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  • iOS - Unit tests for KVO/delegate codes

    - by ZhangChn
    I am going to design a MVC pattern. It could be either designed as a delegate pattern, or a Key-Value-Observing(KVO), to notify the controller about changing models. The project requires certain quality control procedures to conform to those verification documents. My questions: Does delegate pattern fit better for unit testing than KVO? If KVO fits better, would you please suggest some sample codes?

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  • self referencing tables, good or bad?

    - by NimChimpsky
    Representing geographical locations within an application, the design of the underlying data model suggests two clear options (or maybe more?). One table with a self referencing parent_id column uk - london (london parent id = UK id) or two tables, with a one to many relationship using a foreign key. My preference is for one self-refercing table as it easily allows to extend into as many sub regions as required. IN general do people veer away from self referencing tables, or are they A-OK ?

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  • Interaction of a GUI-based App and Windows Service

    - by psubsee2003
    I am working on personal project that will be designed to help manage my media library, specifically recordings created by Windows Media Center. So I am going to have the following parts to this application: A Windows Service that monitors the recording folder. Once a new recording is completed that meets specific criteria, it will call several 3rd party CLI Applications to remove the commercials and re-encode the video into a more hard-drive friendly format. A controller GUI to be able to modify settings of the service, specifically add new shows to watch for, and to modify parameters for the CLI Applications A standalone (GUI-based) desktop application that can perform many of the same functions as the windows service, expect manually on specific files instead of automatically based on specific criteria. (It should be mentioned that I have limited experience with an application of this complexity, and I have absolutely zero experience with Windows Services) Since the 1st and 3rd bullet share similar functionality, my design plan is to pull the common functionality into a separate library shared by both parts applications, but these 2 components do not need to interact otherwise. The 2nd and 3rd bullets seem to share some common functionality, both will have a GUI, both will have to help define similar parameters (one to send to the service and the other to send directly to the CLI applications), so I can see some advantage to combining them into the same application. On the other hand, the standalone application (bullet #3) really does not need to interact with the service at all, except for possibly sharing a few common default parameters that can easily be put into an XML in a common location, so it seems to make more sense to just keep everything separate. The controller GUI (2nd bullet) is where I am stuck at the moment. Do I just roll this functionality (allow for user interaction with the service to update settings and criteria) into the standalone application? Or would it be a better design decision to keep them separate? Specifically, I'm worried about adding the complexity of communicating with the Windows Service to the standalone application when it doesn't need it. Is WCF the right approach to allow the controller GUI to interact with the Windows Service? Or is there a better alternative? At the moment, I don't envision a need for a significant amount of interaction, maybe just adding a new task once in a while and occasionally tweaking a parameter, but when something is changed, I do expect the windows service to immediately use the new settings.

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  • How to refactor a method which breaks "The law of Demeter" principle?

    - by dreza
    I often find myself breaking this principle (not intentially, just through bad design). However recently I've seen a bit of code that I'm not sure of the best approach. I have a number of classes. For simplicity I've taken out the bulk of the classes methods etc public class Paddock { public SoilType Soil { get; private set; } // a whole bunch of other properties around paddock information } public class SoilType { public SoilDrainageType Drainage { get; private set; } // a whole bunch of other properties around soil types } public class SoilDrainageType { // a whole bunch of public properties that expose soil drainage values public double GetProportionOfDrainage(SoilType soil, double blockRatio) { // This method does a number of calculations using public properties // exposed off SoilType as well as the blockRatio value in some conditions } } In the code I have seen in a number of places calls like so paddock.Soil.Drainage.GetProportionOfDrainage(paddock.Soil, paddock.GetBlockRatio()); or within the block object itself in places it's Soil.Drainage.GetProportionOfDrainage(this.Soil, this.GetBlockRatio()); Upon reading this seems to break "The Law of Demeter" in that I'm chaining together these properties to access the method I want. So my thought in order to adjust this was to create public methods on SoilType and Paddock that contains wrappers i.e. on paddock it would be public class Paddock { public double GetProportionOfDrainage() { return Soil.GetProportionOfDrainage(this.GetBlockRatio()); } } on the SoilType it would be public class SoilType { public double GetProportionOfDrainage(double blockRatio) { return Drainage.GetProportionOfDrainage(this, blockRatio); } } so now calls where it used would be simply // used outside of paddock class where we can access instances of Paddock paddock.GetProportionofDrainage() or this.GetProportionOfDrainage(); // if used within Paddock class This seemed like a nice alternative. However now I have a concern over how would I enforce this usage and stop anyone else from writing code such as paddock.Soil.Drainage.GetProportionOfDrainage(paddock.Soil, paddock.GetBlockRatio()); rather than just paddock.GetProportionOfDrainage(); I need the properties to remain public at this stage as they are too ingrained in usage throughout the code block. However I don't really want a mixture of accessing the method on DrainageType directly as that seems to defeat the purpose altogether. What would be the appropiate design approach in this situation? I can provide more information as required to better help in answers. Is my thoughts on refactoring this even appropiate or should is it best to leave it as is and use the property chaining to access the method as and when required?

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  • Why are MVC & TDD not employed more in game architecture?

    - by secoif
    I will preface this by saying I haven't looked a huge amount of game source, nor built much in the way of games. But coming from trying to employ 'enterprise' coding practices in web apps, looking at game source code seriously hurts my head: "What is this view logic doing in with business logic? this needs refactoring... so does this, refactor, refactorrr" This worries me as I'm about to start a game project, and I'm not sure whether trying to mvc/tdd the dev process is going to hinder us or help us, as I don't see many game examples that use this or much push for better architectural practices it in the community. The following is an extract from a great article on prototyping games, though to me it seemed exactly the attitude many game devs seem to use when writing production game code: Mistake #4: Building a system, not a game ...if you ever find yourself working on something that isn’t directly moving your forward, stop right there. As programmers, we have a tendency to try to generalize our code, and make it elegant and be able to handle every situation. We find that an itch terribly hard not scratch, but we need to learn how. It took me many years to realize that it’s not about the code, it’s about the game you ship in the end. Don’t write an elegant game component system, skip the editor completely and hardwire the state in code, avoid the data-driven, self-parsing, XML craziness, and just code the damned thing. ... Just get stuff on the screen as quickly as you can. And don’t ever, ever, use the argument “if we take some extra time and do this the right way, we can reuse it in the game”. EVER. is it because games are (mostly) visually oriented so it makes sense that the code will be weighted heavily in the view, thus any benefits from moving stuff out to models/controllers, is fairly minimal, so why bother? I've heard the argument that MVC introduces a performance overhead, but this seems to me to be a premature optimisation, and that there'd more important performance issues to tackle before you worry about MVC overheads (eg render pipeline, AI algorithms, datastructure traversal, etc). Same thing regarding TDD. It's not often I see games employing test cases, but perhaps this is due to the design issues above (mixed view/business) and the fact that it's difficult to test visual components, or components that rely on probablistic results (eg operate within physics simulations). Perhaps I'm just looking at the wrong source code, but why do we not see more of these 'enterprise' practices employed in game design? Are games really so different in their requirements, or is a people/culture issue (ie game devs come from a different background and thus have different coding habits)?

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  • Chapter 7–Enforced Data Protection

    - by drsql
    As the book progresses, I find myself veering from the original stated outline quite a bit, because as I teach about this more (and I am teaching a daylong db design class in August at http://www.sqlsolstice.com/ … shameless plug, but it is on topic :) I start to find that a given order works better. Originally I had slated myself to talk more about modeling here for three chapters, then get back to the more implementation topics to finish out the book, but now I am going to keep plugging through...(read more)

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  • Speaking at SQL Saturday #39 in NYC!

    - by andyleonard
    I am honored to present Applied SSIS Design Patterns and Introduction to Incremental Loads at SQL Saturday #39 in New York City! If you're there and you read this blog, be sure to stop by and introduce yourself! :{> Andy Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!...(read more)

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  • Should I use multiple column primary keys or add a new column?

    - by Covar
    My current database design makes use of a multiple column primary key to use existing data (that would be unique anyway) instead of creating an additional column assigning each entry an arbitrary key. I know that this is allowed, but was wondering if this is a practice that I might want to use cautiously and possibly avoid (much like goto in C). So what are some of the disadvantages I might see in this approach or reasons I might want a single column key?

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  • Designing for visually impaired gamers

    - by Aku
    Globally the number of people of all ages visually impaired is estimated to be 285 million, of whom 39 million are blind. — World Health Organisation, 2010. (That's 4.2% and 0.6% of the world population.) Most videogames put a strong emphasis on visuals in their content delivery. Visually impaired gamers are largely left out. How do I design a game to be accessible to visually impaired gamers?

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  • Recommended readings for a sofware construction mini-course [on hold]

    - by Aivar
    I'm going to organize a mini-course for CS students who have completed CS1 (Python) and CS2 (Java). I'd like to show them more principled approach to programming practice and design, something along the lines of McConnel's Code Complete. If I had enough copies of Code Complete, I would assign some readings from that book. Can you recommend some freely available material (books, blog posts, articles, essays) for such a course? (I'd prefer to avoid topics specific to OOP and focus on more universal principles.)

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  • What norms/standards should I follow when writing a functional spec?

    - by user970696
    I would like to know what documents (ISO?) should I follow when I write a functional specification. Or what should designers follow when creating the system design? I was told that there was a progress in last years but was not told what the progress was in (college professor). Thank you EDIT: I do not speak about document content etc. but about standards for capturing requirements, for business analysis.

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  • Overused or abused programming techniques

    - by Anto
    Are there any techniques in programming that you find to be overused (IE used way more excessively than what they should be) or abused, or used a bit for everything, while not being a really good solution to many of the problems which people attempt to solve with it. It could be regular expressions, some kind of design pattern or maybe an algorithm, or something completely different. Maybe you think people abuse multiple inheritance etc.

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  • Learning WPF GUI design

    - by Jon
    GUI's written using WPF seem to be closer to a Web 2.0 feel than older Winforms development has been; do you know of any good quality references online or books which give a general overview of how to design nice WPF applications? I saw this StackOverflow question where some GUI design books are mentioned, but am interested in information specifically for WPF. http://stackoverflow.com/questions/1193001/is-wpf-silverlight-design-worth-learning Thanks!

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  • Non-Relational Database Design

    - by Ian Varley
    I'm interested in hearing about design strategies you have used with non-relational "nosql" databases - that is, the (mostly new) class of data stores that don't use traditional relational design or SQL (such as Hypertable, CouchDB, SimpleDB, Google App Engine datastore, Voldemort, Cassandra, SQL Data Services, etc.). They're also often referred to as "key/value stores", and at base they act like giant distributed persistent hash tables. Specifically, I want to learn about the differences in conceptual data design with these new databases. What's easier, what's harder, what can't be done at all? Have you come up with alternate designs that work much better in the non-relational world? Have you hit your head against anything that seems impossible? Have you bridged the gap with any design patterns, e.g. to translate from one to the other? Do you even do explicit data models at all now (e.g. in UML) or have you chucked them entirely in favor of semi-structured / document-oriented data blobs? Do you miss any of the major extra services that RDBMSes provide, like relational integrity, arbitrarily complex transaction support, triggers, etc? I come from a SQL relational DB background, so normalization is in my blood. That said, I get the advantages of non-relational databases for simplicity and scaling, and my gut tells me that there has to be a richer overlap of design capabilities. What have you done? FYI, there have been StackOverflow discussions on similar topics here: the next generation of databases changing schemas to work with Google App Engine choosing a document-oriented database

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  • Design view disappeared from Interface Builder

    - by skywalker168
    All of a sudden, the visual design window disappeared from my Interface Builder. It is a regular UIView, has some UIImageView, UILabel, and UIButtons on it. When I open IB, I can see the document window (with File's Owner, First Responder and View in it), Library and Inspector, but the visual design window disappeared. Double click on "View" in the document window doesn't do anything. If I go to List mode, I can see all the components on the view, but just can no longer find the visual design window. All other XIB can open just fine, only this XIB lost its design window. First I thought maybe it was hidden somewhere on the screen. Tried all kinds of things, even rebooting the computer, but nothing helped. Can anyone help? Thanks in advance! By the way, I'm running SDK 3.2 Beta 3.

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  • Database design question

    - by Lijo
    Hi Team, I have an interesting database design problem that I formulated while travelling by a bus, coming back from my home. Design a normalized database for a bus ticketing system (not reservation system). In each trip, the conductor of the bus will give tickets to its passengers after collecting fare from them. Passengers travel from a various source places to various destination places. The system must be able to give a report of the places for which the number of passengers was more than 2. Suppose the stops for the bus are L1,L2, L3 and L4 Suppose passenger P1 travels from L1 to L4. P2 travels from L2 to L4. P3 travels from L3 to L4. The report should list only (L3-L4) for which it has more than 2 travelers. Can you please help me to solve the following problems 1) Design a normalized database 2) Write a query for the report 3) Is there any site that gives these kinds of interesting database design questions and answers? Thanks Lijo

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  • Best Design for creating Historic Reports on GAE

    - by charming30
    My App requires Daily reports based on various user activities. My current design does not sum the daily totals in database, which means I must compute them everytime. For example A report that shows Top 100 users based on the number of submissions they have made on a given day. For such a report If I have 50,000 users, what is the best way to create daily report? How to create monthly and yearly report with such data? If this is not a good design, then how to deal with such design decision when the metrics of the report are not clear during db design and by the time it is clear we already have huge data with limited parameters (fields). Please advice.

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  • Ios development with design issues

    - by user3651999
    I don't know this question wether have been asked or not. But i research and found nothing.So my problem is i kinda new in IOS development. In android we can edit or customize design using UI and code(XML file). I prefer code.Does IOs have such file to edit/customize the design?Because I saw people always edit their design using the built-in UI rather than coding .I mean in design part not in function part.I would love using code any suggestion? Apperciate for any reply!

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  • Kantar publie ses statistiques sur l'évolution trimestrielle du marché du smartphone, Samsung se rapproche d'Apple aux USA

    Kantar publie ses statistiques sur l'évolution trimestrielle du marché du smartphone, Samsung se rapproche d'Apple aux USA L'agence Kantar vient de publier les chiffres du dernier trimestre (achevé en en fin avril 2014) sur le marché mondial du smartphone. Au niveau européen, très peu de changement sont notés par rapport à l'année dernière où Android s'est octroyé 70,7 % de part de marché contre 72,4 % de février à avril 2014, ce qui représente une progression de 1,7 point. Windows Phone a occupé...

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  • Fitting it together, database, reporting, applications in C#

    - by alvonellos
    Introduction Preamble I was hesitant to post this, since it's an application whose intricate details are defined elsewhere, and answers may not be helpful to others. Within the past few weeks (I was actually going to write a blog post about this after I finished) I've discovered that the barrier I'm encountering is one that's actually quite common for newer developers. This question is not so much about a specific thing as it is about piecing those things together. I've searched the internet far and wide, and found many tutorials on how to create applications that are kind of similar to what I'm looking for. I've also looked at hiring another, more experienced, developer to help me along, but all I've gotten are unqualified candidates that don't have the experience necessary and won't take care of the client or project like I will. I'd rather have the project never transpire than to release a solution that is half-baked. I've asked professors at my school, but they've not turned up answers to my question. I'm an experienced developer, and I've written many applications that are -- very abstractly -- close to what I'm doing, but my experiences from those applications aren't giving me enough leverage to solve this particular problem. I just hope that posting this article isn't a mistake for me to write. Project Description I have a project I'm working on for a client that is a rewrite of an application, originally written in Foxpro 2.6 by someone before me, that performs some analysis (which, sadly, I'm not allowed to disclose as per of my employment contract) on financial data. One day, after a long talk between the client and I -- where he intimately described his frustrations with all the bugs I've been hacking out of this code for 6 months now -- he told me to just rewrite it and gave me a month to write a good 1/8 of this 65k LOC Foxpro monstrosity. this 65k line of code foxpro monstrosity. It'll take me a good 3 - 6 months to rewrite this software (I know things the original programmer did not, like inheritance) going as I am right now, but I'm quickly discovering that I'm going to need to use databases. Prior to this contract I didn't even know about foxpro, and so I've had to learn foxpro on the fly, write procedures and make modifications to the database. I've actually come to like it, and this project would be rewritten in Foxpro if it were still a supported language, because over the past few months, I've come to like the features of Foxpro that make it so easy to develop data-driven applications. I once perfomed an experiment, comparing C# to Foxpro. What took me 45 minutes in C# took me two in Foxpro, and I knew C# prior to Foxpro. I was hoping to leverage the power of C#, but it intimidates me that in foxpro, you can have one line of code and be using a database. Prior to this, I have never written any serious database development from scratch. All the applications that I've written are in a different league. They are either completely data-naive or data-naive enough that I can get away with not using a database through serialization or by designing algorithms that work with the data in a manner that is stateless, so there is no need to worry about databases. I've come to realize, very quickly, that serialization and my efficacy with data structures has been my crutch all these years that's prevented me from adventuring into databases, and has consequently hindered my success in real-world programming. Sure, I've written some database stuff in Perl and Python, and I've done forms and worked with relational databases and tables, I'm a wizard in Access and Excel (seriously) and can do just about anything, but it just feels unnatural writing SQL code in another language... I don't mind writing SQL, and I don't It's that bridge between the database and the program code that drives me absolutely bonkers. I hope I'm not the only one to think this, but it bothers me that I have to create statements like the following string sSql = "SELECT * from tablename" When there's really no reason for that kind of unchecked language binding between two languages and two API's. Don't get my wrong, SQL is great, but I don't like the idea that, when executing commands on a SQL database, that one must intermix database and application software, and there's no database independence, which means that different versions of different databases can break code. This isn't very nice. The nicest thing about Foxpro is the cohesiveness between programming language and database. It's so easy, and Foxpro makes it easy, because the tool just fits the task. I can see why so many developers have created a career with this language, because it lowered the barrier of entry to data-driven applications that so many businesses need. It was wonderful. For my purposes today, with the demands and need for community support, extensibility, and language features, Foxpro isn't a solution that I feel would be the right tool for the job. I'm also worried about working too heavy with the database, because I've seen data-driven .NET applications have issues with database caches, running out of memory, and objects in the database not being collected. (Memory leaks) And OH the queries. Which one, how, and why? There are a plethora of different ways that a database can be setup, I think I counted 5 or 6 different kinds of database applications alone that I can chose from. That is a great mountain for me to climb when I don't even know where to begin when it comes to writing data-driven applications. The problem isn't that I don't know SQL or that I don't know C#. I know both and have worked with both extensively. It's making them work together that's the problem, and it's something I've never done in C# before. Reports The client likes paper. The data needs to be printed out in a format that is extensible, layered, and easy to use. I have never done reporting before, and so this is a bit of a problem. From the data source comes crystal reports, and so there's a dependency on the database, from what I understand. Code reuse A large part of the design decision that I've gone through so far is to break the task of writing a piece of this software into routines and modular DLL's and so forth such that much of the code can be reused. For example, when I setup this database, I want to be able to reuse the same database code over and over again. I also want to make sure that when the day comes that another developer is here, that he/she will be able to pick up just where I left off. The quicker I develop these applications, the better off I am. Tasks & Goals In my project, I need to write routines that apply algorithms and look for predefined patterns in financial data. Additionally, I need to simulate trading based on predefined algorithms and data. Then I need to prepare reports on that data. Additionally, I need to have a way to change the code base for this application quickly and effectively, without hacking together some band-aid solution for a problem that really needs a trauma ward. Special Considerations The solution must be fast, run quickly on existing hardware, and not be too much of a pain to maintain and write. I understand that anything I write I'm married to -- I'm responsible for the things that I write because my reputation and livelihood is dependent on it. Do I really need a database? What about performance? Performance was such a big issue that I hand wrote a data structure that is capable of performing 2 billion operations, using a total of 4 gigs of memory in under 1/4 of a second using the standard core two duo processor. I could not find a similar, pre-written data structure in C# to perform this task. What setup do I use in terms of database? What about reporting? I'd prefer to have PDF's generated, but I'd like to be able to visually sketch those reports and then just have a ReportFactory of some sort, that when I pass some variables in, it just does that data. About Me I'm a lone developer for a small business in this area. This is the first time I've done this and I've never had the breadth and depth of my knowledge tested. I'm incredibly frustrated with this project because I feel incredibly overwhelmed with the task at hand. I'm looking for that entry level point where I can draw a line and say "this is what I need to do" Conclusion I may have not been clear enough on my post. I'm still new to this whole thing, and I've been doing my best to contribute back to the community that I've leached so much knowledge from. I'd be glad to edit my post and add more information if possible. I'm looking for a big-picture solution or design process that helps me get off the ground in this world of data-driven applications, because I have a feeling that it's going to be concentric to my entire career as a programmer for some time. Specifically, if you didn't get it from the rest of the post (I may not have been clear enough) I really need some guidance as to where to go in terms of the design decisions for this project. Some things that'll be useful will be a pro/con list for the different kinds of database projects available in VS2010. I've tried, but generating that list has been as hard as solving the problem itself... If you could walk a developer writing a data-driven application for the first time in C#, how would you do that? Where would you point them to?

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