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• Upstart: How does rc job work / order of (contradicting) "start on ..." and "stop on ..." stanzas

  - by Binarus

  Hi, I just can't understand how Upstart's rc job definition in Natty 11.04 works. To illustrate the problem, here is the definition (empty lines and comments are left out): start on runlevel [0123456] stop on runlevel [!$RUNLEVEL] export RUNLEVEL export PREVLEVEL console output env INIT_VERBOSE task exec /etc/init.d/rc $RUNLEVEL Let's suppose we currently are in runlevel 2 and the rc job is stopped (that is exactly the situation after booting my box and logging in via SSH). Now, let's assume that the system switches to runlevel 3, for example due to a command like "telinit 3" given by root. What will happen to the rc job? Obviously, the rc job will be started since it is currently stopped and the event runlevel 3 is matching the start events. But from now on, things are unclear to me: According to the manual $RUNLEVEL evaluates to the new runlevel when the job is started (that means 3 in our example). Therefore, the next stanza "stop on runlevel [!$RUNLEVEL]" translates to "stop on runlevel [!3]"; that means we have a first stanza which will trigger the job, but the second stanza will never stop the job and seems to be useless. Since I know that the Ubuntu / Upstart people won't do useless things, I must be heavily misunderstanding something. I would be grateful for any explanation. While trying to understand this, an additional question came to my mind. If I had contradicting start and stop triggers, for example start on foo stop on foo what would happen? I swear I never will do that, but I am nevertheless very interested in how Upstart handles that on the theoretical level. Thank you very much! Editing the question as a reaction on geekosaur's first answer: I can see the parallelism, but it is not that easy (at least, not to me). Let's assume the job aurrently is still running, and a new runlevel event comes in (of course, the new runlevel is different from the current one). Then, the following should happen: 1) The job is single instance. That means that "start on ..." won't be triggered since the job is currently running; $RUNLEVEL is not touched. 2) "stop on ..." will be triggered since the new runlevel is different from $RUNLEVEL, so the job will be aborted. 3) Now, the job is stopped and waiting. I can't see how it is restarted with the new runlevel. AFAIK, initctl emits events only once, so "start on ..." won't be triggered and the new runlevel won't be entered. I know that I still misunderstanding something, and I am grateful for explanations. Thank you very much!

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• OS X is based on the codex Gigas the devils bible: Android OS n 4.4 Dio Ra Egyptian deity why is that?

  - by user215250

  GUESS WHO? The Internet and all computers are based on a mathematical number system that seems to be 3, 4, 6, 8 and 10. The HTTP is 888P and UTF-8 and Windows 8 and 8 gigas of RAM(88) on a 64biTOS X-10 or Aten(satan) why is it allowed to be so evil and who all knows about it? Is this activity illegal and should I sew these companies for being involved in satanic practices? iC3 iC3 iC3 I do see XP (X) Chi and (P) Rho a monogram and symbol for Christ, consisting of the superimposed Greek letters. The X is ten, The X code, OS X(O Satan) and codex The Gigas the Devil bible and the P is Payne, The House of Payne in which God dwells. Windows 8, Google Android and Apples OS X are the foundation on which we operarte on the Internet and our Mobiles devices. What is it that these 3 companies have chosen to base their OS’s on such evil? Windows 8 is windows hate H8, HH and H8. Said to be the Devil. Google’s (UGLE) M the Masonic M behind Android OS.in 4.4 is Dio (R) DNA O Sin and 44 is the Devils name in Twain’s The Mysterious Stranger. Apple’s evil (i) OS X (ou-es-ten) O Satan them all beat (B8) considering Apple put their first product on the market for $666.66. The Holy Grail of computers they say. Your Excellency, Lord and King OS2 Eisus Uni Peg Unix: The Unicorn Pegasus Jesus Christ

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• Why implement DB connection pointer object as a reference counting pointer? (C++)

  - by DVK

  At our company one of the core C++ classes (Database connection pointer) is implemented as a reference counting pointer. To be clear, the objects are NOT DB connections themselves, but pointers to a DB connection object. The library is very old, and nobody who designed is around anymore. So far, nether I, nor any C++ experts in the company that I asked have come up with a good reason for why this particular design was chosen. Any ideas? It is introducing some problems (partially due to awful reference pointer implementation used), and I'm trying to understand if this design actually has some deep underlying reasons? The usage pattern these days seems to be that the DB connection pointer object is returned by a DB connection manager class, and it's somewhat unclear whether DB connection pointers were designed to be able to be used independently of DB connection manager.

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• Plan variable and call dependencies

  - by Gerenuk

  I'd like to write down the design of my program to understand the dependencies and calls better. I know there are class diagrams which show inheritance and attribute variables. However I'd also like to document the input parameters to method functions and in particular which calls the methods function executes inside (e.g. on the input parameters). Also sometimes it might be useful to show how actual objects are connected (if there is a standard structure). This way I can have a better understanding of the modules and design before starting to program. Can you suggest a method to do this software design? It should be one-to-one to programming code structure so that I really notice all quirks beforehand (instead of high-level design where thing are hard to implement without further work). Maybe some special diagram or tool or a combination? It is static dependency and call design rather than time dependent execution monitoring. (I use Python if you have any specialized recommendations).

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• Sending object C from class A to class B

  - by user278618

  Hi, I can't figure out how to design classes in my system. In classA I create object selenium (it simulates user actions at website). In this ClassA I create another objects like SearchScreen, Payment_Screen and Summary_Screen. # -*- coding: utf-8 -*- from selenium import selenium import unittest, time, re class OurSiteTestCases(unittest.TestCase): def setUp(self): self.verificationErrors = [] self.selenium = selenium("localhost", 5555, "*chrome", "http://www.someaddress.com/") time.sleep(5) self.selenium.start() def test_buy_coffee(self): sel = self.selenium sel.open('/') sel.window_maximize() search_screen=SearchScreen(self.selenium) search_screen.choose('lavazza') payment_screen=PaymentScreen(self.selenium) payment_screen.fill_test_data() summary_screen=SummaryScreen(selenium) summary_screen.accept() def tearDown(self): self.selenium.stop() self.assertEqual([], self.verificationErrors) if __name__ == "__main__": unittest.main() It's example SearchScreen module: class SearchScreen: def __init__(self,selenium): self.selenium=selenium def search(self): self.selenium.click('css=button.search') I want to know if there is anything ok with a design of those classes?

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• Writing Great Software

  - by 01010011

  Hi, I'm currently reading Head First's Object Oriented Analysis and Design. The book states that to write great software (i.e. software that is well-designed, well-coded, easy to maintain, reuse, and extend) you need to do three things: Firstly, make sure the software does everything the customer wants it to do Once step 1 is completed, apply Object Oriented principles and techniques to eliminate any duplicate code that might have slipped in Once steps 1 and 2 are complete, then apply design patterns to make sure the software is maintainable and reusable for years to come. My question is, do you follow these steps when developing great software? If not, what steps do you usually follow inorder to ensure it's well designed, well-coded, easy to maintain, reuse and extend?

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• What is the right way to implement communication between java objects?

  - by imoschak

  I'm working on an academic project which simulates a rather large queuing procedure in java. The core of the simulator rests within one package where there exist 8 classes, each one implementing a single concept. Every class in the project follows SRP. These classes encapsulate the behavior of the simulator and inter-connect every other class in the project. The problem that has arisen is that most of these 8 classes are, as is logical i think, tightly coupled and each one has to have working knowledge of every other class in this package in order to be able to call methods from it when needed. The application needs only one instance of each class so it might be better to create static fields for each class in a new class and use that to make calls -instead of preserving a reference in each class for every other class in the package (which I'm certain that is incorrect)-, but is this considered a correct design solution? or is there a design pattern maybe that better suits my needs?

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• The right way to implement communication between java objects

  - by imoschak

  I'm working on an academic project which simulates a rather large queuing procedure in java. The core of the simulator rests within one package where there exist 8 classes each one implementing a single concept. Every class in the project follows SRP. These classes encapsulate the behavior of the simulator and inter-connect every other class in the project. The problem that I has arisen is that most of these 8 classes are, as is logical i think, tightly coupled and each one has to have working knowledge of every other class in this package in order to be able to call methods from it when needed. The application needs only one instance of each class so it might be better to create static fields for each class in a new class and use that to make calls -instead of preserving a reference in each class for every other class in the package (which I'm certain that is incorrect)-, but is this considered a correct design solution? or is there a design pattern maybe that better suits my needs?

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• DATE function does not support all the dates in DAX by design #powerpivot #tabular #dax

  - by Marco Russo (SQLBI)

  The DATE function in DAX has this simple syntax: DATE( <year>, <month>, <day> ) If you are like me, you never read the BOL notes that says in a clear way that it supports dates beginning with March 1, 1900. In fact, I was wrongly assuming that it would have supported any date that can be represented in a Date data type in Data Models, so all the dates beginning with January 1, 1900. The funny thing is that in some of the BOL documentation you will find that Date data type supports dates after March 1, 1900 (which seems not including that date, but this is a detail…). But we should not digress. The real issue is that if you try to call the DATE function passing values between January 1 and February 28, 1900, you will see a different day as a result. evaluate row ( "x", DATE( 1900, 1, 1 ) ) -- return WRONG result -- [x] 12/31/1899 12:00:00 AM   evaluate row ( "x", DATE( 1901, 2, 29 ) ) -- return WRONG result -- [x] 2/28/1900 12:00:00 AM   evaluate row ( "x", DATE( 1900, 3, 1 ) ) -- return CORRECT result -- [x] 3/1/1900 12:00:00 AM As usual, this is not a bug. It is “by design”. The DATE function works in this way in Excel. And also in Excel it was “by design”. In this case the design is having the same bug of Lotus 1-2-3 that handled 1900 a leap year, even though it isn’t. The first release of Lotus 1-2-3 is dated 1983. I hope many of my readers are younger than that. I tried to open a bug in Connect. Please vote it. I would like if Microsoft changed this type of items from “by design” (as we can expect) to “by genetic disease”. Or by “historical respect”, in order to be more politically correct.

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• Oracle Fusion Applications Design Patterns Now Available

  - by Frank Nimphius

  "The Oracle Fusion Applications user experience design patterns are published! These new, reusable usability solutions and best-practices, which will join Oracle dashboard patterns and guidelines that are already available online, are used by Oracle to artfully bring to life a new standard in the user experience, or UX, of enterprise applications. Now, the Oracle applications development community can benefit from the science behind the Oracle Fusion Applications user experience, too.These Oracle Fusion Applications UX Design Patterns, or blueprints, enable Oracle applications developers and system implementers everywhere to leverage professional usability insight when [...]  designing exciting, new, highly usable applications -- in the cloud or on-premise.  Based on the Oracle Application Development Framework (ADF) components, the Oracle Fusion Applications patterns and guidelines are proven with real users and in the Applications UX usability labs, so you can get right to work coding productivity-enhancing designs that provide an advantage for your entire business.  What’s the best way to get started? We’ve made that easy, too. The Design Filter Tool (DeFT) selects the best pattern for your user type and task. Simply adapt your selection for your own task flow and content, and you’re on your way to a really great applications user experience. More Oracle applications design patterns and training are coming your way in the future. To provide feedback on the sets that are currently available, let us know in the comments section or use the contact form provided."

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• design in agile process

  - by ying

  Recently I had an interview with dev team in a company. The team uses agile + TDD. The code exercise implements a video rental store which generates statement to calc total rental fee for each type of video (new release, children, etc) for a customer. The existing code use object like: Statement to generate statement and calc fee where big switch statement sits to use enum to determine how to calc rental fee customer holds a list of rentals movie base class and derived class for each type of movie (NEW, CHILDREN, ACTION, etc) The code originally doesn't compile as the owner was assumed to be hit by a bus. So here is what I did: outlined the improvement over object model to have better responsibility for each class. use strategy pattern to replace switch statement and weave them in config But the team says it's waste of time because there is no requirement for it and UAT test suite works and is the only guideline goes into architecture decision. The underlying story is just to get pricing feature out and not saying anything about how to do it. So the discussion is focused on why should time be spent on refactor the switch statement. In my understanding, agile methodology doesn't mean zero design upfront and such code smell should be avoided at the beginning. Also any unit/UAT test suite won't detect such code smell, otherwise sonar, findbugs won't exist. Here I want to ask: is there such a thing called agile design in the agile methodology? Just like agile documentation. how to define agile design upfront? how to know enough is enough? In my understanding, ballpark architecture and data contract among components should be defined before/when starting project, not the details. Am I right? anyone can explain what the team is really looking for in this kind of setup? is it design aspect or agile aspect? how to implement minimum viable product concept in the agile process in the real world project? Is it must that you feel embarrassed to be MVP?

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• MVC repository pattern design decision

  - by bradjive

  I have an asp .net MVC application and recently started implementing the repository pattern with a service validation layer, much like this. I've been creating one repository/service for each model that I create. Is this overkill? Instead, should I create one repository/service for each logical business area that provides CRUD for many different models? To me, it seems like I'm either cluttering the project tree with many files or cluttering a class with many methods. 6 one way half dozen the other. Can you think of any good arguments either way?

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• OO design - car rental

  - by gkid123

  AnHow would you implement the following car hierarchy along with the accessor functions and a CarRental class which contains the container to store them? A car rental company wants to keep track of its cars. Each vehicle has a license plate and a brand. Currently the company has SUV and Sedans. SUV have an optional third row seat, sedan’s have an optional sport package. Each car can be queried to inquire the number of passengers it can carry.

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• Fiscal year handling strategies in database design

  - by Sapphire

  By fiscal year I mean all the data in the database (in all tables) that occurred in the particular year. Lets say that we are building an application that allows user to choose from different years. What way of implementing this would you prefer, and why: Separate fiscal year data based on multiple separate database instances (for example, on every fiscal year start you could create a new instance with no data) Have everything in one database, but with logic that automatically separates records from different years. Personally, I have "seen" both methods, and I would choose the second. The only argument I can think of for the first method is to have less records in case that these are really big databases - but still, you could "archive" old records by joining them in summaries or by some other way. What do you think?

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• Database design for summarized data

  - by holden

  I have a new table I'm going to add to a bunch of other summarized data, basically to take some of the load off by calculating weekly avgs. My question is whether I would be better off with one model over the other. One model with days of the week as a column with an additional column for price or another model as a series of fields for the DOW each taking a price. I'd like to know which would save me in speed and/or headaches? Or at least the trade off. IE. ID OBJECT_ID MON TUE WED THU FRI SAT SUN SOURCE OR ID OBJECT_ID DAYOFWEEK PRICE SOURCE

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• XNA Class Design with Structs

  - by Nate Bross

  I'm wondering how you'd recommend designin a class, given the fact that XNA Framework uses Struct all over the place? For example, a spite class, which may require a Vector2 and a Rectangle (both defined as Struct) to be accessed outside of the class. The issue come in when you try to write code like this: class Item { public Vetor2 Position {get; set;} public Item() { Position = new Vector2(5,5); } } Item i = new Item(); i.Positon.X = 20; // fails with error 'Cannot modify the return value of Item because it is not a variable.' // you must write code like this var pos = i.Position; pos.X++; i.Position = pos; The second option compiles and works, but it is just butt ugly. Is there a better way?

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• Web-design / UI advice

  - by Damian

  I'm working on a website on a Fmylife style. Now the homepage is the page showing the list of the latest posts. But I think there is a problem with that: The most "interesting" page is the one showing the top posts of the last days, but that page has very few visits compared to the main page. I suppose that's only because the main page is the "default" one. So, I've been thinking of making a home page that shows no posts (only one at the top of the page) but 4 big buttons showing the visitors what are the options to browse the content. But I'm also afraid that most users will not click any option and leave the site having seen no posts. So I don't know what to do. Obviously I have no idea of what will be good from a usability/efficiency point of view. Maybe a mix of the two options will be the best, but I don't know how to mix them. Any advice or idea will be greatly appreciated. The current home page looks like this: http://soquestion.latest.secretsapp.appspot.com/latest The new home page would look like this: http://soquestion.latest.secretsapp.appspot.com/

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• Fluent interface design and code smell

  - by Jiho Han

  public class StepClause { public NamedStepClause Action1() {} public NamedStepClause Action2() {} } public class NamedStepClause : StepClause { public StepClause Step(string name) {} } Basically, I want to be able to do something like this: var workflow = new Workflow().Configure() .Action1() .Step("abc").Action2() .Action2() .Step("def").Action1(); So, some "steps" are named and some are not. The thing I do not like is that the StepClause has knowledge of its derived class NamedStepClause. I tried a couple of things to make this sit better with me. I tried to move things out to interfaces but then the problem just moved from the concrete to the interfaces - INamedStepClause still need to derive from IStepClause and IStepClause needs to return INamedStepClause to be able to call Step(). I could also make Step() part of a completely separate type. Then we do not have this problem and we'd have: var workflow = new Workflow().Configure() .Step().Action1() .Step("abc").Action2() .Step().Action2() .Step("def").Action1(); Which is ok but I'd like to make the step-naming optional if possible. I found this other post on SO here which looks interesting and promising. What are your opinions? I'd think the original solution is completely unacceptable or is it? By the way, those action methods will take predicates and functors and I don't think I want to take an additional parameter for naming the step there. The point of it all is, for me, is to only define these action methods in one place and one place only. So the solutions from the referenced link using generics and extension methods seem to be the best approaches so far.

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• MVVM Good Design. DataSet or a RowViewModel

  - by LnDCobra

  I have just started learning MVVM and having a dilemna. If I have a a main ViewModel and inside this model I have a number of datasets. Now should I be creating a new ViewModel for each row inside the dataset? Or expose the DataSet itself as a DependencyProperty? For now the dataset has about 20 rows inside it, and the thought of iterating through each row to create a ViewModel binding to each row.... might not be the best option for performance reasons and memory reasons in the future, like when there are 1000+ rows. Should I still go ahead and create a RowViewModel and iterate through the dataset? And have an ObservableCollection of it or just expose the dataset? Any help would be greatly appreciated.

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• Value vs Entity objects (Domain Driven Design)

  - by StackUnderflow

  I have just started reading DDD. I am unable to completely grasp the concept of Entity vs Value objects.. Can someone please explain the problems (maintainability, performance.. etc) a system could face when a Value object is designed as a Entity object. Example would be great... Thanks

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• Language Design: Combining Gotos and Functions

  - by sub

  I'm designing and currently rethinking a low-level interpreted programming language with similarities to assembler. I very soon came across the functions/loops/gotos decision problem and thought that while loops like while and for would be too high-level and unfitting, gotos would be too low level, unmaintainable and generally evil again. Functions like you know them from most languages that have return values and arguments aren't fitting in the language's concept either. So I tried to figure out something between a function and a goto which is capable of Recursion Efficient loops After some thinking I came up with the idea of subroutines: They have a beginning and an end like a function They have a name but no arguments like a goto You can go into one with jump and go out of it again before its end with return (doesn't give back any result, only stops the subroutine) Handled just like normal code - Global scope like goto So I wanted to know: Is the idea above good? What are the (dis)advantages? Would there be a better combination of function and goto or even a completely new idea?

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• Another design-related C++ question

  - by Kotti

  Hi! I am trying to find some optimal solutions in C++ coding patterns, and this is one of my game engine - related questions. Take a look at the game object declaration (I removed almost everything, that has no connection with the question). // Abstract representation of a game object class Object : public Entity, IRenderable, ISerializable { // Object parameters // Other not really important stuff public: // @note Rendering template will never change while // the object 'lives' Object(RenderTemplate& render_template, /* params */) : /*...*/ { } private: // Object rendering template RenderTemplate render_template; public: /** * Default object render method * Draws rendering template data at (X, Y) with (Width, Height) dimensions * * @note If no appropriate rendering method overload is specified * for any derived class, this method is called * * @param Backend & b * @return void * @see */ virtual void Render(Backend& backend) const { // Render sprite from object's // rendering template structure backend.RenderFromTemplate( render_template, x, y, width, height ); } }; Here is also the IRenderable interface declaration: // Objects that can be rendered interface IRenderable { /** * Abstract method to render current object * * @param Backend & b * @return void * @see */ virtual void Render(Backend& b) const = 0; } and a sample of a real object that is derived from Object (with severe simplifications :) // Ball object class Ball : public Object { // Ball params public: virtual void Render(Backend& b) const { b.RenderEllipse(/*params*/); } }; What I wanted to get is the ability to have some sort of standard function, that would draw sprite for an object (this is Object::Render) if there is no appropriate overload. So, one can have objects without Render(...) method, and if you try to render them, this default sprite-rendering stuff is invoked. And, one can have specialized objects, that define their own way of being rendered. I think, this way of doing things is quite good, but what I can't figure out - is there any way to split the objects' "normal" methods (like Resize(...) or Rotate(...)) implementation from their rendering implementation? Because if everything is done the way described earlier, a common .cpp file, that implements any type of object would generally mix the Resize(...), etc methods implementation and this virtual Render(...) method and this seems to be a mess. I actually want to have rendering procedures for the objects in one place and their "logic implementation" - in another. Is there a way this can be done (maybe alternative pattern or trick or hint) or this is where all this polymorphic and virtual stuff sucks in terms of code placement?

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• Python class design - Splitting up big classes into multiple ones to group functionality

  - by Ivo Wetzel

  OK I've got 2 really big classes 1k lines each that I currently have split up into multiple ones. They then get recombined using multiple inheritance. Now I'm wondering, if there is any cleaner/better more pythonic way of doing this. Completely factoring them out would result in endless amounts of self.otherself.do_something calls, which I don't think is the way it should be done. To make things clear here's what it currently looks like: from gui_events import GUIEvents # event handlers from gui_helpers import GUIHelpers # helper methods that don't directly modify the GUI # GUI.py class GUI(gtk.Window, GUIEvents, GUIHelpers): # general stuff here stuff here One problem that is result of this is Pylint complaining giving me trillions of "init not called" / "undefined attribute" / "attribute accessed before definition" warnings.

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• Query Object Pattern (Design Pattern)

  - by The Elite Gentleman

  Hi Guys, I need to implement a Query Object Pattern in Java for my customizable search interface (of a webapp I'm writing). Does anybody know where I can get an example/tutorial of Query Object Pattern (Martin Fowler's QoP)? Thanks in Advance ADDITION How to add a Query Pattern to an existing DAO pattern?

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• Design by contract: predict methods needed, discipline yourself and deal with code that comes to min

  - by fireeyedboy

  I like the idea of designing by contract a lot (at least, as far as I understand the principal). I believe it means you define intefaces first before you start implementing actual code, right? However, from my limited experience (3 OOP years now) I usually can't resist the urge to start coding pretty early, for several reasons: because my limited experience has shown me I am unable to predict what methods I will be needing in the interface, so I might as well start coding right away. or because I am simply too impatient to write out the whole interfaces first. or when I do try it, I still wind up implementing bits of code already, because I fear I might forget this or that imporant bit of code, that springs to mind when I am designing the interfaces. As you see, especially with the last two points, this leads to a very disorderly way of doing thing. Tasks get mixed up. I should draw a clear line between designing interfaces and actual coding. If you, unlike me, are a good/disciplined planner, as intended above, how do you: ...know the majority of methods you will be needing up front so well? Especially if it's components that implement stuff you are not familiar with yet. ...keep yourself from resisting the urge to start coding right away? ...deal with code that comes to mind when you are designing the intefaces?

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