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• Layering Design Pattern in Java clean code style

  - by zeraDev

  As a Java developer, I am developing trying to use the clean code rules. But in my team we are facing a concrete problem: We have a business layer offering a service called "createObject", this service makes a lot of operation which can result to problem. E.g: parentObjectDontExist, objectAlreadyExist, dontHaveAuthorizationToCreate, operationFailed... and we want the UI using this service to display different information messages depending which error occurred. In old java dev, we should have create all signed exception type and throw it in createObject. As Clean code says, it is forbidden to use Exception for business logic AND signed exceptions are evil... Why not...But i don't know how to solved this problem and i don't want to use return code. How do you do? Thanks for youre experience return.

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• Is there a standard for machine-readable descriptions of RESTful services?

  - by ecmendenhall

  I've interacted with a few RESTful APIs that provided excellent documentation for humans and descriptive URIs, but none of them seem to return machine-readable descriptions of themselves. It's not too tough to write methods of my own that assemble the right paths, and many language-specific API libraries are already just wrappers around RESTful requests. But the next level of abstraction seems really useful: a library that could read in an API's own machine readable documentation and generate the wrappers automatically, perhaps with a call to some standard URI like base_url + '/documentation' Are there any standards for machine-readable API documentation? Am I doing REST wrong? I am a relatively new programmer, but this seems like a good idea.

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• Web programming, standard way to deal with a response that takes time to complete

  - by wobbily_col

  With normal form submission I use the pattern Post / Redirect / Get, when processing the forms. I have a database application built with Django. I want to allow the users to select a number of items from the database, then launch a computationally intensive task based on those items. I expect the task to take between 10 minutes and 2 hours to complete. Is there a standard approach to dealing with requests like this (i.e. that don't return immediately)? Ideally there would be some way to display the progress.

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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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• Any recommended books/resources on component-based design?

  - by user1163640

  I come from a background with heavy use of the classical object-oriented paradigm for software development. The company I am a part of switched to Unity not too long ago, and we're all very excited to get started using it However, one aspect that have sparked my interested, and which I think will become a very important part of our future development, is Unity's approach to component-based design with scripting; with less focus on typical hierarchical aspect. Question I was wondering if anyone could recommend any good books on this subject? I have had trouble finding any books or books with reliable reviews, and was wondering if anyone more experienced here had something to say on the issue? Any other kind of resource would be excellent too, I'm just interested in getting to learn everything I can about it. This is not meant as a discussion about best books or resources on the topic, but simply a question regarding any resources that any of you find useful. Thank you all for your time!

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• Is programming or computer science in general, all about algorithms?

  - by wakandan

  As a grad student, I find it more and more common for prestigious companies (like Google, Facebook, Microsoft,...) to put algorithm questions in their test and interviews. A few startups I applied to also asked about algorithms. I wonder if algorithms fluency is the most important thing for software developer in those companies? If the answer being yes, what are the best method or resources for one to learn & practice about algorithms effectively? I can't seem to get interested in solving seemingly too complicated problems found in most textbook or websites. Though easily understand basic algorithms (like quicksort, bubblesort,...), I find it immensely difficult to remember and reuse them later. Thanks. P/S: If you ask me what I like, it's building good softwares to solve users' problems innovatively. I suppose that does not necessarily mean the software has to be very complicated.

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• Dynamic Strategy Pattern [migrated]

  - by Karl Barker

  So I'm writing a web service architecture which includes FunctionProvider classes which do the actual processing of requests, and a main Endpoint class which receives and delegates requests to the proper FunctionProvider. I don't know exactly the FunctionProviders available at runtime, so I need to be able to 'register' (if that's the right word) them with my main Endpoint class, and query them to see if they match an incoming request. public class MyFunc implements FunctionProvider{ static { MyEndpoint.register(MyFunc); } public Boolean matchesRequest(Request req){...} public void processRequest(Request req){...} } public class MyEndpoint{ private static ArrayList<FunctionProvider> functions = new ArrayList<FunctionProvider>(); public void register(Class clz){ functions.add(clz); } public void doPost(Request request){ //find the FunctionProvider in functions //matching the request } } I've really not done much reflective Java like this (and the above is likely wrong, but hopefully demonstrates my intentions). What's the nicest way to implement this without getting hacky?

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• How do you balance between "do it right" and "do it ASAP" in your daily work?

  - by Flot2011

  I find myself pondering this question times and times again. I want to do things the right way, to write a clean, understandable, correct code that is easy to maintain, but what I really do pretty often is writing a patch upon patch just because there is no time, clients are waiting, a bug should be fixed overnight, the company is losing money on this problem, a manager is pressing hard etc. etc. I know perfectly well that in a long shot I am wasting much more time on these patches, but as this time is spread over months of work, nobody cares. Also, as one of my managers used to say, we don't know if there will be this long shot if we will not fix it now. I am sure I am not the only one entrapped in this endless real/ideal choices. So how you, fellow programmers, are coping with this?

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• Torvalds' quote about good programmer

  - by beyeran

  Accidentally I've stumbled upon the following quote by Linus Torvalds: "Bad programmers worry about the code. Good programmers worry about data structures and their relationships." I've thought about it for the last few days and I'm still confused (which is probably not a good sign), hence I wanted to discuss the following: What interpretation of this possible/makes sense? What can be applied/learned from it?

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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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• Settings object with singleton pattern

  - by axis

  I need to build an object that will have only one instance because this Object is dedicated to the storage of vital settings for my application and I would like to avoid a misuse of this type or a conflict at run-time. The most popular solution for this, according to the internet, is the Singleton pattern. But I would like to know about other ideas or solutions for this; also I would like to know if other solutions can be much more easy to grasp for an user of this hypothetical library. Thanks.

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• Event Aggregator.. not getting a response, how to determine completion?

  - by Duncan_m

  I'm rewriting a vehicle tracking application, a google maps based thing.. The users are able to search for a vehicle by typing a few characters of the vehicles "callsign". My application is based around a sort of "event bus" within Backbone.. when a search occurs I send a message on the bus saying something like "does anyone match this?".. If a marker matches the search term it responds with a sort of "yes, I match!".. My challenge arises when no-one matches, I get no response.. it feels a little hacky to "wait a little while" and check if a response has been recieved.. The application is based around Backbone.js and using the Event Aggregator pattern described in the answer to this question on Stack Overflow: http://stackoverflow.com/questions/7708195/access-function-in-one-view-from-another-in-backbone-js Is there a well defined design pattern that might assist me here? Sending a request for a response and not getting any responses?

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• What's is the point of PImpl pattern while we can use interface for same purpose in C++?

  - by ZijingWu

  I see a lot of source code which using PIMPL idiom in C++. I assume Its purposes are hidden the private data/type/implementation, so it can resolve dependence, and then reduce compile time and header include issue. But interface class in C++ also have this capability, it can also used to hidden data/type and implementation. And to hidden let the caller just see the interface when create object, we can add an factory method in it declaration in interface header. The comparison is: Cost: The interface way cost is lower, because you doesn't even need to repeat the public wrapper function implementation void Bar::doWork() { return m_impl->doWork(); }, you just need to define the signature in the interface. Well understand: The interface technology is more well understand by every C++ developer. Performance: Interface way performance not worse than PIMPL idiom, both an extra memory access. I assume the performance is same. Following is the pseudocode code to illustrate my question: // Forward declaration can help you avoid include BarImpl header, and those included in BarImpl header. class BarImpl; class Bar { public: // public functions void doWork(); private: // You doesn't need to compile Bar.cpp after change the implementation in BarImpl.cpp BarImpl* m_impl; }; The same purpose can be implement using interface: // Bar.h class IBar { public: virtual ~IBar(){} // public functions virtual void doWork() = 0; }; // to only expose the interface instead of class name to caller IBar* createObject(); So what's the point of PIMPL?

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• Are there new flexible texteditors? [closed]

  - by RParadox

  Vi(m) and Emacs are almost 40 years old. Why are they still the standard, and what attempts have been made at coming up with a new flexible editor? Are there any features which can not be built into vim/emacs? My question is similar to this one: Time to drop Emacs and vi? No one had a suggestion, which surprises me. I would have thought that the core of a texteditor is very small and that people brew their own. Perhaps nobody wants to deal with supporting all the modes? Edit to clarify my question: Instead of writing modes and scripts I ask myself, why there is not a much lightweight project, which lets people custom the editor more directly? Vim has 365395 LOC (C lines all included), Emacs 1.5 million LOC. Why is there a project with say 50k LOC, which is the core, why people can use more freely? Perhaps there is such project, I haven't looked very far. I thought about putting together modules from Vim myself and experimenting with some ideas. The core of editing shouldn't be more than 10k? Vim has a lot optimizations which is really an overkill nowadays. Basically I'm looking for a code base for my own editor and Vi/Emacs are I believe not intended to be used in this way. Bill Joy said the following about vi. http://web.cecs.pdx.edu/~kirkenda/joy84.html The fundamental problem with vi is that it doesn't have a mouse and therefore you've got all these commands. In some sense, its backwards from the kind of thing you'd get from a mouse-oriented thing. I think multiple levels of undo would be wonderful, too. But fundamentally, vi is still ed inside. You can't really fool it. Its like one of those pinatas - things that have candy inside but has layer after layer of paper mache on top. It doesn't really have a unified concept. I think if I were going to go back - I wouldn't go back, but start over again.

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• iOS app with a lot of text

  - by rdurand

  I just asked a question on StackOverflow, but I'm thinking that a part of it belongs here, as questions about design pattern are welcomed by the faq. Here is my situation. I have developed almost completely a native iOS app. The last section I need to implement is all the rules of a sport, so that's a lot of text. It has one main level of sections, divided in subsections, containing a lot of structured text (paragraphs, a few pictures, bulleted/numbered lists, tables). I have absolutely no problem with coding, I'm just looking for advice to improve and make the best design pattern possible for my app. My first shot (the last one so far) was a UITableViewController containing the sections, sending the user to another UITableViewController with the subsections of the selected section, and then one strange last UITableViewController where the cells contain UITextViews, sections header help structure the content, etc. What I would like is your advice on how to improve the structure of this section. I'm perfectly ready to destroy/rebuild the whole thing, I'm really lost in my design here.. As I said on SO, I've began to implement a UIWebView in a UIViewController, showing a html page with JQuery Mobile to display the content, and it's fine. My question is more about the 2 views taking the user to that content. I used UITableViewControllers because that's what seemed the most appropriate for a structured hierarchy like this one. But that doesn't seem like the best solution in term of user experience.. What structure / "view-flow" / kind of presentation would you try to implement in my situation? As always, any help would be greatly appreciated! Just so you can understand better the hierarchy, with a simple example : -----> Section 1 -----> SubSection 1.1 -----> Content | -----> SubSection 1.2 -----> Content | -----> SubSection 1.3 -----> Content | | | UINavigationController -------> Section 2 -----> SubSection 2.1 -----> Content | -----> SubSection 2.2 -----> Content | -----> SubSection 2.3 -----> Content | -----> SubSection 2.4 -----> Content | -----> SubSection 2.5 -----> Content | -----> Section 3 -----> SubSection 3.1 -----> Content -----> SubSection 3.2 -----> Content |------------------| |--------------------| |-------------| 1 UITableViewController 3 UITableViewControllers 10 UIViewControllers (3 rows) (with different with a UIWebView number of rows)

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• HTML5 article tag application for the iPad

  - by dspencer

  I've used article tags on websites. My understanding and practice is to use the article tag for publication content. I always use HTML/HTML5 tags as their intended purposes and not at will. Recently, I've seen an HTML template that uses the article tag for the non-publication page content such as the content of an About Us page or any other generic page. I asked the why it was used this way and the (vague) explanation was that it had to do with the way the iPad read the tag. Is this true?

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• Best approach for tracking dependent state

  - by Pace

  Let's pretend I work on a project tracking application. The application is a database backed, server hosted, web application. In this application there are Projects which have many Activities which have many Tasks. A Task has two date fields an originalDueDate and a projectedDueDate. In addition, there are dynamic fields on the Activities and the Projects which indicate whether the Activity or Project is behind schedule based on the projected due dates of the child tasks and various other variables such as remaining buffer time, etc. There are a number of things that can cause the projectedDueDate to change. For example, an employee working on the project may (via a server request) enter in a shipping delay. Alternatively, a site may (via a server request) enter in an unexpected closure. When any of these things occur I need to not only update the projectedDueDate of the Task but also trigger the corresponding Project and Activity to update as well. What is the best way to do this? I've thought of the observer pattern but I don't keep a single copy of all these objects in memory. When a request comes in, I query the Task in from the database, at that point there is no associated Activity in memory that would be a listener. I could remove the ability to query for Tasks and force the application to query first by Project, then by Activity (in context of Project), then by task (in context of Activity) adding the observer relationships at each step but I'm not sure if that is the best way. I could setup a database event listening system so when a Task modified event is dispatched I have a handler which queries for the Activity at that point. I could simply setup a two-way relationship between Task and Activity so that the Task knows about the parent Activity and when the Task updates his state the Task grabs his parent and updates state. Right now I'm stuck considering all the options and am wondering if any single approach (doesn't have to be a listed approach) is jumping out at others as the best approach.

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• Writing and Understanding code

  - by Kitex

  I can write code. I can read code but I can't implement good code. How to develop deep understanding of any framework or stuff that we are working on? Is it looking into documentation and working on it? I have seen in this form that people that have great understanding of things they are working on. How is this possible? How to not scrape on the surface only? How to manage time vs learning vs productivity?

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• How to structure reading of commands given at a(n interactive) CLI prompt?

  - by Anto

  Let's say I have a program called theprogram (the marketing team was on strike when the product was to be named). I start that program by typing, perhaps not surprisingly, the program name as a command into a command prompt. After that, I get into a loop (from the users standpoint, an interactive command-line prompt), where one command will be read from the user, and depending on what command was given, the program will execute some instructions. I have been doing something like the following (in C-like pseudocode): main_loop{ in=read_input(); if(in=="command 1") do_something(); else if(in=="command 2") do_something_else(); ... } (In a real program, I would probably encapsulate more things into different procedures, this is just an example.) This works well for a small amount of commands, but let's say you have 100, 1000 or even 10 000 of them (the manual would be huge!). It is clearly a bad idea to have 10 000 ifs and else ifs after each other, for instance, the program would be hard to read, hard to maintain, contain a lot of boilerplate code... Yeah, you don't want to do that, so what approach would you recommend me to use (I will probably never use 10 000 commands in a program, but the solution should, at least preferably, be able to scale to that kind of massive (?) problems. The solution doesn't have to allow for arguments to the commands)?

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• Guidelines or Design pattern to develop configurable software

  - by Rumit Parakhiya

  I want to develop an application which would have it's own framework, using which developer can implement functionality very easily. Developer shouldn't have to code for each and every page or report. But, he can do it very easily by just configuring it using the framework provided. Some nice examples of it is SAP and Tally. They have got their own framework, using which anybody having knowledge of it can customize or extend functionality of the product. But, as I am beginner in this direction, I don't have any idea about where to start. Can anybody point me to some design pattern which I can follow or some similar open source software which I can refer?

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• Is it a bad practice to have an interface to define constants?

  - by FabianB

  I am writing a set of junit test classes in java. There are several constants, for example strings that I will need in different test classes. I am thinking about an interface that defines them and every test class would implement it. The benefits I see there are: easy access to constants: "MY_CONSTANT" instead of "ThatClass.MY_CONSTANT" each constant defined only once Is this approach rather a good or bad practice? I feel like abusing the concept of interfaces a little bit. You can answer generally about interfaces/constants, but also about unit tests if there is something special about it.

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• Domain Model and Querying

  - by Tyrsius

  I am new to DDD, having worked only in Transaction-Script apps with an anemic model, or just Big Balls of Mud, so please forgive any terminology I abuse. I am trying to understand the proper separation between the domain model and the repository. What is the proper way to construct a domain object that is coming from a database, assuming the (incredibly simplified) need to query for objects by status (returns enumerable), or by ID. Should a factory be building the objects, exposing methods for GetByStatus() and GetByID(), using a DIed repository? Should a repository be called directly, knowing how to build a domain model from the DTO? Should the domain model have a constructor for get by ID, using a DIed repoistory to load the initial state, using some other (?) method for the list? I am not really sure what the best way would be, and this question has an answer advocating each one (these are certainly mutuallu exclusive).

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• What Design Pattern is separating transform converters

  - by RevMoon

  For converting a Java object model into XML I am using the following design: For different types of objects (e.g. primitive types, collections, null, etc.) I define each its own converter, which acts appropriate with respect to the given type. This way it can easily extended without adding code to a huge if-else-then construct. The converters are chosen by a method which tests whether the object is convertable at all and by using a priority ordering. The priority ordering is important so let's say a List is not converted by the POJO converter, even though it is convertable as such it would be more appropriate to use the collection converter. What design pattern is that? I can only think of a similarity to the command pattern.

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• How to implement string matching based on a pattern

  - by Vincent Rischmann

  I was asked to build a tool that can identify if a string match a pattern. Example: {1:20} stuff t(x) {a,b,c} would match: 1 stuff tx a 20 stuff t c It is a sort of regex but with a different syntax Parentheses indicate an optional value {1:20} is a interval; I will have to check if the token is a number and if it is between 1 and 20 {a,b,c} is just an enumeration; it can be either a or b or c Right now I implemented this with a regex, and the interval stuff was a pain to do. On my own time I tried implementing some kind of matcher by hand, but it turns out it's not that easy to do. By experimenting I ended up with a function that generates a state table from the pattern and a state machine. It worked well until I tried to implement the optional value, and I got stuck and how to generate the state table. After that I searched how I could do this, and that led me to stuff like LL parser, LALR parser, recursive-descent parser, context-free grammars, etc. I never studied any of this so it's hard to know what is relevant here, but I think this is what I need: A grammar A parser which generates states from the grammar and a pattern A state machine to see if a string match the states So my first question is: Is this right ? And second question, what do you recommend I read/study to be able to implement this ?

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• Should I be concerned that I can't program very fast without Google? [closed]

  - by seth

  Possible Duplicate: Google is good or bad for programmer? I'm currently in college to be a software engineer, and one of the main principles taught to us is how to learn for ourselves, and how to search the web when we have a doubt. This leads to a proactive attitude - when I need something, I go get it. Recently, I started wondering how much development would I be able to do without internet access and the answer bugged me quite a bit. I know the concept of the languages and how to use them, but I was amazed by how "slow" things were without having the Google to help in the development. Most of the problems I have are related to specific syntax. For example, reading and writing to a file in Java. I have done this about a dozen times in my life, yet every time I need to do it, I end up googling "read file java" and refreshing my memory. I completely understand the code and fully understand what it does, but I am sure that without Google it would take me a few tries to get the code correct. Is this normal? Should I be worried and try to change something in my programming behaviour?

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