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  • How to separate model and view with Core Data?

    - by andrewebling
    I have a subclass of UIView which draws itself based on data held in a corresponding model class, which is a subclass of NSManagedObject. The problem is, some fields in the data model (e.g. the position of the view) are already held in the view (i.e. the frame property in this case). I then have a data duplication/synchronization problem to solve. To complicate matters further, the view needs to update in response to changes made to the data model and the data model needs to be updated in responses made to the view (e.g. the user dragging it to a new location). What's the best way to solve this? Using KVO and references in both directions? Or is there a better approach?

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  • What difference between Web Apps & Descktop app shoud one keep in mind to model the system right?

    - by simple
    Sometimes it seems like some architectural techniques are not for the Web application I am building and then I just go and code =(, Though I really want to make a habit to architect system before moving to the code, as when I just code I endup writing some useless components which then I rewrite =(, So can you just point out some differences between web apps and desktop ones ?

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  • Separation of business logic

    - by bruno
    When I was optimizing my architecture of our applications in our website, I came to a problem that I don't know the best solution for. Now at the moment we have a small dll based on this structure: Database <-> DAL <-> BLL the Dal uses Business Objects to pass to the BLL that will pass it to the applications that uses this dll. Only the BLL is public so any application that includes this dll, can see the bll. In the beginning, this was a good solution for our company. But when we are adding more and more applications on that Dll, the bigger the Bll is getting. Now we dont want that some applications can see Bll-logic from other applications. Now I don't know what the best solution is for that. The first thing I thought was, move and separate the bll to other dll's which i can include in my application. But then must the Dal be public, so the other dll's can get the data... and that I seems like a good solution. My other solution, is just to separate the bll in different namespaces, and just include only the namespaces you need in the applications. But in this solution, you can get directly access to other bll's if you want. So I'm asking for your opinions.

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  • 2d Game Making > Where can someone get Free Tilesets?

    - by Iscariot
    I have been scouring the internet for free tilesets that are open to you. I have found http://lostgarden.com/ It does not seem very useful. There are a few things here and there, but overall not much to really make a game off of. http://www.flyingyogi.com/fun/spritelib.html Spritelib is a little better it has some useful information, but is still the graphics are more in the 8bit variety. http://reinerstileset.4players.de/ This is heavily stylized and its hard to have this match with any other free tile-sets available. All other sites I have found have just been rips from games and those are protected by a copyright and remain unusable. Right now I need simple objects to build the inside of buildings, but I have seem to have come up short in that area. I have plenty of things for outside of buildings, but nothing for in. I am hoping someone else has had this problem and has found a solution. If not, I hope the information I have provided can help someone else in their conquest.

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  • What is the Rule of Thumb on Exposing Encapsulated Class Methods

    - by javamonkey79
    Consider the following analogy: If we have a class: "Car" we might expect it to have an instance of "Engine" in it. As in: "The car HAS-A engine". Similarly, in the "Engine" class we would expect an instance of "Starting System" or "Cooling System" which each have their appropriate sub-components. By the nature of encapsulation, is it not true that the car "HAS-A" "radiator hose" in it as well as the engine? Therefore, is it appropriate OO to do something like this: public class Car { private Engine _engine; public Engine getEngine() { return _engine; } // is it ok to use 'convenience' methods of inner classes? // are the following 2 methods "wrong" from an OO point of view? public RadiatorHose getRadiatorHose() { return getCoolingSystem().getRadiatorHose(); } public CoolingSystem getCoolingSystem() { return _engine.getCoolingSystem(); } } public class Engine { private CoolingSystem _coolingSystem; public CoolingSystem getCoolingSystem() { return _coolingSystem; } } public class CoolingSystem { private RadiatorHose _radiatorHose; public RadiatorHose getRadiatorHose() { return _radiatorHose; } } public class RadiatorHose {//... }

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  • which is better, creating a view or a new table?

    - by Carson
    I have some demanding mysql queries that are needed to grap same datasets from several mysql tables. I am thinking of creating a table or view to gather all demanding columns from other tables, so as to increase performance. If I create that table, I may need to do extra insert / update / delete operation each time other tables updated. if I create view, I am worrying if the performance can be greatly improved. Because data from other tables are changing very frequently. Most likely, the view may need to be created first everytime before selecting it. Any ideas? e.g. how to cache? other extra measures I can do?

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  • CRUD operations; do you notify whether the insert,update etc. went well ?

    - by danielovich
    Hi guys. I have a simple question for you (i hope) :) I have pretty much always used void as a "return" type when doing CRUD operations on data. Eg. Consider this code: public void Insert(IAuctionItem item) { if (item == null) { AuctionLogger.LogException(new ArgumentNullException("item is null")); } _dataStore.DataContext.AuctionItems.InsertOnSubmit((AuctionItem)item); _dataStore.DataContext.SubmitChanges(); } and then considen this code: public bool Insert(IAuctionItem item) { if (item == null) { AuctionLogger.LogException(new ArgumentNullException("item is null")); } _dataStore.DataContext.AuctionItems.InsertOnSubmit((AuctionItem)item); _dataStore.DataContext.SubmitChanges(); return true; } It actually just comes down to whether you should notify that something was inserted (and went well) or not ?

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  • What's wrong with foreign keys?

    - by kronoz
    I remember hearing Joel mention in the podcast that he'd barely ever used a foreign key (if I remember correctly). However, to me they seem pretty vital to avoid duplication and subsequent data integrity problems throughout your database. Do people have some solid reasons as to why (to avoid a discussion in lines with SO principals)? Edit: "I've yet to have a reason to create a foreign key, so this might be my first reason to actually set up one."

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  • Writing my own implementation of stl-like Iterator in C++.

    - by Negai
    Good evening everybody, I'm currently trying to understand the intrinsics of iterators in various languages i.e. the way they are implemented. For example, there is the following class exposing the list interface. template<class T> class List { public: virtual void Insert( int beforeIndex, const T item ) throw( ListException ) =0 ; virtual void Append( const T item ) =0; virtual T Get( int position ) const throw( ListException ) =0; virtual int GetLength() const =0; virtual void Remove( int position ) throw( ListException ) =0; virtual ~List() =0 {}; }; According to GoF, the best way to implement an iterator that can support different kinds of traversal is to create the base Iterator class (friend of List) with protected methods that can access List's members. The concrete implementations of Iterator will handle the job in different ways and access List's private and protected data through the base interface. From here forth things are getting confusing. Say, I have class LinkedList and ArrayList, both derived from List, and there are also corresponding iterators, each of the classes returns. How can I implement LinkedListIterator? I'm absolutely out of ideas. And what kind of data can the base iterator class retrieve from the List (which is a mere interface, while the implementations of all the derived classes differ significantly) ? Sorry for so much clutter. Thanks.

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  • Change object on client side or on server side

    - by Polina Feterman
    I'm not sure what is the best practice. I have some big and complex objects (NOT flat). In that object I have many related objects - for example Invoice is the main class and one of it's properties is invoiceSupervisor - a big class by it's own called User. User can also be not flat and have department property - also an object called Department. For example I want create new Invoice. First way: I can present to client several fields to fill in. Some of them will be combos that I will need to fill with available values. For example available invoiceSupervisors. Then all the chosen values I can send to server and on server I can create new Invoice and assign all chosen values to that new Invoice. Then I will need to assign new supervisor I will pull the chosen User by id that user picked up on server from combobox. I might do some verification on the User such as does the user applicable to be invoice supervisor. Then I will assign the User object to invoiceSupervisor. Then after filling all properties I will save the new invoice. Second way: In the beginning I can call to server to get a new Invoice. Then on client I can fill all chosen values , for example I can call to server to get new User object and then fill it's id from combobox and assign the User as invoiceSupervisor. After filling the Invoice object on client I can send it to server and then the server will save the new invoice. Before saving server can run some validations as well. So what is the best approach - to make the object on client and send it to server or to collect all values from client and to make a new object on server using those values ?

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  • How much to put in a Repository class?

    - by chobo
    When using the repository pattern is it recommended to have one Repository class for each database table? Would I also map one service layer class to one repository class. I'm having a hard time trying to understand how much stuff one repository or service layer class should have. Thanks!

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  • Simple OOP-related question.

    - by M4design
    This question came to my mind quite a few times. Let my explain my question through an example. Say I've got two classes: 1- Grid. 2- Cell. Now the location of the cell 'should' be stored in the grid class, not in the cell class itself. Say that the cell wanted to get its location through a method in the grid. How can it do that? Keep in mind that the cell was created/initialised by the Grid class. What good OO approach to solve this problem? Thank you

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  • Global variable in a recursive function how to keep it at zero?

    - by Grammin
    So if I have a recursive function with a global variable var_: int var_; void foo() { if(var_ == 3) return; else var_++; foo(); } and then I have a function that calls foo() so: void bar() { foo(); return; } what is the best way to set var_ =0 everytime foo is called thats not from within itself. I know I could just do: void bar() { var_ =0; foo(); return; } but I'm using the recursive function a lot and I don't want to call foo and forget to set var_=0 at a later date. Does anyone have any suggestions on how to solve this? Thanks, Josh

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  • Locking DB w/ Large Reads (Ruby-on-Rails/Heroku)

    - by Splashlin
    Currently I have a Web API running on Heroku that is constantly writing information we're collecting from other data sources (currently theres about half a GB of data and it's growing very quickly). We're looking to add a reporting system on top of the current database that we can use to extract useful information out of the DB. The problem is that when we're running reports we're locking the DB and any other sites communicating with the DB are timing out. Does anyone have any solutions on how to solve this type of issue? Amazon RDS seems to have some interesting stuff with database replication but I don't know if that will solve my problems. Any advice would be greatly appreciated. Thanks

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  • Cure for puzzle piece programming habbits?

    - by Recursion
    Even though I went to a decent CS school, I was still taught with the mentality of programming with puzzle pieces. By puzzle pieces I mean, looking up code segments at each step of the development process and adding them together as needed. Eventually gathering all of the pieces and having a properly working program. So as an example, if in my program the next step is to tokenize a string, I go to google and search "how do I tokenize a string in language". All instead of critically thinking about its implementation. I personally don't think its a very good way to program and I always seem to forget everything that I have searched for. So how can I get out of this puzzle piece mode of programmer that I was taught.

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  • MSSQL Server using multiple ID Numbers

    - by vincer
    I have an web application that creates printable forms, these forms have a unique number on them, the problem is I have 2 forms that separate numbers need to be created for them. ie) Form1- Numbered 2000000-2999999 Form2- Numbered 3000000-3999999 dbo.test2 - is my form information table Tsel - is my autoinc table for the 3000000 series numbers Tadv - is my autoinc table for the 2000000 series numbers What I have done is create 2 tables with just autoinc row (one for 2000000 series numbers and one for 3000000 series numbers), I then created a trigger to add a record to the coresponding table, read back the autoinc number and add it to my table that stores the form information including the just created autoinc number for the right series of forms. Although it does work, I'm concerned that the numbers will get messed up under load. I'm not sure the @@IDENTITY will always return the right value when many people are using the system. (I cannot have duplicates and I need to use the numbering form show above. Thanks for any help See code below. ** TRIGGER ** CREATE TRIGGER MAKEANID2 ON dbo.test2 AFTER INSERT AS SET NOCOUNT ON declare @someid int declare @someid2 int declare @startfrom int declare @test1 varchar(10) select @someid=@@IDENTITY select @test1 = (Select name1 from test2 where sysid = @someid ) if @test1 = 'select' begin insert into Tsel Default values select @someid2 = @@IDENTITY end if @test1 = 'adv' begin insert into Tadv Default values select @someid2 = @@IDENTITY end update test2 set name2=(@someid2) where sysid = @someid SET NOCOUNT OFF

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  • Static assembly initialization

    - by ph0enix
    I'm attempting to develop an Interceptor framework (in C#) where I can simply implement some interfaces, and through the use of some static initialization, register all my Interceptors with a common Dispatcher to be invoked at a later time. The problem lies in the fact that my Interceptor implementations are never actually referenced by my application so the static constructors never get called, and as a result, the Interceptors are never registered. If possible, I would like to keep all references to my Interceptor libraries out of my application, as this is my way of (hopefully) enforcing loose coupling across different modules. Hopefully this makes some sense. Let me know if there's anything I can clarify... Does anyone have any ideas, or perhaps a better way to go about implementing my Interceptor pattern? TIA, Jeremy

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  • I built my rails app with sqlite and without specifying any db field sizes, Is my app now foobared for production?

    - by Tim Santeford
    I've been following a lot of good tutorials on building rails apps but I seem to be missing the whole specifying and validating db field sizes part. I love not needing to have to think about it when roughing out an app (I would have never done this with a PHP or ASP.net app). However, now that I'm ready to go to production, I think I might have done myself a disservice by not specifying field sizes as I went. My production db will be MySQL. What is the best practice here? Do I need to go through all of my migration files and specify sizes, update all the models with validation, and update all my form partial views with input max widths? or am I missing a critical step in my development process?

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