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  • Good design cannot be over-design

    - by ??? Shengyuan Lu
    Many engineers intend to design software to build "flexible" system in which many design patterns and interfaces there. Eventually too many interfaces and complex inheritances mess up the system. In most cases I think the improper design caused the mess, rather than not over-design. If design is reasonable, it's hard to be over. Alternatively, If we don't have enough skill to achieve flexible design, we choose to plain and practical design. What's your opinion about my understanding?

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  • design pattern advice: graph -> computation

    - by csetzkorn
    I have a domain model, persisted in a database, which represents a graph. A graph consists of nodes (e.g. NodeTypeA, NodeTypeB) which are connected via branches. The two generic elements (nodes and branches will have properties). A graph will be sent to a computation engine. To perform computations the engine has to be initialised like so (simplified pseudo code): Engine Engine = new Engine() ; Object ID1 = Engine.AddNodeTypeA(TypeA.Property1, TypeA.Property2, …, TypeA.Propertyn); Object ID2 = Engine.AddNodeTypeB(TypeB.Property1, TypeB.Property2, …, TypeB.Propertyn); Engine.AddBranch(ID1,ID2); Finally the computation is performed like this: Engine.DoSomeComputation(); I am just wondering, if there are any relevant design patterns out there, which help to achieve the above using good design principles. I hope this makes sense. Any feedback would be very much appreciated.

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  • Evolution email forgets all settings after reboot

    - by jbrendel
    My Evolution email client keeps forgetting all settings after a reboot or even a logout/login! Please help! I have recently installed Ubuntu 12.04 on a new laptop. To move my Evolution settings and email over to the new machine, I selected "backup", which creates a single tar.gz archive of all Evolution settings and mail. I copied the file to the new computer, started Evolution which presented me with the startup assistant. I selected 'restore from backup', pointed at the tar.gz file and all was beautifully restored. All seemed to work just fine. However, after a reboot I noticed that Evolution seems to have forgotten all settings: I get the startup assistant again when I start Evolution. I checked that the .conf/evolution and .local/share/evolution directories were still present, yet, none of that seemed to matter, it wanted me to restore from a backup again. The version of Ubuntu (12.04) and Evolution (3.2.3) are the same on the old and new laptop. Just stopping and restarting Evolution does not cause this problem. Even if I manually kill all Evolution related processes, the settings will be remembered and it can start up no problem. The problem only happens on logout/login or reboot. Any help is greatly appreciated! Thank you very much!

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  • How should I design a correct OO design in case of a Business-logic wide operation

    - by Mithir
    EDIT: Maybe I should ask the question in a different way. in light of ammoQ's comment, I realize that I've done something like suggested which is kind of a fix and it is fine by me. But I still want to learn for the future, so that if I develop new code for operations similar to this, I can design it correctly from the start. So, if I got the following characteristics: The relevant input is composed from data which is connected to several different business objects All the input data is validated and cross-checked Attempts are made in order to insert the data to the DB All this is just a single operation from Business side prospective, meaning all of the cross checking and validations are just side effects. I can't think of any other way but some sort of Operator/Coordinator kind of Object which activates the entire procedure, but then I fall into a Functional-Decomposition kind of code. so is there a better way in doing this? Original Question In our system we have many complex operations which involve many validations and DB activities. One of the main Business functionality could have been designed better. In short, there were no separation of layers, and the code would only work from the scenario in which it was first designed at, and now there were more scenarios (like requests from an API or from other devices) So I had to redesign. I found myself moving all the DB code to objects which acts like Business to DB objects, and I've put all the business logic in an Operator kind of a class, which I've implemented like this: First, I created an object which will hold all the information needed for the operation let's call it InformationObject. Then I created an OperatorObject which will take the InformationObject as a parameter and act on it. The OperatorObject should activate different objects and validate or check for existence or any scenario in which the business logic is compromised and then make the operation according to the information on the InformationObject. So my question is - Is this kind of implementation correct? PS, this Operator only works on a single Business-wise Operation.

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  • How to port email from evolution to thunderbird?

    - by jim
    I updated ubuntu to 11.10 using the update notification. I am also switching from Xubuntu to ubuntu - gnome interface. I have been using evolution for years and would like to port the emails to thunderbird. I have looked at the similar questions with no luck and the thunderbird help on manually importing. Most of these assume that the evolution file structure is similar to the evolution file structure. When I set up thunderbird it seems to have imported the contacts from evolution (and actually removed them from evolution. However no mail got transferred. I found the evolution mail in ~/.local/share/evolution/mail/local . this has folders.db and 3 directories - cur ,tmp, and new. then there are the hidden files and directories. Each directory has three related files with extensions .cmeta, .ibex.index, and .ibex.index.data. Then all the directories had files that seem to contain the individual messages. I have not looked at rhyme or reason to the file numbering/naming scheme. is there a nice way to import these files?

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  • Why is Evolution the default mail/calendar package?

    - by Android Eve
    Why is Evolution the default mail/calendar package that comes with Ubuntu? Why not Thunderbird + Lightning? Are there any features in Evolution that are not available in Thunderbird + Lightning? Can I use the Evolution database via a Samba network share, on a Windows XP or 7 client, just like I can do with Thunderbird? What happens if I uninstall Evolution from my 10.04 system? Will I lose any integrated functionality built into the system?

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  • How to import Evolution application data from home folder backup

    - by Wolter Hellmund
    I had many folders and filters and mail in general in Evolution on my previous Ubuntu install, which I thought would be available for me for I had backed up my home directory. I have copied now Evolution related folders to my new home directory, and Evolution is not showing either the folders I had or any of the filters. To be more precise, I have copied the mail folder to ~/.config/evolution/ but that hasn't changed anything, as I said.

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  • problems using evolution Contacts with an DavMail LDAP Proxy for an Exchange server

    - by WegDamit
    i have an davmail proxy setup for accessing an Exchnage 200x server. eMail works fine in Thunderbird and Evolution (IMAP...) LDAP Contacts/Address Book works in TB, but not on Evolution. It seems that Evolution does not try the given credentials. The entered LDAP Auth is never send to the DaVMail Proxy. anonymous access to ou=people forbidden davmail.ui.tray.DavGatewayTray.displayMessage(DavGatewayTray.java:96) It the same conf for TB and in Evolution so i looks like an issue with Evolution to me. Does it take some different cponfig than TB for the credentials? Anybody got this conf workin an can give me some hints? Thanks, WegDamit

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  • Loose Coupling in Object Oriented Design

    - by m3th0dman
    I am trying to learn GRASP and I found this explained (here on page 3) about Low Coupling and I was very surprised when I found this: Consider the method addTrack for an Album class, two possible methods are: addTrack( Track t ) and addTrack( int no, String title, double duration ) Which method reduces coupling? The second one does, since the class using the Album class does not have to know a Track class. In general, parameters to methods should use base types (int, char ...) and classes from the java.* packages. I tend to diasgree with this; I believe addTrack(Track t) is better than addTrack(int no, String title, double duration) due to various reasons: It is always better for a method to as fewer parameters as possible (according to Uncle Bob's Clean Code none or one preferably, 2 in some cases and 3 in special cases; more than 3 needs refactoring - these are of course recommendations not holly rules). If addTrack is a method of an interface, and the requirements need that a Track should have more information (say year or genre) then the interface needs to be changed and so that the method should supports another parameter. Encapsulation is broke; if addTrack is in an interface, then it should not know the internals of the Track. It is actually more coupled in the second way, with many parameters. Suppose the no parameter needs to be changed from int to long because there are more than MAX_INT tracks (or for whatever reason); then both the Track and the method need to be changed while if the method would be addTrack(Track track) only the Track would be changed. All the 4 arguments are actually connected with each other, and some of them are consequences from others. Which approach is better?

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  • Design suggestions needed to create a MathBuilder framework

    - by Darf Zon
    Let explain what I'm trying to create. I'm creating a framework, the idea is to provide base classes to generate a math problem. Why do I need this framework? Because at first time, I realized when I create a new math problem I always do the same steps. Configuration settings such range numbers. For example if I'm developing multiplications, in beginner level only generate the first number between 2-5 or in advanced level, the first number will be between 6- 9, for example. Generate problem method. All the time I need to invoke a method like this to generate the problem. This one receives the configuration settings and generate the number according to them. And generate the object with the respective data. Validate the problem. Sometimes the problem generated is not valid. For example, supposed I'm creating fractions in most simplified, if I receive 2/4, the program should detect that this is not valid and must generate another like this one, 1/4. Load the view. All of them, have a custom view (please watch below the images). All of the problems must know how to CHECK if the user result is correct. All of this problems has answers. Some of them just require one answer, anothers may require more than one, so I guess a way to maintain flexibility to the developer has all the answers he wanna used. At the beginning I started using PRISM. Generate modules for each math problem was the idea and load it in the main system. I guess are the most important things of this idea. Let me showing some problems which I create in a WPF standalone program. Here I have a math problem about areas. When I generate the problem a set to the view the object and it draw it. In beginner level, I set in the configuration settings that just load square types. But in advance level, can load triangles and squares randomly. In this another, generate a binary problem like addition, subtraction, multiplication or division. Above just generate a single problem. The idea of this is to show a test o quiz, I mean get a worksheet (this I call as a collection of problems) where the user can answer it. I hope gets the idea with my ugly drawing. How to load this math problems? As I said above, I started using PRISM, and each module contains a math problem kind. This is a snapshot of my first demo. Below show the modules loaded, and center the respective configurations or levels. Until momment, I have no idea to start creating this software. I just know that I need a question | problem class, response class, user class. But I get lost about what properties should have to contain in it. Please give a little hand of this framework. I put much effort on this question, so if any isn't clear, let me know to clarify it.

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  • Starting to create a MathBuilder framework, help to start creating the design

    - by Darf Zon
    Let explain what I'm trying to create. I'm creating a framework, the idea is to provide base classes to generate a math problem. Why do I need this framework? Because at first time, I realized when I create a new math problem I always do the same steps. Configuration settings such range numbers. For example if I'm developing multiplications, in beginner level only generate the first number between 2-5 or in advanced level, the first number will be between 6- 9, for example. Generate problem method. All the time I need to invoke a method like this to generate the problem. This one receives the configuration settings and generate the number according to them. And generate the object with the respective data. Validate the problem. Sometimes the problem generated is not valid. For example, supposed I'm creating fractions in most simplified, if I receive 2/4, the program should detect that this is not valid and must generate another like this one, 1/4. Load the view. All of them, have a custom view (please watch below the images). All of the problems must know how to CHECK if the user result is correct. All of this problems has answers. Some of them just require one answer, anothers may require more than one, so I guess a way to maintain flexibility to the developer has all the answers he wanna used. At the beginning I started using PRISM. Generate modules for each math problem was the idea and load it in the main system. I guess are the most important things of this idea. Let me showing some problems which I create in a WPF standalone program. Here I have a math problem about areas. When I generate the problem a set to the view the object and it draw it. In beginner level, I set in the configuration settings that just load square types. But in advance level, can load triangles and squares randomly. In this another, generate a binary problem like addition, subtraction, multiplication or division. Above just generate a single problem. The idea of this is to show a test o quiz, I mean get a worksheet (this I call as a collection of problems) where the user can answer it. I hope gets the idea with my ugly drawing. How to load this math problems? As I said above, I started using PRISM, and each module contains a math problem kind. This is a snapshot of my first demo. Below show the modules loaded, and center the respective configurations or levels. Until momment, I have no idea to start creating this software. I just know that I need a question | problem class, response class, user class. But I get lost about what properties should have to contain in it. Please give a little hand of this framework. I put much effort on this question, so if any isn't clear, let me know to clarify it.

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  • Accidental deletion of the Gmail (IMAP) Trash 'System Label' in Evolution

    - by user20635
    I am using 11.04 and Evolution 2.32.2 I accidentally deleted the Gmail (IMAP) Trash 'System Label' in Evolution. Because this is Gmail object and (not a label per say), it is not deletable in Gmail. Under my Gmail account settings, I have made sure that both, 'Show in Label List' and 'Show in IMAP' are checked. That being said, I cannot seem to restore this IMAP folder in Evolution. I deleted the affected mail account, re-created, restarted Evolution, and no change. Any thoughts? Thanks.

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  • Duplication in parallel inheritance hierarchies

    - by flamingpenguin
    Using an OO language with static typing (like Java), what are good ways to represent the following model invariant without large amounts of duplication. I have two (actually multiple) flavours of the same structure. Each flavour requires its own (unique to that flavour data) on each of the objects within that structure as well as some shared data. But within each instance of the aggregation only objects of one (the same) flavour are allowed. FooContainer can contain FooSources and FooDestinations and associations between the "Foo" objects BarContainer can contain BarSources and BarDestinations and associations between the "Bar" objects interface Container() { List<? extends Source> sources(); List<? extends Destination> destinations(); List<? extends Associations> associations(); } interface FooContainer() extends Container { List<? extends FooSource> sources(); List<? extends FooDestination> destinations(); List<? extends FooAssociations> associations(); } interface BarContainer() extends Container { List<? extends BarSource> sources(); List<? extends BarDestination> destinations(); List<? extends BarAssociations> associations(); } interface Source { String getSourceDetail1(); } interface FooSource extends Source { String getSourceDetail2(); } interface BarSource extends Source { String getSourceDetail3(); } interface Destination { String getDestinationDetail1(); } interface FooDestination extends Destination { String getDestinationDetail2(); } interface BarDestination extends Destination { String getDestinationDetail3(); } interface Association { Source getSource(); Destination getDestination(); } interface FooAssociation extends Association { FooSource getSource(); FooDestination getDestination(); String getFooAssociationDetail(); } interface BarAssociation extends Association { BarSource getSource(); BarDestination getDestination(); String getBarAssociationDetail(); }

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  • EVOLUTION: No such Calendar

    - by Dennis
    I am using a google calendar with evolution for quite a while now. I was never having any troubles. Just recently, I suppose just after an update, whenever I want to create a new event in evolution (for the just mentioned google calendar) I get the err message "No such calendar". When I dismiss changes an re-open evolution the entry has been added anyway. This is somewhat annoying. I googled, but haven't found anything yet which suggests that it not problem many people have!? Looking for help, maybe someone here knows an answer! I appreciate any suggestion! Cheers, Dennis

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  • Gmail address book in Evolution does not work

    - by wouter205
    I added my Gmail address book to evolution, but it gives my an error every time, even when choosing "use secure connection" in the address book options. The error is (I translated it on my own): unable to open address book. This is because you entered a wrong URI or the server is unavailable at the moment. Details: cannot open book: source already loaded! Sometimes, when I click the button 'reject error', it does load the address book but when I return to evolution after a while, it gives me the same error and sometimes I cannot load the address book. This is very annoying since I have to use evolution a lot.

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  • Evolution has no access to couchdb

    - by berkes
    Evolution gives the error "Cannot open addressbook". "We were unable to open this addressbook. This either means you have entered an incorrect URI, or the server is unreachable". "Details: Operation not permitted". (rough translation from Dutch). Enabling verbose logging in (desktop)couchdb tells me roughly the same: [info] [<0.7875.1>] 127.0.0.1 - - 'PUT' /contacts/ 400 [debug] [<0.7875.1>] httpd 400 error response: {"error":"invalid_consumer","reason":"Invalid consumer (key or signature method)."} It seems that evolution tries to fetch the contacts, then couchdb denies access, and then evolution fails to do a proper oauth. This is on Ubuntu 10.10, with its default dektopcouch 1.0.1. Any hints on where to start would be most appreciated :)

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  • Design patterns and multiple programming language

    - by Eduard Florinescu
    I am referring here to the design patterns found in the GOF book. First how I see it, there are a few peculiarities to design pattern and knowing multiple language knowledge, for example in Java you really need a singleton but in Python you can do without it you write a module, I saw somewhere a wiki trying to write all GOF patterns for JavaScript and the entries where empty, I guess because it might be a daunting task. If there is someone who is using design patterns and is programming in multiple programming languages supporting the OOP paradigm and can give me a hint on how should I approach design patterns that might help me in all languages I use(Java, JavaScript, Python, Ruby): Can I write good application without knowing exactly the GOF design patterns or I might need some of them which might be crucial and if yes which one, are they alternatives to GOF for specific languages, and should a programmer or a team make its own design patterns set?

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  • Design patterns and multiple programming languages

    - by Eduard Florinescu
    I am referring here to the design patterns found in the GOF book. First, how I see it, there are a few peculiarities to design pattern and knowing multiple languages, for example in Java you really need a singleton but in Python you can do without it you write a module, I saw somewhere a wiki trying to write all GOF patterns for JavaScript and all the entries were empty, I guess because it might be a daunting task to do that adaptation. If there is someone who is using design patterns and is programming multiple languages supporting the OOP paradigm and can give me a hint on how should I approach design patterns. An approach that might help me in all languages I use(Java, JavaScript, Python, Ruby): Can I write good application without knowing exactly the GOF design patterns or I might need just some of them which might be crucial and if yes which one, are there alternatives to GOF for specific languages, and should a programmer or a team make their own design patterns set?

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  • How to conciliate OOAD and Database Design?

    - by user1620696
    Recently I've studied about object oriented analysis and design and I liked a lot about it. In every place I've read people say that the idea is to start with the minimum set of requirements and go improving along the way, revisiting this each iteration and making it better as we contiuously develop and contact the customer interested in the software. In particular, one course from Lynda.com said a lot of that: we don't want to spend a lot of time planing everything upfront, we just want to have the minimum to get started and then improve this each iteration. Now, I've also seem a course from the same guy about database design, and there he says differently. He says that although when working with object orientation he likes the agile iterative approach, for database design we should really spend a lot of time planing things upfront instead of just going along the way with the minimum. But this confuses me a little. Indeed, the database will persist important data from our domain model and perhaps configurations of the software and so on. Now, if I'm going to continuously revist the analysis and design of the model, it seems the database design should change also. In the same way, if we plan all the database upfront it seems we are also planing all the model upfront, so the two ideas seems to be incompatible. I really like agile iterative approach, but I'm also looking at getting better design for the database also, so when working with agile iterative approach, how should we deal with the database design?

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  • Is the design notion of layers contrived?

    - by Bruce
    Hi all I'm reading through Eric Evans' awesome work, Domain-Driven Design. However, I can't help feeling that the 'layers' model is contrived. To expand on that statement, it seems as if it tries to shoe-horn various concepts into a specific, neat model, that of layers talking to each other. It seems to me that the layers model is too simplified to actually capture the way that (good) software works. To expand further: Evans says: "Partition a complex program into layers. Develop a design within each layer that is cohesive and that depends only on the layers below. Follow standard architectural patterns to provide loose coupling to the layers above." Maybe I'm misunderstanding what 'depends' means, but as far as I can see, it can either mean a) Class X (in the UI for example) has a reference to a concrete class Y (in the main application) or b) Class X has a reference to a class Y-ish object providing class Y-ish services (ie a reference held as an interface). If it means (a), then this is clearly a bad thing, since it defeats re-using the UI as a front-end to some other application that provides Y-ish functionality. But if it means (b), then how is the UI any more dependent on the application, than the application is dependent on the UI? Both are decoupled from each other as much as they can be while still talking to each other. Evans' layer model of dependencies going one way seems too neat. First, isn't it more accurate to say that each area of the design provides a module that is pretty much an island to itself, and that ideally all communication is through interfaces, in a contract-driven/responsibility-driven paradigm? (ie, the 'dependency only on lower layers' is contrived). Likewise with the domain layer talking to the database - the domain layer is as decoupled (through DAO etc) from the database as the database is from the domain layer. Neither is dependent on the other, both can be swapped out. Second, the idea of a conceptual straight line (as in from one layer to the next) is artificial - isn't there more a network of intercommunicating but separate modules, including external services, utility services and so on, branching off at different angles? Thanks all - hoping that your responses can clarify my understanding on this..

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  • software architecture (OO design) refresher course

    - by PeterT
    I am lead developer and team lead in a small RAD team. Deadlines are tight and we have to release often, which we do, and this is what keep the business happy. While we (the development team) are trying to maintain the quality of the code (clean and short methods), I can't help but notice that the overall quality of the OO design&architecture is getting worse over the time - the library we are working on is gradually reducing itself to a "bag of functions". Well, we try to use the design patterns, but since we don't really have much time for a design as such we are mostly using the creational ones. I have read Code Complete / Design Patterns (GOF & enterprise) / Progmatic Programmer / and many books from Effective XXX series. Should I re-read them again as I have read them a long time ago and forgotten quite a lot, or there are other / better OO design / software architeture books been published since then which I should definitely read? Any ideas, recommendations on how can I get the situation under control and start improving the architecture. The way I see it - I will start improving the architectural / design quality of software components I am working on and then will start helping other team members once I find what is working for me.

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  • Exchange with Evolution or any other mail client

    - by Oscar Godson
    I see other questions about this, no answers and no one with a completely similar question. I work for a place with an Exchange 2007 server. There is an http://owa.ourserver.com that is accessible from anywhere. I've tried every combo I can think of for Evolution - Microsoft Exchange, including the MAPI plugin, but then I read that, that doesn't work on OWA Exchange email servers and I can't get it to connect at all that way. If there is no way to connect via Evolution, is there another mail client? I tried Thunderbird, but I couldn't get it to work with Exchange either...

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  • Evolution and thunderbird sharing same mail data?

    - by balki
    Hi, I have been using Evolution for a quite long and it has downloaded around 1.6GBs of mails from gmail. I want to try thunderbird but I dont want to re download everything again. Is that possible to have both clients sharing same data? I'll make sure I don't use both at the same time if that matters. I'll move to thunderbird fully if I'm happy with it. Problems I face with evolution is that I have to have the GUI running always if I want to get instant alerts and send mail immediately. Also it loads the messages slow and even after I move to the next mail, it slowly downloads all the linked images before moving on.

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  • Cannot save password in Evolution?

    - by mhmdrizmi
    I'm using evolution in lubuntu. Configuring the email accounts is OK. Then a window appears asking for the mail password. There is an option to add the password to the keyring. When this is checked nothing happens. The window doesn't close either. When I repeat the same steps with the option to add the password unchecked, it works fine. But I have to enter the passwords every time I start evolution. I guess it's a problem with the keyring (just a guess). How can I fix this ?

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