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  • Architecture design with MyBatis mappers

    - by Wolf
    I am creating rest web service for providing data. I am using Spring MVC for handling rest requests, and MyBatis for data access. Application should be designed in the way that it should be easy to change the data access implementation (for example to hibernate or something else) and it has to be fast (so I am trying to avoid unnecessary overcomplication of design). Now my question is about the general design of layers. I would normally use DAO interface and then different implementations for different data access strategies, but MyBatis uses interfaces to access the data. So I can think of 2 possible models but I am not sure which one is better or if there is any other nice way: Controller layer - uses Service layer interfaces services are then implemented for each data access stretegy - for example for mybatis: service implementation uses Mapper classes to access data and do whatever it needs to do with them and sends them to controller layer Controller layer - uses Service layer - service layer uses DAO interfaces DAOs are then implemented for each data access strategy - for example for mybatis: DAO class uses mapper interface to access data and sends them to service layer, service layer then do whatever it needs to do with them and sends them to controller layer I prefer the first strategy as it seems to be less complicated, but then I would have to write all of the service code for another data access again. What do you think? Thank You

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  • Developing Web Portal

    - by Ya Basha
    I'm php, Ruby on Rails and HTML5 developer I need some advises and suggestions for a web portal project that I will build from scratch. This is my first time to build a web portal, Which developing scripting language you prefer and why? and how I should start planing my project as it will contains many modules. I'm excited to start building this project and I want to build it in the right way with planing, if you know some web resources that help me decide and plan my project please give them to me. Best Regards,

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  • Setter Validation can affect performance?

    - by TiagoBrenck
    Whitin a scenario where you use an ORM to map your entities to the DB, and you have setter validations (nullable, date lower than today validation, etc) every time the ORM get a result, it will pass into the setter to instance the object. If I have a grid that usually returns 500 records, I assume that for each record it passes on all validations. If my entity has 5 setter validations, than I have passed in 2.500 validations. Does those 2.500 validations will affect the performance? If was 15.000 validation, it will be different? In my opinion, and according to this answer (http://stackoverflow.com/questions/4893558/calling-setters-from-a-constructor/4893604#4893604), setter validation is usefull than constructors validation. Is there a way to avoid unecessary validation, since I am safe that the values I send to DB when saving the entity wont change until I edit it on my system?

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  • When should I make the first commit to source control?

    - by Kendall Frey
    I'm never sure when a project is far enough along to first commit to source control. I tend to put off committing until the project is 'framework-complete' and primarily commit features from then on. (I haven't done any personal projects large enough to have a core framework too big for this.) I have a feeling this isn't best practice, though I'm not sure what all could go wrong. Let's say, for example, I have a project which consists of a single code file. It will take about 10 lines of boilerplate code, and 100 lines to get the project working with extremely basic functionality (1 or 2 features). Should I first check in: The empty file? The boilerplate code? The first features? At some other point? Also, what are the reasons to check in at a specific point?

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  • Vectorization of matlab code for faster execution

    - by user3237134
    My code works in the following manner: 1.First, it obtains several images from the training set 2.After loading these images, we find the normalized faces,mean face and perform several calculation. 3.Next, we ask for the name of an image we want to recognize 4.We then project the input image into the eigenspace, and based on the difference from the eigenfaces we make a decision. 5.Depending on eigen weight vector for each input image we make clusters using kmeans command. Source code i tried: clear all close all clc % number of images on your training set. M=1200; %Chosen std and mean. %It can be any number that it is close to the std and mean of most of the images. um=60; ustd=32; %read and show images(bmp); S=[]; %img matrix for i=1:M str=strcat(int2str(i),'.jpg'); %concatenates two strings that form the name of the image eval('img=imread(str);'); [irow icol d]=size(img); % get the number of rows (N1) and columns (N2) temp=reshape(permute(img,[2,1,3]),[irow*icol,d]); %creates a (N1*N2)x1 matrix S=[S temp]; %X is a N1*N2xM matrix after finishing the sequence %this is our S end %Here we change the mean and std of all images. We normalize all images. %This is done to reduce the error due to lighting conditions. for i=1:size(S,2) temp=double(S(:,i)); m=mean(temp); st=std(temp); S(:,i)=(temp-m)*ustd/st+um; end %show normalized images for i=1:M str=strcat(int2str(i),'.jpg'); img=reshape(S(:,i),icol,irow); img=img'; end %mean image; m=mean(S,2); %obtains the mean of each row instead of each column tmimg=uint8(m); %converts to unsigned 8-bit integer. Values range from 0 to 255 img=reshape(tmimg,icol,irow); %takes the N1*N2x1 vector and creates a N2xN1 matrix img=img'; %creates a N1xN2 matrix by transposing the image. % Change image for manipulation dbx=[]; % A matrix for i=1:M temp=double(S(:,i)); dbx=[dbx temp]; end %Covariance matrix C=A'A, L=AA' A=dbx'; L=A*A'; % vv are the eigenvector for L % dd are the eigenvalue for both L=dbx'*dbx and C=dbx*dbx'; [vv dd]=eig(L); % Sort and eliminate those whose eigenvalue is zero v=[]; d=[]; for i=1:size(vv,2) if(dd(i,i)>1e-4) v=[v vv(:,i)]; d=[d dd(i,i)]; end end %sort, will return an ascending sequence [B index]=sort(d); ind=zeros(size(index)); dtemp=zeros(size(index)); vtemp=zeros(size(v)); len=length(index); for i=1:len dtemp(i)=B(len+1-i); ind(i)=len+1-index(i); vtemp(:,ind(i))=v(:,i); end d=dtemp; v=vtemp; %Normalization of eigenvectors for i=1:size(v,2) %access each column kk=v(:,i); temp=sqrt(sum(kk.^2)); v(:,i)=v(:,i)./temp; end %Eigenvectors of C matrix u=[]; for i=1:size(v,2) temp=sqrt(d(i)); u=[u (dbx*v(:,i))./temp]; end %Normalization of eigenvectors for i=1:size(u,2) kk=u(:,i); temp=sqrt(sum(kk.^2)); u(:,i)=u(:,i)./temp; end % show eigenfaces; for i=1:size(u,2) img=reshape(u(:,i),icol,irow); img=img'; img=histeq(img,255); end % Find the weight of each face in the training set. omega = []; for h=1:size(dbx,2) WW=[]; for i=1:size(u,2) t = u(:,i)'; WeightOfImage = dot(t,dbx(:,h)'); WW = [WW; WeightOfImage]; end omega = [omega WW]; end % Acquire new image % Note: the input image must have a bmp or jpg extension. % It should have the same size as the ones in your training set. % It should be placed on your desktop ed_min=[]; srcFiles = dir('G:\newdatabase\*.jpg'); % the folder in which ur images exists for b = 1 : length(srcFiles) filename = strcat('G:\newdatabase\',srcFiles(b).name); Imgdata = imread(filename); InputImage=Imgdata; InImage=reshape(permute((double(InputImage)),[2,1,3]),[irow*icol,1]); temp=InImage; me=mean(temp); st=std(temp); temp=(temp-me)*ustd/st+um; NormImage = temp; Difference = temp-m; p = []; aa=size(u,2); for i = 1:aa pare = dot(NormImage,u(:,i)); p = [p; pare]; end InImWeight = []; for i=1:size(u,2) t = u(:,i)'; WeightOfInputImage = dot(t,Difference'); InImWeight = [InImWeight; WeightOfInputImage]; end noe=numel(InImWeight); % Find Euclidean distance e=[]; for i=1:size(omega,2) q = omega(:,i); DiffWeight = InImWeight-q; mag = norm(DiffWeight); e = [e mag]; end ed_min=[ed_min MinimumValue]; theta=6.0e+03; %disp(e) z(b,:)=InImWeight; end IDX = kmeans(z,5); clustercount=accumarray(IDX, ones(size(IDX))); disp(clustercount); Running time for 50 images:Elapsed time is 103.947573 seconds. QUESTIONS: 1.It is working fine for M=50(i.e Training set contains 50 images) but not for M=1200(i.e Training set contains 1200 images).It is not showing any error.There is no output.I waited for 10 min still there is no output. I think it is going infinite loop.What is the problem?Where i was wrong?

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  • Objective C and ios development training courses feedback

    - by Mutuelinvestor
    I'm thinking about taking an Objective C / iphone/ipad development training course. Pragmatic Studio and Big Nerd Ranch appear to be the key players. I'd love to hear any feed back from anyone who has completed training with Pragmatic, Big Nerd or others. I'd interested in quality of instruction, how much you learned, strengths, weaknesses and any other valuable insights. Its a pretty big financial commitment for me and I want to get the most bang for my buck. Thanks in advance for your input.

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  • What defines code readability?

    - by zxcdw
    It is often said that readability is perhaps the most important quality-defining measure of a given piece of code for reasons concerning maintainability, ease of understanding and use. What defines the word readable in context of program source code? What kind of definitive aspects are there to code readability? I would be grateful with code examples of readable code, along with reasoning why it is readable.

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  • C++ Library API Design

    - by johannes
    I'm looking for a good resource for learning about good API design for C++ libraries, looking at shared objects/dlls etc. There are many resources on writing nice APIs, nice classes, templates and so on at source level, but barely anything about putting things together in shared libs and executables. Books like Large-Scale C++ Software Design by John Lakos are interesting but massively outdated. What I'm looking for is advice i.e. on handling templates. With templates in my API I often end up with library code in my executable (or other library) so if I fix a bug in there I can't simply roll out the new library but have to recompile and redistribute all clients of that code. (and yes, I know some solutions like trying to instantiate at least the most common versions inside the library etc.) I'm also looking for other caveats and things to mind for keeping binary compatibility while working on C++ libraries. Is there a good website or book on such things?

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  • Should I organize my folders by business domain or by technical domain?

    - by Florian Margaine
    For example, if I'm using some MVC-like architecture, which folder structure should I use: domain1/ controller model view domain2/ controller model view Or: controllers/ domain1 domain2 models/ domain1 domain2 views/ domain1 domain2 I deliberately left out file extensions to keep this question language-agnostic. Personally, I'd prefer to separate by business domain (gut feeling), but I see that most/many frameworks separate by technical domain. Why whould I choose one over the other?

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  • SQL, moving million records from a database to other database [migrated]

    - by Ryoma
    I am a C# developer, I am not really good with SQL. I have a simple questions here. I need to move more than 50 millions records from a database to other database. I tried to use the import function in ms SQL, however it got stuck because the log was full (I got an error message The transaction log for database 'mydatabase' is full due to 'LOG_BACKUP'). The database recovery model was set to simple. My friend said that importing millions records using task-import data will cause the log to be massive and told me to use loop instead to transfer the data, does anyone know how and why? thanks in advance

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  • Architecture for Social Graph data that has a Time Frame Associated?

    - by Jay Stevens
    I am adding some "social" type features to an existing application. There are a limited # of node & edge types. Overall the data itself is relatively small (50,000 - 70,000 for each type of node) there will be a number of edges (relationships) between them (almost all directional). This, I know, is relatively easy to represent with an SDF store (such as BrightstarDB) or something like Microsoft's Trinity (or really many of the noSQL options). The thing that, I think, makes this a unique use case is that each relationship will have a timeframe associated with it (start and end dates). Right now, I'm thinking of just storing this in a relational structure and dealing with the headaches of "traversing the graph", but I'm looking for suggestions on a better approach (both in terms of data structure and server): Column ================ From_Node_ID Relationship To_Node_ID StartDate EndDate Any suggestions or thoughts are welcomed.

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  • High Salaried Investment Banking Jobs for Developers — What are the pitfalls?

    - by Jaywalker
    This question might make more sense to somebody having multi-threaded programming experience in Java/ C++ with some job experience in London / Singapore. There is a huge market of Investment Banking development jobs with astonishingly high salaries (sometimes more than 100K pounds per year). Can someone with experience as a front office/trading developer tell what are the requirements to land this type job? What are the downside that i should be ready for?

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  • Which web framework to use under Backbonejs?

    - by egidra
    For a previous project, I was using Backbonejs alongside Django, but I found out that I didn't use many features from Django. So, I am looking for a lighter framework to use underneath a Backbonejs web app. I never used Django built in templates. When I did, it was to set up the initial index page, but that's all. I did use the user management system that Django provided. I used the models.py, but never views.py. I used urls.py to set up which template the user would hit upon visiting the site. I noticed that the two features that I used most from Django was South and Tastypie, and they aren't even included with Django. Particularly, django-tastypie made it easy for me to link up my frontend models to my backend models. It made it easy to JSONify my front end models and send them to Tastypie. Although, I found myself overriding a lot of tastypie's methods for GET, PUT, POST requests, so it became useless. South made it easy to migrate new changes to the database. Although, I had so much trouble with South. Is there a framework with an easier way of handling database modifications than using South? When using South with multiple people, we had the worse time keeping our databases synced. When someone added a new table and pushed their migration to git, the other two people would spend days trying to use South's automatic migration, but it never worked. I liked how Rails had a manual way of migrating databases. Even though I used Tastypie and South a lot, I found myself not actually liking them because I ended up overriding most Tastypie methods for each Resource, and I also had the worst trouble migrating new tables and columns with South. So, I would like a framework that makes that process easier. Part of my problem was that they are too "magical". Which framework should I use? Nodejs or a lighter Python framework? Which works best with my above criteria?

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  • Is it normal needing time to understand code i wrote recently

    - by user1478167
    By recently i mean some weeks ago. I am trying to continue a project i left 2 weeks ago and i need time to understand some functions i wrote(not copied from somewhere) and it takes me time. Normally i don't need to because my functions,methods etc are black boxes but when i need to change something it's really hard. Does this mean i write bad code? I am still in school and i am the only who writes/uses the code so i don't have feedback, but i am afraid that if it is difficult for me to understand it, it would be 10 times more difficult for someone else. What should i do? I write a lot of comments but most of the time are useless when reviewing. Do you have any suggestions?

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  • Database Schema Usage

    - by CrazyHorse
    I have a question regarding the appropriate use of SQL Server database schemas and was hoping that some database gurus might be able to offer some guidance around best practice. Just to give a bit of background, my team has recently shrunk to 2 people and we have just been merged with another 6 person team. My team had set up a SQL Server environment running off a desktop backing up to another desktop (and nightly to the network), whilst the new team has a formal SQL Server environment, running on a dedicated server, with backups and maintenance all handled by a dedicated team. So far it's good news for my team. Now to the query. My team designed all our tables to belong to a 3-letter schema name (e.g. User = USR, General = GEN, Account = ACC) which broadly speaking relate to specific applications, although there is a lot of overlap. My new team has come from an Access background and have implemented their tables within dbo with a 3-letter perfix followed by "_tbl" so the examples above would be dbo.USR_tblTableName, dbo.GEN_tblTableName and dbo.ACC_tblTableName. Further to this, neither my old team nor my new team has gone live with their SQL Servers yet (we're both coincidentally migrating away from Access environments) and the new team have said they're willing to consider adopting our approach if we can explain how this would be beneficial. We are not anticipating handling table updates at schema level, as we will be using application-level logins. Also, with regards to the unwieldiness of the 7-character prefix, I'm not overly concerned myself as we're using LINQ almost exclusively so the tables can simply be renamed in the DMBL (although I know that presents some challenges when we update the DBML). So therefore, given that both teams need to be aligned with one another, can anyone offer any convincing arguments either way?

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  • Is there a rule of thumb for what a bing map's zoom setting should be based on how many miles you want to display?

    - by Clay Shannon
    If a map contains pushpins/waypoints that span only a couple of miles, the map should be zoomed way in and show a lot of detail. If the pushpins/waypoints instead cover vast areas, such as hundreds or even thousands of miles, it should be zoomed way out. That's clear. My question is: is there a general guideline for mapping (no pun intended) Bing Maps zoom levels to a particular number of miles that separate the furthest apart points? e.g., is there some chart that has something like: Zoom level N shows 2 square miles Zoom level N shows 5 square miles etc.?

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  • Programming and Ubiquitous Language (DDD) in a non-English domain

    - by Sandor Drieënhuizen
    I know there are some questions already here that are closely related to this subject but none of them take Ubiquitous Language as the starting point so I think that justifies this question. For those who don't know: Ubiquitous Language is the concept of defining a (both spoken and written) language that is equally used across developers and domain experts to avoid inconsistencies and miscommunication due to translation problems and misunderstanding. You will see the same terminology show up in code, conversations between any team member, functional specs and whatnot. So, what I was wondering about is how to deal with Ubiquitous Language in non-English domains. Personally, I strongly favor writing programming code in English completely, including comments but ofcourse excluding constants and resources. However, in a non-English domain, I'm forced to make a decision either to: Write code reflecting the Ubiquitous Language in the natural language of the domain. Translate the Ubiquitous Language to English and stop communicating in the natural language of the domain. Define a table that defines how the Ubiquitous Language translates to English. Here are some of my thoughts based on these options: 1) I have a strong aversion against mixed-language code, that is coding using type/member/variable names etc. that are non-English. Most programming languages 'breathe' English to a large extent and most of the technical literature, design pattern names etc. are in English as well. Therefore, in most cases there's just no way of writing code entirely in a non-English language so you end up with mixed languages anyway. 2) This will force the domain experts to start thinking and talking in the English equivalent of the UL, something that will probably not come naturally to them and therefore hinders communication significantly. 3) In this case, the developers communicate with the domain experts in their native language while the developers communicate with each other in English and most importantly, they write code using the English translation of the UL. I'm sure I don't want to go for the first option and I think option 3 is much better than option 2. What do you think? Am I missing other options? UPDATE Today, about year later, having dealt with this issue on a daily basis, I have to say that option 3 has worked out pretty well for me. It wasn't as tedious as I initially feared and translating in real time while talking to the client wasn't a problem either. I also found the following advantages to be true, based on my experience. Translating the UL makes you pay more attention to defining the UL and even the domain itself, especially when you don't know how to translate a term and you have to start looking through dictionaries etc. This has even caused me to reconsider domain modeling decisions a few times. It helps you make your knowledge of the English language more profound. Obviously, your code is much more pleasant to look at instead of being a mind boggling obscenity.

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  • When should we use weak entities when modelling a database?

    - by Songo
    This is basically a question about what are weak entities? When should we use them? How should they be modeled? What is the main difference between normal entities and weak entities? Does weak entities correspond to value objects when doing Domain Driven Design? To help keep the question on topic here is an example taken from Wikipedia that people can use to answer these question: In this example OrderItem was modeled as a weak entity, but I can't understand why it can't be modeled as a normal entity. Another question is what if I want to track the order history (i.e. the changes in it status) would that be a normal or weak entity?

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  • RMS java web framework

    - by Kamil Tomšík
    We're currently reconsidering technologies and frameworks to get more agile with "simple" RMS CRUD-based projects. In short, short-living things like this Right now we have custom extension on top of SmartGWT but after some time it has proven not to be enough flexible. I also personally dislike that java-js compilation process and the whole GWT codebase. Not only its ugly designed, it also makes certain low-level js things very complicated if not completely impossible. So what I'm looking for is: closest to web as possible, like JSF or possibly Tapestry, it is very important to be able get "low" and weave framework if necessary. Happens more often than we thought. datagrid capable - Ext.js & PrimeFaces looks pretty good, Vaadin does too. db-schema generators (optional, no matter in which way) If it were only on me, I'd probably stick to Ext.js + custom rest-based java solution, possibly generated from database schema (not sure about concrete tooling yet) I only does have experience with vanilla Ext.js, vanilla GWT and JSF 2.0 / Seam, so it kinda hard for me to judge or even propose other frameworks. What would be your proposition? What are the problems you've faced, what was your solution and how hard do you think it was to deal with them in "big picture"?

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  • Splitting up a Rails/Ruby app onto multiple servers

    - by craig.kaminsky
    We recently moved a large application to two machines, both running the same codebase. I. Machine A Web server for public facing application Receives web hook call backs from our ESP Handles a few large, list-processing jobs (uploaded spreadsheets with data) II. Machine B Manages a massive set of (background) jobs but, primarily, focuses on building and assembling newsletters Runs all integration with our NetSuite platform Runs all system maintenance (read: DB) jobs To me, having these two apps running the same codebase (a large, monolithic Rails application) seems 'wrong'. I am wondering if anyone has advice on how to better break up the code for these two apps. While they both need the same DB and, ultimately, the same model code, Machine B has no need for Controllers and Views and it feels wasteful running a full-stack Rails app for its tasks. A couple things came to mind but I'm not sure if I'm trying to solve a problem that doesn't exist: Break the models out into a sub-module on git and include into both apps Build out the Mahcine B app in plain Ruby or a lighter framework like Sinatra (where I could use ActiveRecord with Sinatra in combo with a sub-module for the model folder). I'm new to this scenario and appreciate any and all feedback or direction! Thank you.

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  • How to document/verify consistent layering?

    - by Morten
    I have recently moved to the dark side: I am now a CUSTOMER of software development -- mainly websites. With this new role comes new concerns. As a programmer i know how solid an application becomes when it is properly layered, and I want to use this knowledge in my new job. I don't want business logic in my presentation layer, and certainly not presentation stuff in my data layer. Thus, I want to be able to demand from my supllier that they document the level of layering, and how neat and consistent the layering is. The big question is: How is the level of layering documented to me as a customer, and is that a reasonable demmand for me to have, so I don't have to look in the code (I'm not supposed to do that anymore)?

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  • GRE subject Computer science

    - by Maddy.Shik
    How do I prepare for the GRE Computer Science subject test? Are there any standard text books I should follow? Agree that its under graduation level and one doesn't need to dig to deep for it. I have done my computer engineering from a college who ranks in top 20 in India. So may be my curriculum has not been that good as compared to international students. Since now i want to get admission in to world renowned university's Ph. D. program. I want to enhance my basic skills up to a level to beat other international students in competition. I want to know good book references which are recommended by professors in international school like CMU, MIT, Standford etc. Like for Algorithms Coreman is considered very good. Good books builds concepts from very basic so that one doesn't need to mug up even a basic concepts. Coreman is just too good with good blend of Mathematics and programming concepts. Definitely Test paper are must but that can be practiced once one has read text books thoroughly. Besides its been 2 years i passed out from college so its is essential for me to revise all concepts from text books. Please tell me standard text books for each subject like Computer Architecture, Database Design, Operating Systems, Discrete Maths etc.

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  • What is the difference between WCF service and a simple Web service in developing using .NET Framework?

    - by Steve Johnson
    My questions are: What is the difference between WCF service and a simple Web service in .NET Framework? What a WCF Service can do which a .NET Web service cant? In other words, what are the limitation of .NET Web services which were overcome in WCF services? I understand that WCF are REST based and .NET web services are SOAP based. But I need to know more than that. How a developer will make a design decision whether to developer a Web service or a WCF service?

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  • Best C# database communication technique

    - by user65439
    A few days ago I read a reply to a question where people said that the days of writing queries within your c# code are long gone. I'm not sure what the specific person meant with the comment but it got me thinking. At the company I'm currently working at we maintain an assembly containing all the queries to the database (let's call it Queries), this assembly is reference by a QueryService (Retrieve the correct queries) assembly which in turn is referenced by a UnitOfWork assembly (The database connector classes, we have different connector classes for SQL, MySQL etc.). We use these three assemblies to perform operations on our database and all queries/commands are written in our C# code. Is there a better way to communicate with the database and is there a better way to communicate with different database types?

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  • Qt Certification Exams

    - by karlphillip
    I'm wondering about doing a Qt Certification Exam this year, but I'm not 100% sure the investment is worth. I'm considering it because I think it could be a nice + on my resume, and as you know, I'm all for improving my software engineer persona. As I already earn a BSc and MSc degrees in computer stuff, I guess I see the certification process as some kind of adventure. Anyway, I know I'll spend a lot of time preparing myself for the exam and I just wanted to know if a Qt certification is worth the effort. Apparently there are 2 certificates that you can get in the Qt world: Nokia Certified Qt Developer (basic) Nokia Certified Qt Specialist (advanced) Nowadays I build cross-platform software in C++ and this exam would fit beautifully in my resume. My main concern is that, given the obscure future of Qt, I might be throwing time and money out the window. I'm looking for some advice regarding the usefulness of such certifications.

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