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• Templates for forms, tabs etc? - Patterntap alternatives

  - by Marco Demaio

  I used to find http://www.patterntap.com quite useful to get design inspiration for forms, tabs, and other web elements etc. Unfortunately after the ZURB acquisition of Patterntap now they enforce you to sign in with your Twitter account in order to simply view larger images of patterns provided by the crowd. So in some way it's not free anymore. Do you know of alternatives to patterntap that are free and you are not obliged to sign in?

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• Representing complex object dependencies

  - by max

  I have several classes with a reasonably complex (but acyclic) dependency graph. All the dependencies are of the form: class X instance contains an attribute of class Y. All such attributes are set during initialization and never changed again. Each class' constructor has just a couple parameters, and each object knows the proper parameters to pass to the constructors of the objects it contains. class Outer is at the top of the dependency hierarchy, i.e., no class depends on it. Currently, the UI layer only creates an Outer instance; the parameters for Outer constructor are derived from the user input. Of course, Outer in the process of initialization, creates the objects it needs, which in turn create the objects they need, and so on. The new development is that the a user who knows the dependency graph may want to reach deep into it, and set the values of some of the arguments passed to constructors of the inner classes (essentially overriding the values used currently). How should I change the design to support this? I could keep the current approach where all the inner classes are created by the classes that need them. In this case, the information about "user overrides" would need to be passed to Outer class' constructor in some complex user_overrides structure. Perhaps user_overrides could be the full logical representation of the dependency graph, with the overrides attached to the appropriate edges. Outer class would pass user_overrides to every object it creates, and they would do the same. Each object, before initializing lower level objects, will find its location in that graph and check if the user requested an override to any of the constructor arguments. Alternatively, I could rewrite all the objects' constructors to take as parameters the full objects they require. Thus, the creation of all the inner objects would be moved outside the whole hierarchy, into a new controller layer that lies between Outer and UI layer. The controller layer would essentially traverse the dependency graph from the bottom, creating all the objects as it goes. The controller layer would have to ask the higher-level objects for parameter values for the lower-level objects whenever the relevant parameter isn't provided by the user. Neither approach looks terribly simple. Is there any other approach? Has this problem come up enough in the past to have a pattern that I can read about? I'm using Python, but I don't think it matters much at the design level.

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• In database table design, how does "Virtual Goods" affect table design -- should we create an instan

  - by Jian Lin

  When we design a database table for a DVD rental company, we actually have a movie, which is an abstract idea, and a physical DVD, so for each rental, we have a many-to-many table with fields such as: TransactionID UserID DvdID RentedDate RentalDuration AmountPaid but what about with virtual goods? For example, if we let a user rent a movie online for 3 days, we don't actually have a DVD, so we may have a table: TransactionID UserID MovieID RentedDate RentalDuration AmountPaid should we create a record for each instance of "virtual good"? For example, what if this virtual good (the movie) can be authorized to be watched on 3 devices (with 3 device IDs), then should we then create a virtual good record in the VirtualGoods table, each with a VirtualGoodID and then another table that has VirtualGoodID DeviceID to match up the movie with the DeviceIDs? We can also just use the TransactionID as the VirtualGoodID. Are there circumstances where we may want to create a record to record this "virtual good" in a VirtualGoods table?

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• Storage Configuration

  - by jchang

  Storage performance is not inherently complicated subject. The concepts are relatively simple. In fact, scaling storage performance is far easier compared with the difficulties encounters in scaling processor performance in NUMA systems. Storage performance is achieved by properly distributing IO over: 1) multiple independent PCI-E ports (system memory and IO bandwith is key) 2) multiple RAID controllers or host bus adapters (HBAs) 3) multiple storage IO channels (SAS or FC, complete path) most importantly,...(read more)

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• Storage Configuration

  - by jchang

  Storage performance is not inherently complicated subject. The concepts are relatively simple. In fact, scaling storage performance is far easier compared with the difficulties encounters in scaling processor performance in NUMA systems. Storage performance is achieved by properly distributing IO over: 1) multiple independent PCI-E ports (system memory and IO bandwith is key) 2) multiple RAID controllers or host bus adapters (HBAs) 3) multiple storage IO channels (SAS or FC, complete path) most importantly,...(read more)

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• The History of Digital Storage [Infographic]

  - by Jason Fitzpatrick

  From punch cards to hard drives to cloud based storage, how we stash our data away has changed quite a bit in the last century. Courtesy of Mashable, we have an infographic detailing the evolution of storage and comparing storage size, speed, and prices over the decades. Hit up the link below for a higher resolution image. The History of Digital Storage [Mashable] How To Create a Customized Windows 7 Installation Disc With Integrated Updates How to Get Pro Features in Windows Home Versions with Third Party Tools HTG Explains: Is ReadyBoost Worth Using?

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• What do you do if you reach a design dead-end in evolutionary methods like Agile or XP?

  - by Dipan Mehta

  As I was reading Martin Fowler's famous blog post Is Design Dead?, one of the striking impressions I got is that given the fact that in Agile Methodology and Extreme Programming, the design as well as programming is evolutionary, there are always points where things need to get refactored. It may be possible that when a programmer's level is good, and they understand design implications and don't make critical mistakes, the code continues to evolve. However, in a normal context, what is the ground reality in this context? In a normal day given some significant development goes into product, and when critical change occurs in requirement isn't it a constraint that how much ever we wish, fundamental design aspects cannot be modified? (without throwing away major part of the code). Is it not quite likely that one reaches dead-end on any further possible improvement on design and requirements? I am not advocating any non-Agile practice here, but I want to know from people who practice agile or iterative or evolutionary development methods, as for their real experiences. Have you ever reached such dead-ends? How have you managed to avoid it or escaped it? Or are there measures to ensure that design remains clean and flexible as it evolves?

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• Online Storage and security concerns

  - by Megge

  I plan to set up a small fileserver. I already own a small server at HostEurope (VirtualServer L, 250GB space), but they don't offer enough space (there is the HostEurope Cloud, but paying for bandwidth isn't an option here, video-streaming should be possible) Requirements summarized: Storage: 2TB, Users: ~15, Filesizes: < 100GB, should be easily reachable (Mount as a networkdrive or at least have solid "communication" software) My first question would be: Where can I get halfway affordable online storages? And how should I connect them to my server? Getting an additional server is a bit overkill, as I know no hoster which allows 2 TB on a small 2 Ghz Dual Core 2 GB RAM thingy (that would be enough by far, I just need much space), and connecting it via NFS or FTP over Internet seems a bit strange and cripples performance. Do you have any advice where I could get that storage service from? (I sent HostEurope a custom request today, but they didn't answer till now. If they can provide me with that space, this question will be irrelevant, but the 2nd one is the more important one anway, don't do much more than recommend me some based on experience, you don't have to crawl hours through hosting services) livedrive for example offers 5 TB for 17€ / month, I'd be happy with 2 TB for 20 €, the caveat is: It doesn't allow multiple users, which leads me to my second question: Where are the security problems? Which protocol is sufficient (I want private and "public" folders etc. the usual "every user has its own and a public space"-thing), secure and fast? (I'd tend to (S)FTP, problem with FTP is: Most of those hosting services don't even allow FTP with mutliple users and single users lead me into "hacking" a solution (you could map the basic folder structure on the main server and just mount every subfolder from the storage, things get difficult with a public folder with 644 permissions though) Is useing something like PKI or 802.1X overkill for private uses?

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• Enterprise Manager 12c ? ZFS Storage Appliance

  - by user13138569

  ?????????????? Enterprise Manager 12c ??? Sun ZFS Storage Appliance ????????????????????? ???Enterprise Manager ?? Sun ZFS Storage Appliance ?????????????? Enterprise Manager ????????????????? 3??? Sun ZFS Stoarage Appliance ??????????????????? My Oracle Support ???Oracle Technology Network ???????????????????????????? ?????????????????????????? Oracle ZFS Storage Appliance Plugin Downloads Sun ZFS Storage Appliance ????????????????????????????? P.3 ???????????Appliance ???????????? Workflow ?????????? Enterprise Manager ???????????? P.10 ???????????????????????????????????????????Enterprise Manager 11g ??????????????????????? ??????????????????????????? ??????????????????????Sun ZFS Storage Appliance ??????????Database ???????????????????????????????Enterprise Manager ???????????????????????

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• Object oriented wrapper around a dll

  - by Tom Davies

  So, I'm writing a C# managed wrapper around a native dll. The dll contains several hundred functions. In most cases, the first argument to each function is an opaque handle to a type internal to the dll. So, an obvious starting point for defining some classes in the wrapper would be to define classes corresponding to each of these opaque types, with each instance holding and managing the opaque handle (passed to its constructor) Things are a little awkward when dealing with callbacks from the dll. Naturally, the callback handlers in my wrapper have to be static, but the callbacks arguments invariable contain an opaque handle. In order to get from the static callback back to an object instance, I've created a static dictionary in each class, associating handles with class instances. In the constructor of each class, an entry is put into the dictionary, and this entry is then removed in the Destructors. When I receive a callback, I can then consult the dictionary to retrieve the class instance corresponding to the opaque reference. Are there any obvious flaws to this? Something that seems to be a problem is that the existence static dictionary means that the garbage collector will not act on my class instances that are otherwise unreachable. As they are never garbage collected, they never get removed from the dictionary, so the dictionary grows. It seems I might have to manually dispose of my objects, which is something absolutely would like to avoid. Can anyone suggest a good design that allows me to avoid having to do this?

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• How do we keep dependent data structures up to date?

  - by Geo

  Suppose you have a parse tree, an abstract syntax tree, and a control flow graph, each one logically derived from the one before. In principle it is easy to construct each graph given the parse tree, but how can we manage the complexity of updating the graphs when the parse tree is modified? We know exactly how the tree has been modified, but how can the change be propagated to the other trees in a way that doesn't become difficult to manage? Naturally the dependent graph can be updated by simply reconstructing it from scratch every time the first graph changes, but then there would be no way of knowing the details of the changes in the dependent graph. I currently have four ways to attempt to solve this problem, but each one has difficulties. Nodes of the dependent tree each observe the relevant nodes of the original tree, updating themselves and the observer lists of original tree nodes as necessary. The conceptual complexity of this can become daunting. Each node of the original tree has a list of the dependent tree nodes that specifically depend upon it, and when the node changes it sets a flag on the dependent nodes to mark them as dirty, including the parents of the dependent nodes all the way down to the root. After each change we run an algorithm that is much like the algorithm for constructing the dependent graph from scratch, but it skips over any clean node and reconstructs each dirty node, keeping track of whether the reconstructed node is actually different from the dirty node. This can also get tricky. We can represent the logical connection between the original graph and the dependent graph as a data structure, like a list of constraints, perhaps designed using a declarative language. When the original graph changes we need only scan the list to discover which constraints are violated and how the dependent tree needs to change to correct the violation, all encoded as data. We can reconstruct the dependent graph from scratch as though there were no existing dependent graph, and then compare the existing graph and the new graph to discover how it has changed. I'm sure this is the easiest way because I know there are algorithms available for detecting differences, but they are all quite computationally expensive and in principle it seems unnecessary so I'm deliberately avoiding this option. What is the right way to deal with these sorts of problems? Surely there must be a design pattern that makes this whole thing almost easy. It would be nice to have a good solution for every problem of this general description. Does this class of problem have a name?

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• How to avoid having very large objects with Domain Driven Design

  - by Pablojim

  We are following Domain Driven Design for the implementation of a large website. However by putting the behaviour on the domain objects we are ending up with some very large classes. For example on our WebsiteUser object, we have many many methods - e.g. dealing with passwords, order history, refunds, customer segmentation. All of these methods are directly related to the user. Many of these methods delegate internally to other child object but this still results in some very large classes. I'm keen to avoid exposing lots of child objects e.g. user.getOrderHistory().getLatestOrder(). What other strategies can be used to avoid this problems?

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• Subclassing to avoid line length

  - by Super User

  The standard line length of code is 80 characters per line. This is accepted and followed by the most of programmers. I working on a state machine of a character and is necessary for me follow this too. I have four classes who pass this limit. I can subclass each class in two more and then avoid the line length limit. class Stand class Walk class Punch class Crouch The new classes would be StandLeft, StandRight and so on. Stand, Walk, Punch and Crouch would be then abstract classes. The question if there is a limit for the long of the hierarchies tree or this is depends of the case.

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• Why should ViewModel route actions to Controller when using the MVCVM pattern?

  - by Lea Hayes

  When reading examples across the Internet (including the MSDN reference) I have found that code examples are all doing the following type of thing: public class FooViewModel : BaseViewModel { public FooViewModel(FooController controller) { Controller = controller; } protected FooController Controller { get; private set; } public void PerformSuperAction() { // This just routes action to controller... Controller.SuperAction(); } ... } and then for the view: public class FooView : BaseView { ... private void OnSuperButtonClicked() { ViewModel.PerformSuperAction(); } } Why do we not just do the following? public class FooView : BaseView { ... private void OnSuperButtonClicked() { ViewModel.Controller.SuperAction(); // or, even just use a shortcut property: Controller.SuperAction(); } }

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• How do I handle priority and propagation in an event system?

  - by Peeter

  Lets say I have a simple event system with the following syntax: object = new Object(); object.bind("my_trigger", function() { print "hello"; }); object.bind("my_trigger", function() { print "hello2"; }); object.trigger("my_trigger"); How could I make sure hello2 is printed out first (I do not want my code to depend on which order the events are binded). Ontop of that, how would I prevent my events from propagating (e.g. I want to stop every other event from being executed)

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• DDD: service contains two repository

  - by tikhop

  Does it correct way to have two repository inside one service and will it be an application or domain service? Suppose I have a Passenger object that should contains Passport (government id) object. I am getting Passenger from PassengerRepository. PassengerRepository create request to server and obtain data (json) than parse received data and store inside repository. I have confused because I want to store Passport as Entity and put it to PassportRepository but all information about password contains inside json than i received above. I guess that I should create a PassengerService that will be include PassengerRepository and PassportRepository with several methods like removePassport, addPassport, getAllPassenger and etc. UPDATE: So I guess that the better way is represent Passport as VO and store all passports inside Passenger aggregate. However there is another question: Where I should put the methods (methods calls server api) for management passenger's passport. I think the better place is so within Passenger aggregate.

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• Drive not able to be added to Storage Spaces

  - by Bram Vanroy

  I am having difficulties trying to create a storage space. I have four Hard Drives in my computer. Samsung 128Gb SSD x2 Caviar Green 2TB Older 320 Gb drive I want to merge the two last ones. The problem is, that the 2TB drive does not show up in the configuration screen.: I formatted both hard drives so that can't be it. Any help is appreciated. Edit: larger view: http://bramvanroy.be/files/images/storagespaces.jpg

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• New: ZFS Storage Appliance Videos

  - by Roxana Babiciu

  Check out part one of a new video series for ZFS Storage Appliance. In video #1, you’ll learn about the advantages built into Oracle’s ZS3 Storage Appliance that come from the unique position that Oracle holds in the market. In video #2, you’ll learn how best to monitor large ZS3 installations as well as the use of Enterprise Manager as a complement to dtrace analytics at the ZFS Storage Appliance device level.

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• Sun ZFS Storage Appliance 7120, 7320 ??????

  - by user13138569

  Sun ZFS Storage Appliance 7320 ????????????????????? 7120 ??????????????? ????????????????????????????? Sun ZFS Storage Appliance 7320 ????? Memory 24GB,48GB,72GB 96GB, 144GB ??????(??) 288TB 432TB ???????????(??) 16 24 Shelf? 4 6 Sun ZFS Storage Appliance 7120 ????? Memory 24GB 48GB ????????????????????????????????? 2011.1.2.1 ??????????

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• sg_map & lsscsi showing old storage version

  - by PratapSingh

  I am using SUN storage and recently upgraded/refreshed my ISCSI LUN storage. We have replicated old storage to new storage and attached to our servers. I can see at SUN storage side that storage is attached to server and also from server when I run the below command it prints the following output : iscsiadm -m session tcp: [1] 10.1.1.10:3260,2 iqn.86-03.com.sun:02:afsfsf58-c56a-6ba8-a944-addd258687cd The above storage is SUN STORAGE 7420 But when I run sg_map or lsscsi command it prints different version: lsscsi disk SUN Sun Storage 7410 1.0 /dev/sda disk SUN Sun Storage 7410 1.0 /dev/sdb disk SUN Sun Storage 7410 1.0 /dev/sdc disk SUN Sun Storage 7410 1.0 /dev/sdd Output of ls on "/dev/disk/by-path/" ls -1 /dev/disk/by-path/ ip-10.1.1.10:3260-iscsi-iqn.86-03.com.sun:02:afsfsf58-c56a-6ba8-a944-addd258687cd-lun-0 ip-10.1.1.10:3260-iscsi-iqn.86-03.com.sun:02:afsfsf58-c56a-6ba8-a944-addd258687cd-lun-0-part1 ip-10.1.1.10:3260-iscsi-iqn.86-03.com.sun:02:afsfsf58-c56a-6ba8-a944-addd258687cd-lun-18 ip-10.1.1.10:3260-iscsi-iqn.86-03.com.sun:02:afsfsf58-c56a-6ba8-a944-addd258687cd-lun-18-part1 ip-10.1.1.10:3260-iscsi-iqn.86-03.com.sun:02:afsfsf58-c56a-6ba8-a944-addd258687cd-lun-2 ip-10.1.1.10:3260-iscsi-iqn.86-03.com.sun:02:afsfsf58-c56a-6ba8-a944-addd258687cd-lun-2-part1 ip-10.1.1.10:3260-iscsi-iqn.86-03.com.sun:02:afsfsf58-c56a-6ba8-a944-addd258687cd-lun-4 ip-10.1.1.10:3260-iscsi-iqn.86-03.com.sun:02:afsfsf58-c56a-6ba8-a944-addd258687cd-lun-4-part1 ip-10.1.1.10:3260-iscsi-iqn.86-03.com.sun:02:afsfsf58-c56a-6ba8-a944-addd258687cd-lun-6 ip-10.1.1.10:3260-iscsi-iqn.86-03.com.sun:02:afsfsf58-c56a-6ba8-a944-addd258687cd-lun-6-part1 I have rebooted server twice but still I am getting the same output as given above.

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• My proposed design is usually worse than my colleague's - how do I get better?

  - by user151193

  I have been programming for couple of years and am generally good when it comes to fixing problems and creating small-to-medium scripts, however, I'm generally not good at designing large scale programs in object oriented way. Few questions Recently, a colleague who has same number of years of experience as me and I were working on a problem. I was working on a problem longer than him, however, he came up with a better solution and in the end we're going to use his design. This really affected me. I admit his design is better, but I wanted to come up with a design as good as his. I'm even contemplating quitting the job. Not sure why but suddenly I feel under some pressure e.g. what would juniors think of me and etc? Is it normal? Or I'm thinking a little too much into this? My job involves programming in Python. I try to read source code but how do you think I can improve me design skills? Are there any good books or software that I should study? Please enlighten me. I will really appreciate your help.

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• A PHP design pattern for the model part [PHP Zend Framework]

  - by Matthieu

  I have a PHP MVC application using Zend Framework. As presented in the quickstart, I use 3 layers for the model part : Model (business logic) Data mapper Table data gateway (or data access object, i.e. one class per SQL table) The model is UML designed and totally independent of the DB. My problem is : I can't have multiple instances of the same "instance/record". For example : if I get, for example, the user "Chuck Norris" with id=5, this will create a new model instance wich members will be filled by the data mapper (the data mapper query the table data gateway that query the DB). Then, if I change the name to "Duck Norras", don't save it in DB right away, and re-load the same user in another variable, I have "synchronisation" problems... (different instances for the same "record") Right now, I use the Multiton pattern : like Singleton, but multiple instances indexed by a key (wich is the user ID in our example). But this is complicating my developpement a lot, and my testings too. How to do it right ?

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• Interface Design Problem: Storing Result of Transactions

  - by jboyd

  Requirements: multiple sources of input (social media content) into a system multiple destinations of output (social media api's) sources and destinations WILL be added some pseudo: IContentProvider contentProvider = context.getBean("contentProvider"); List<Content> toPost = contentProvider.getContent(); for (Content c : toPost) { SocialMediaPresence smPresence = socialMediaService.getSMPresenceBySomeId(c.getDestId()); smPresence.hasTwitter(); smPresence.hasFacebook(); //just to show what this is smPresence.postContent(c); //post content could fail for some SM platforms, but shoulnd't be lost forever } So now I run out of steam, I need to know what content has been successfully posted, and if it hasn't gone too all platforms, or if another platform were added in the future that content needs to go out for it as well (therefore my content provider will need to not only know if content has gone out, but for what platforms). I'm not looking for code, although sample/pseudo is fine... I'm looking for an approach to this problem that I can implement

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• Expose subset of a class - design question

  - by thanikkal

  Suppose i have a product class with about close to 100 properties. Now for some operations (Say tax calculation) i dont really need this bulky product type, rather only a subset that has price related properties. I am not sure if i should create different snap shots(class) of products that just has the properties that i am interested in. what would be the ideal approach so that i don't unnecessarily pass around unsought fluff? Thanks in advance.

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• Choosing a design pattern for a class that might change it's internal attributes

  - by the_drow

  I have a class that holds arbitrary state and it's defined like this: class AbstractFoo { }; template <class StatePolicy> class Foo : public StatePolicy, public AbstractFoo { }; The state policy contains only protected attributes that represent the state. The state might be the same for multiple behaviors and they can be replaced at runtime. All Foo objects have the same interface to abstract the state itself and to enable storing Foo objects in containers. I would like to find the least verbose and the most maintainable way to express this.

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