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• Designing a chain of states

  - by devoured elysium

  I want to model a kind of FSM(Finite State Machine). I have a sequence of states (let's say, from StateA to StateZ). This sequence is called a Chain and is implemented internally as a List. I will add states by the order I want them to run. My purpose is to be able to make a sequence of actions in my computer (for example, mouse clicks). (I know this has been done a zillion times). So a state is defined as a: boolean Precondition() <- Checks to see if for this state, some condition is true. For example, if I want to click in the Record button of a program, in this method I would check if the program's process is running or not. If it is, go to the next state in the chain list, otherwise, go to what was defined as the fail state (generally is the first state of them all). IState GetNextState() <- Returns the next state to evaluate. If Precondition() was sucessful, it should yield the next state in the chain otherwise it should yield the fail state. Run() Simply checks the Precondition() and sets the internal data so GetNextState() works as expected. So, a naive approach to this would be something like this: Chain chain = new Chain(); //chain.AddState(new State(Precondition, FailState, NextState) <- Method structure chain.AddState(new State(new WinampIsOpenCondition(), null, new <problem here, I want to referr to a state that still wasn't defined!>); The big problem is that I want to make a reference to a State that at this point still wasn't defined. I could circumvent the problem by using strings when refrering to states and using an internal hashtable, but isn't there a clearer alternative? I could just pass only the pre-condition and failure states in the constructor, having the chain just before execution put in each state the correct next state in a public property but that seems kind of awkward.

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• Where do you put your dependencies?

  - by The All Foo

  If I use the dependency injection pattern to remove dependencies they end up some where else. For example, Snippet 1, or what I call Object Maker. I mean you have to instantiate your objects somewhere...so when you move dependency out of one object, you end up putting it another one. I see that this consolidates all my dependencies into one object. Is that the point, to reduce your dependencies so that they all reside in a single ( as close to as possible ) location? Snippet 1 - Object Maker <?php class ObjectMaker { public function makeSignUp() { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); $SignUpObject = new ControlSignUp(); $SignUpObject->setObjects($DatabaseObject, $TextObject, $MessageObject); return $SignUpObject; } public function makeSignIn() { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); $SignInObject = new ControlSignIn(); $SignInObject->setObjects($DatabaseObject, $TextObject, $MessageObject); return $SignInObject; } public function makeTweet( $DatabaseObject = NULL, $TextObject = NULL, $MessageObject = NULL ) { if( $DatabaseObject == 'small' ) { $DatabaseObject = new Database(); } else if( $DatabaseObject == NULL ) { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); } $TweetObject = new ControlTweet(); $TweetObject->setObjects($DatabaseObject, $TextObject, $MessageObject); return $TweetObject; } public function makeBookmark( $DatabaseObject = NULL, $TextObject = NULL, $MessageObject = NULL ) { if( $DatabaseObject == 'small' ) { $DatabaseObject = new Database(); } else if( $DatabaseObject == NULL ) { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); } $BookmarkObject = new ControlBookmark(); $BookmarkObject->setObjects($DatabaseObject,$TextObject,$MessageObject); return $BookmarkObject; } }

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• Building a structure/object in a place other than the constructor

  - by Vishal Naidu

  I have different types of objects representing the same business entity. UIObject, PowershellObject, DevCodeModelObject, WMIObject all are different representation to the same entity. So say if the entity is Animal then I have AnimalUIObject, AnimalPSObject, AnimalModelObject, AnimalWMIObject, etc. Now the implementations of AnimalUIObject, AnimalPSObject, AnimalModelObject are all in separate assemblies. Now my scenario is I want to verify the contents of business entity Animal irrespective of the assembly it came from. So I created a GenericAnimal class to represent the Animal entity. Now in GenericAnimal I added the following constructors: GenericAnimal(AnimalUIObject) GenericAnimal(AnimalPSObject) GenericAnimal(AnimalModelObject) Basically I made GenericAnimal depend on all the underlying assemblies so that while verifying I deal with this abstraction. Now the other approach to do this is have GenericAnimal with an empty constructor an allow these underlying assemblies to have a Transform() method which would build the GenericAnimal. Both approaches have some pros and cons: The 1st approach: Pros: All construction logic is in one place in one class GenericAnimal Cons: GenericAnimal class must be touched every-time there is a new representation form. The 2nd approach: Pros: construction responsibility is delegated to the underlying assembly. Cons: As construction logic is spread accross assemblies, tomorrow if I need to add a property X in GenericAnimal then I have to touch all the assemblies to change the Transform method. Which approach looks better ? or Which would you consider a lesser evil ? Is there any alternative way better than the above two ?

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• To share a table or not share?

  - by acidzombie24

  Right now on my (beta) site i have a table called user data which stores name, hash(password), ipaddr, sessionkey, email and message number. Now i would like the user to have a profile description, signature, location (optional) and maybe other things. Should i have this in a separate mysql table? or should i share the table? and why?

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• Compressing a database to a single file?

  - by Assimilater

  Hi all. In my contact manager program I have been storing information by reading and writing comma delimited files for each individual contact, and storing notes in a file for each note, and I'm wondering how I could go about shrinking them all into one file effectively. I have attempted using data entry tools in the visual studio toolbox and template class, though I have never quite figured out how to use them. What would be especially convenient is if I could store data as data type IOwner (a class I created) as opposed to strings. I'd also need to figure out how to tell the program what to do when a file is opened (I've noticed in the properties how to associate a file type with the program though am not sure how to tell it what to do when it's opened). Edit: How about rephrasing the question: I have a class IContact with various properties some of them being lists of other class objects. I have a public list of IContact. Can I write Contacts as List(Of IContact) to a file as opposed to a bunch of strings? Second part of the question: I have associated .cms files with my program. But if a user opens the file, what code should the program run through in an attempt to deal with the file? This file is going to contain data that the program needs to read, how do I tell it to read a file when the program is opened vicariously because the file was opened? Does this make the question clearer?

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• Best Practice for CouchDB Document Versioning

  - by Groundwater

  Following my question here I am exmploring ideas for a generic approach to document versioning in CouchDB. While I imagine there may be no canonical approach, I had the following idea and am looking for feedback. I would like to maintain readable document ids as much as possible, so a document existing at /document1 would contain a pointer document to all existing versions on the system. The actual revision documents would be at something like /document1/308ef032a3801a where 308ef032a3801a is some random number or hash. Example The pointer document { "_id" : "document1", "versions" : [ "document1/308ef032a3801a" ] } The version document { "_id" : "document1/308ef032a3801a", ... actual content }

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• Practical refactoring

  - by ahb

  I've read about refactoring and probably did it before I even knew about it, however I don't really know much about it is actually done and what it practically means. What, from your view, is refactoring? How and when do you do it?

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• Function returning a class containing a function returning a class

  - by Scott

  I'm working on an object-oriented Excel add-in to retrieve information from our ERP system's database. Here is an example of a function call: itemDescription = Macola.Item("12345").Description Macola is an instance of a class which takes care of database access. Item() is a function of the Macola class which returns an instance of an ItemMaster class. Description() is a function of the ItemMaster class. This is all working correctly. Items can be be stored in more than one location, so my next step is to do this: quantityOnHand = Macola.Item("12345").Location("A1").QuantityOnHand Location() is a function of the ItemMaster class which returns an instance of the ItemLocation class (well, in theory anyway). QuantityOnHand() is a function of the ItemLocation class. But for some reason, the ItemLocation class is not even being intialized. Public Function Location(inventoryLocation As String) As ItemLocation Set Location = New ItemLocation Location.Item = item_no Location.Code = inventoryLocation End Function In the above sample, the variable item_no is a member variable of the ItemMaster class. Oddly enough, I can successfully instantiate the ItemLocation class outside of the ItemMaster class in a non-class module. Dim test As New ItemLocation test.Item = "12345" test.Code = "A1" quantityOnHand = test.QuantityOnHand Is there some way to make this work the way I want? I'm trying to keep the API as simple as possible. So that it only takes one line of code to retrieve a value.

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• Approaching Java from a Ruby perspective

  - by Travis

  There are plenty of resources available to a Java developer for getting a jump-start into Ruby/Rails development. The reverse doesn't appear to be true. What resources would you suggest for getting up-to-date on the current state of java technologies? How about learning how to approach DRY (don't repeat yourself) without the use of metaprogramming? Or how to approach various scenarios where a ruby developer is used to passing in a function (proc/lambda/block) as an argument (callbacks, etc)?

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• How do I correct feature envy in this case?

  - by RMorrisey

  I have some code that looks like: class Parent { private Intermediate intermediateContainer; public Intermediate getIntermediate(); } class Intermediate { private Child child; public Child getChild() {...} public void intermediateOp(); } class Child { public void something(); public void somethingElse(); } class Client { private Parent parent; public void something() { parent.getIntermediate().getChild().something(); } public void somethingElse() { parent.getIntermediate().getChild().somethingElse(); } public void intermediate() { parent.getIntermediate().intermediateOp(); } } I understand that is an example of the "feature envy" code smell. The question is, what's the best way to fix it? My first instinct is to put the three methods on parent: parent.something(); parent.somethingElse(); parent.intermediateOp(); ...but I feel like this duplicates code, and clutters the API of the Parent class (which is already rather busy). Do I want to store the result of getIntermediate(), and/or getChild(), and keep my own references to these objects?

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• Bad idea to have the same object, have a different side effect after method call.

  - by Nathan W

  Hi all, I'm having a bit of a gesign issue(again). Say I have this Buttonpad object: now this object is a wrapper object over one in a com object. At the moment it has a method on it called CreateInto(IComObject). Now to make a new button pad in the Com Object. You do: ButtonPad pad = new ButtonPad(); pad.Title = "Hello"; // Set some more properties. pad.CreateInto(Cominstance); The createinfo method will excute the right commands to buid the button pad in the com object. After it has been created it any calls against it are foward to the underlying object for change so: pad.Title = "New title"; will call the com object to set the title and also set the internal title variable. Basically any calls before the CreateInfo method only affect the .NET object anything after has the side effect of calling the com object also. I'm not very good at sequence diagrams but here is my attempt to explain whats going on: This doesn't feel good to me, it feels like I'm lying to the user about what the button pad does. I was going to have a object called WrappedButtonPad, which is returned from CreateInto and the user could make calls against that to make changes to the Com Object, but I feel having two objects that almost do the same thing but only differ by names might be even worse. Are these valid designs, or am I right to be worried? How else would you handle a object the can create and query a com object?

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• application specific seed data population

  - by user339108

  Env: JBoss, (h2, MySQl, postgres), JPA, Hibernate 3.3.x @Id @GeneratedValue(strategy = IDENTITY) private Integer key; Currently our primary keys are created using the above annotation. We expect to support a large number of users (~million users), what key should be used. Should it be Integer or Long or should I use the unsigned versions of the above declarations. We have a j2ee application which needs to be populated with some seed data on installation. On purchase, the customer creates his own data on top of the application. We just want to make sure that there is enough room to ship, modify or add data for future releases. What would be the best mechanism to support this, we had looked at starting all table identifiers from a certain id (say 1000) but this mandates modifying primary key generation to have table or sequence based generators and we have around ~100 tables. We are not sure if this is the right strategy for this. If we use a signed integer approach for the key, would it make sense to have the seed data as everything starting from 0 and below (i.e -ve numbers), so that all customer specific data will be available on 0 and above (i.e. +ve numbers)

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• Store children in database preserving information about their order

  - by GUZ

  I am designing database tables for a master-detail scenario. The specific requirement is that it is necessary to store information about the order of children. I see some possible solutions (like adding a column representing a position in the sequence, or a column with foreign key to the previous child) but I would like to know the best practices how to solve such problems. Best regards Lukasz Glaz

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• Interpreter in C++: Function table storage problem

  - by sub

  In my interpreter I have built-in functions available in the language like print exit input, etc. These functions can obviously be accessed from inside the language. The interpreter then looks for the corresponding function with the right name in a vector and calls it via a pointer stored with its name. So I gather all these functions in files like io.cpp, string.cpp, arithmetic.cpp. But I have to add every function to the function list in the interpreter in order for it to be found. So in these function files I have things like: void print( arg ) { cout << arg.ToString; } I'd add this print function to the interpreter function list with: interpreter.AddFunc( "print", print ); But where should I call the interpreter.AddFunc? I can't just put it there below the print function as it has to be in a function according to the C++ syntax. Where and how should all the functions be added to the list?

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• Application Code Redesign to reduce no. of Database Hits from Performance Perspective

  - by Rachel

  Scenario I want to parse a large CSV file and inserts data into the database, csv file has approximately 100K rows of data. Currently I am using fgetcsv to parse through the file row by row and insert data into Database and so right now I am hitting database for each line of data present in csv file so currently database hit count is 100K which is not good from performance point of view. Current Code: public function initiateInserts() { //Open Large CSV File(min 100K rows) for parsing. $this->fin = fopen($file,'r') or die('Cannot open file'); //Parsing Large CSV file to get data and initiate insertion into schema. while (($data=fgetcsv($this->fin,5000,";"))!==FALSE) { $query = "INSERT INTO dt_table (id, code, connectid, connectcode) VALUES (:id, :code, :connectid, :connectcode)"; $stmt = $this->prepare($query); // Then, for each line : bind the parameters $stmt->bindValue(':id', $data[0], PDO::PARAM_INT); $stmt->bindValue(':code', $data[1], PDO::PARAM_INT); $stmt->bindValue(':connectid', $data[2], PDO::PARAM_INT); $stmt->bindValue(':connectcode', $data[3], PDO::PARAM_INT); // Execute the statement $stmt->execute(); $this->checkForErrors($stmt); } } I am looking for a way wherein instead of hitting Database for every row of data, I can prepare the query and than hit it once and populate Database with the inserts. Any Suggestions !!! Note: This is the exact sample code that I am using but CSV file has more no. of field and not only id, code, connectid and connectcode but I wanted to make sure that I am able to explain the logic and so have used this sample code here. Thanks !!!

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• Innovative seminar topic

  - by sijith

  Hi, I don't know whether its the right place to ask this question. I want some good seminar topic which suits for a cooperate culture company. I need topic either in management side or technical side which is innovative and interesting which gives much interest to employees

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• Should I store logging information in main database table?

  - by Mike

  For example, say I have a table of products. Should I store logging information such as who it was created by, last edited by, last updated date, ... Or should I separate the logging information in say an auditing table if the logging information is not relevant to the actual application? Thank you.

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• How do you determine how coarse or fine-grained a 'responsibility' should be when using the single r

  - by Mark Rogers

  In the SRP, a 'responsibility' is usually described as 'a reason to change', so that each class (or object?) should have only one reason someone should have to go in there and change it. But if you take this to the extreme fine-grain you could say that an object adding two numbers together is a responsibility and a possible reason to change. Therefore the object should contain no other logic, because it would produce another reason for change. I'm curious if there is anyone out there that has any strategies for 'scoping', the single-responsibility principle that's slightly less objective?

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• Single-Page Web Apps: Client-side datastores & server persistence

  - by fig-gnuton

  How should client-side datastores & persistence be handled in a single-page web application? Global vars vs. DI/IoC: Should datastores be assigned to global variables so any part of the application can access them? Or should they be dependency injected where required? Server persistence: Assuming a datastore's data needn't always be persisted to the server immediately, should the datastore itself handle persistence? If not, then what class should handle persistence and how should the persistence class fit into the client-side architecture overall? Is the datastore considered the model in MVC, or is it something else since it just stores raw data?

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• Rails architecture questions

  - by justinbach

  I'm building a Rails site that, among other things, allows users to build their own recipe repository. Recipes are entered either manually or via a link to another site (think epicurious, cooks.com, etc). I'm writing scripts that will scrape a recipe from these sites given a link from a user, and so far (legal issues notwithstanding) that part isn't giving me any trouble. However, I'm not sure where to put the code that I'm writing for these scraper scripts. My first thought was to put it in the recipes model, but it seems a bit too involved to go there; would a library or a helper be more appropriate? Also, as I mentioned, I'm building several different scrapers for different food websites. It seems to me that the elegant way to do this would be to define an interface (or abstract base class) that determines a set of methods for constructing a recipe object given a link, but I'm not sure what the best approach would be here, either. How might I build out these OO relationships, and where should the code go?

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• Unique visitor counting in ASP.NET MVC

  - by Max

  I'd like to do visitor tracking similar to how stackoverflow does it.. By reading through numerous posts, I've figured out some details already: Count only 1 IP hit per 15 minutes (if anonymous) Count only 1 unique user-Login (per day?) Now that leaves the question of the real implementation.. Should I log the two factors live into a table (and increase count) | IP | timestamp | pageurl | Or do the counting AFTERWARDS (e.g. using IIS log files - which don't include the user, right? I know there're some similar posts outside, but NONE really has a great solution in my opinion yet..

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• Does OOP make sense for small scripts?

  - by Fabian

  I mostly write small scripts in python, about 50 - 250 lines of code. I usually don't use any objects, just straightforward procedural programming. I know OOP basics and I have used object in other programming languages before, but for small scripts I don't see how objects would improve them. But maybe that is just my limited experience with OOP. Am I missing something by not trying harder to use objects, or does OOP just not make a lot of sense for small scripts?

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• How I can make Recycle Bin for Database ?Application?

  - by Wael Dalloul

  Hi, I have database application, I want to allow the user to restore the deleted records from the database, like in windows we have Recycle bin for files I want to do the same thing but for database records, Assume that I have a lot of related tables that have a lot of fields. Edit: let's say that I have the following structures: Reports table RepName primary key ReportData Users table ID primary key Name UserReports table RepName primary key UserID primary key IsDeleted now if I put isdeleted field in UserReports table, the user can't add same record again if it marked as deleted, because the record is already and this will make duplication.

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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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• Best datastructure for this relationship...

  - by Travis

  I have a question about database 'style'. I need a method of storing user accounts. Some users "own" other user accounts (sub-accounts). However not all user accounts are owned, just some. Is it best to represent this using a table structure like so... TABLE accounts ( ID ownerID -> ID name ) ...even though there will be some NULL values in the ownerID column for accounts that do not have an owner. Or would it be stylistically preferable to have two tables, like so. TABLE accounts ( ID name ) TABLE ownedAccounts ( accountID -> accounts(ID) ownerID -> accounts(ID) ) Thanks for the advice.

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