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• Android From Local DB (DAO) to Server sync (JSON) - Design issue

  - by Taiko

  I sync data between my local DB and a Server. I'm looking for the cleanest way to modelise all of this. I have a com.something.db package That contains a Data Helper and couple of DAO classes that represents objects stored in the db (I didn't write that part) com.something.db --public DataHelper --public Employee @DatabaseField e.g. "name" will be an actual column name in the DB -name @DatabaseField -salary etc... (all in all 50 fields) I have a com.something.sync package That contains all the implementation detail on how to send data to the server. It boils down to a ConnectionManager that is fed by different classes that implements a 'Request' interface com.something.sync --public interface ConnectionManager --package ConnectionManagerImpl --public interface Request --package LoginRequest --package GetEmployeesRequest My issue is, at some point in the sync process, I have to JSONise and de-JSONise my data (E.g. the Employee class). But I really don't feel like having the same Employee class be responsible for both his JSONisation and his actual representation inside the local database. It really doesn't feel right, because I carefully decoupled the rest, I am only stuck on this JSON thing. What should I do ? Should I write 3 Employee classes ? EmployeeDB @DatabaseField e.g. "name" will be an actual column name in the DB -name @DatabaseField -salary -etc... 50 fields EmployeeInterface -getName -getSalary -etc... 50 fields EmployeeJSON -JSON_KEY_NAME = "name" The JSON key happens to be the same as the table name, but it isn't requirement -name -JSON_KEY_SALARY = "salary" -salary -etc... 50 fields It feels like a lot of duplicates. Is there a common pattern I can use there ?

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• Inventory management system design problem

  - by Steve F

  What are the conventions for item batch identifiers in inventory management systems? For example: A retail supermarket can order 'Item X' from either 'Supplier A' or 'Supplier B'. When it completes an order for the item from either supplier, it needs to store the record of the receipt. Inventory quantity for the item is increased upon receipt of the order. However it is also required to store some record of the supplier. Thus some sort of batch identifier is required. This batch identifier will uniquely identify the item received and the supplier from whom it is received. A new batch is created each time items are received in stock (for example, after an order). Hence, for purposes of accounting / auditing, information available to identify an item after it was sold comprises of ITEM_CODE, ITEM_NAME, BATCH_CODE. The BATCH_CODE is unique and is associated with DATE_RECEIVED, SUPPLIER_CODE, QTY_RECEIVED. Is this a complete system specification for the above scenario or has anything significant been left out?

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• How one could use a live editor

  - by Sathvik

  I was thinking about a live editing environment where code / a source file is synchronized so that, changes made by one user would be carried across to all others editing the file. Something like Google Wave, but for code. Could this kind of an environment be better for the code, as changes are shared instantly? (with revision-control, of course) Has anyone tried (or has had a need for) using a shared environment for code?

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• How Would You Design This Table?

  - by sooprise

  I have to create a table where each row needs to store 50 number values. Each row will always need to store 50 number values. If this was a smaller number of values, I would just make fields for each of the values, but because there are 50, this approach seems a bit cumbersome (but since it will always be 50 values, maybe this is the correct approach?). Is there a way to store an array of values in a field? This seems like a nice solution, but the concept is almost identical to creating a relational database.

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• How to design brain games [on hold]

  - by samesky

  I will wonder if anybody has some information about designing games for brain improvement. Recently lumosity is into a gear. I guess they research a lot or have experts. But is there any other research paper that is publicly available for designing the brain games ? Any equation or data that can help? Or what characteristics a brain game should have ? I am getting interested on this and search internet a lot, but unfortunately I could not find the core structure of it. It will really a helpful for me if somebody can give some information. Thank you.

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• design an extendible and pluggable business logic flow handler in php

  - by Broncha

  I am working on a project where I need to allow a pluggable way to inject business processes in the normal data flow. eg There is an ordering system. The standard flow of the application is A consumer orders an item. Pays for it and card is authorized. Admin captures the payment. Order is marked as complete and item is shipped. But this process may vary (extra steps in between) for different clients. Say a client would need to validate the location of the consumer before he is presented with a credit card form, OR his policies might require some other processes in between. I am thinking of using State Pattern for processing orders, saving the current state of the order in database, and initializing the state of order from the saved state. I would also need some mechanism, where a small plugin would be able to inject business specific states in the state machine. Am I thinking the right way? Are there already implemented patterns for this kind of situation? I am working with Codeigniter and basically this would mean for me, to redirect to proper controller according to the current state of the order. Like, if the state of the order is unconfirmed then redirect the user to details page and then change the state to pending. If some client would need to do some validation, then register an intermediate state between unconfirmed and pending Please suggest.

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• Android design advice - services & broadcast receivers

  - by basudz

  I'm in the process of learning the Android SDK and creating some projects to get a grasp on the system. The current project I'm working with works just fine but I'd like to get some advice about other ways I can go about designing it. Here's what it needs to do. When a text message is received from a specific number, it should fire off a toast message that repeats at a certain interval for a specific duration. To make this work, I created an SMS BroadcastReceiver and checked the incoming messages for the number I'm looking for. If found, an IntentService would be started that would pull out the interval and duration from saved shared prefs. The IntentService would then fire off a broadcast. The BroadcastReceiver for this would catch it and use the AlarmManager to handle the toast message repetitions. This all works just fine, but I'm wondering if there's a cleaner or more efficient way of going about doing this? Any suggestions or advice?

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• What OO Design to use ( is there a Design Pattern )?

  - by Blundell

  I have two objects that represent a 'Bar/Club' ( a place where you drink/socialise). In one scenario I need the bar name, address, distance, slogon In another scenario I need the bar name, address, website url, logo So I've got two objects representing the same thing but with different fields. I like to use immutable objects, so all the fields are set from the constructor. One option is to have two constructors and null the other fields i.e: class Bar { private final String name; private final Distance distance; private final Url url; public Bar(String name, Distance distance){ this.name = name; this.distance = distance; this.url = null; } public Bar(String name, Url url){ this.name = name; this.distance = null; this.url = url; } // getters } I don't like this as you would have to null check when you use the getters In my real example the first scenario has 3 fields and the second scenario has about 10, so it would be a real pain having two constructors, the amount of fields I would have to declare null and then when the object are in use you wouldn't know which Bar you where using and so what fields would be null and what wouldn't. What other options do I have? Two classes called BarPreview and Bar? Some type of inheritance / interface? Something else that is awesome?

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• Advice needed on Process - Service Design

  - by user99314

  Need some advice from experts on designing a flow. Create a service that will read a csv file which may contain anywhere over 6000+ rows of individual ids as shown in the sample below. Need to read that file and go to oracle database and fetch a vname,vnumber,vid of each id in the csv and then go to document repository i.e. Oracle UCM and download all documents matching vname,vnumber,vid there can be =0 documents for each vname,vnumber,vid and save them on a file system. UCM exposes a webservice to dowload the documents. Finally create a new csv appending the filenames that are downloaded for each id. Need to keep track of any errors but need to make sure to go over the whole ids in the csv to download the documents and skip in case of errors. Need some advice on how to go about designing this as there may be over 6000+ rows in a csv file and looping it and hitting the database for each individual id and then hitting a UCM may be a bit expensive so open for any idea. How to go by designing this solution. Wondering if messaging can be helpful here or offloading process of getting the vname,vnumber,vid to pl/sql packages, creating staging tables etc. Initial csv that contains ids: **ID** 12345a 12s345 3456fr we9795 we9797 Final csv output: **ID Files Downloaded from UCM** 12345a a.pdf,b.doc,d.txt 12s345 a1.pdf,s2.pdf,f4.gif 3456fr b.xls we9795 we9797 x.doc Thanks

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• How can I design multi-threaded application for larger user base

  - by rokonoid

  Here's my scenario, I need to develop a scalable application. My user base may be over 100K, every user has 10 or more small tasks. Tasks check every minute with a third party application through web services, retrieving data which is written in the database, then the data is forwarded to it's original destination. So here's the processing of a small task: while(true){ Boolean isNewInformationAvailable = checkWhetherInformationIsAvailableOrNot(); If(isNewInformationAvailable ==true){ fetchTheData(); writeToDatabase(); findTheDestination(); deliverTheData(); isAvailable =false; } } As the application is large, how should I approach designing this? I'm going to use Java to write it. Should I use concurrency, and how would you manage the concurrency?

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• Tips on a tool to measure code quality?

  - by Cristi Diaconescu

  I'm looking for a tool that can provide code quality metrics. For instance it could report very long functions (spaghetti code) very complex classes (which could contain do-it-all code) ... While we're on the (subjective:-) subject of code quality, what other code metrics would you suggest? I'm targetting C#/.NET code, but I'm sure this could extend to most programming languages.

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• Visual Studio 2013 Static Code Analysis in depth: What? When and How?

  - by Hosam Kamel

  In this post I'll illustrate in details the following points What is static code analysis? When to use? Supported platforms Supported Visual Studio versions How to use Run Code Analysis Manually Run Code Analysis Automatically Run Code Analysis while check-in source code to TFS version control (TFSVC) Run Code Analysis as part of Team Build Understand the Code Analysis results & learn how to fix them Create your custom rule set Q & A References What is static Rule analysis? Static Code Analysis feature of Visual Studio performs static code analysis on code to help developers identify potential design, globalization, interoperability, performance, security, and a lot of other categories of potential problems according to Microsoft's rules that mainly targets best practices in writing code, and there is a large set of those rules included with Visual Studio grouped into different categorized targeting specific coding issues like security, design, Interoperability, globalizations and others. Static here means analyzing the source code without executing it and this type of analysis can be performed through automated tools (like Visual Studio 2013 Code Analysis Tool) or manually through Code Review which already supported in Visual Studio 2012 and 2013 (check Using Code Review to Improve Quality video on Channel9) There is also Dynamic analysis which performed on executing programs using software testing techniques such as Code Coverage for example. When to use? Running Code analysis tool at regular intervals during your development process can enhance the quality of your software, examines your code for a set of common defects and violations is always a good programming practice. Adding that Code analysis can also find defects in your code that are difficult to discover through testing allowing you to achieve first level quality gate for you application during development phase before you release it to the testing team. Supported platforms .NET Framework, native (C and C++) Database applications. Support Visual Studio versions All version of Visual Studio starting Visual Studio 2013 (except Visual Studio Test Professional) check Feature comparisons Create and modify a custom rule set required Visual Studio Premium or Ultimate. How to use? Code Analysis can be run manually at any time from within the Visual Studio IDE, or even setup to automatically run as part of a Team Build or check-in policy for Team Foundation Server. Run Code Analysis Manually To run code analysis manually on a project, on the Analyze menu, click Run Code Analysis on your project or simply right click on the project name on the Solution Explorer choose Run Code Analysis from the context menu Run Code Analysis Automatically To run code analysis each time that you build a project, you select Enable Code Analysis on Build on the project's Property Page Run Code Analysis while check-in source code to TFS version control (TFSVC) Team Foundation Version Control (TFVC) provides a way for organizations to enforce practices that lead to better code and more efficient group development through Check-in policies which are rules that are set at the team project level and enforced on developer computers before code is allowed to be checked in. (This is available only if you're using Team Foundation Server) Require permissions on Team Foundation Server: you must have the Edit project-level information permission set to Allow typically your account must be part of Project Administrators, Project Collection Administrators, for more information about Team Foundation permissions check http://msdn.microsoft.com/en-us/library/ms252587(v=vs.120).aspx In Team Explorer, right-click the team project name, point to Team Project Settings, and then click Source Control. In the Source Control dialog box, select the Check-in Policy tab. Click Add to create a new check-in policy. Double-click the existing Code Analysis item in the Policy Type list to change the policy. Check or Uncheck the policy option based on the configurations you need to perform as illustrated below: Enforce check-in to only contain files that are part of current solution: code analysis can run only on files specified in solution and project configuration files. This policy guarantees that all code that is part of a solution is analyzed. Enforce C/C++ Code Analysis (/analyze): Requires that all C or C++ projects be built with the /analyze compiler option to run code analysis before they can be checked in. Enforce Code Analysis for Managed Code: Requires that all managed projects run code analysis and build before they can be checked in. Check Code analysis rule set reference on MSDN What is Rule Set? Rule Set is a group of code analysis rules like the example below where Microsoft.Design is the rule set name where "Do not declare static members on generic types" is the code analysis rule Once you configured the Analysis rule the policy will be enabled for all the team member in this project whenever a team member check-in any source code to the TFSVC the policy section will highlight the Code Analysis policy as below TFS is a very extensible platform so you can simply implement your own custom Code Analysis Check-in policy, check this link for more details http://msdn.microsoft.com/en-us/library/dd492668.aspx but you have to be aware also about compatibility between different TFS versions check http://msdn.microsoft.com/en-us/library/bb907157.aspx Run Code Analysis as part of Team Build With Team Foundation Build (TFBuild), you can create and manage build processes that automatically compile and test your applications, and perform other important functions. Code Analysis can be enabled in the Build Definition file by selecting the correct value for the build process parameter "Perform Code Analysis" Once configure, Kick-off your build definition to queue a new build, Code Analysis will run as part of build workflow and you will be able to see code analysis warning as part of build report Understand the Code Analysis results & learn how to fix them Now after you went through Code Analysis configurations and the different ways of running it, we will go through the Code Analysis result how to understand them and how to resolve them. Code Analysis window in Visual Studio will show all the analysis results based on the rule sets you configured in the project file properties, let's dig deep into what each result item contains: 1 Check ID The unique identifier for the rule. CheckId and Category are used for in-source suppression of a warning.       2 Title The title of warning message       3 Description A description of the problem or suggested fix 4 File Name File name and the line of code number which violate the code analysis rule set 5 Category The code analysis category for this error 6 Warning /Error Depend on how you configure it in the rule set the default is Warning level 7 Action Copy: copy the warning information to the clipboard Create Work Item: If you're connected to Team Foundation Server you can create a work item most probably you may create a Task or Bug and assign it for a developer to fix certain code analysis warning Suppress Message: There are times when you might decide not to fix a code analysis warning. You might decide that resolving the warning requires too much recoding in relation to the probability that the issue will arise in any real-world implementation of your code. Or you might believe that the analysis that is used in the warning is inappropriate for the particular context. You can suppress individual warnings so that they no longer appear in the Code Analysis window. Two options available: In Source inserts a SuppressMessage attribute in the source file above the method that generated the warning. This makes the suppression more discoverable. In Suppression File adds a SuppressMessage attribute to the GlobalSuppressions.cs file of the project. This can make the management of suppressions easier. Note that the SuppressMessage attribute added to GlobalSuppression.cs also targets the method that generated the warning. It does not suppress the warning globally.       Visual Studio makes it very easy to fix Code analysis warning, all you have to do is clicking on the Check Id hyperlink if you are not aware how to fix the warring and you'll be directed to MSDN online or local copy based on the configuration you did while installing Visual Studio and you will find all the information about the warring including how to fix it. Create a Custom Code Analysis Rule Set The Microsoft standard rule sets provide groups of rules that are organized by function and depth. For example, the Microsoft Basic Design Guidelines Rules and the Microsoft Extended Design Guidelines Rules contain rules that focus on usability and maintainability issues, with added emphasis on naming rules in the Extended rule set, you can create and modify a custom rule set to meet specific project needs associated with code analysis. To create a custom rule set, you open one or more standard rule sets in the rule set editor. Create and modify a custom rule set required Visual Studio Premium or Ultimate. You can check How to: Create a Custom Rule Set on MSDN for more details http://msdn.microsoft.com/en-us/library/dd264974.aspx Q & A Visual Studio static code analysis vs. FxCop vs. StyleCpp http://www.excella.com/blog/stylecop-vs-fxcop-difference-between-code-analysis-tools/ Code Analysis for SharePoint Apps and SPDisposeCheck? This post lists some of the rule set you can run specifically for SharePoint applications and how to integrate SPDisposeCheck as well. Code Analysis for SQL Server Database Projects? This post illustrate how to run static code analysis on T-SQL through SSDT ReSharper 8 vs. Visual Studio 2013? This document lists some of the features that are provided by ReSharper 8 but are missing or not as fully implemented in Visual Studio 2013. References A Few Billion Lines of Code Later: Using Static Analysis to Find Bugs in the Real World http://cacm.acm.org/magazines/2010/2/69354-a-few-billion-lines-of-code-later/fulltext What is New in Code Analysis for Visual Studio 2013 http://blogs.msdn.com/b/visualstudioalm/archive/2013/07/03/what-is-new-in-code-analysis-for-visual-studio-2013.aspx Analyze the code quality of Windows Store apps using Visual Studio static code analysis http://msdn.microsoft.com/en-us/library/windows/apps/hh441471.aspx [Hands-on-lab] Using Code Analysis with Visual Studio 2012 to Improve Code Quality http://download.microsoft.com/download/A/9/2/A9253B14-5F23-4BC8-9C7E-F5199DB5F831/Using%20Code%20Analysis%20with%20Visual%20Studio%202012%20to%20Improve%20Code%20Quality.docx Originally posted at "Hosam Kamel| Developer & Platform Evangelist" http://blogs.msdn.com/hkamel

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• How can I promote clean coding at my workplace?

  - by Michael

  I work with a lot of legacy Java and RPG code on an internal company application. As you might expect, a lot of the code is written in many different styles, and often is difficult to read because of poorly named variables, inconsistent formatting, and contradictory comments (if they're there at all). Also, a good amount of code is not robust. Many times code is pushed to production quickly by the more experienced programmers, while code by newer programmers is held back by "code reviews" that IMO are unsatisfactory. (They usually take the form of, "It works, must be ok," than a serious critique of the code.) We have a fair number of production issues, which I feel could be lessened by giving more thought to the original design and testing. I have been working for this company for about 4 months, and have been complimented on my coding style a couple of times. My manager is also a fan of cleaner coding than is the norm. Is it my place to try to push for better style and better defensive coding, or should I simply code in the best way I can, and hope that my example will help others see how cleaner, more robust code (as well as aggressive refactoring) will result in less debugging and change time?

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• How should Code Review be Carried Out?

  - by Graviton

  My previous question has to do with how to advance code review among the developers. Here I am interested in how the code review session should be carried out, so that both the reviewer and reviewed are feeling comfortable about it. I have done some code review before, but the experience sucks big time. My previous manager would come to us-- on an ad hoc basis-- and tell us to explain our code to him. Since he wasn't very familiar with the code base, I spent a huge amount of times explaining just the most basic structure of my code to him. This took a long time and by the time we were done, we were both exhausted. Then he would raise issues with my code. Most issues he raised were cosmetic in nature ( e.g, don't use region for this code block, change the variable name from xxx to yyy even though the later makes even less sense, and so on). We did this a few rounds, and the review session didn't derive much benefits for us, and we stopped. What do you have to do, in order to make code review a natural, enjoyable, thought stimulating, bug-fixing and mutual-learning experience?

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• Checking preconditions or not

  - by Robert Dailey

  I've been wanting to find a solid answer to the question of whether or not to have runtime checks to validate input for the purposes of ensuring a client has stuck to their end of the agreement in design by contract. For example, consider a simple class constructor: class Foo { public: Foo( BarHandle bar ) { FooHandle handle = GetFooHandle( bar ); if( handle == NULL ) { throw std::exception( "invalid FooHandle" ); } } }; I would argue in this case that a user should not attempt to construct a Foo without a valid BarHandle. It doesn't seem right to verify that bar is valid inside of Foo's constructor. If I simply document that Foo's constructor requires a valid BarHandle, isn't that enough? Is this a proper way to enforce my precondition in design by contract? So far, everything I've read has mixed opinions on this. It seems like 50% of people would say to verify that bar is valid, the other 50% would say that I shouldn't do it, for example consider a case where the user verifies their BarHandle is correct, but a second (and unnecessary) check is also being done inside of Foo's constructor.

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• Confused about implementing Single Responsibility Principle

  - by HichemSeeSharp

  Please bear with me if the question looks not well structured. To put you in the context of my issue: I am building an application that invoices vehicles stay duration in a parking. In addition to the stay service there are some other services. Each service has its own calculation logic. Here is an illustration (please correct me if the design is wrong): public abstract class Service { public int Id { get; set; } public bool IsActivated { get; set; } public string Name { get; set } public decimal Price { get; set; } } public class VehicleService : Service { //MTM : many to many public virtual ICollection<MTMVehicleService> Vehicles { get; set; } } public class StayService : VehicleService { } public class Vehicle { public int Id { get; set; } public string ChassisNumber { get; set; } public DateTime? EntryDate { get; set; } public DateTime? DeliveryDate { get; set; } //... public virtual ICollection<MTMVehicleService> Services{ get; set; } } Now, I am focusing on the stay service as an example: I would like to know at invoicing time which class(es) would be responsible for generating the invoice item for the service and for each vehicle? This should calculate the duration cost knowing that the duration could be invoiced partially so the like is as follows: not yet invoiced stay days * stay price per day. At this moment I have InvoiceItemsGenerator do everything but I am aware that there is a better design.

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• A better alternative to incompatible implementations for the same interface?

  - by glenatron

  I am working on a piece of code which performs a set task in several parallel environments where the behaviour of the different components in the task are similar but quite different. This means that my implementations are quite different but they are all based on the relationships between the same interfaces, something like this: IDataReader -> ContinuousDataReader -> ChunkedDataReader IDataProcessor -> ContinuousDataProcessor -> ChunkedDataProcessor IDataWriter -> ContinuousDataWriter -> ChunkedDataWriter So that in either environment we have an IDataReader, IDataProcessor and IDataWriter and then we can use Dependency Injection to ensure that we have the correct one of each for the current environment, so if we are working with data in chunks we use the ChunkedDataReader, ChunkedDataProcessor and ChunkedDataWriter and if we have continuous data we have the continuous versions. However the behaviour of these classes is quite different internally and one could certainly not go from a ContinuousDataReader to the ChunkedDataReader even though they are both IDataProcessors. This feels to me as though it is incorrect ( possibly an LSP violation? ) and certainly not a theoretically correct way of working. It is almost as though the "real" interface here is the combination of all three classes. Unfortunately in the project I am working on with the deadlines we are working to, we're pretty much stuck with this design, but if we had a little more elbow room, what would be a better design approach in this kind of scenario?

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• Use decorator and factory together to extend objects?

  - by TheClue

  I'm new to OOP and design pattern. I've a simple app that handles the generation of Tables, Columns (that belong to Table), Rows (that belong to Column) and Values (that belong to Rows). Each of these object can have a collection of Property, which is in turn defined as an enum. They are all interfaces: I used factories to get concrete instances of these products, depending on circumnstances. Now I'm facing the problem of extending these classes. Let's say I need another product called "SpecialTable" which in turn has some special properties or new methods like 'getSomethingSpecial' or an extended set of Property. The only way is to extend/specialize all my elements (ie. build a SpecialTableFactory, a SpecialTable interface and a SpecialTableImpl concrete)? What to do if, let's say, I plan to use standard methods like addRow(Column column, String name) that doesn't need to be specialized? I don't like the idea to inherit factories and interfaces, but since SpecialTable has more methods than Table i guess it cannot share the same factory. Am I wrong? Another question: if I need to define product properties at run time (a Table that is upgraded to SpecialTable at runtime), i guess i should use a decorator. Is it possible (and how) to combine both factory and decorator design? Is it better to use a State or Strategy pattern, instead?

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• Advancing Code Review and Unit Testing Practice

  - by Graviton

  As a team lead managing a group of developers with no experience ( and see no need) in code review and unit testing, how can you advance code review and unit testing practice? How are you going to create a way so that code review and unit testing to naturally fit into the developer's flow? One of the resistance of these two areas is that "we are always tight on dateline, so no time for code review and unit testing". Another resistance for code review is that we currently don't know how to do it. Should we review the code upon every check-in, or review the code at a specified date?

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• Memento with optional state?

  - by Korey Hinton

  EDIT: As pointed out by Steve Evers and pdr, I am not correctly implementing the Memento pattern, my design is actually State pattern. Menu Program I built a console-based menu program with multiple levels that selects a particular test to run. Each level more precisely describes the operation. At any level you can type back to go back one level (memento). Level 1: Server Type? [1] Server A [2] Server B Level 2: Server environment? [1] test [2] production Level 3: Test type? [1] load [2] unit Level 4: Data Collection? [1] Legal docs [2] Corporate docs Level 4.5 (optional): Load Test Type [2] Multi TIF [2] Single PDF Level 5: Command Type? [1] Move [2] Copy [3] Remove [4] Custom Level 6: Enter a keyword [setup, cleanup, run] Design States PROBLEM: Right now the STATES enum is the determining factor as to what state is BACK and what state is NEXT yet it knows nothing about what the current memento state is. Has anyone experienced a similar issue and found an effective way to handle mementos with optional state? static enum STATES { SERVER, ENVIRONMENT, TEST_TYPE, COLLECTION, COMMAND_TYPE, KEYWORD, FINISHED } Possible Solution (Not-flexible) In reference to my code below, every case statement in the Menu class could check the state of currentMemo and then set the STATE (enum) accordingly to pass to the Builder. However, this doesn't seem flexible very flexible to change and I'm struggling to see an effective way refactor the design. class Menu extends StateConscious { private State state; private Scanner reader; private ServerUtils utility; Menu() { state = new State(); reader = new Scanner(System.in); utility = new ServerUtils(); } // Recurring menu logic public void startPromptingLoop() { List<State> states = new ArrayList<>(); states.add(new State()); boolean redoInput = false; boolean userIsDone = false; while (true) { // get Memento from last loop Memento currentMemento = states.get(states.size() - 1) .saveMemento(); if (currentMemento == null) currentMemento = new Memento.Builder(0).build(); if (!redoInput) System.out.println(currentMemento.prompt); redoInput = false; // prepare Memento for next loop Memento nextMemento = null; STATES state = STATES.values()[states.size() - 1]; // get user input String selection = reader.nextLine(); switch (selection) { case "exit": reader.close(); return; // only escape case "quit": nextMemento = new Memento.Builder(first(), currentMemento, selection).build(); states.clear(); break; case "back": nextMemento = new Memento.Builder(previous(state), currentMemento, selection).build(); if (states.size() <= 1) { states.remove(0); } else { states.remove(states.size() - 1); states.remove(states.size() - 1); } break; case "1": nextMemento = new Memento.Builder(next(state), currentMemento, selection).build(); break; case "2": nextMemento = new Memento.Builder(next(state), currentMemento, selection).build(); break; case "3": nextMemento = new Memento.Builder(next(state), currentMemento, selection).build(); break; case "4": nextMemento = new Memento.Builder(next(state), currentMemento, selection).build(); break; default: if (state.equals(STATES.CATEGORY)) { String command = selection; System.out.println("Executing " + command + " command on: " + currentMemento.type + " " + currentMemento.environment); utility.executeCommand(currentMemento.nickname, command); userIsDone = true; states.clear(); nextMemento = new Memento.Builder(first(), currentMemento, selection).build(); } else if (state.equals(STATES.KEYWORD)) { nextMemento = new Memento.Builder(next(state), currentMemento, selection).build(); states.clear(); nextMemento = new Memento.Builder(first(), currentMemento, selection).build(); } else { redoInput = true; System.out.println("give it another try"); continue; } break; } if (userIsDone) { // start the recurring menu over from the beginning for (int i = 0; i < states.size(); i++) { if (i != 0) { states.remove(i); // remove all except first } } reader = new Scanner(System.in); this.state = new State(); userIsDone = false; } if (!redoInput) { this.state.restoreMemento(nextMemento); states.add(this.state); } } } }

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• Is loose coupling w/o use cases an anti-pattern?

  - by dsimcha

  Loose coupling is, to some developers, the holy grail of well-engineered software. It's certainly a good thing when it makes code more flexible in the face of changes that are likely to occur in the foreseeable future, or avoids code duplication. On the other hand, efforts to loosely couple components increase the amount of indirection in a program, thus increasing its complexity, often making it more difficult to understand and often making it less efficient. Do you consider a focus on loose coupling without any use cases for the loose coupling (such as avoiding code duplication or planning for changes that are likely to occur in the foreseeable future) to be an anti-pattern? Can loose coupling fall under the umbrella of YAGNI?

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• Why is nesting or piggybacking errors within errors bad in general?

  - by dietbuddha

  Why is nesting or piggybacking errors within errors bad in general? To me it seems bad intuitively, but I'm suspicious in that I cannot adequately articulate why it is bad. This may be because it is not in general bad and that it is only bad in specific instances. Why is it detrimental to design error/exception handling in such a way. The specific instance is that of a REST service. There is a desire by some to use http errors (specifically the 500 response) as a way to indicate any problem with specific instances of a resource. An example of an instance resource in this case would be: http://server/ticket/80 # instance http://server/ticket # not an instance So this is the behavior that is being proposed. If ticket 80 does not exist return a http response code of 500. Within the body of the error return the "real" error as an additional error code and description. If the ticket resource doesn't exist return a response code of 404.

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• USE case to Class Diagram - How do I?

  - by 01010011

  Hi, I would like your guidance on how to create classes and their relationships (generalization, association, aggregation and composition) accurately from my USE case diagram (please see below). I am trying to create this class diagram so I can use it to create a simple online PHP application that allows the user to register an account, login and logout, and store, search and retrieve data from a MySQL database. Are my classes correct? Or should I create more classes? And if so, what classes are missing? What relationships should I use when connecting the register, login, logout, search_database and add_to_database to the users? I'm new to design patterns and UML class diagrams but from my understanding, the association relationship relates one object with another object; the aggregation relationship is a special kind of association that allows "a part" to belong to more than one "whole" (e.g. a credit card and its PIN - the PIN class can also be used in a debit card class); and a composition relationship is a special form of aggregation that allows each part to belong to only one whole at a time. I feel like I have left out some classes or something because I just can't seem to find the relationships from my understanding of relationships. Any assistance will be really appreciated. Thanks in advance. USE CASE DIAGRAM CLASS DIAGRAM

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• Strategies for invoking subclass methods on generic objects

  - by Brad Patton

  I've run into this issue in a number of places and have solved it a bunch of different ways but looking for other solutions or opinions on how to address. The scenario is when you have a collection of objects all based off of the same superclass but you want to perform certain actions based only on instances of some of the subclasses. One contrived example of this might be an HTML document made up of elements. You could have a superclass named HTMLELement and subclasses of Headings, Paragraphs, Images, Comments, etc. To invoke a common action across all of the objects you declare a virtual method in the superclass and specific implementations in all of the subclasses. So to render the document you could loop all of the different objects in the document and call a common Render() method on each instance. It's the case where again using the same generic objects in the collection I want to perform different actions for instances of specific subclass (or set of subclasses). For example (an remember this is just an example) when iterating over the collection, elements with external links need to be downloaded (e.g. JS, CSS, images) and some might require additional parsing (JS, CSS). What's the best way to handle those special cases. Some of the strategies I've used or seen used include: Virtual methods in the base class. So in the base class you have a virtual LoadExternalContent() method that does nothing and then override it in the specific subclasses that need to implement it. The benefit being that in the calling code there is no object testing you send the same message to each object and let most of them ignore it. Two downsides that I can think of. First it can make the base class very cluttered with methods that have nothing to do with most of the hierarchy. Second it assumes all of the work can be done in the called method and doesn't handle the case where there might be additional context specific actions in the calling code (i.e. you want to do something in the UI and not the model). Have methods on the class to uniquely identify the objects. This could include methods like ClassName() which return a string with the class name or other return values like enums or booleans (IsImage()). The benefit is that the calling code can use if or switch statements to filter objects to perform class specific actions. The downside is that for every new class you need to implement these methods and can look cluttered. Also performance could be less than some of the other options. Use language features to identify objects. This includes reflection and language operators to identify the objects. For example in C# there is the is operator that returns true if the instance matches the specified class. The benefit is no additional code to implement in your object hierarchy. The only downside seems to be the lack of using something like a switch statement and the fact that your calling code is a little more cluttered. Are there other strategies I am missing? Thoughts on best approaches?

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• What should you do differently when designing websites for an embedded web server

  - by Roger Attrill

  When designing a website to be accessed from an embedded webserver such as KLone, what do you need to do differently compared to a 'standard' web server. I'm talking about considerations at the front end design stage, before the actual building and coding up. For example, typically in such situations, memory size is a premium, so I guess larger images are out, and maybe more attention should be focused on achieving a good look and feel using CSS/Javascript rather than bitmap images.

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