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• Checking preconditions or not

  - by Robert Dailey

  I've been wanting to find a solid answer to the question of whether or not to have runtime checks to validate input for the purposes of ensuring a client has stuck to their end of the agreement in design by contract. For example, consider a simple class constructor: class Foo { public: Foo( BarHandle bar ) { FooHandle handle = GetFooHandle( bar ); if( handle == NULL ) { throw std::exception( "invalid FooHandle" ); } } }; I would argue in this case that a user should not attempt to construct a Foo without a valid BarHandle. It doesn't seem right to verify that bar is valid inside of Foo's constructor. If I simply document that Foo's constructor requires a valid BarHandle, isn't that enough? Is this a proper way to enforce my precondition in design by contract? So far, everything I've read has mixed opinions on this. It seems like 50% of people would say to verify that bar is valid, the other 50% would say that I shouldn't do it, for example consider a case where the user verifies their BarHandle is correct, but a second (and unnecessary) check is also being done inside of Foo's constructor.

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• Confused about implementing Single Responsibility Principle

  - by HichemSeeSharp

  Please bear with me if the question looks not well structured. To put you in the context of my issue: I am building an application that invoices vehicles stay duration in a parking. In addition to the stay service there are some other services. Each service has its own calculation logic. Here is an illustration (please correct me if the design is wrong): public abstract class Service { public int Id { get; set; } public bool IsActivated { get; set; } public string Name { get; set } public decimal Price { get; set; } } public class VehicleService : Service { //MTM : many to many public virtual ICollection<MTMVehicleService> Vehicles { get; set; } } public class StayService : VehicleService { } public class Vehicle { public int Id { get; set; } public string ChassisNumber { get; set; } public DateTime? EntryDate { get; set; } public DateTime? DeliveryDate { get; set; } //... public virtual ICollection<MTMVehicleService> Services{ get; set; } } Now, I am focusing on the stay service as an example: I would like to know at invoicing time which class(es) would be responsible for generating the invoice item for the service and for each vehicle? This should calculate the duration cost knowing that the duration could be invoiced partially so the like is as follows: not yet invoiced stay days * stay price per day. At this moment I have InvoiceItemsGenerator do everything but I am aware that there is a better design.

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• A better alternative to incompatible implementations for the same interface?

  - by glenatron

  I am working on a piece of code which performs a set task in several parallel environments where the behaviour of the different components in the task are similar but quite different. This means that my implementations are quite different but they are all based on the relationships between the same interfaces, something like this: IDataReader -> ContinuousDataReader -> ChunkedDataReader IDataProcessor -> ContinuousDataProcessor -> ChunkedDataProcessor IDataWriter -> ContinuousDataWriter -> ChunkedDataWriter So that in either environment we have an IDataReader, IDataProcessor and IDataWriter and then we can use Dependency Injection to ensure that we have the correct one of each for the current environment, so if we are working with data in chunks we use the ChunkedDataReader, ChunkedDataProcessor and ChunkedDataWriter and if we have continuous data we have the continuous versions. However the behaviour of these classes is quite different internally and one could certainly not go from a ContinuousDataReader to the ChunkedDataReader even though they are both IDataProcessors. This feels to me as though it is incorrect ( possibly an LSP violation? ) and certainly not a theoretically correct way of working. It is almost as though the "real" interface here is the combination of all three classes. Unfortunately in the project I am working on with the deadlines we are working to, we're pretty much stuck with this design, but if we had a little more elbow room, what would be a better design approach in this kind of scenario?

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• Use decorator and factory together to extend objects?

  - by TheClue

  I'm new to OOP and design pattern. I've a simple app that handles the generation of Tables, Columns (that belong to Table), Rows (that belong to Column) and Values (that belong to Rows). Each of these object can have a collection of Property, which is in turn defined as an enum. They are all interfaces: I used factories to get concrete instances of these products, depending on circumnstances. Now I'm facing the problem of extending these classes. Let's say I need another product called "SpecialTable" which in turn has some special properties or new methods like 'getSomethingSpecial' or an extended set of Property. The only way is to extend/specialize all my elements (ie. build a SpecialTableFactory, a SpecialTable interface and a SpecialTableImpl concrete)? What to do if, let's say, I plan to use standard methods like addRow(Column column, String name) that doesn't need to be specialized? I don't like the idea to inherit factories and interfaces, but since SpecialTable has more methods than Table i guess it cannot share the same factory. Am I wrong? Another question: if I need to define product properties at run time (a Table that is upgraded to SpecialTable at runtime), i guess i should use a decorator. Is it possible (and how) to combine both factory and decorator design? Is it better to use a State or Strategy pattern, instead?

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• Memento with optional state?

  - by Korey Hinton

  EDIT: As pointed out by Steve Evers and pdr, I am not correctly implementing the Memento pattern, my design is actually State pattern. Menu Program I built a console-based menu program with multiple levels that selects a particular test to run. Each level more precisely describes the operation. At any level you can type back to go back one level (memento). Level 1: Server Type? [1] Server A [2] Server B Level 2: Server environment? [1] test [2] production Level 3: Test type? [1] load [2] unit Level 4: Data Collection? [1] Legal docs [2] Corporate docs Level 4.5 (optional): Load Test Type [2] Multi TIF [2] Single PDF Level 5: Command Type? [1] Move [2] Copy [3] Remove [4] Custom Level 6: Enter a keyword [setup, cleanup, run] Design States PROBLEM: Right now the STATES enum is the determining factor as to what state is BACK and what state is NEXT yet it knows nothing about what the current memento state is. Has anyone experienced a similar issue and found an effective way to handle mementos with optional state? static enum STATES { SERVER, ENVIRONMENT, TEST_TYPE, COLLECTION, COMMAND_TYPE, KEYWORD, FINISHED } Possible Solution (Not-flexible) In reference to my code below, every case statement in the Menu class could check the state of currentMemo and then set the STATE (enum) accordingly to pass to the Builder. However, this doesn't seem flexible very flexible to change and I'm struggling to see an effective way refactor the design. class Menu extends StateConscious { private State state; private Scanner reader; private ServerUtils utility; Menu() { state = new State(); reader = new Scanner(System.in); utility = new ServerUtils(); } // Recurring menu logic public void startPromptingLoop() { List<State> states = new ArrayList<>(); states.add(new State()); boolean redoInput = false; boolean userIsDone = false; while (true) { // get Memento from last loop Memento currentMemento = states.get(states.size() - 1) .saveMemento(); if (currentMemento == null) currentMemento = new Memento.Builder(0).build(); if (!redoInput) System.out.println(currentMemento.prompt); redoInput = false; // prepare Memento for next loop Memento nextMemento = null; STATES state = STATES.values()[states.size() - 1]; // get user input String selection = reader.nextLine(); switch (selection) { case "exit": reader.close(); return; // only escape case "quit": nextMemento = new Memento.Builder(first(), currentMemento, selection).build(); states.clear(); break; case "back": nextMemento = new Memento.Builder(previous(state), currentMemento, selection).build(); if (states.size() <= 1) { states.remove(0); } else { states.remove(states.size() - 1); states.remove(states.size() - 1); } break; case "1": nextMemento = new Memento.Builder(next(state), currentMemento, selection).build(); break; case "2": nextMemento = new Memento.Builder(next(state), currentMemento, selection).build(); break; case "3": nextMemento = new Memento.Builder(next(state), currentMemento, selection).build(); break; case "4": nextMemento = new Memento.Builder(next(state), currentMemento, selection).build(); break; default: if (state.equals(STATES.CATEGORY)) { String command = selection; System.out.println("Executing " + command + " command on: " + currentMemento.type + " " + currentMemento.environment); utility.executeCommand(currentMemento.nickname, command); userIsDone = true; states.clear(); nextMemento = new Memento.Builder(first(), currentMemento, selection).build(); } else if (state.equals(STATES.KEYWORD)) { nextMemento = new Memento.Builder(next(state), currentMemento, selection).build(); states.clear(); nextMemento = new Memento.Builder(first(), currentMemento, selection).build(); } else { redoInput = true; System.out.println("give it another try"); continue; } break; } if (userIsDone) { // start the recurring menu over from the beginning for (int i = 0; i < states.size(); i++) { if (i != 0) { states.remove(i); // remove all except first } } reader = new Scanner(System.in); this.state = new State(); userIsDone = false; } if (!redoInput) { this.state.restoreMemento(nextMemento); states.add(this.state); } } } }

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• USE case to Class Diagram - How do I?

  - by 01010011

  Hi, I would like your guidance on how to create classes and their relationships (generalization, association, aggregation and composition) accurately from my USE case diagram (please see below). I am trying to create this class diagram so I can use it to create a simple online PHP application that allows the user to register an account, login and logout, and store, search and retrieve data from a MySQL database. Are my classes correct? Or should I create more classes? And if so, what classes are missing? What relationships should I use when connecting the register, login, logout, search_database and add_to_database to the users? I'm new to design patterns and UML class diagrams but from my understanding, the association relationship relates one object with another object; the aggregation relationship is a special kind of association that allows "a part" to belong to more than one "whole" (e.g. a credit card and its PIN - the PIN class can also be used in a debit card class); and a composition relationship is a special form of aggregation that allows each part to belong to only one whole at a time. I feel like I have left out some classes or something because I just can't seem to find the relationships from my understanding of relationships. Any assistance will be really appreciated. Thanks in advance. USE CASE DIAGRAM CLASS DIAGRAM

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• Separation of domain and ui layer in a composite

  - by hansmaad

  Hi all, i'm wondering if there is a pattern how to separate the domain logic of a class from the ui responsibilities of the objects in the domain layer. Example: // Domain classes interface MachinePart { CalculateX(in, out) // Where do we put these: // Draw(Screen) ?? // ShowProperties(View) ?? // ... } class Assembly : MachinePart { CalculateX(in, out) subParts } class Pipe : MachinePart { CalculateX(in, out) length, diamater... } There is an application that calculates the value X for machines assembled from many machine parts. The assembly is loaded from a file representation and is designed as a composite. Each concrete part class stores some data to implement the CalculateX(in,out) method to simulate behaviour of the whole assembly. The application runs well but without GUI. To increase the usability a GUi should be developed on top of the existing implementation (changes to the existing code are allowed). The GUI should show a schematic graphical representation of the assembly and provide part specific dialogs to edit several parameters. To achieve these goals the application needs new functionality for each machine part to draw a schematic representation on the screen, show a property dialog and other things not related to the domain of machine simulation. I can think of some different solutions to implement a Draw(Screen) functionality for each part but i am not happy with each of them. First i could add a Draw(Screen) method to the MachinePart interface but this would mix-up domain code with ui code and i had to add a lot of functionality to each machine part class what makes my domain model hard to read and hard to understand. Another "simple" solution is to make all parts visitable and implement ui code in visitors but Visitor does not belong to my favorite patterns. I could derive UI variants from each machine part class to add the UI implementation there but i had to check if each part class is suited for inheritance and had to be careful on changes to the base classes. My currently favorite design is to create a parallel composite hierarchy where each component stores data to define a machine part, has implementation for UI methods and a factory method which creates instances of the corresponding domain classes, so that i can "convert" a UI assembly to a domain assembly. But there are problems to go back from the created domain hierarchy to the UI hierarchy for showing calculation results in the drawing for example (imagine some parts store some values during the calculation i want to show in the schematic representation after the simluation). Maybe there are some proven patterns for such problems?

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• Linux Access physical memory (NOR flash)

  - by Kevin

  Hello, I am trying to access a Linux system's NOR flash memory. I tried use __raw_readl(xxxxx) (through io_p2v) to read NOR memory data, but I failed. Is there any way I can access that memory? Will driver /dev/mem work for this? I guess not. it is only for the RAM maybe. Can anyone help?

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• Business Continuity for EBS Using Oracle 11g Physical Standby DB

  - by Steven Chan

  Our Applications Technology Group database architects have released two new documents covering the use of Oracle Data Guard to create physical standby databases for Oracle E-Business Suite environments:Business Continuity for Oracle E-Business Release 12 Using Oracle 11g Physical Standby Database (Note 1070033.1)Business Continuity for Oracle E-Business Release 11i Using Oracle 11g Physical Standby Database (Note 1068913.1)

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• What should you do differently when designing websites for an embedded web server

  - by Roger Attrill

  When designing a website to be accessed from an embedded webserver such as KLone, what do you need to do differently compared to a 'standard' web server. I'm talking about considerations at the front end design stage, before the actual building and coding up. For example, typically in such situations, memory size is a premium, so I guess larger images are out, and maybe more attention should be focused on achieving a good look and feel using CSS/Javascript rather than bitmap images.

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• What is the greatest design flaw you have faced in any programming language?

  - by Anto

  All programming languages are having their design flaws simply because not a single language can be perfect, just as with most (all?) other things. That aside, which design fault in a programming language has annoyed you the most through your history as a programmer? Note that if a language is "bad" just because it isn't designed for a specific thing isn't a design flaw, but a feature of design, so don't list such annoyances of languages. If a language is illsuited for what it is designed for, that is of course a flaw in the design. Implementation specific things and under the hood things do not count either.

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• Development: SDK for Social Net

  - by loldop

  I have a task: development sdk for social networking service like facebook, twitter and etc. At now i'm developing facebook-extension-sdk which based on facebook-ios-sdk 3.0. But not all social networking services have good sdks. And all time i improved my facebook-extension-sdk, when i see ugly code :( Please, advise me good techniques to development these sdks (like design-patterns or your own experience or good books/sites). Thanks!

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• How do I write code that doesn't suck? [closed]

  - by Afnan

  My friends and I would like to write a C# desktop application, and would like some guidance on how to make sure the code base is professional and well-kept. Should we use classes or interfaces for our inheritance patterns (which is better)? What are the best practices for professional applications? How do we know what sloppy code looks like, and how do we avoid creating sloppy code? Are there any best practices regarding the design of Winforms applications?

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• Oracle Solaris Zones Physical to virtual (P2V)

  - by user939057

  IntroductionThis document describes the process of creating and installing a Solaris 10 image build from physical system and migrate it into a virtualized operating system environment using the Oracle Solaris 10 Zones Physical-to-Virtual (P2V) capability.Using an example and various scenarios, this paper describes how to take advantage of theOracle Solaris 10 Zones Physical-to-Virtual (P2V) capability with other Oracle Solaris features to optimize performance using the Solaris 10 resource management advanced storage management using Solaris ZFS plus improving operating system visibility with Solaris DTrace. The most common use for this tool is when performing consolidation of existing systems onto virtualization enabled platforms, in addition to that we can use the Physical-to-Virtual (P2V) capability  for other tasks for example backup your physical system and move them into virtualized operating system environment hosted on the Disaster Recovery (DR) site another option can be building an Oracle Solaris 10 image repository with various configuration and a different software packages in order to reduce provisioning time.Oracle Solaris ZonesOracle Solaris Zones is a virtualization and partitioning technology supported on Oracle Sun servers powered by SPARC and Intel processors.This technology provides an isolated and secure environment for running applications. A zone is a virtualized operating system environment created within a single instance of the Solaris 10 Operating System.Each virtual system is called a zone and runs a unique and distinct copy of the Solaris 10 operating system.Oracle Solaris Zones Physical-to-Virtual (P2V)A new feature for Solaris 10 9/10.This feature provides the ability to build a Solaris 10 images from physical system and migrate it into a virtualized operating system environmentThere are three main steps using this tool1. Image creation on the source system, this image includes the operating system and optionally the software in which we want to include within the image. 2. Preparing the target system by configuring a new zone that will host the new image.3. Image installation on the target system using the image we created on step 1. The host, where the image is built, is referred to as the source system and the host, where theimage is installed, is referred to as the target system. Benefits of Oracle Solaris Zones Physical-to-Virtual (P2V)Here are some benefits of this new feature:  Simple- easy build process using Oracle Solaris 10 built-in commands.  Robust- based on Oracle Solaris Zones a robust and well known virtualization technology.  Flexible- support migration between V series servers into T or -M-series systems.For the latest server information, refer to the Sun Servers web page. PrerequisitesThe target Oracle Solaris system should be running the latest version of the patching patch cluster. and the minimum Solaris version on the target system should be Solaris 10 9/10.Refer to the latest Administration Guide for Oracle Solaris for a complete procedure on how todownload and install Oracle Solaris. NOTE: If the source system that used to build the image is an older version then the targetsystem, then during the process, the operating system will be upgraded to Solaris 10 9/10(update on attach).Creating the Image Used to distribute the software.We will create an image on the source machine. We can create the image on the local file system and then transfer it to the target machine, or build it into a NFS shared storage andmount the NFS file system from the target machine.Optional  before creating the image we need to complete the software installation that we want to include with the Solaris 10 image.An image is created by using the flarcreate command:Source # flarcreate -S -n s10-system -L cpio /var/tmp/solaris_10_up9.flarThe command does the following:  -S specifies that we skip the disk space check and do not write archive size data to the archive (faster).  -n specifies the image name.  -L specifies the archive format (i.e cpio). Optionally, we can add descriptions to the archive identification section, which can help to identify the archive later.Source # flarcreate -S -n s10-system -e "Oracle Solaris with Oracle DB10.2.0.4" -a "oracle" -L cpio /var/tmp/solaris_10_up9.flarYou can see example of the archive identification section in Appendix A: archive identification section.We can compress the flar image using the gzip command or adding the -c option to the flarcreate commandSource # gzip /var/tmp/solaris_10_up9.flarAn md5 checksum can be created for the image in order to ensure no data tamperingSource # digest -v -a md5 /var/tmp/solaris_10_up9.flar Moving the image into the target system.If we created the image on the local file system, we need to transfer the flar archive from the source machine to the target machine.Source # scp /var/tmp/solaris_10_up9.flar target:/var/tmpConfiguring the Zone on the target systemAfter copying the software to the target machine, we need to configure a new zone in order to host the new image on that zone.To install the new zone on the target machine, first we need to configure the zone (for the full zone creation options see the following link: http://docs.oracle.com/cd/E18752_01/html/817-1592/index.html  )ZFS integrationA flash archive can be created on a system that is running a UFS or a ZFS root file system.NOTE: If you create a Solaris Flash archive of a Solaris 10 system that has a ZFS root, then bydefault, the flar will actually be a ZFS send stream, which can be used to recreate the root pool.This image cannot be used to install a zone. You must create the flar with an explicit cpio or paxarchive when the system has a ZFS root.Use the flarcreate command with the -L archiver option, specifying cpio or pax as themethod to archive the files. (For example, see Step 1 in the previous section).Optionally, on the target system you can create the zone root folder on a ZFS file system inorder to benefit from the ZFS features (clones, snapshots, etc...).Target # zpool create zones c2t2d0 Create the zone root folder:Target # chmod 700 /zones Target # zonecfg -z solaris10-up9-zonesolaris10-up9-zone: No such zone configuredUse 'create' to begin configuring a new zone.zonecfg:solaris10-up9-zone> createzonecfg:solaris10-up9-zone> set zonepath=/zoneszonecfg:solaris10-up9-zone> set autoboot=truezonecfg:solaris10-up9-zone> add netzonecfg:solaris10-up9-zone:net> set address=192.168.0.1zonecfg:solaris10-up9-zone:net> set physical=nxge0zonecfg:solaris10-up9-zone:net> endzonecfg:solaris10-up9-zone> verifyzonecfg:solaris10-up9-zone> commitzonecfg:solaris10-up9-zone> exit Installing the Zone on the target system using the imageInstall the configured zone solaris10-up9-zone by using the zoneadm command with the install -a option and the path to the archive.The following example shows how to create an Image and sys-unconfig the zone.Target # zoneadm -z solaris10-up9-zone install -u -a/var/tmp/solaris_10_up9.flarLog File: /var/tmp/solaris10-up9-zone.install_log.AJaGveInstalling: This may take several minutes...The following example shows how we can preserve system identity.Target # zoneadm -z solaris10-up9-zone install -p -a /var/tmp/solaris_10_up9.flar Resource management Some applications are sensitive to the number of CPUs on the target Zone. You need tomatch the number of CPUs on the Zone using the zonecfg command:zonecfg:solaris10-up9-zone>add dedicated-cpuzonecfg:solaris10-up9-zone> set ncpus=16DTrace integrationSome applications might need to be analyzing using DTrace on the target zone, you canadd DTrace support on the zone using the zonecfg command:zonecfg:solaris10-up9-zone>setlimitpriv="default,dtrace_proc,dtrace_user" Exclusive IP stack An Oracle Solaris Container running in Oracle Solaris 10 can have a shared IP stack with the global zone, or it can have an exclusive IP stack (which was released in Oracle Solaris 10 8/07). An exclusive IP stack provides a complete, tunable, manageable and independent networking stack to each zone. A zone with an exclusive IP stack can configure Scalable TCP (STCP), IP routing, IP multipathing, or IPsec. For an example of how to configure an Oracle Solaris zone with an exclusive IP stack, see the following example zonecfg:solaris10-up9-zone set ip-type=exclusivezonecfg:solaris10-up9-zone> add netzonecfg:solaris10-up9-zone> set physical=nxge0 When the installation completes, use the zoneadm list -i -v options to list the installedzones and verify the status.Target # zoneadm list -i -vSee that the new Zone status is installedID NAME STATUS PATH BRAND IP0 global running / native shared- solaris10-up9-zone installed /zones native sharedNow boot the ZoneTarget # zoneadm -z solaris10-up9-zone bootWe need to login into the Zone order to complete the zone set up or insert a sysidcfg file beforebooting the zone for the first time see example for sysidcfg file in Appendix B: sysidcfg filesectionTarget # zlogin -C solaris10-up9-zoneTroubleshootingIf an installation fails, review the log file. On success, the log file is in /var/log inside the zone. Onfailure, the log file is in /var/tmp in the global zone.If a zone installation is interrupted or fails, the zone is left in the incomplete state. Use uninstall -F to reset the zone to the configured state.Target # zoneadm -z solaris10-up9-zone uninstall -FTarget # zonecfg -z solaris10-up9-zone delete -FConclusionOracle Solaris Zones P2V tool provides the flexibility to build pre-configuredimages with different software configuration for faster deployment and server consolidation.In this document, I demonstrated how to build and install images and to integrate the images with other Oracle Solaris features like ZFS and DTrace.Appendix A: archive identification sectionWe can use the head -n 20 /var/tmp/solaris_10_up9.flar command in order to access theidentification section that contains the detailed description.Target # head -n 20 /var/tmp/solaris_10_up9.flarFlAsH-aRcHiVe-2.0section_begin=identificationarchive_id=e4469ee97c3f30699d608b20a36011befiles_archived_method=cpiocreation_date=20100901160827creation_master=mdet5140-1content_name=s10-systemcreation_node=mdet5140-1creation_hardware_class=sun4vcreation_platform=SUNW,T5140creation_processor=sparccreation_release=5.10creation_os_name=SunOScreation_os_version=Generic_142909-16files_compressed_method=nonecontent_architectures=sun4vtype=FULLsection_end=identificationsection_begin=predeploymentbegin 755 predeployment.cpio.ZAppendix B: sysidcfg file sectionTarget # cat sysidcfgsystem_locale=Ctimezone=US/Pacificterminal=xtermssecurity_policy=NONEroot_password=HsABA7Dt/0sXXtimeserver=localhostname_service=NONEnetwork_interface=primary {hostname= solaris10-up9-zonenetmask=255.255.255.0protocol_ipv6=nodefault_route=192.168.0.1}name_service=NONEnfs4_domain=dynamicWe need to copy this file before booting the zoneTarget # cp sysidcfg /zones/solaris10-up9-zone/root/etc/

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• What is a useful pattern to maintaining an object state in a one to many relationship?

  - by ahenderson

  I am looking for a design for my application, here are the players(classes) involved. struct Transform { // Uses a matrix to transform the position. // Also acts acts as the state of a Dialog. Position transform(Position p); //other methods. }; struct Dialog { // There are multiple dialog for the user to transform the output. Transform& t; void ChangeTranformation(){t.rotate(360);} } struct Algorithm { //gives us a position based on an implementation. For example this can return points on a circle or line. Transform& t; Position m_p; Dialog& d; Position GetCurrentPosition(){ return t.transform(m_p);} //other methods. } Properties I need: Each algorithms has one dialog and each dialog can have many algorithms associated with it. When the user selects an algorithm a dialog associated with that algorithm is displayed. If the user selects a different algorithm then re-selects back the state is restored in the dialog. Basically I want a good design pattern to maintain the state of the dialog given that many algorithms use it and they can be switched back and forth. Does anyone have any suggestions? Here is a use case: Dialog1 has a single edit box to control the radius. Algorithm1 generates points on a unit circle. Algorithm2 is the same as Algorithm1. The user has selected Algorithm1 and entered 2 into the edit box. This will generate points on a circle of radius 2. The user then selects Algorithm2 and enters 10 into the edit box of Dialog1. This will generate points on a circle of radius 10. Finally Algorithm1 is selected again. The edit box of Dialog1 should show 2 and points on a circle of radius 2 should be generated.

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• How can you tell whether to use Composite Pattern or a Tree Structure, or a third implementation?

  - by Aske B.

  I have two client types, an "Observer"-type and a "Subject"-type. They're both associated with a hierarchy of groups. The Observer will receive (calendar) data from the groups it is associated with throughout the different hierarchies. This data is calculated by combining data from 'parent' groups of the group trying to collect data (each group can have only one parent). The Subject will be able to create the data (that the Observers will receive) in the groups they're associated with. When data is created in a group, all 'children' of the group will have the data as well, and they will be able to make their own version of a specific area of the data, but still linked to the original data created (in my specific implementation, the original data will contain time-period(s) and headline, while the subgroups specify the rest of the data for the receivers directly linked to their respective groups). However, when the Subject creates data, it has to check if all affected Observers have any data that conflicts with this, which means a huge recursive function, as far as I can understand. So I think this can be summed up to the fact that I need to be able to have a hierarchy that you can go up and down in, and some places be able to treat them as a whole (recursion, basically). Also, I'm not just aiming at a solution that works. I'm hoping to find a solution that is relatively easy to understand (architecture-wise at least) and also flexible enough to be able to easily receive additional functionality in the future. Is there a design pattern, or a good practice to go by, to solve this problem or similar hierarchy problems? EDIT: Here's the design I have: The "Phoenix"-class is named that way because I didn't think of an appropriate name yet. But besides this I need to be able to hide specific activities for specific observers, even though they are attached to them through the groups. A little Off-topic: Personally, I feel that I should be able to chop this problem down to smaller problems, but it escapes me how. I think it's because it involves multiple recursive functionalities that aren't associated with each other and different client types that needs to get information in different ways. I can't really wrap my head around it. If anyone can guide me in a direction of how to become better at encapsulating hierarchy problems, I'd be very glad to receive that as well.

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• Flags with deferred use

  - by Trenton Maki

  Let's say I have a system. In this system I have a number of operations I can do but all of these operations have to happen as a batch at a certain time, while calls to activate and deactivate these operations can come in at any time. To implement this, I could use flags like doOperation1 and doOperation2 but this seems like it would become difficult to maintain. Is there a design pattern, or something similar, that addresses this situation?

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• Associating an Object with other Objects and Properties of those Objects

  - by alzoid

  I am looking for some help with designing some functionality in my application. I already have something similar designed but this problem is a little different. Background: In my application we have different Modules. Data in each module can be associated to other modules. Each Module is represented by an Object in our application. Module 1 can be associated with Module 2 and Module 3. Currently I use a factory to provide the proper DAO for getting and saving this data. It looks something like this: class Module1Factory { public static Module1BridgeDAO createModule1BridgeDAO(int moduleid) { switch (moduleId) { case Module.Module2Id: return new Module1_Module2DAO(); case Module.Module3Id: return new Module1_Module3DAO(); default: return null; } } } Module1_Module2 and Module1_Module3 implement the same BridgeModule interface. In the database I have a Table for every module (Module1, Module2, Module3). I also have a bridge table for each module (they are many to many) Module1_Module2, Module1_Module3 etc. The DAO basically handles all code needed to manage the association and retrieve its own instance data for the calling module. Now when we add new modules that associate with Module1 we simply implement the ModuleBridge interface and provide the common functionality. New Development We are adding a new module that will have the ability to be associated with other Modules as well as specific properties of that module. The module is basically providing the user the ability to add their custom forms to our other modules. That way they can collect additional information along with what we provide. I want to start associating my Form module with other modules and their properties. Ie if Module1 has a property Category, I want to associate an instance From data with that property. There are many Forms. If a users creates an instance of Module2, they may always want to also have certain form(s) attached to that Module2 instance. If they create an instance of Module2 and select Category 1, then I may want additional Form(s) created. I prototyped something like this: Form FormLayout (contains the labels and gui controls) FormModule (associates a form with all instances of a module) Form Instance (create an instance of a form to be filled out) As I thought about it I was thinking about making a new FormModule table/class/dao for each Module and Property that I add. So I might have: FormModule1 FormModule1Property1 FormModule1Property2 FormModule1Property3 FormModule1Property4 FormModule2 FormModule3 FormModule3Property1 Then as I did previously, I would use a factory to get the proper DAO for dealing with all of these. I would hand it an array of ids representing different modules and properties and it would return all of the DAOs that I need to call getForms(). Which in turn would return all of the forms for that particular bridge. Some points This will be for a new module so I dont need to expand on the factory code I provided. I just wanted to show an example of what I have done in the past. The new module can be associated with: Other Modules (ie globally for any instance of that module data), Other module properties (ie only if the Module instance has a certian value in one of its properties) I want to make it easy for developers to add associations with other modules and properties easily Can any one suggest any design patterns or strategy's for achieving this? If anything is unclear please let me know. Thank you, Al

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• Kubuntu 12.04 - Touchpad and keyboard stopped working at random

  - by StepTNT

  As in the title, I've got this problem with my Kubuntu 12.04. At first I've thought that the whole system was hung, but it happened again 5 minutes ago and, while the keyboard and the touchpad stopped working, the music was still playing, so I guess that's just an "input" problem, because the system was still working! Any solution? Is there some data that you need to know about my setup? EDIT: Added my lshw outout description: Notebook product: N53SV () vendor: ASUSTeK Computer Inc. version: 1.0 serial: B2N0AS17695408A width: 64 bits capabilities: smbios-2.6 dmi-2.6 vsyscall32 configuration: boot=normal chassis=notebook family=N uuid=8083F2DA-A43E-E081-3F3F-BCAEC55F8AA1 *-core description: Motherboard product: N53SV vendor: ASUSTeK Computer Inc. physical id: 0 version: 1.0 serial: BSN12345678901234567 slot: MIDDLE *-firmware description: BIOS vendor: American Megatrends Inc. physical id: 0 version: N53SV.214 date: 08/10/2011 size: 64KiB capacity: 2496KiB capabilities: pci upgrade shadowing cdboot bootselect edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer acpi usb smartbattery biosbootspecification *-cpu description: CPU product: Intel(R) Core(TM) i7-2630QM CPU @ 2.00GHz vendor: Intel Corp. physical id: 4 bus info: cpu@0 version: Intel(R) Core(TM) i7-2630QM CPU @ 2.00GHz serial: To Be Filled By O.E.M. slot: CPU 1 size: 800MHz capacity: 4GHz width: 64 bits clock: 100MHz capabilities: x86-64 fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer xsave avx lahf_lm ida arat epb xsaveopt pln pts tpr_shadow vnmi flexpriority ept vpid cpufreq configuration: cores=4 enabledcores=1 threads=2 *-cache description: L1 cache physical id: 5 slot: L1-Cache size: 32KiB capacity: 32KiB capabilities: internal write-back instruction *-memory description: System Memory physical id: 40 slot: System board or motherboard size: 10GiB *-bank:0 description: SODIMM DDR3 Synchronous 1333 MHz (0,8 ns) product: 99U5428-040.A00LF vendor: Kingston physical id: 0 serial: 103C28C3 slot: ChannelA-DIMM0 size: 4GiB width: 64 bits clock: 1333MHz (0.8ns) *-bank:1 description: SODIMM DDR3 Synchronous 1333 MHz (0,8 ns) product: HMT325S6BFR8C-H9 vendor: Hynix/Hyundai physical id: 1 serial: 58383D1F slot: ChannelA-DIMM1 size: 2GiB width: 64 bits clock: 1333MHz (0.8ns) *-bank:2 description: SODIMM DDR3 Synchronous 1333 MHz (0,8 ns) product: HMT325S6BFR8C-H9 vendor: Hynix/Hyundai physical id: 2 serial: 58183D19 slot: ChannelB-DIMM0 size: 2GiB width: 64 bits clock: 1333MHz (0.8ns) *-bank:3 description: SODIMM DDR3 Synchronous 1333 MHz (0,8 ns) product: HMT325S6BFR8C-H9 vendor: Hynix/Hyundai physical id: 3 serial: 58183C8F slot: ChannelB-DIMM1 size: 2GiB width: 64 bits clock: 1333MHz (0.8ns) *-pci description: Host bridge product: 2nd Generation Core Processor Family DRAM Controller vendor: Intel Corporation physical id: 100 bus info: pci@0000:00:00.0 version: 09 width: 32 bits clock: 33MHz configuration: driver=agpgart-intel resources: irq:0 *-pci:0 description: PCI bridge product: Xeon E3-1200/2nd Generation Core Processor Family PCI Express Root Port vendor: Intel Corporation physical id: 1 bus info: pci@0000:00:01.0 version: 09 width: 32 bits clock: 33MHz capabilities: pci pm msi pciexpress normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:40 ioport:d000(size=4096) memory:db000000-dc0fffff ioport:c0000000(size=301989888) *-generic UNCLAIMED description: Unassigned class product: Illegal Vendor ID vendor: Illegal Vendor ID physical id: 0 bus info: pci@0000:01:00.0 version: ff width: 32 bits clock: 66MHz capabilities: bus_master vga_palette cap_list configuration: latency=255 maxlatency=255 mingnt=255 resources: memory:db000000-dbffffff memory:c0000000-cfffffff memory:d0000000-d1ffffff ioport:d000(size=128) memory:dc000000-dc07ffff *-display description: VGA compatible controller product: 2nd Generation Core Processor Family Integrated Graphics Controller vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 09 width: 64 bits clock: 33MHz capabilities: msi pm vga_controller bus_master cap_list rom configuration: driver=i915 latency=0 resources: irq:47 memory:dc400000-dc7fffff memory:b0000000-bfffffff ioport:e000(size=64) *-communication description: Communication controller product: 6 Series/C200 Series Chipset Family MEI Controller #1 vendor: Intel Corporation physical id: 16 bus info: pci@0000:00:16.0 version: 04 width: 64 bits clock: 33MHz capabilities: pm msi bus_master cap_list configuration: driver=mei latency=0 resources: irq:48 memory:df00b000-df00b00f *-usb:0 description: USB controller product: 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 vendor: Intel Corporation physical id: 1a bus info: pci@0000:00:1a.0 version: 05 width: 32 bits clock: 33MHz capabilities: pm debug ehci bus_master cap_list configuration: driver=ehci_hcd latency=0 resources: irq:16 memory:df008000-df0083ff *-multimedia description: Audio device product: 6 Series/C200 Series Chipset Family High Definition Audio Controller vendor: Intel Corporation physical id: 1b bus info: pci@0000:00:1b.0 version: 05 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list configuration: driver=snd_hda_intel latency=0 resources: irq:49 memory:df000000-df003fff *-pci:1 description: PCI bridge product: 6 Series/C200 Series Chipset Family PCI Express Root Port 1 vendor: Intel Corporation physical id: 1c bus info: pci@0000:00:1c.0 version: b5 width: 32 bits clock: 33MHz capabilities: pci pciexpress msi pm normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:41 ioport:c000(size=4096) memory:de600000-deffffff ioport:d4200000(size=10485760) *-pci:2 description: PCI bridge product: 6 Series/C200 Series Chipset Family PCI Express Root Port 2 vendor: Intel Corporation physical id: 1c.1 bus info: pci@0000:00:1c.1 version: b5 width: 32 bits clock: 33MHz capabilities: pci pciexpress msi pm normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:42 ioport:b000(size=4096) memory:ddc00000-de5fffff ioport:d3700000(size=10485760) *-network description: Wireless interface product: AR9285 Wireless Network Adapter (PCI-Express) vendor: Atheros Communications Inc. physical id: 0 bus info: pci@0000:03:00.0 logical name: wlan0 version: 01 serial: 48:5d:60:f2:2c:fd width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=ath9k driverversion=3.2.0-24-generic firmware=N/A ip=192.168.1.6 latency=0 link=yes multicast=yes wireless=IEEE 802.11bgn resources: irq:17 memory:ddc00000-ddc0ffff *-pci:3 description: PCI bridge product: 6 Series/C200 Series Chipset Family PCI Express Root Port 4 vendor: Intel Corporation physical id: 1c.3 bus info: pci@0000:00:1c.3 version: b5 width: 32 bits clock: 33MHz capabilities: pci pciexpress msi pm normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:43 ioport:a000(size=4096) memory:dd200000-ddbfffff ioport:d2c00000(size=10485760) *-usb description: USB controller product: FL1000G USB 3.0 Host Controller vendor: Fresco Logic physical id: 0 bus info: pci@0000:04:00.0 version: 04 width: 32 bits clock: 33MHz capabilities: pm msi pciexpress xhci bus_master cap_list configuration: driver=xhci_hcd latency=0 resources: irq:19 memory:dd200000-dd20ffff *-pci:4 description: PCI bridge product: 6 Series/C200 Series Chipset Family PCI Express Root Port 6 vendor: Intel Corporation physical id: 1c.5 bus info: pci@0000:00:1c.5 version: b5 width: 32 bits clock: 33MHz capabilities: pci pciexpress msi pm normal_decode bus_master cap_list configuration: driver=pcieport resources: irq:44 ioport:9000(size=4096) memory:dc800000-dd1fffff ioport:d2100000(size=10485760) *-network description: Ethernet interface product: RTL8111/8168B PCI Express Gigabit Ethernet controller vendor: Realtek Semiconductor Co., Ltd. physical id: 0 bus info: pci@0000:05:00.0 logical name: eth0 version: 06 serial: bc:ae:c5:5f:8a:a1 size: 10Mbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=half firmware=rtl_nic/rtl8168e-2.fw latency=0 link=no multicast=yes port=MII speed=10Mbit/s resources: irq:46 ioport:9000(size=256) memory:d2104000-d2104fff memory:d2100000-d2103fff *-usb:1 description: USB controller product: 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 vendor: Intel Corporation physical id: 1d bus info: pci@0000:00:1d.0 version: 05 width: 32 bits clock: 33MHz capabilities: pm debug ehci bus_master cap_list configuration: driver=ehci_hcd latency=0 resources: irq:23 memory:df007000-df0073ff *-isa description: ISA bridge product: HM65 Express Chipset Family LPC Controller vendor: Intel Corporation physical id: 1f bus info: pci@0000:00:1f.0 version: 05 width: 32 bits clock: 33MHz capabilities: isa bus_master cap_list configuration: latency=0 *-storage description: SATA controller product: 6 Series/C200 Series Chipset Family 6 port SATA AHCI Controller vendor: Intel Corporation physical id: 1f.2 bus info: pci@0000:00:1f.2 logical name: scsi0 logical name: scsi2 version: 05 width: 32 bits clock: 66MHz capabilities: storage msi pm ahci_1.0 bus_master cap_list emulated configuration: driver=ahci latency=0 resources: irq:45 ioport:e0b0(size=8) ioport:e0a0(size=4) ioport:e090(size=8) ioport:e080(size=4) ioport:e060(size=32) memory:df006000-df0067ff *-disk description: ATA Disk product: ST9750420AS vendor: Seagate physical id: 0 bus info: scsi@0:0.0.0 logical name: /dev/sda version: 0002 serial: 5WS0A7QR size: 698GiB (750GB) capabilities: partitioned partitioned:dos configuration: ansiversion=5 signature=e0c5913d *-volume:0 description: Windows FAT volume vendor: MSDOS5.0 physical id: 1 bus info: scsi@0:0.0.0,1 logical name: /dev/sda1 version: FAT32 serial: 4ce5-3acb size: 3004MiB capacity: 3004MiB capabilities: primary fat initialized configuration: FATs=2 filesystem=fat *-volume:1 description: EXT4 volume vendor: Linux physical id: 2 bus info: scsi@0:0.0.0,2 logical name: /dev/sda2 logical name: / version: 1.0 serial: c198cc2a-d86a-4460-a4d5-3fc0b21e439c size: 28GiB capacity: 28GiB capabilities: primary journaled extended_attributes large_files huge_files dir_nlink recover extents ext4 ext2 initialized configuration: created=2012-03-15 16:53:54 filesystem=ext4 lastmountpoint=/ modified=2012-05-02 18:52:04 mount.fstype=ext4 mount.options=rw,relatime,errors=remount-ro,user_xattr,acl,barrier=1,data=ordered mounted=2012-05-09 19:06:01 state=mounted *-volume:2 description: Windows NTFS volume physical id: 3 bus info: scsi@0:0.0.0,3 logical name: /dev/sda3 version: 3.1 serial: 4c1cdebc-ec09-2947-a3b5-c1f9f1cddc1c size: 152GiB capacity: 152GiB capabilities: primary bootable ntfs initialized configuration: clustersize=4096 created=2011-02-22 16:02:47 filesystem=ntfs label=OS state=clean *-volume:3 description: Extended partition physical id: 4 bus info: scsi@0:0.0.0,4 logical name: /dev/sda4 size: 514GiB capacity: 514GiB capabilities: primary extended partitioned partitioned:extended *-logicalvolume:0 description: Linux swap / Solaris partition physical id: 5 logical name: /dev/sda5 capacity: 10GiB capabilities: nofs *-logicalvolume:1 description: HPFS/NTFS partition physical id: 6 logical name: /dev/sda6 capacity: 504GiB *-cdrom description: DVD-RAM writer product: BD-MLT UJ240AS vendor: MATSHITA physical id: 1 bus info: scsi@2:0.0.0 logical name: /dev/cdrom logical name: /dev/cdrw logical name: /dev/dvd logical name: /dev/dvdrw logical name: /dev/sr0 version: 1.00 capabilities: removable audio cd-r cd-rw dvd dvd-r dvd-ram configuration: ansiversion=5 status=nodisc *-serial UNCLAIMED description: SMBus product: 6 Series/C200 Series Chipset Family SMBus Controller vendor: Intel Corporation physical id: 1f.3 bus info: pci@0000:00:1f.3 version: 05 width: 64 bits clock: 33MHz configuration: latency=0 resources: memory:df005000-df0050ff ioport:e040(size=32)

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• Design Question - how do you break the dependency between classes using an interface?

  - by Seth Spearman

  Hello, I apologize in advance but this will be a long question. I'm stuck. I am trying to learn unit testing, C#, and design patterns - all at once. (Maybe that's my problem.) As such I am reading the Art of Unit Testing (Osherove), and Clean Code (Martin), and Head First Design Patterns (O'Reilly). I am just now beginning to understand delegates and events (which you would see if you were to troll my SO questions of recent). I still don't quite get lambdas. To contextualize all of this I have given myself a learning project I am calling goAlarms. I have an Alarm class with members you'd expect (NextAlarmTime, Name, AlarmGroup, Event Trigger etc.) I wanted the "Timer" of the alarm to be extensible so I created an IAlarmScheduler interface as follows... public interface AlarmScheduler { Dictionary<string,Alarm> AlarmList { get; } void Startup(); void Shutdown(); void AddTrigger(string triggerName, string groupName, Alarm alarm); void RemoveTrigger(string triggerName); void PauseTrigger(string triggerName); void ResumeTrigger(string triggerName); void PauseTriggerGroup(string groupName); void ResumeTriggerGroup(string groupName); void SetSnoozeTrigger(string triggerName, int duration); void SetNextOccurrence (string triggerName, DateTime nextOccurrence); } This IAlarmScheduler interface define a component that will RAISE an alarm (Trigger) which will bubble up to my Alarm class and raise the Trigger Event of the alarm itself. It is essentially the "Timer" component. I have found that the Quartz.net component is perfectly suited for this so I have created a QuartzAlarmScheduler class which implements IAlarmScheduler. All that is fine. My problem is that the Alarm class is abstract and I want to create a lot of different KINDS of alarm. For example, I already have a Heartbeat alarm (triggered every (int) interval of minutes), AppointmentAlarm (triggered on set date and time), Daily Alarm (triggered every day at X) and perhaps others. And Quartz.NET is perfectly suited to handle this. My problem is a design problem. I want to be able to instantiate an alarm of any kind without my Alarm class (or any derived classes) knowing anything about Quartz. The problem is that Quartz has awesome factories that return just the right setup for the Triggers that will be needed by my Alarm classes. So, for example, I can get a Quartz trigger by using TriggerUtils.MakeMinutelyTrigger to create a trigger for the heartbeat alarm described above. Or TriggerUtils.MakeDailyTrigger for the daily alarm. I guess I could sum it up this way. Indirectly or directly I want my alarm classes to be able to consume the TriggerUtils.Make* classes without knowing anything about them. I know that is a contradiction, but that is why I am asking the question. I thought about putting a delegate field into the alarm which would be assigned one of these Make method but by doing that I am creating a hard dependency between alarm and Quartz which I want to avoid for both unit testing purposes and design purposes. I thought of using a switch for the type in QuartzAlarmScheduler per here but I know it is bad design and I am trying to learn good design. If I may editorialize a bit. I've decided that coding (predefined) classes is easy. Design is HARD...in fact, really hard and I am really fighting feeling stupid right now. I guess I want to know if you really smart people took a while to really understand and master this stuff or should I feel stupid (as I do) because I haven't grasped it better in the couple of weeks/months I have been studying. You guys are awesome and thanks in advance for your answers. Seth

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• DB Design Pattern - Many to many classification / categorised tagging.

  - by Robin Day

  I have an existing database design that stores Job Vacancies. The "Vacancy" table has a number of fixed fields across all clients, such as "Title", "Description", "Salary range". There is an EAV design for "Custom" fields that the Clients can setup themselves, such as, "Manager Name", "Working Hours". The field names are stored in a "ClientText" table and the data stored in a "VacancyClientText" table with VacancyId, ClientTextId and Value. Lastly there is a many to many EAV design for custom tagging / categorising the vacancies with things such as Locations/Offices the vacancy is in, a list of skills required. This is stored as a "ClientCategory" table listing the types of tag, "Locations, Skills", a "ClientCategoryItem" table listing the valid values for each Category, e.g., "London,Paris,New York,Rome", "C#,VB,PHP,Python". Finally there is a "VacancyClientCategoryItem" table with VacancyId and ClientCategoryItemId for each of the selected items for the vacancy. There are no limits to the number of custom fields or custom categories that the client can add. I am now designing a new system that is very similar to the existing system, however, I have the ability to restrict the number of custom fields a Client can have and it's being built from scratch so I have no legacy issues to deal with. For the Custom Fields my solution is simple, I have 5 additional columns on the Vacancy Table called CustomField1-5. This removes one of the EAV designs. It is with the tagging / categorising design that I am struggling. If I limit a client to having 5 categories / types of tag. Should I create 5 tables listing the possible values "CustomCategoryItems1-5" and then an additional 5 many to many tables "VacancyCustomCategoryItem1-5" This would result in 10 tables performing the same storage as the three tables in the existing system. Also, should (heaven forbid) the requirements change in that I need 6 custom categories rather than 5 then this will result in a lot of code change. Therefore, can anyone suggest any DB Design Patterns that would be more suitable to storing such data. I'm happy to stick with the EAV approach, however, the existing system has come across all the usual performance issues and complex queries associated with such a design. Any advice / suggestions are much appreciated. The DBMS system used is SQL Server 2005, however, 2008 is an option if required for any particular pattern.

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• Why is good UI design so hard for some Developers?

  - by Chris Ballance

  Some of us just have a hard time with the softer aspects of UI design (myself especially). Are "back-end coders" doomed to only design business logic and data layers? Is there something we can do to retrain our brain to be more effective at designing pleasing and useful presentation layers? Colleagues have recommended a few books me including The Design of Sites, Don't make me think and Why Software sucks , but I am wondering what others have done to remove their deficiencies in this area?

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• how good should a developer be in design and animation?

  - by scatman

  how good should a developer (especially web developer) be in design and animation? should he know how to create flash animations? how to use image processing programs like photoshop.... i am asking this question because i am a computer science student, and all my courses are programming related (no courses about design). when i develop a web application i usually use "wizards" for animation coz i suck at design...

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• What design patters are the worst or most narrowly defined?

  - by Akku

  For every programming project, Managers with past programming experience try to shine when they recommend some design patterns for your project. I like design patterns when they make sense or if you need a scalbale solution. I've used Proxies, Observers and Command patterns in a positive way for example, and do so every day. But I'm really hesitant to use say a Factory pattern if there's only one way to create an object, as a factory might make it all easier in the future, but complicates the code and is pure overhead. So, my question is in respect to my future career and my answer to manager types throwing random pattern-names around: Which design patterns did you use, that threw you back overall? Which are the worst design patterns, that you shouldn't have a look at if it's not that only single situation where it makes sense (read: which design patterns are very narrowly defined)? (It's like I was looking for the negative reviews of an overall good product of amazon to see what bugged people most in using design patterns). And I'm not talking about Anti-Patterns here, but about Patterns that are usually thought of as "good" patterns.

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• What design patterns are the worst or most narrowly defined?

  - by Akku

  For every programming project, Managers with past programming experience try to shine when they recommend some design patterns for your project. I like design patterns when they make sense or if you need a scalbale solution. I've used Proxies, Observers and Command patterns in a positive way for example, and do so every day. But I'm really hesitant to use say a Factory pattern if there's only one way to create an object, as a factory might make it all easier in the future, but complicates the code and is pure overhead. So, my question is in respect to my future career and my answer to manager types throwing random pattern-names around: Which design patterns did you use, that threw you back overall? Which are the worst design patterns, that you shouldn't have a look at if it's not that only single situation where it makes sense (read: which design patterns are very narrowly defined)? (It's like I was looking for the negative reviews of an overall good product of amazon to see what bugged people most in using design patterns). And I'm not talking about Anti-Patterns here, but about Patterns that are usually thought of as "good" patterns. Edit: As some answered, the problem is most often that patterns are not "bad" but "used wrong". If you know patterns, that are often misused or even difficult to use, they would also fit as an answer.

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