupported type. u'INSERT INTO studs (sid, name, allocated_rank, allocated_project) VALUES (?, ?, ?, ?, ?, ?, ?)' [1101, 'Muffett,M.', 1, 888 Human-spider relationships (Supervisor id: 123)] If I go back into my code I find that, when I'm copying the preferences from the given text files, it actually refers to the Project class which is mapped to a dictionary, using the unique project id's (pid) as keys. Thus, as I iterate through each student via their rank and to the preferences set, it adds not a project id, but the reference to the project id from the projects dictionary. students[sid].preferences[int(rank)].add(projects[int(pid)]) Now this is very useful to me since I can find out all I want to about a student's preferred projects without having to run another check to pull up information about the project id. The form you see in the error has the object print information passed as: return "%s %s (Supervisor id: %s)" %(self.proj_id, self.proj_name, self.proj_sup) My questions are: I'm trying to store an object in a database field aren't I? Would the correct way then, be copying the project information (project id, name, etc) into its own table, referenced by the unique project id? That way I can just have the project id field for one of the student tables just be an integer id and when I need more information, just join the tables? So and so forth for other tables? If the above makes sense, then how does one maintain the relationship with a column of information in one table which is a key index on another table? Does this boil down into a database design problem? Are there any other elegant ways of accomplishing this? Apologies if this is a very long-winded question. It's rather crucial for me to solve this, so I've tried to explain as much as I can, whilst attempting to show that I'm trying (key word here sadly) to understand what could be going wrong.

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• What is good practice in .NET system architecture design concerning multiple models and aggregates

  - by BuzzBubba

  I'm designing a larger enterprise architecture and I'm in a doubt about how to separate the models and design those. There are several points I'd like suggestions for: - models to define - way to define models Currently my idea is to define: Core (domain) model Repositories to get data to that domain model from a database or other store Business logic model that would contain business logic, validation logic and more specific versions of forms of data retrieval methods View models prepared for specifically formated data output that would be parsed by views of different kind (web, silverlight, etc). For the first model I'm puzzled at what to use and how to define the mode. Should this model entities contain collections and in what form? IList, IEnumerable or IQueryable collections? - I'm thinking of immutable collections which IEnumerable is, but I'd like to avoid huge data collections and to offer my Business logic layer access with LINQ expressions so that query trees get executed at Data level and retrieve only really required data for situations like the one when I'm retrieving a very specific subset of elements amongst thousands or hundreds of thousands. What if I have an item with several thousands of bids? I can't just make an IEnumerable collection of those on the model and then retrieve an item list in some Repository method or even Business model method. Should it be IQueryable so that I actually pass my queries to Repository all the way from the Business logic model layer? Should I just avoid collections in my domain model? Should I void only some collections? Should I separate Domain model and BusinessLogic model or integrate those? Data would be dealt trough repositories which would use Domain model classes. Should repositories be used directly using only classes from domain model like data containers? This is an example of what I had in mind: So, my Domain objects would look like (e.g.) public class Item { public string ItemName { get; set; } public int Price { get; set; } public bool Available { get; set; } private IList<Bid> _bids; public IQueryable<Bid> Bids { get { return _bids.AsQueryable(); } private set { _bids = value; } } public AddNewBid(Bid newBid) { _bids.Add(new Bid {.... } } Where Bid would be defined as a normal class. Repositories would be defined as data retrieval factories and used to get data into another (Business logic) model which would again be used to get data to ViewModels which would then be rendered by different consumers. I would define IQueryable interfaces for all aggregating collections to get flexibility and minimize data retrieved from real data store. Or should I make Domain Model "anemic" with pure data store entities and all collections define for business logic model? One of the most important questions is, where to have IQueryable typed collections? - All the way from Repositories to Business model or not at all and expose only solid IList and IEnumerable from Repositories and deal with more specific queries inside Business model, but have more finer grained methods for data retrieval within Repositories. So, what do you think? Have any suggestions?

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• Looking for a better design: A readonly in-memory cache mechanism

  - by Dylan Lin

  Hi all, I have a Category entity (class), which has zero or one parent Category and many child Categories -- it's a tree structure. The Category data is stored in a RDBMS, so for better performance, I want to load all categories and cache them in memory while launching the applicaiton. Our system can have plugins, and we allow the plugin authors to access the Category Tree, but they should not modify the cached items and the tree(I think a non-readonly design might cause some subtle bugs in this senario), only the system knows when and how to refresh the tree. Here are some demo codes: public interface ITreeNode<T> where T : ITreeNode<T> { // No setter T Parent { get; } IEnumerable<T> ChildNodes { get; } } // This class is generated by O/R Mapping tool (e.g. Entity Framework) public class Category : EntityObject { public string Name { get; set; } } // Because Category is not stateless, so I create a cleaner view class for Category. // And this class is the Node Type of the Category Tree public class CategoryView : ITreeNode<CategoryView> { public string Name { get; private set; } #region ITreeNode Memebers public CategoryView Parent { get; private set; } private List<CategoryView> _childNodes; public IEnumerable<CategoryView> ChildNodes { return _childNodes; } #endregion public static CategoryView CreateFrom(Category category) { // here I can set the CategoryView.Name property } } So far so good. However, I want to make ITreeNode interface reuseable, and for some other types, the tree should not be readonly. We are not able to do this with the above readonly ITreeNode, so I want the ITreeNode to be like this: public interface ITreeNode<T> { // has setter T Parent { get; set; } // use ICollection<T> instead of IEnumerable<T> ICollection<T> ChildNodes { get; } } But if we make the ITreeNode writable, then we cannot make the Category Tree readonly, it's not good. So I think if we can do like this: public interface ITreeNode<T> { T Parent { get; } IEnumerable<T> ChildNodes { get; } } public interface IWritableTreeNode<T> : ITreeNode<T> { new T Parent { get; set; } new ICollection<T> ChildNodes { get; } } Is this good or bad? Are there some better designs? Thanks a lot! :)

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• Signals and threads - good or bad design decision?

  - by Jens

  I have to write a program that performs highly computationally intensive calculations. The program might run for several days. The calculation can be separated easily in different threads without the need of shared data. I want a GUI or a web service that informs me of the current status. My current design uses BOOST::signals2 and BOOST::thread. It compiles and so far works as expected. If a thread finished one iteration and new data is available it calls a signal which is connected to a slot in the GUI class. My question(s): Is this combination of signals and threads a wise idea? I another forum somebody advised someone else not to "go down this road". Are there potential deadly pitfalls nearby that I failed to see? Is my expectation realistic that it will be "easy" to use my GUI class to provide a web interface or a QT, a VTK or a whatever window? Is there a more clever alternative (like other boost libs) that I overlooked? following code compiles with g++ -Wall -o main -lboost_thread-mt <filename>.cpp code follows: #include <boost/signals2.hpp> #include <boost/thread.hpp> #include <boost/bind.hpp> #include <iostream> #include <iterator> #include <string> using std::cout; using std::cerr; using std::string; /** * Called when a CalcThread finished a new bunch of data. */ boost::signals2::signal<void(string)> signal_new_data; /** * The whole data will be stored here. */ class DataCollector { typedef boost::mutex::scoped_lock scoped_lock; boost::mutex mutex; public: /** * Called by CalcThreads call the to store their data. */ void push(const string &s, const string &caller_name) { scoped_lock lock(mutex); _data.push_back(s); signal_new_data(caller_name); } /** * Output everything collected so far to std::out. */ void out() { typedef std::vector<string>::const_iterator iter; for (iter i = _data.begin(); i != _data.end(); ++i) cout << " " << *i << "\n"; } private: std::vector<string> _data; }; /** * Several of those can calculate stuff. * No data sharing needed. */ struct CalcThread { CalcThread(string name, DataCollector &datcol) : _name(name), _datcol(datcol) { } /** * Expensive algorithms will be implemented here. * @param num_results how many data sets are to be calculated by this thread. */ void operator()(int num_results) { for (int i = 1; i <= num_results; ++i) { std::stringstream s; s << "["; if (i == num_results) s << "LAST "; s << "DATA " << i << " from thread " << _name << "]"; _datcol.push(s.str(), _name); } } private: string _name; DataCollector &_datcol; }; /** * Maybe some VTK or QT or both will be used someday. */ class GuiClass { public: GuiClass(DataCollector &datcol) : _datcol(datcol) { } /** * If the GUI wants to present or at least count the data collected so far. * @param caller_name is the name of the thread whose data is new. */ void slot_data_changed(string caller_name) const { cout << "GuiClass knows: new data from " << caller_name << std::endl; } private: DataCollector & _datcol; }; int main() { DataCollector datcol; GuiClass mc(datcol); signal_new_data.connect(boost::bind(&GuiClass::slot_data_changed, &mc, _1)); CalcThread r1("A", datcol), r2("B", datcol), r3("C", datcol), r4("D", datcol), r5("E", datcol); boost::thread t1(r1, 3); boost::thread t2(r2, 1); boost::thread t3(r3, 2); boost::thread t4(r4, 2); boost::thread t5(r5, 3); t1.join(); t2.join(); t3.join(); t4.join(); t5.join(); datcol.out(); cout << "\nDone" << std::endl; return 0; }

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• Is there a way to put relationships/contraints into CSS?

  - by hekevintran

  In every design tool or art principle I've heard of, relationships are a central theme. By relationships I mean the thing you can do in Adobe Illustrator to specify that the height of one shape is equal to half the height of another. You cannot express this information in CSS. CSS hard-codes all values. Using a language like LESS that allows variables and arithmetic you can get closer to relationships but it's still a CSS variant. This inability in my mind is the biggest problem with CSS. CSS is supposed to be a language that describes the visual component of a Web page but it ignores relationships and contraints, ideas that are at the core of art. How possible is it to imagine a new Web design language that can express relationships and contraints that can be implemented in JavaScript using the current CSS properties?

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• how to avoid returning mocks from a mocked object list

  - by koen

  I'm trying out mock/responsibility driven design. I seem to have problems to avoid returning mocks from mocks in the case of finder objects. An example could be an object that checks whether the bills from last month are paid. It needs a service that retrieves a list of bills for that. So I need to mock that service that retrieves the bills. At the same time I need that mock to return mocked Bills (since I don't want my test to rely on the correctness bill implementation). Is my design flawed? Is there a better way to test this? Or is this the way it will need to be when using finder objects (the finding of the bills in this case)?

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• Moving My Blog

  - by Hirt

  Oracle has, unfortunately, moved to a new blogging platform. For security reasons, it is no longer possible to use external tools, such as Windows Live Writer. Since this makes it too time consuming for me to blog, I've decided to only use my private blog, even for work related blog entries. This is where you can find my blog entries, from now on:http://hirt.se/blog/ Note that it is hosted on the poor server in my garage, hooked up to an ADSL-modem. It will probably be dog slow. Sorry for that.

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• Why implement DB connection pointer object as a reference counting pointer? (C++)

  - by DVK

  At our company one of the core C++ classes (Database connection pointer) is implemented as a reference counting pointer. To be clear, the objects are NOT DB connections themselves, but pointers to a DB connection object. The library is very old, and nobody who designed is around anymore. So far, nether I, nor any C++ experts in the company that I asked have come up with a good reason for why this particular design was chosen. Any ideas? It is introducing some problems (partially due to awful reference pointer implementation used), and I'm trying to understand if this design actually has some deep underlying reasons? The usage pattern these days seems to be that the DB connection pointer object is returned by a DB connection manager class, and it's somewhat unclear whether DB connection pointers were designed to be able to be used independently of DB connection manager.

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• Plan variable and call dependencies

  - by Gerenuk

  I'd like to write down the design of my program to understand the dependencies and calls better. I know there are class diagrams which show inheritance and attribute variables. However I'd also like to document the input parameters to method functions and in particular which calls the methods function executes inside (e.g. on the input parameters). Also sometimes it might be useful to show how actual objects are connected (if there is a standard structure). This way I can have a better understanding of the modules and design before starting to program. Can you suggest a method to do this software design? It should be one-to-one to programming code structure so that I really notice all quirks beforehand (instead of high-level design where thing are hard to implement without further work). Maybe some special diagram or tool or a combination? It is static dependency and call design rather than time dependent execution monitoring. (I use Python if you have any specialized recommendations).

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• Sending object C from class A to class B

  - by user278618

  Hi, I can't figure out how to design classes in my system. In classA I create object selenium (it simulates user actions at website). In this ClassA I create another objects like SearchScreen, Payment_Screen and Summary_Screen. # -*- coding: utf-8 -*- from selenium import selenium import unittest, time, re class OurSiteTestCases(unittest.TestCase): def setUp(self): self.verificationErrors = [] self.selenium = selenium("localhost", 5555, "*chrome", "http://www.someaddress.com/") time.sleep(5) self.selenium.start() def test_buy_coffee(self): sel = self.selenium sel.open('/') sel.window_maximize() search_screen=SearchScreen(self.selenium) search_screen.choose('lavazza') payment_screen=PaymentScreen(self.selenium) payment_screen.fill_test_data() summary_screen=SummaryScreen(selenium) summary_screen.accept() def tearDown(self): self.selenium.stop() self.assertEqual([], self.verificationErrors) if __name__ == "__main__": unittest.main() It's example SearchScreen module: class SearchScreen: def __init__(self,selenium): self.selenium=selenium def search(self): self.selenium.click('css=button.search') I want to know if there is anything ok with a design of those classes?

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• Writing Great Software

  - by 01010011

  Hi, I'm currently reading Head First's Object Oriented Analysis and Design. The book states that to write great software (i.e. software that is well-designed, well-coded, easy to maintain, reuse, and extend) you need to do three things: Firstly, make sure the software does everything the customer wants it to do Once step 1 is completed, apply Object Oriented principles and techniques to eliminate any duplicate code that might have slipped in Once steps 1 and 2 are complete, then apply design patterns to make sure the software is maintainable and reusable for years to come. My question is, do you follow these steps when developing great software? If not, what steps do you usually follow inorder to ensure it's well designed, well-coded, easy to maintain, reuse and extend?

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• What is the right way to implement communication between java objects?

  - by imoschak

  I'm working on an academic project which simulates a rather large queuing procedure in java. The core of the simulator rests within one package where there exist 8 classes, each one implementing a single concept. Every class in the project follows SRP. These classes encapsulate the behavior of the simulator and inter-connect every other class in the project. The problem that has arisen is that most of these 8 classes are, as is logical i think, tightly coupled and each one has to have working knowledge of every other class in this package in order to be able to call methods from it when needed. The application needs only one instance of each class so it might be better to create static fields for each class in a new class and use that to make calls -instead of preserving a reference in each class for every other class in the package (which I'm certain that is incorrect)-, but is this considered a correct design solution? or is there a design pattern maybe that better suits my needs?

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• The right way to implement communication between java objects

  - by imoschak

  I'm working on an academic project which simulates a rather large queuing procedure in java. The core of the simulator rests within one package where there exist 8 classes each one implementing a single concept. Every class in the project follows SRP. These classes encapsulate the behavior of the simulator and inter-connect every other class in the project. The problem that I has arisen is that most of these 8 classes are, as is logical i think, tightly coupled and each one has to have working knowledge of every other class in this package in order to be able to call methods from it when needed. The application needs only one instance of each class so it might be better to create static fields for each class in a new class and use that to make calls -instead of preserving a reference in each class for every other class in the package (which I'm certain that is incorrect)-, but is this considered a correct design solution? or is there a design pattern maybe that better suits my needs?

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• DATE function does not support all the dates in DAX by design #powerpivot #tabular #dax

  - by Marco Russo (SQLBI)

  The DATE function in DAX has this simple syntax: DATE( <year>, <month>, <day> ) If you are like me, you never read the BOL notes that says in a clear way that it supports dates beginning with March 1, 1900. In fact, I was wrongly assuming that it would have supported any date that can be represented in a Date data type in Data Models, so all the dates beginning with January 1, 1900. The funny thing is that in some of the BOL documentation you will find that Date data type supports dates after March 1, 1900 (which seems not including that date, but this is a detail…). But we should not digress. The real issue is that if you try to call the DATE function passing values between January 1 and February 28, 1900, you will see a different day as a result. evaluate row ( "x", DATE( 1900, 1, 1 ) ) -- return WRONG result -- [x] 12/31/1899 12:00:00 AM   evaluate row ( "x", DATE( 1901, 2, 29 ) ) -- return WRONG result -- [x] 2/28/1900 12:00:00 AM   evaluate row ( "x", DATE( 1900, 3, 1 ) ) -- return CORRECT result -- [x] 3/1/1900 12:00:00 AM As usual, this is not a bug. It is “by design”. The DATE function works in this way in Excel. And also in Excel it was “by design”. In this case the design is having the same bug of Lotus 1-2-3 that handled 1900 a leap year, even though it isn’t. The first release of Lotus 1-2-3 is dated 1983. I hope many of my readers are younger than that. I tried to open a bug in Connect. Please vote it. I would like if Microsoft changed this type of items from “by design” (as we can expect) to “by genetic disease”. Or by “historical respect”, in order to be more politically correct.

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• Oracle Fusion Applications Design Patterns Now Available

  - by Frank Nimphius

  "The Oracle Fusion Applications user experience design patterns are published! These new, reusable usability solutions and best-practices, which will join Oracle dashboard patterns and guidelines that are already available online, are used by Oracle to artfully bring to life a new standard in the user experience, or UX, of enterprise applications. Now, the Oracle applications development community can benefit from the science behind the Oracle Fusion Applications user experience, too.These Oracle Fusion Applications UX Design Patterns, or blueprints, enable Oracle applications developers and system implementers everywhere to leverage professional usability insight when [...]  designing exciting, new, highly usable applications -- in the cloud or on-premise.  Based on the Oracle Application Development Framework (ADF) components, the Oracle Fusion Applications patterns and guidelines are proven with real users and in the Applications UX usability labs, so you can get right to work coding productivity-enhancing designs that provide an advantage for your entire business.  What’s the best way to get started? We’ve made that easy, too. The Design Filter Tool (DeFT) selects the best pattern for your user type and task. Simply adapt your selection for your own task flow and content, and you’re on your way to a really great applications user experience. More Oracle applications design patterns and training are coming your way in the future. To provide feedback on the sets that are currently available, let us know in the comments section or use the contact form provided."

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• design in agile process

  - by ying

  Recently I had an interview with dev team in a company. The team uses agile + TDD. The code exercise implements a video rental store which generates statement to calc total rental fee for each type of video (new release, children, etc) for a customer. The existing code use object like: Statement to generate statement and calc fee where big switch statement sits to use enum to determine how to calc rental fee customer holds a list of rentals movie base class and derived class for each type of movie (NEW, CHILDREN, ACTION, etc) The code originally doesn't compile as the owner was assumed to be hit by a bus. So here is what I did: outlined the improvement over object model to have better responsibility for each class. use strategy pattern to replace switch statement and weave them in config But the team says it's waste of time because there is no requirement for it and UAT test suite works and is the only guideline goes into architecture decision. The underlying story is just to get pricing feature out and not saying anything about how to do it. So the discussion is focused on why should time be spent on refactor the switch statement. In my understanding, agile methodology doesn't mean zero design upfront and such code smell should be avoided at the beginning. Also any unit/UAT test suite won't detect such code smell, otherwise sonar, findbugs won't exist. Here I want to ask: is there such a thing called agile design in the agile methodology? Just like agile documentation. how to define agile design upfront? how to know enough is enough? In my understanding, ballpark architecture and data contract among components should be defined before/when starting project, not the details. Am I right? anyone can explain what the team is really looking for in this kind of setup? is it design aspect or agile aspect? how to implement minimum viable product concept in the agile process in the real world project? Is it must that you feel embarrassed to be MVP?

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• MVC repository pattern design decision

  - by bradjive

  I have an asp .net MVC application and recently started implementing the repository pattern with a service validation layer, much like this. I've been creating one repository/service for each model that I create. Is this overkill? Instead, should I create one repository/service for each logical business area that provides CRUD for many different models? To me, it seems like I'm either cluttering the project tree with many files or cluttering a class with many methods. 6 one way half dozen the other. Can you think of any good arguments either way?

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