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• Simple SSH public/private key question

  - by James R.

  I am trying to learn this instead of just following guides so I can recommend proper actions when people do ask (and they do). Here is what I got down. First, generate both key with command such as this: ssh-keygen -b 2048 -t rsa -C comment -f ~/.ssh/id_rsa Then you push the public part of the key into authorized_keys2 file cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys2 (and then chmod it to 600 or similar) And you download the private key to your computer (id_rsa) and feed that in to Putty to be read and authenticate. Are these the correct steps to setting this public/private key authentication for passwordless login to SSH?

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• How to avoid having very large objects with Domain Driven Design

  - by Pablojim

  We are following Domain Driven Design for the implementation of a large website. However by putting the behaviour on the domain objects we are ending up with some very large classes. For example on our WebsiteUser object, we have many many methods - e.g. dealing with passwords, order history, refunds, customer segmentation. All of these methods are directly related to the user. Many of these methods delegate internally to other child object but this still results in some very large classes. I'm keen to avoid exposing lots of child objects e.g. user.getOrderHistory().getLatestOrder(). What other strategies can be used to avoid this problems?

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• Subclassing to avoid line length

  - by Super User

  The standard line length of code is 80 characters per line. This is accepted and followed by the most of programmers. I working on a state machine of a character and is necessary for me follow this too. I have four classes who pass this limit. I can subclass each class in two more and then avoid the line length limit. class Stand class Walk class Punch class Crouch The new classes would be StandLeft, StandRight and so on. Stand, Walk, Punch and Crouch would be then abstract classes. The question if there is a limit for the long of the hierarchies tree or this is depends of the case.

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• Why should ViewModel route actions to Controller when using the MVCVM pattern?

  - by Lea Hayes

  When reading examples across the Internet (including the MSDN reference) I have found that code examples are all doing the following type of thing: public class FooViewModel : BaseViewModel { public FooViewModel(FooController controller) { Controller = controller; } protected FooController Controller { get; private set; } public void PerformSuperAction() { // This just routes action to controller... Controller.SuperAction(); } ... } and then for the view: public class FooView : BaseView { ... private void OnSuperButtonClicked() { ViewModel.PerformSuperAction(); } } Why do we not just do the following? public class FooView : BaseView { ... private void OnSuperButtonClicked() { ViewModel.Controller.SuperAction(); // or, even just use a shortcut property: Controller.SuperAction(); } }

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• How do I handle priority and propagation in an event system?

  - by Peeter

  Lets say I have a simple event system with the following syntax: object = new Object(); object.bind("my_trigger", function() { print "hello"; }); object.bind("my_trigger", function() { print "hello2"; }); object.trigger("my_trigger"); How could I make sure hello2 is printed out first (I do not want my code to depend on which order the events are binded). Ontop of that, how would I prevent my events from propagating (e.g. I want to stop every other event from being executed)

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• DDD: service contains two repository

  - by tikhop

  Does it correct way to have two repository inside one service and will it be an application or domain service? Suppose I have a Passenger object that should contains Passport (government id) object. I am getting Passenger from PassengerRepository. PassengerRepository create request to server and obtain data (json) than parse received data and store inside repository. I have confused because I want to store Passport as Entity and put it to PassportRepository but all information about password contains inside json than i received above. I guess that I should create a PassengerService that will be include PassengerRepository and PassportRepository with several methods like removePassport, addPassport, getAllPassenger and etc. UPDATE: So I guess that the better way is represent Passport as VO and store all passports inside Passenger aggregate. However there is another question: Where I should put the methods (methods calls server api) for management passenger's passport. I think the better place is so within Passenger aggregate.

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• A PHP design pattern for the model part [PHP Zend Framework]

  - by Matthieu

  I have a PHP MVC application using Zend Framework. As presented in the quickstart, I use 3 layers for the model part : Model (business logic) Data mapper Table data gateway (or data access object, i.e. one class per SQL table) The model is UML designed and totally independent of the DB. My problem is : I can't have multiple instances of the same "instance/record". For example : if I get, for example, the user "Chuck Norris" with id=5, this will create a new model instance wich members will be filled by the data mapper (the data mapper query the table data gateway that query the DB). Then, if I change the name to "Duck Norras", don't save it in DB right away, and re-load the same user in another variable, I have "synchronisation" problems... (different instances for the same "record") Right now, I use the Multiton pattern : like Singleton, but multiple instances indexed by a key (wich is the user ID in our example). But this is complicating my developpement a lot, and my testings too. How to do it right ?

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• Varchar with trailing spaces as a Primary Key in SQL Server 2008

  - by cacaupt

  Is it possible to have a varchar column as a primary key with values like 'a ' and 'a', is gives always this error "Violation of PRIMARY KEY constraint" in MS SQL Server 2008. In Oracle dons't give any error. BTW I'm not implementing this way I'm only trying to migrate the data from oracle to sql server. Regards

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• Using datetime float representation as primary key

  - by devanalyst

  From my experience I have learn that using an surrogate INT data type column as primary key esp. an IDENTITY key column offers better performance than using GUID or char/varchar data type column as primary key. I try to use IDENTITY key as primary key wherever possible. But recently I came across a schema where the tables were horizontally partitioned and were managed via a Partitioned view. So the tables could not have an IDENTITY column since that would make the Partitioned View non updatable. One work around for this was to create a dummy 'keygenerator' table with an identity column to generate IDs for primary key. But this would mean having a 'keygenerator' table for each of the Partitioned View. My next thought was to use float as a primary key. The reason is the following key algorithm that I devised DECLARE @KEY FLOAT SET @KEY = CONVERT(FLOAT,GETDATE())/100000.0 SET @KEY = @EMP_ID + @KEY Heres how it works. CONVERT(FLOAT,GETDATE()) gives float representation of current datetime since internally all datetime are represented by SQL as a float value. CONVERT(FLOAT,GETDATE())/100000.0 converts the float representation into complete decimal value i.e. all digits are pushed to right side of ".". @KEY = @EMP_ID + @KEY adds the Employee ID which is an integer to this decimal value. The logic is that the Employee ID is guaranteed to be unique across sessions since an employee cannot connect to an application more than once at the same time. And for the same employee each time a key will be generated the current datetime will be unique. In all an unique key across all employee sessions and across time. So for Emp Ids 11 and 12, I have key values like 12.40046693321566357, 11.40046693542361111 But my concern whether float data type as primary key offer benefits compared to choosing GUID or char/varchar as primary keys. Also important thing is because of partitioning the float column is going to be part of a composite key.

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• Tell git which private key to use

  - by jrdioko

  ssh has the -i option to tell it which private key file to use when authenticating: -i identity_file Selects a file from which the identity (private key) for RSA or DSA authentication is read. The default is ~/.ssh/identity for protocol ver- sion 1, and ~/.ssh/id_rsa and ~/.ssh/id_dsa for protocol version 2. Iden- tity files may also be specified on a per-host basis in the configuration file. It is possible to have multiple -i options (and multiple identities specified in configuration files). Is there a similar way to tell git which private key file to use when on a system with multiple private keys in the .ssh directory?

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• How to revoke gnupg public key without private key?

  - by danijelc

  Long story short I have an key generated with seahorse and mistakenly deleted it from my system. I do remember passphrase but I don't have this key anywhere on my system. Scanned trough Ask Ubuntu but couldn't find any aplicabile solution on similar issue. However public key is still updated on keyring servers and I would like to revoke it. Since I have no revocation certificate and I can't get hold of private key (only public key is available from keyservers which I imported to seahorse) I have no idea how to accomplish it. Spent some time searching for solution acros net, various manuals and so on, but so far no luck. gpg --list-secret-keys - returns no output at all. gpg --list-keys - returns public key info gpg --gen-revoke *user-id* - returns - gpg: secret key *user-id* not found: eof gpg (GnuPG) version 1.4.11. Anyone able to suggest a solution?

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• My proposed design is usually worse than my colleague's - how do I get better?

  - by user151193

  I have been programming for couple of years and am generally good when it comes to fixing problems and creating small-to-medium scripts, however, I'm generally not good at designing large scale programs in object oriented way. Few questions Recently, a colleague who has same number of years of experience as me and I were working on a problem. I was working on a problem longer than him, however, he came up with a better solution and in the end we're going to use his design. This really affected me. I admit his design is better, but I wanted to come up with a design as good as his. I'm even contemplating quitting the job. Not sure why but suddenly I feel under some pressure e.g. what would juniors think of me and etc? Is it normal? Or I'm thinking a little too much into this? My job involves programming in Python. I try to read source code but how do you think I can improve me design skills? Are there any good books or software that I should study? Please enlighten me. I will really appreciate your help.

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• Interface Design Problem: Storing Result of Transactions

  - by jboyd

  Requirements: multiple sources of input (social media content) into a system multiple destinations of output (social media api's) sources and destinations WILL be added some pseudo: IContentProvider contentProvider = context.getBean("contentProvider"); List<Content> toPost = contentProvider.getContent(); for (Content c : toPost) { SocialMediaPresence smPresence = socialMediaService.getSMPresenceBySomeId(c.getDestId()); smPresence.hasTwitter(); smPresence.hasFacebook(); //just to show what this is smPresence.postContent(c); //post content could fail for some SM platforms, but shoulnd't be lost forever } So now I run out of steam, I need to know what content has been successfully posted, and if it hasn't gone too all platforms, or if another platform were added in the future that content needs to go out for it as well (therefore my content provider will need to not only know if content has gone out, but for what platforms). I'm not looking for code, although sample/pseudo is fine... I'm looking for an approach to this problem that I can implement

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• MySQL primary/foreign key size?

  - by David

  I seem to see a lot of people arbitrarily assigning large sizes to primary/foreign key fields in their MySQL schemas, such as INT(11) and even BIGINT(20) as WordPress uses. Now correct me if I'm wrong, but even an INT(4) would support (unsigned) values up to over 4 billion. Change it to INT(5) and you allow for values up to a quadrillion, which is more than you would ever need, unless possibly you're storing geodata at NASA/Google, which I'm sure most of us aren't. Is there a reason people use such large sizes for their primary keys? Seems like a waste to me...

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• Expose subset of a class - design question

  - by thanikkal

  Suppose i have a product class with about close to 100 properties. Now for some operations (Say tax calculation) i dont really need this bulky product type, rather only a subset that has price related properties. I am not sure if i should create different snap shots(class) of products that just has the properties that i am interested in. what would be the ideal approach so that i don't unnecessarily pass around unsought fluff? Thanks in advance.

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• Choosing a design pattern for a class that might change it's internal attributes

  - by the_drow

  I have a class that holds arbitrary state and it's defined like this: class AbstractFoo { }; template <class StatePolicy> class Foo : public StatePolicy, public AbstractFoo { }; The state policy contains only protected attributes that represent the state. The state might be the same for multiple behaviors and they can be replaced at runtime. All Foo objects have the same interface to abstract the state itself and to enable storing Foo objects in containers. I would like to find the least verbose and the most maintainable way to express this.

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• Book Review: Pro SQL Server 2008 Relational Database Design and Implementation

  - by Alexander Kuznetsov

  Investing in proper database design is a very efficient way to cut maintenance costs. If we expect a system to last, we need to make sure it has a good solid foundation - high quality database design. Surely we can and sometimes do cut corners and save on database design to get things done faster. Unfortunately, such cutting corners frequently comes back and bites us: we may end up spending a lot of time solving issues caused by poor design. So, solid understanding of relational database design is...(read more)

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• Are there any GUI or user interface design patterns? [closed]

  - by Niranjan Kala

  I was curious about GUI design patterns, so I searched and got some information, including a list of UI patterns for the web. This UI patterns website says that: UI Patterns is a growing collection of User Interface Design Principles and User Interface Usability Patterns present on web applications and sites today. Are there any other design patterns for constructing websites or other user interfaces? Are there any books that describe these patterns? I'm particularly interested in patterns for Windows desktop development and web development in the .NET platform.

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• Is there a definitive reference on Pinball playfield design?

  - by World Engineer

  I'm looking at designing tables for Future Pinball but I'm not sure where to start as I've little background in game design per se. I've played scores of pinball tables over the years so I've a fairly good idea of what is "fun" in those terms. However, I'd like to know if there is a definitive "bible" of pinball design as far as layout and scoring/mode design goes. I've looked but there doesn't seem to be anything really coherent that I could find. Is it simply a lost art or am I missing some buried gem?

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• Better alternative to autonumber primary keys

  - by Comrad_Durandal

  I am looking for a better primary key than the autonumber data type, namely for the reason that it's limited to a long integer, when I really just need the field to reflect a number or text string that will never ever repeat, no matter HOW many records are added or deleted from the table. The problem is I am not sure how to implement something like turning the current date and time into a hexadecimal string and using that as a unique field I can use as a primary key. Am I just being too paranoid about running out of space?

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• Tool to Convert table base design to table less design

  - by brz dot net

  What is the best optimized way to convert table base design to table less design? the layout should be cross browser compatible and SEO Friendly. Is there any tool/editor which converts existing table base design to table less design? Is there any option in dreamweaver to convert the design in tableless?

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• mysql complex key or + auto increment key (guid)

  - by darko

  Hi, I have not very big db. I am using auto increment primary keys and in my case there is no problem with that. GUID is not necessary. I have a table containing this fields: from_destination to_testination shipper quantity Where the fields 1,2,3 needs to be unique. Also I have second table that for the fields 1,2,3 stores bought quantities per day One to many. from_destination to_destination shipper date reserved_quantity case 1 Is it better to make fields 1,2,3 as primary complex key in the first table and the same fields in the second table to be foreign key First table from_destination | to_destination | primary shipper | quaitity Second table second_id - autoincrement primary from_destination | to_destination | foreign key shipper | date reserved_quantity Case 2 or just to add auto increment filed in the first table and make fields 1,2,3 unique. In the second table there will be one ingeger foreign key pointing to the first table, and one auto increment key for the table. First table first_id - autoincrement primary from_destination | to_destination | unique shipper | quaitity Second table second_id - autoincrement primary first_id - forein date reserved_quantity If so why we need complex keys, when we can have one field auto increment or GUID and all other fields that are candidates for complex key to be unique. Regards

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• Why not expose a primary key

  - by Angelo Neuschitzer

  In my education I have been told that it is a flawed idea to expose actual primary keys (not only DB keys, but all primary accessors) to the user. I always thought it to be a security problem (because an attacker could attempt to read stuff not their own). Now I have to check if the user is allowed to access anyway, so is there a different reason behind it? Also, as my users have to access the data anyway I will need to have a public key for the outside world somewhere in between. Now that public key has the same problems as the primary key, doesn't it?

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• Primary key/foreign Key naming convention

  - by Jeremy

  In our dev group we have a raging debate regarding the naming convention for Primary and Foreign Keys. There's basically two schools of thought in our group: 1) Primary Table (Employee) Primary Key is called ID Foreign table (Event) Foreign key is called EmployeeID 2) Primary Table (Employee) Primary Key is called EmployeeID Foreign table (Event) Foreign key is called EmployeeID I prefer not to duplicate the name of the table in any of the columns (So I prefer option 1 above). Conceptually, it is consisted with a lot of the recommended practices in other languages, where you don't use the name of the object in its property names. I think that naming the foreign key EmployeeID (or Employee_ID might be better) tells the reader that it is the ID column of the Employee Table. Some others prefer option 2 where you name the primary key prefixed with the table name so that the column name is the same throughout the database. I see that point, but you now can not visually distinguish a primary key from a foreign key. Also, I think it's redundant to have the table name in the column name, because if you think of the table as an entity and a column as a property or attribute of that entity, you think of it as the ID attribute of the Employee, not the EmployeeID attribute of an employee. I don't go an ask my coworker what his PersonAge or PersonGender is. I ask him what his Age is. So like I said, it's a raging debate and we go on and on and on about it. I'm interested to get some new perspective.

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• how should I design Objects around this business requirement?

  - by brainydexter

  This is the business requirement: " A Holiday Package (e.g. New York NY Holiday Package) can be offered in different ways based on the Origin city: From New Delhi to NY From Bombay to NY NY itself ( Land package ) (Bold implies default selection) a. and b. User can fly from either New Delhi or Bombay to NY. c. NY is a Land package, where a user can reach NY by himself and is a standalone holidayPackage. " Let's say I have a class that represents HolidayPackage, Destination (aka City). public class HolidayPackage{ Destination holidayCity; ArrayList<BaseHolidayPackageVariant> variants; BaseHolidayPackageVariant defaultVariant; } public abstract class BaseHolidayPackageVariant { private Integer variantId; private HolidayPackage holidayPackage; private String holidayPackageType; } public class LandHolidayPackageVariant extends BaseHolidayPackageVariant{ } public class FlightHolidayPackageVariant extends BaseHolidayPackageVariant{ private Destination originCity; } What data structure/objects should I design to support: options a default within those options Sidenote: A HolidayPackage can also be offered in different ways based on Hotel selections. I'd like to follow a design which I can leverage to support that use case in the future. This is the backend design I have in mind.

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