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  • Keeping a domain model consistent with actual data

    - by fstuijt
    Recently domain driven design got my attention, and while thinking about how this approach could help us I came across the following problem. In DDD the common approach is to retrieve entities (or better, aggregate roots) from a repository which acts as a in-memory collection of these entities. After these entities have been retrieved, they can be updated or deleted by the user, however after retrieval they are essentially disconnected from the data source and one must actively inform the repository to update the data source and make is consistent again with our in-memory representation. What is the DDD approach to retrieving entities that should remain connected to the data source? For example, in our situation we retrieve a series of sensors that have a specific measurement during retrieval. Over time, these measurement values may change and our business logic in the domain model should respond to these changes properly. E.g., domain events may be raised if a sensor value exceeds a predefined threshold. However, using the repository approach, these sensor values are just snapshots, and are disconnected from the data source. Does any of you have an idea on how to solve this following the DDD approach?

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  • Is there a common programming term for the problems of adding features to an already-featureful program?

    - by Jeremy Friesner
    I'm looking for a commonly used programming term to describe a software-engineering phenomenon, which (for lack of a better way to describe it) I'll illustrate first with a couple of examples-by-analogy: Scenario 1: We want to build/extend a subway system on the outskirts of a small town in Wyoming. There are the usual subway-problems to solve, of course (hiring the right construction company, choosing the best route, buying the subway cars), but other than that it's pretty straightforward to implement the system because there aren't a huge number of constraints to satisfy. Scenario 2: Same as above, except now we need to build/extend the subway system in downtown Los Angeles. Here we face all of the problems we did in case (1), but also additional problems -- most of the applicable space is already in use, and has a vocal constituency which will protest loudly if we inconvenience them by repurposing, redesigning, or otherwise modifying the infrastructure that they rely on. Because of this, extensions to the system happen either very slowly and expensively, or they don't happen at all. I sometimes see a similar pattern with software development -- adding a new feature to a small/simple program is straightforward, but as the program grows, adding further new features becomes more and more difficult, if only because it is difficult to integrate the new feature without adversely affecting any of the large number of existing use-cases or user-constituencies. (even with a robust, adaptable program design, you run into the problem of the user interface becoming so elaborate that the program becomes difficult to learn or use) Is there a term for this phenomenon?

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  • Depending on fixed version of a library and ignore its updates

    - by Moataz Elmasry
    I was talking to a technical boss yesterday. Its about a project in C++ that depends on opencv and he wanted to include a specific opencv version into the svn and keep using this version ignoring any updates which I disagreed with.We had a heated discussion about that. His arguments: Everything has to be delivered into one package and we can't ask the client to install external libraries. We depend on a fixed version so that new updates of opencv won't screw our code. We can't guarantee that within a version update, ex from 3.2.buildx to 3.2.buildy. Buildy the function signatures won't change. My arguments: True everything has to be delivered to the client as one package,but that's what build scripts are for. They download the external libraries and create a bundle. Within updates of the same version 3.2.buildx to 3.2.buildy its impossible that a signature change, unless it is a really crappy framework, which isn't the case with opencv. We deprive ourselves from new updates and features of that library. If there's a bug in the version we took, and even if there's a bug fix later, we won't be able to get that fix. Its simply ineffiecient and anti design to depend on a certain version/build of an external library as it makes our project difficult in the future to adopt to new changes. So I'd like to know what you guys think. Does it really make sense to include a specific version of external library in our svn and keep using it ignoring all updates?

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  • How can we best petition to bring Adobe creative software to Ubuntu?

    - by Sixthlaw
    Now I know its not as simple as asking for Adobe to support their design software on Ubuntu, but is there a way for the community and Canonical to make known to Adobe the rapidly growing amount of Linux users, and their desire for this great set of tools OFFICIALLY? I know that many of the answers I receive might be of the fashion "Its not going to happen", "use the free tools provided" or "Who knows it might happen in the near future", but this IS not what I am looking for. I have noticed, on sites like www.OmgUbuntu.com, there are links to pages where people can "like" the idea. Is there a way to try and get the whole community on board with this one, even Canonical, and as stated above, put forward this proposal to Adobe. The current requests for an Adobe CS, for Linux, are in dribs and drabs scattered all of the internet. Now is the best time to come up with productive solutions on how we can best gather statistics on the amount of people willing to buy the Adobe CS. These are the words of an Adobe employee: "I have forwarded this feedback on to the appropriate team who will consider it for future releases of Adobe software." The larger amount of people we have unified in the ONE community proposal, the greater chance we have of getting the software. How can we make this happen?

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  • What are solutions and tradeoffs to maintain search result consistency in a web application

    - by iammichael
    Consider a web application with a custom search function that must display the results in a paged manner (twenty per page with up to hundreds of thousands of total results) and the ability to drill down to individual results that maintain next/previous links to navigate through the results. Re-executing the search on each page request to get the appropriate results for that page of data can be too expensive (up to 15s per search). Also, since the underlying data can change frequently (e.g. addition of new results), re-executing could cause the next/previous functionality to result in inconsistent behavior (e.g. the same results reappearing on a later page after having been viewed on an earlier page). What options exist to ensure the search results can be viewed across multiple pages in a consistent manner, and what tradeoffs does each option have in terms of network, CPU, memory, and storage requirements? EDIT: I thought caching the query search results was an obvious necessity. The question is really asking about where to cache the result set and what tradeoffs might exist to each. For example, storing the ids of the entities in the result set on the client, or storing the IDs of the entities themselves in the users session on the web server, or in a temporary table in the database. I'm not looking specifically for a single solution as different scenarios may result in different approaches (and such a question would be more suited for stackoverflow.com rather than here), but more of a design comparison between the possible approaches.

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  • Static / Shared Helper Functions vs Built-In Methods

    - by Nathan
    This is a simple question but a design consideration that I often run across in my day to day development work. Lets say that you have a class that represents some kinds of collection. Public Class ModifiedCustomerOrders Public Property Orders as List(Of ModifiedOrders) End Class Within this class you do all kinds of important work, such as combining many different information sources and, eventually, build the Modified Customer Orders. Now, you have different processes that consume this class, each of which needs a slightly different slice of the ModifiedCustomerOrders items. To enable this, you want to add filtering functionality. How do you go about this? Do you: Add Filtering calls to the ModifiedCustomerOrders class so that you can say: MyOrdersClass.RemoveCanceledOrders() Create a Static / Shared "tooling" class that allows you to call: OrdersFilters.RemoveCanceledOrders(MyOrders) Create an extension method to accomplish the same feat as #2 but with less typing: MyOrders.RemoveCanceledOrders() Create a "Service" method that handles the getting of Orders as appropriate to the calling function, while using one of the previous approaches "under the hood". OrdersService.GetOrdersForProcessA() Others? I tend to prefer the tooling / extension method approaches as they make testing a little bit simpler. Although I dependency inject all my sourcing data into the ModifiedCustomerOrders, having it as part of the class makes it a little bit more complicated to test. Typically, I choose to use extension methods where I am doing parameterless transformations / filters. As they get more complex, I will move it into a static class instead. Thoughts on this approach? How would you approach it?

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  • Should I think about switching to another platform as a .Net developer? [closed]

    - by A. Karimi
    I’ve been a developer for about 10 years and I’ve almost worked on Microsoft stack. At the last several years I’ve been introduced to some good practices such as IoC and other primary design patterns. Now I feel so much comfortable using these patterns and concepts and I’m very angry why we didn’t do that earlier! They exist and used by many developers since more than 5 years ago but why I and many of my colleagues began using them a little later. As you may know Java developers are more ahead in these fields (concepts, patterns and …) than .Net developers. Am I right? Now the question is, “Why we (as .NET developers) weren’t ahead so much? Isn’t it because we are using Microsoft stack?”. I know ALT.NET but why we are trying make a closed ecosystem open and finding alternatives for Microsoft Echo Chamber, while there are natively open ecosystems like Java!? I've always liked most of the Microsoft works very much but I’m worried about this issue. I am even ask myself should I move to another platform?

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  • Correct way to inject dependencies in Business logic service?

    - by Sri Harsha Velicheti
    Currently the structure of my application is as below Web App -- WCF Service (just a facade) -- Business Logic Services -- Repository - Entity Framework Datacontext Now each of my Business logic service is dependent on more than 5 repositories ( I have interfaces defined for all the repos) and I am doing a Constructor injection right now(poor mans DI instead of using a proper IOC as it was determined that it would be a overkill for our project). Repositories have references to EF datacontexts. Now some of the methods in the Business logic service require only one of the 5 repositories, so If I need to call that method I would end up instantiating a Service which will instatiate all 5 repositories which is a waste. An example: public class SomeService : ISomeService { public(IFirstRepository repo1, ISecondRepository repo2, IThirdRepository repo3) {} // My DoSomething method depends only on repo1 and doesn't use repo2 and repo3 public DoSomething() { //uses repo1 to do some stuff, doesn't use repo2 and repo3 } public DoSomething2() { //uses repo2 and repo3 to do something, doesn't require repo1 } public DoSomething3() { //uses repo3 to do something, doesn't require repo1 and repo2 } } Now if my I have to use DoSomething method on SomeService I end up creating both IFirstRepository,ISecondRepository and IThirdRepository but using only IFirstRepository, now this is bugging me, I can seem to accept that I am un-necessarily creating repositories and not using them. Is this a correct design? Are there any better alternatives? Should I be looking at Lazy instantiation Lazy<T> ?

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  • Motivation for service layer (instead of just copying dlls)?

    - by BornToCode
    I'm creating an application which has 2 different UIs so I'm making it with a service layer which I understood is appropriate for such case. However I found myself just creating web methods for every single method I have in the BL layer, so the services basically built from methods that looks like this: return customers_bl.Get_Customer_Prices(customer_id); I understood that a main point of the service layer is to prevent duplication of code so I asked myself - well, why not just import the BL.dll (and the DAL.dll) to the other UI, and whenever making a change re-copy the dll files, it might not be so 'neat', but is the all purpose of the service layer to prevent this? {I know something is wrong in my approach, I'm probably missing the importance of service layer, I'd like to get more motivation to create another layer, especially because as it is I found that many of my BL functions ALREADY looks like: return customers_dal.Get_Customer_Prices(cust_id) which led me to ask: was it really necessary to create the BL just because on several functions I actually have LOGIC inside the BL?} so I'm looking for more motivation to creating ONE MORE layer, I'm sure it's not just to make it more convenient that I won't have to re-copy the dlls on changes? Am I grasping it wrong? Any simple guidelines on how to design service layer (corresponding to all the BL layer functions or not? any simple example?) any enlightenment on the subject?

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  • Need ideas on how to give my levels structure

    - by akuritsu
    I am making an iOS game for a project at school. It is going to be a tiny bit like Fruit Ninja, as in it will have different things on the screen, and when you hit them, they die, and you get points. The trouble is that unlike Fruit Ninja, my game will have different types of sprites, all doing different things (moving different places, doing different things, etc). The one thing that is bad about having all of these sprites that do different things is that it is hard for them to look neat on the screen all together. I was planning on having a couple of different gamemodes: Time Trial You have 120 seconds to kill as many sprites as possible. Survival You have three lives, every time you try to hit a sprite and miss, you lose a life. ???? Whatever I think of. I am a rookie to game design in general, and I don't know the best way to make my game look good, and play well. I could have all of these sprites on the screen at the same time, or I could have them come in waves, for example 10 of sprite_a come on, and once they are killed, 10 of sprite_b come on, etc... Please give me your opinion about which one I should code. If you have any other suggestions for either a third gamemode, or a completely different way to make the levels, feel free to tell me.

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  • Motivation for a service layer (instead of just copying dlls)?

    - by BornToCode
    I'm creating an application which has 2 different UIs so I'm making it with a service layer which I understood is appropriate for such scenario. However I found myself just creating web methods for every single method I have in the BL layer, so the services basically built from methods that looks like this: return customers_bl.Get_Customer_Prices(customer_id); I understood that a main point of the service layer is to prevent duplication of code so I asked myself - why not just import the BL.DLL (and the dal.dll) to the other UI, and whenever making a change re-copy the dlls, it might not be so 'neat', but still less hassle than one more layer? {I know something is wrong in my approach, I'm probably missing the importance of service layer, I'd like to get more motivation to create another layer, especially because as it is I found that many of my BL functions ALREADY looks like: return customers_dal.Get_Customer_Prices(cust_id) which led me to ask: was it really necessary to create the BL just because on several functions I actually have LOGIC inside the BL?} so I'm looking for more motivation to creating ONE MORE layer, I'm sure it's not just to make it more convenient that I won't have to re-copy the dlls on changes? Am I grasping it wrong? Any simple guidelines on how to design service layer (corresponding to all the BL layer functions or not? any simple example?) any enlightenment on the subject?

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  • Did I Inadvertently Create a Mediator in my MVC?

    - by SoulBeaver
    I'm currently working on my first biggish project. It's a frontend facebook application that has, since last Tuesday, spanned some 6000-8000 LOC. I say this because I'm using the MVC, an architecture I have never rigidly enforced in any of my hobby projects. I read part of the PureMVC book, but I didn't quite grasp the concept of the Mediator. Since I didn't understand and didn't see the need for it, my project has yet to use a single mediator. Yesterday I went back to the design board because of some requirement changes and noticed that I could move all UI elements out of the View and into its own class. The View essentially only managed the lifetime of the UI and all events from the UI or Model. Technically, the View has now become a 'Mediator' between the Model and UI. Therefore, I realized today, I could just move all my UI stuff back into the View and create a mediator class that handles all events from the view and model. Is my understanding correct in thinking that I have devolved my View as it currently is (handling events from the Model and UI) into a Mediator and that the UI class is what should be the View?

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  • How to pass dynamic information between a form and a service? [closed]

    - by qminator
    I have a design problem and hopefully the braintrust which is stack exchange can help. I have a generic form, which loads a dataset and displays it. It never has direct knowledge of what it contains but can pass it to a service for manipulation (via an Onclick event for example). However, the form might need to alter its behaviour based on the manipulation by the service. Example: The service realises this dataset requires sending of an email by the user and needs to send an instruction to the form to open up a mail form. My idea is thus: I'm thinking about passing back some type of key/name dictionary, filled with commands which the service requires. They could then be interpeted by the form without it need to reference something specific. Example: IF the service decides that the dataset needs to refresh it would send back a key/name pair, I might even be able to chain commands. Refreshing the dataset and sending a mail. Refresh / "Foo" Mail / "[email protected]" The form would reference an action explicitly (Refresh or Mail) but not the instructions themselves. Is this a valid idea or am I wasting time?

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  • Which are the best ways to organize view hierarchies in GUI interfaces?

    - by none
    I'm currently trying to figure out the best techniques for organizing GUI view hierarchies, that is dividing a window into several panels which are in turn divided into other components. I've given a look to the Composite Design Pattern, but I don't know if I can find better alternatives, so I'd appreciate to know if using the Composite is a good idea, or it would be better looking for some other techniques. I'm currently developing in Java Swing, but I don't think that the framework or the language can have a great impact on this. Any help will be appreciated. ---------EDIT------------ I was currently developing a frame containing three labels, one button and a text field. At the button pressed, the content inside the text field would be searched, and the results written inside the three labels. One of my typical structure would be the following: MainWindow | Main panel | Panel with text field and labels. | Panel with search button Now, as the title explains, I was looking for a suitable way of organizing both the MainPanel and the other two panels. But here came problems, since I'm not sure whether organizing them like attributes or storing inside some data structure (i.e. LinkedList or something like this). Anyway, I don't really think that both my solution are really good, so I'm wondering if there are really better approaches for facing this kind of problems. Hope it helps

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  • Should sanity be a property of a programmer or a program?

    - by toplel32
    I design and implement languages, that can range from object notations to markup languages. In many cases I have considered restrictions in favor of sanity (common knowledge), like in the case of control characters in identifiers. There are two consequences to consider before doing this: It takes extra computation It narrows liberty I'm interested to learn how developers think of decisions like this. As you may know Microsoft C# is very open on the contrary. If you really want to prefix your integer as Long with 'l' instead of 'L' and so risk other developers of confusing '1' and 'l', no problem. If you want to name your variables in non-latin script so they will contrast with C#'s latin keywords, no problem. Or if you want to distribute a string over multiple lines and so break a series of indentation, no problem. It is cheap to ensure consistency with restrictions and this makes it tempting to implement. But in the case of disallowing non-latin characters (concerning the second example), it means a discredit to Unicode, because one would not take full advantage of its capacity.

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  • On Developing Web Services with Global State

    - by user74418
    I'm new to web programming. I'm more experienced and comfortable with client-side code. Recently, I've been dabbling in web programming through Python's Google App Engine. I ran into some difficulty while trying to write some simple apps for the purposes of learning, mainly involving how to maintain some kind of consistent universally-accessible state for the application. I tried to write a simple queueing management system, the kind you would expect to be used in a small clinic, or at a cafeteria. Typically, this is done with hardware. You take a number from a ticketing machine, and when your number is displayed or called you approach the counter for service. Alternatively, you could be given a small pager, which will beep or vibrate when it is your turn to receive service. The former is somewhat better in that you have an idea of how many people are still ahead of you in the queue. In this situation, the global state is the last number in queue, which needs to be updated whenever a request is made to the server. I'm not sure how to best to store and maintain this value in a GAE context. The solution I thought of was to keep the value in the Datastore, attempt to query it during a ticket request, update the value, and then re-store it with put. My problem is that I haven't figured out how to lock the resource so that other requests do not check the value while it is in the middle of being updated. I am concerned that I may end up ticket requests that have the same queue number. Also, the whole solution feels awkward to me. I was wondering if there was a more natural way to accomplish this without having to go through the Datastore. Can anyone with more experience in this domain provide some advice on how to approach the design of the above application?

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  • Getting Requirements Right

    - by Tim Murphy
    Originally posted on: http://geekswithblogs.net/tmurphy/archive/2013/10/28/getting-requirements-right.aspxI had a meeting with a stakeholder who stated “I bet you wish I wasn’t in these meetings”.  She said this because she kept changing what we thought the end product should look like.  My reply was that it would be much worse if she came in at the end of the project and told us we had just built the wrong solution. You have to take the time to get the requirements right.  Be honest with all involved parties as to the amount of time it is taking to refine the requirements.  The only thing worse than wrong requirements is a surprise in budget overages.  If you give open visibility to your progress then management has the ability to shift priorities if needed. In order to capture the best requirements use different approaches to help your stakeholders to articulate their needs.  Use mock ups and matrix spread sheets to allow them to visualize and confirm that everyone has the same understanding.  The goals isn’t to record every last detail, but to have the major landmarks identified so there are fewer surprises along the way. Help the team members to understand that you all have the same goal.  You want to create the best possible solution for the given business problem.  If you do this everyone involved will do there best to outline a picture of what is to be built and you will be able to design an appropriate solution to fill those needs more easily. Technorati Tags: requirements gathering,PSC Group,PSC

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  • Redesigning my website has destroyed my SEO

    - by user20721
    Unfortunately i read an article on how to avoid destroying your websites SEO from a redesign article AFTER its was too late! Here is the article (http://www.searchenginejournal.com/how-to-avoid-seo-disaster-during-a-website-redesign/42824/) On 20 November 12 completely redesigned our www.retromodern.com.au . We get ALL our customers from our website as we do not have a shop. Since that dreaded day a month ago the phone pretty much stopped, basically no emails, Google rankings down and Google analytics have halved by 50%. Yesterday i did some research into as as i had no idea that a re-design of a website could have such a damaging effect - yes i am a novice and use a WYSIWYG type web builder. There are lots of info on how to AVOID this from happening BUT what do i do as i have already made the mistake? Yesterday i reloaded my OLD site with my new pages in the background hoping this would be a start. I really have no idea of how to get out of this mess. Please please help. Thanks in Advance. Monique

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  • How should I implement Transaction database EJB 3.0

    - by JamesBoyZ
    In the CustomerTransactions entity, I have the following field to record what the customer bought: @ManyToMany private List<Item> listOfItemsBought; When I think more about this field, there's a chance it may not work because merchants are allowed to change item's information (e.g. price, discount, etc...). Hence, this field will not be able to record what the customer actually bought when the transaction occurred. At the moment, I can only think of 2 ways to make it work. I will record the transaction details into a String field. I feel that this way would be messy if I need to extract some information about the transaction later on. Whenever the merchant changes an item's information, I will not update directly to that item's fields. Instead, I will create another new item with all the new information and keep the old item untouched. I feel that this way is better because I can easily extract information about the transaction later on. However, the bad side is that my Item table may contain a lot of rows. I'd be very grateful if someone could give me an advice on how I should tackle this problem. UPDATE: I'd like to add more information about the current design. public class Customer implements Serializable { @OneToMany private List<CustomerTransactions> listOfTransactions; } public class CustomerTransactions implements Serializable { @ManyToMany private List<Item> listOfItemsBought; } public class Merchant implements Serializable { @OneToMany private List<Item> listOfSellingItems; }

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  • Hide or Show singleton?

    - by Sinker
    Singleton is a common pattern implemented in both native libraries of .NET and Java. You will see it as such: C#: MyClass.Instance Java: MyClass.getInstance() The question is: when writing APIs, is it better to expose the singleton through a property or getter, or should I hide it as much as possible? Here are the alternatives for illustrative purposes: Exposed(C#): private static MyClass instance; public static MyClass Instance { get { if (instance == null) instance = new MyClass(); return instance; } } public void PerformOperation() { ... } Hidden (C#): private static MyClass instance; public static void PerformOperation() { if (instance == null) { instance = new MyClass(); } ... } EDIT: There seems to be a number of detractors of the Singleton design. Great! Please tell me why and what is the better alternative. Here is my scenario: My whole application utilises one logger (log4net/log4j). Whenever, the program has something to log, it utilises the Logger class (e.g. Logger.Instance.Warn(...) or Logger.Instance.Error(...) etc. Should I use Logger.Warn(...) or Logger.Warn(...) instead? If you have an alternative to singletons that addresses my concern, then please write an answer for it. Thank you :)

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  • Why using Fragments?

    - by ahmed_khan_89
    I have read the documentation and some other questions' threads about this topic and I don't really feel convinced; I don't see clearly the limits of use of this technique. Fragments are now seen as a Best Practice; every Activity should be basically a support for one or more Fragments and not call a layout directly. Fragments are created in order to: allow the Activity to use many fragments, to change between them, to reuse these units... == the Fragment is totally dependent to the Context of an activity , so if I need something generic that I can reuse and handle in many Activities, I can create my own custom layouts or Views ... I will not care about this additional Complexity Developing Layer that fragments would add. a better handling to different resolution == OK for tablets/phones in case of long process that we can show two (or more) fragments in the same Activity in Tablets, and one by one in phones. But why would I use fragments always ? handling callbacks to navigate between Fragments (i.e: if the user is Logged-in I show a fragment else I show another fragment). === Just try to see how many bugs facebook SDK Log-in have because of this, to understand that it is really (?) ... considering that an Android Application is based on Activities... Adding another life cycles in the Activity would be better to design an Application... I mean the modules, the scenarios, the data management and the connectivity would be better designed, in that way. === This is an answer of someone who's used to see the Android SDK and Android Framework with a Fragments vision. I don't think it's wrong, but I am not sure it will give good results... And it is really abstract... ==== Why would I complicate my life, coding more, in using them always? else, why is it a best practice if it's just a tool for some cases? what are these cases?

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  • ResourceSerializable: an alternate to ORM and ActiveRecord

    - by Levi Morrison
    A few opinionated reasons I don't like the traditional ORM and ActiveRecord patterns: They work only with a database. Sometimes I'm dealing with objects from an API and other objects from a database. All the implementations I have seen don't allow for that. Feel free to clue me in if I'm wrong on this. They are brittle. Changes in the database will likely break your implemenation. Some implementations can help reduce this, but a few of the ones I've seen don't. Their very design is influenced by the database. If I want to switch to using an API, I'll have to redesign the object to get it to work (likely). It seems to violate the single-responsibility pattern. They know what they are and how they act, but they also know how they are created, destroyed and saved? Seems a bit much. What about an approach that is somewhat more familiar in PHP: implementing an interface? In php 5.4, we'll have the JsonSerializable interface that defines the data to be json_encoded, so users will become accustomed to this type of thing. What if there was a ResourceSerializable interface? This is still an ORM by name, but certainly not by tradition. interface ResourceSerializable { /** * Returns the id that identifies the resource. */ function resourceId(); /** * Returns the 'type' of the resource. */ function resourceType(); /** * Returns the data to be serialized. */ function resourceSerialize(); } Things might be poorly named, I'll take suggestions. Notes: ResourceId will work for API's and databases. As long as your primary key in the database is the same as the resource ID in the API, there is no conflict. All of the API's I've worked with have a unique ID for the resource, so I don't see any issues there. ResourceType is the group or type associated with the resource. You can use this to map the resource to an API call or a database table. If the ResourceType was person, it could map to /api/1/person/{resourceId} and the table persons (or people, if it's smart enough). resourceSerialize() returns the data to be stored. Keys would identify API parameters and database table columns. This also seems easier to test than ActiveRecord / Orm implemenations. I haven't done much automated testing on traditional ActiveRecord/ORM implemenations, so this is merely a guess. But it seems that I being able to create objects independently of the library helps me. I don't have to use load() to get an existing resource, I can simply create one and set all the right properties. This is not so easy in the ActiveRecord / Orm implemenations I've dealt with. Downsides: You need another object to serialize it. This also means you have more code in general as you have to use more objects. You have to map resource types to API calls and database tables. This is even more work, but some ORMs and ActiveRecord implementations require you to map objects to table names anyway. Are there other downsides that you see? Does this seem feasible to you? How would you improve it? Note: I almost asked this on StackOverflow because it might be too vague for their standards, but I'm still not really familiar with programmers.stackexchange.com, so please help me improve my question if it doesn't shape up to standards here.

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  • Would this be a good web application architecture?

    - by Gustav Bertram
    My problem Our MVC based framework does not allow us to cache only part of our output. Ideally we want to cahce static and semi-static bits, and run dynamic bits. In addition, we need to consider data caching that reacts to database changes. My idea The concept I came up with was to represent a page as a tree of XML fragment objects. (I say XML, but I mean XHTML). Some of the fragments are dynamic, and can pull their data directly from models or other sources, but most of the fragments are static scaffolding. If a subtree of fragments is completely static, then I imagine that they could unfold into pure XML that would then be cached as the text representation of their parent element. This process would ideally continue until we are left with a root element that contains all of the static XML, and has a couple of dynamic XML fragments that are resolved and attached to the relevant nodes of the XML tree just before the page is displayed. In addition to separating content into dynamic and static fragments, some fragments could be dynamic and cached. A simple expiry time which propagates up through the XML fragment tree would indicate that a specific fragment should periodically be refreshed. A newspaper section or front page does not need to be updated each second. Minutes or sometimes even longer is sufficient. Other fragments would be dynamic and uncached. Typically too many articles are viewed for them to be cached - the cache would overflow. Some individual articles may be cached if they are extremely popular. Functional notes The folding mechanism could be to be smart enough to judge when it would be more profitable to fold a dynamic cached fragment and propagate the expiry date to the parent fragment, or to keep it separate and simple attach to the XML tree when resolving the page. If some dynamic cached fragments are associated to database objects through mechanisms like a globally unique content id, then changes to the database could trigger changes to the output cache. If fragments store the identifiers of parent fragments, then they could trigger a refolding process that would then include the updated data. A set of pure XML with an ordered array of fragment objects (that each store the identifying information of the node to which they should be attached), can be resolved in a fairly simple way by walking the XML tree, and merging the data from the fragments. Because it is not necessary to parse and construct the entire tree in memory before attaching nodes, processing should be fairly fast. The identifiers of each fragment would be a combination of relevant identity data and the type of fragment object. Cached parent fragments would contain references to these identifiers, in order to then either pull them from the fragment cache, or to run their code. The controller's responsibility is reduced to making changes to the database, and telling the root XML fragment object to render itself. The Question My question has two parts: Is this a good design? Are there any obvious flaws I'm missing? Has somebody else thought of this before? References? Is there an existing alternative that I should consider? A cool templating engine maybe?

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  • Validation and authorization in layered architecture

    - by SonOfPirate
    I know you are thinking (or maybe yelling), "not another question asking where validation belongs in a layered architecture?!?" Well, yes, but hopefully this will be a little bit of a different take on the subject. I am a firm believer that validation takes many forms, is context-based and varies at each level of the architecture. That is the basis for the post - helping to identify what type of validation should be performed in each layer. In addition, a question that often comes up is where authorization checks belong. The example scenario comes from an application for a catering business. Periodically during the day, a driver may turn in to the office any excess cash they've accumulated while taking the truck from site to site. The application allows a user to record the 'cash drop' by collecting the driver's ID, and the amount. Here's some skeleton code to illustrate the layers involved: public class CashDropApi // This is in the Service Facade Layer { [WebInvoke(Method = "POST")] public void AddCashDrop(NewCashDropContract contract) { // 1 Service.AddCashDrop(contract.Amount, contract.DriverId); } } public class CashDropService // This is the Application Service in the Domain Layer { public void AddCashDrop(Decimal amount, Int32 driverId) { // 2 CommandBus.Send(new AddCashDropCommand(amount, driverId)); } } internal class AddCashDropCommand // This is a command object in Domain Layer { public AddCashDropCommand(Decimal amount, Int32 driverId) { // 3 Amount = amount; DriverId = driverId; } public Decimal Amount { get; private set; } public Int32 DriverId { get; private set; } } internal class AddCashDropCommandHandler : IHandle<AddCashDropCommand> { internal ICashDropFactory Factory { get; set; } // Set by IoC container internal ICashDropRepository CashDrops { get; set; } // Set by IoC container internal IEmployeeRepository Employees { get; set; } // Set by IoC container public void Handle(AddCashDropCommand command) { // 4 var driver = Employees.GetById(command.DriverId); // 5 var authorizedBy = CurrentUser as Employee; // 6 var cashDrop = Factory.CreateCashDrop(command.Amount, driver, authorizedBy); // 7 CashDrops.Add(cashDrop); } } public class CashDropFactory { public CashDrop CreateCashDrop(Decimal amount, Employee driver, Employee authorizedBy) { // 8 return new CashDrop(amount, driver, authorizedBy, DateTime.Now); } } public class CashDrop // The domain object (entity) { public CashDrop(Decimal amount, Employee driver, Employee authorizedBy, DateTime at) { // 9 ... } } public class CashDropRepository // The implementation is in the Data Access Layer { public void Add(CashDrop item) { // 10 ... } } I've indicated 10 locations where I've seen validation checks placed in code. My question is what checks you would, if any, be performing at each given the following business rules (along with standard checks for length, range, format, type, etc): The amount of the cash drop must be greater than zero. The cash drop must have a valid Driver. The current user must be authorized to add cash drops (current user is not the driver). Please share your thoughts, how you have or would approach this scenario and the reasons for your choices.

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  • Binary data instead of actual image in C#

    - by acadia
    Hello, I am using the below mentioned library to create a barcode which is storing in a specified location as shown below: My question is, is there a way instead of saving it to a png file I get byte data? thanks Code39 code = new Code39("10090"); code.Paint().Save("c:/NewBARCODE.png", ImageFormat.Png); using System; using System.Collections.Generic; using System.Drawing; using System.Drawing.Imaging; using System.Diagnostics; namespace BarCode39 { public class Code39Settings { private int height = 60; public int BarCodeHeight { get { return height; } set { height = value; } } private bool drawText = true; public bool DrawText { get { return drawText; } set { drawText = value; } } private int leftMargin = 10; public int LeftMargin { get { return leftMargin; } set { leftMargin = value; } } private int rightMargin = 10; public int RightMargin { get { return rightMargin; } set { rightMargin = value; } } private int topMargin = 10; public int TopMargin { get { return topMargin; } set { topMargin = value; } } private int bottomMargin = 10; public int BottomMargin { get { return bottomMargin; } set { bottomMargin = value; } } private int interCharacterGap = 2; public int InterCharacterGap { get { return interCharacterGap; } set { interCharacterGap = value; } } private int wideWidth = 2; public int WideWidth { get { return wideWidth; } set { wideWidth = value; } } private int narrowWidth = 1; public int NarrowWidth { get { return narrowWidth; } set { narrowWidth = value; } } private Font font = new Font(FontFamily.GenericSansSerif, 12); public Font Font { get { return font; } set { font = value; } } private int codeToTextGapHeight = 10; public int BarCodeToTextGapHeight { get { return codeToTextGapHeight; } set { codeToTextGapHeight = value; } } } public class Code39 { #region Static initialization static Dictionary<char, Pattern> codes; static Code39() { object[][] chars = new object[][] { new object[] {'0', "n n n w w n w n n"}, new object[] {'1', "w n n w n n n n w"}, new object[] {'2', "n n w w n n n n w"}, new object[] {'3', "w n w w n n n n n"}, new object[] {'4', "n n n w w n n n w"}, new object[] {'5', "w n n w w n n n n"}, new object[] {'6', "n n w w w n n n n"}, new object[] {'7', "n n n w n n w n w"}, new object[] {'8', "w n n w n n w n n"}, new object[] {'9', "n n w w n n w n n"}, new object[] {'A', "w n n n n w n n w"}, new object[] {'B', "n n w n n w n n w"}, new object[] {'C', "w n w n n w n n n"}, new object[] {'D', "n n n n w w n n w"}, new object[] {'E', "w n n n w w n n n"}, new object[] {'F', "n n w n w w n n n"}, new object[] {'G', "n n n n n w w n w"}, new object[] {'H', "w n n n n w w n n"}, new object[] {'I', "n n w n n w w n n"}, new object[] {'J', "n n n n w w w n n"}, new object[] {'K', "w n n n n n n w w"}, new object[] {'L', "n n w n n n n w w"}, new object[] {'M', "w n w n n n n w n"}, new object[] {'N', "n n n n w n n w w"}, new object[] {'O', "w n n n w n n w n"}, new object[] {'P', "n n w n w n n w n"}, new object[] {'Q', "n n n n n n w w w"}, new object[] {'R', "w n n n n n w w n"}, new object[] {'S', "n n w n n n w w n"}, new object[] {'T', "n n n n w n w w n"}, new object[] {'U', "w w n n n n n n w"}, new object[] {'V', "n w w n n n n n w"}, new object[] {'W', "w w w n n n n n n"}, new object[] {'X', "n w n n w n n n w"}, new object[] {'Y', "w w n n w n n n n"}, new object[] {'Z', "n w w n w n n n n"}, new object[] {'-', "n w n n n n w n w"}, new object[] {'.', "w w n n n n w n n"}, new object[] {' ', "n w w n n n w n n"}, new object[] {'*', "n w n n w n w n n"}, new object[] {'$', "n w n w n w n n n"}, new object[] {'/', "n w n w n n n w n"}, new object[] {'+', "n w n n n w n w n"}, new object[] {'%', "n n n w n w n w n"} }; codes = new Dictionary<char, Pattern>(); foreach (object[] c in chars) codes.Add((char)c[0], Pattern.Parse((string)c[1])); } #endregion private static Pen pen = new Pen(Color.Black); private static Brush brush = Brushes.Black; private string code; private Code39Settings settings; public Code39(string code) : this(code, new Code39Settings()) { } public Code39(string code, Code39Settings settings) { foreach (char c in code) if (!codes.ContainsKey(c)) throw new ArgumentException("Invalid character encountered in specified code."); if (!code.StartsWith("*")) code = "*" + code; if (!code.EndsWith("*")) code = code + "*"; this.code = code; this.settings = settings; } public Bitmap Paint() { string code = this.code.Trim('*'); SizeF sizeCodeText = Graphics.FromImage(new Bitmap(1, 1)).MeasureString(code, settings.Font); int w = settings.LeftMargin + settings.RightMargin; foreach (char c in this.code) w += codes[c].GetWidth(settings) + settings.InterCharacterGap; w -= settings.InterCharacterGap; int h = settings.TopMargin + settings.BottomMargin + settings.BarCodeHeight; if (settings.DrawText) h += settings.BarCodeToTextGapHeight + (int)sizeCodeText.Height; Bitmap bmp = new Bitmap(w, h, PixelFormat.Format32bppArgb); Graphics g = Graphics.FromImage(bmp); int left = settings.LeftMargin; foreach (char c in this.code) left += codes[c].Paint(settings, g, left) + settings.InterCharacterGap; if (settings.DrawText) { int tX = settings.LeftMargin + (w - settings.LeftMargin - settings.RightMargin - (int)sizeCodeText.Width) / 2; if (tX < 0) tX = 0; int tY = settings.TopMargin + settings.BarCodeHeight + settings.BarCodeToTextGapHeight; g.DrawString(code, settings.Font, brush, tX, tY); } return bmp; } private class Pattern { private bool[] nw = new bool[9]; public static Pattern Parse(string s) { Debug.Assert(s != null); s = s.Replace(" ", "").ToLower(); Debug.Assert(s.Length == 9); Debug.Assert(s.Replace("n", "").Replace("w", "").Length == 0); Pattern p = new Pattern(); int i = 0; foreach (char c in s) p.nw[i++] = c == 'w'; return p; } public int GetWidth(Code39Settings settings) { int width = 0; for (int i = 0; i < 9; i++) width += (nw[i] ? settings.WideWidth : settings.NarrowWidth); return width; } public int Paint(Code39Settings settings, Graphics g, int left) { #if DEBUG Rectangle gray = new Rectangle(left, 0, GetWidth(settings), settings.BarCodeHeight + settings.TopMargin + settings.BottomMargin); g.FillRectangle(Brushes.Gray, gray); #endif int x = left; int w = 0; for (int i = 0; i < 9; i++) { int width = (nw[i] ? settings.WideWidth : settings.NarrowWidth); if (i % 2 == 0) { Rectangle r = new Rectangle(x, settings.TopMargin, width, settings.BarCodeHeight); g.FillRectangle(brush, r); } x += width; w += width; } return w; } } } }

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