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  • which design choose? - pros and cons

    - by Guarava Makanili
    Which of these 3 approches would choose and why? // This is the one I would choose class Car { } class FeeCalculator { public double calculateFee(Car car) { return 0; } } // in that case the problem might be when we use ORM framework and we try to invoke save with parameter Car class Car { private FeeCalculator calculator; public double calculateFee() { return calculator.calculateFee(this); } } class FeeCalculator { public double calculateFee(Car car) { return 0; } } // in that case the problem mentioned above is solved, but I don't like this design class Car { public double calculateFee(FeeCalculator calculator) { return calculator.calculateFee(this); } } class FeeCalculator { public double calculateFee(Car car) { return 0; } }

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  • related categories - database design

    - by mike
    Hello! I'm looking for a little database design advice... I have a spreadsheet with a few columns in it. Column 1 being a list of categories and the rest being related categories(to the category in column 1). I'm trying to figure out what the best way to setup the tables would be... My thought so far is to have a table that just lists the categories then have a table with 2 columns that holds the id of the category and the id of a related category.... Would this be the best way to do this? Any better ideas?

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  • Customers and suppliers database design issue

    - by hectorsq
    I am developing a web application in which I will have customers and suppliers. Initially I thought on using a Customers table and a Suppliers table. Then when I was thinking on bank transactions, I noticed that each transaction needs to refer to a customer or a supplier, so I thought on using a single table named Business in which I will save both customers and suppliers. If I use Customers and Suppliers tables when I want to list the bank transactions I will have to search in both tables to get the company name. If I use a Businesses table I will have to use a business type column, and have the union of possible fields for all businesses types. Any suggestions on the design?

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  • Generic Database table design

    - by Gazeth
    Just trying to figure out the best way to design my table for the following scenario: I have several areas in my system (documents, projects, groups and clients) and each of these can have comments logged against them. My question is should I have one table like this: CommentID DocumentID ProjectID GroupID ClientID etc Where only one of the ids will have data and the rest will be NULL or should I have a seperate CommentType table and have my comments table like this: CommentID CommentTypeID ResourceID (this being the id of the project/doc/client) etc My thoughts are that option 2 would be more efficient from an indexing point of view?

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  • C++ Singleton design pattern

    - by Artem Barger
    Recently I've bumped into a realization/implementation of the Singleton design pattern for C++. It has looked like this (I have adopted it from the real life example): // a lot of methods are omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that the instance field is initiated on the heap. That means there is a memory allocation. What is completely unclear for me is when exactly the memory is going to be deallocated? Or is there a bug and memory leak? It seems like there is a problem in the implementation. My main question is, how do I implement it in the right way?

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  • jQuery: Writing jquery in an object oriented way

    - by anoopkattodi
    Hi all, I am trying to write all my query code in an object oriented way. But I don't know how to implement this for each click function and hover function etc. I also wanted to know: What are the advantages of writing query in object oriented way? For query what is better the object oriented way or in the ordinary way?

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  • Does the following indicate a bad design?

    - by Mewzer
    Hello, I was wondering whether you think the following code usually indicates a bad design ... class X { public: ... private: Y y; }; Class Y { public: Y( X& value ){ x = value; }; private: X& x; } (i.e. there is some sort of cyclic dependency between the classes X and Y).

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  • Which are the best tools for Graphic Designing?

    - by Jen
    Hello, I want to take up Graphic Designing as my profession. I would be designing Logos, Icons, Stationery, Brochures, Handouts, Book Covers, etc. But I am thoroughly confused as to which tools are the best and which books/resources will help me learn these tools and graphic designing like a professional. I am ready to shell out money to purchase the resources. Please help me out! Thanks, Jen

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  • Chef: nested data bag data to template file returns "can't convert String into Integer"

    - by Dalho Park
    I'm creating simple test recipe with a template and data bag. What I'm trying to do is creating a config file from data bag that has simple nested information, but I receive error "can't convert String into Integer" Here are my setting file 1) recipe/default.rb data1 = data_bag_item( 'mytest', 'qa' )['test'] data2 = data_bag_item( 'mytest', 'qa' ) template "/opt/env/test.cfg" do source "test.erb" action :create_if_missing mode 0664 owner "root" group "root" variables({ :pepe1 = data1['part.name'], :pepe2 = data2['transport.tcp.ip2'] }) end 2)my data bag named "mytest" $knife data bag show mytest qa id: qa test: part.name: L12 transport.tcp.ip: 111.111.111.111 transport.tcp.port: 9199 transport.tcp.ip2: 222.222.222.222 3)template file test.erb part.name=<%= @pepe1 % transport.tcp.binding=<%= @pepe2 % Error reurns when I run chef-client on my server, [2013-06-24T19:50:38+00:00] DEBUG: filtered backtrace of compile error: /var/chef/cache/cookbooks/config_test/recipes/default.rb:19:in []',/var/chef/cache/cookbooks/config_test/recipes/default.rb:19:inblock in from_file',/var/chef/cache/cookbooks/config_test/recipes/default.rb:12:in from_file' [2013-06-24T19:50:38+00:00] DEBUG: filtered backtrace of compile error: /var/chef/cache/cookbooks/config_test/recipes/default.rb:19:in[]',/var/chef/cache/cookbooks/config_test/recipes/default.rb:19:in block in from_file',/var/chef/cache/cookbooks/config_test/recipes/default.rb:12:infrom_file' [2013-06-24T19:50:38+00:00] DEBUG: backtrace entry for compile error: '/var/chef/cache/cookbooks/config_test/recipes/default.rb:19:in `[]'' [2013-06-24T19:50:38+00:00] DEBUG: Line number of compile error: '19' Recipe Compile Error in /var/chef/cache/cookbooks/config_test/recipes/default.rb TypeError can't convert String into Integer Cookbook Trace: /var/chef/cache/cookbooks/config_test/recipes/default.rb:19:in []' /var/chef/cache/cookbooks/config_test/recipes/default.rb:19:inblock in from_file' /var/chef/cache/cookbooks/config_test/recipes/default.rb:12:in `from_file' Relevant File Content: /var/chef/cache/cookbooks/config_test/recipes/default.rb: 12: template "/opt/env/test.cfg" do 13: source "test.erb" 14: action :create_if_missing 15: mode 0664 16: owner "root" 17: group "root" 18: variables({ 19 :pepe1 = data1['part.name'], 20: :pepe2 = data2['transport.tcp.ip2'] 21: }) 22: end 23: I tried many things and if I comment out "pepe1 = data1['part.name'],", then :pepe2 = data2['transport.tcp.ip2'] works fine. only nested data "part.name" cannot be set to @pepe1. Does anyone knows why I receive the errors? thanks,

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  • pure-ftpd debian, can't get www-data user working

    - by lynks
    I'm trying to add FTP access to the apache web files, in the past I have done this with an ftpuser and group arrangement. This time I would like to make it possible to login directly as www-data (the default apache user on debian) to make things a bit cleaner. I have checked and re-checked all the common issues; MinUID is set to 1 (www-data has uid 33) www-data has shell set to /bin/bash in /etc/passwd PAMAuthentication is off UnixAuthentication is on I have restarted pure-ftpd using /etc/init.d/pure-ftpd restart My resulting pure-ftpd run is; /usr/sbin/pure-ftpd -l unix -A -Y 1 -u 1 -E -O clf:/var/log/pure-ftpd/transfer.log -8 UTF-8 -B My syslog contains; Oct 7 19:46:40 Debian-60-squeeze-64 pure-ftpd: ([email protected]) [WARNING] Can't login as [www-data]: account disabled And my ftp client is giving me; 530 Sorry, but I can't trust you Am I missing something obvious?

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  • Data recovery on a corrupted 3TB disk

    - by Mark K Cowan
    Short version I probably need software to run a deep-scan recovery (ideally on Linux) to find files on NTFS filesystem. The file data is intact, but the references are no longer present. Analogous to recovering data from a "quick-formatted" partition. Hopefully there is a smarter way available than deep-scan, one which would recover filenames and possibly paths. Long version I have a 3TB disk containing a load of backups. Windows 7 SP1 refused to detect the disk when plugged in directly via SATA, so I put it on a USB/SATA adaptor which seemed to work at first. The SATA/USB adaptor probably does not support disks over 2.2TB though. Windows first asked me if I wanted to 'format' the disk, then later showed me most of the contents but some folder were inaccessible. I stupidly decided to run a CHKDSK on my backup disk, which made the folders accessible but also left them empty. I connected this disk via SATA to my main PC (Arch Linux). I tried: testdisk ntfsundelete ntfsfix --no-action (to look for diagnostically relevant faults, disk was "OK" though) to no avail as the files references in the tables had presumably been zeroed out by CHKDSK, rather than using a typical journal'd deletion). If it is useful at all, a majority of the files that I want to recover are JPEG, Photoshop PSD, and MPEG-3/MPEG-4/AVI/MKV files. If worst comes to worst, I'll just design my own sector scanner and use some simple heuristic-driven analysis to recover raw binary blocks of data from the disk which appears to match the structures of the above file types. I am unfamiliar with the exact workings of NTFS but used to be proficient at recovering FAT32 systems with just a hex-editor, so I can provide any useful diagnostic information if you let me know how to find it! My priorities in ascending order of importance for choosing the accepted answer: Restores directory structure Recovers many filenames in addition to the file data Is free / very cheap Runs on Linux Recovers a majority of file data The last point is the most important, but the more of the higher points you match the more rep you'll probably get :)

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  • Any "Magic Tricks" For Getting Data Back After Windows 7 Install

    - by user163757
    My old man installed Windows 7 without making a proper backup, and now realizes he left behind some important data. He did a true "clean install", so there is no Windows.old folder in the root directory. However, I believe the format performed on the hard drive was only a quick format, so I am hoping there is some chance at data recovery. I took his hard drive out, and have spent a majority of the weekend researching data recovery options. I paid $70 for the GetDataBack software, but have had little success with it. I can see all of the files I want to restore, however they appear corrupt when I try to open them. With that all being said, does anyone know of a viable way to recover some of this data, or is it a lost cause all together?

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  • raid 0 data recovery?

    - by Fred
    HI All, I have two identical seagate 7200.9 500Gb drives confiured as a RAID 0 spanned disk in windows. One of the drives has lost power and wont spin up at all. I know this normally means death for the data on both drives but i have a cunning plan.. DISK 1 - NO POWER RAID 0 DISK DISK 2 - FULLY FUNCTIONAL RAID 0 DISK DISK 3 - FULLY FUNCTIONAL SPARE DISK Copy the working drive (disk 2) data to a third 500GB DISK (disk 3), remove the logic board from the working disk (disk 2) and replace it with the non working logic board on the broken drive (disk 1) , then hopefully recreate the RAID 0 with disk 1 and disk 3, just long enough to get the data off it. Hope this makes sense, here are my questions: Windows disk manager atm recognises disk 2 but wont let me access it in anyway, therefore copying the data off it (or getting a disk image) cant be done in windows. Does anyone know of any software (in linux or self booting) that would allow me to access this disk? Anyone know of any software that will recreate the spanned drive off two disk images Am i missing any key information that means i definitely shouldn't even bother starting this, i know its a long shot anyway but its worth a try unless i definitely cant do it. The irritating thing is that i am sure its a logic board failure on disk 1 as it simply wont power up at all, suddenly no signs of life, so i am sure the data is intact! Any help would be really appreciated! Thanks

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  • Data take on with Drupal 6

    - by Robert MacLean
    We are migrating our current intranet to Drupal 6 and there is a lot of data within the current system which can be classified into: List data, general lists of fields. Common use is phone list of the employees phone numbers. Document repository. Just basically a web version of a file share for documents. I can easily get the data + meta infomation out, but how do I bulk upload the two types of data into Drupal, as uploading the hundred of thousands of items manually is just not acceptable.

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  • Summing up spreadsheet data when a column contains “#N/A”

    - by Doris
    I am using Goggle Spreadsheet to work up some historical stock data and I use a Google function (=googlefinance=…) to import the historical closing prices for a stock, then I work with that data further. But, in that list of data generated from the =googlefinance=… function, one of the amounts comes up as #N/A. I don’t know why, but it happens for various symbols that I have tried. When I use a max function on the array, which includes the N/A line, the max function does not come up with anything but an N/A, so the N/A throws off any further functions. I thought I’d create a second column to the right of the imported data in which I can give it an IF function, something like, If ((A1 <0), "0", A1), with the expectation that it would return 0 if cell A1 is the N/A, and the cell value if it is not N/A. However, this still returns N/A. I also tried an IS BLANK function but that resulted in the same NA. Does anyone have any suggestions for a workaround to eliminate the N/A from an array of numbers that I am trying to work with?

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  • TDWI World Conference Features Oracle and Big Data

    - by Mandy Ho
    Oracle is a Gold Sponsor at this year's TDWI World Conference Series, held at the Manchester Grand Hyatt in San Diego, California - July 31 to Aug 1. The theme of this event is Big Data Tipping Point: BI Strategies in the Era of Big Data. The conference features an educational look at how data is now being generated so quickly that organizations across all industries need new technologies to stay ahead - to understand customer behavior, detect fraud, improve processes and accelerate performance. Attendees will hear how the internet, social media and streaming data are fundamentally changing business intelligence and data warehousing. Big data is reaching critical mass - the tipping point. Oracle will be conducting the following Evening Workshop. To reserve your space, call 1.800.820.5592 ext 10775. Title...:    Integrating Big Data into Your Data Center (or A Big Data Reference Architecture) Date.:    Wed., August 1, 2012, at 7:00 p.m Venue:: Manchester Grand Hyatt, San Diego, Room Weblogs, Social Media, smart meters, senors and other devices generate high volumes of low density information that isn't readily accessible in enterprise data warehouses and business intelligence applications today. But, this data can have relevant business value, especially when analyzed alongside traditional information sources. In this session, we will outline a reference architecture for big data that will help you maximize the value of your big data implementation. You will learn: The key technologies in a big architecture, and their specific use case The integration point of the various technologies and how they fit into your existing IT environment How effectively leverage analytical sandboxes for data discovery and agile development of data driven solutions   At the end of this session you will understand the reference architecture and have the tools to implement this architecture at your company. Presenter: Jean-Pierre Dijcks, Senior Principal Product Manager Don't miss our booth and the chance to meet with our Big data experts on the exhibition floor at booth #306. 

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  • Are certain problems solved more elegantly with AOP?

    - by Winston Ewert
    I've come across the idea of Aspect Oriented Programming, and I have some concerns with it. The basic idea seems to be that we want to take cross-cutting concerns which aren't well modularized using object and modularize them. That is all very fine and well. But the implementation of AOP seems to be that of modifying code from outside of the module. So, for example, an aspect could be written that changes what happens when a particular object is passed as a parameter in a function. This seems to go directly against the idea of modules. I should not be able to modify a module's behavior from outside of that module, otherwise the whole point of modules are overturned. But aspects seem to be doing exactly that! Basically, aspects seems to be a form of code patching. It may useful for some quick hacks; but, as a general principle perhaps its not something you want to do. Aspect Oriented Programming seems to me taking a bad practice and raising to a general design principle. Is AOP a good practice? Are certain programming problems solved more elegantly with AOP?

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  • How do you encode Algebraic Data Types in a C#- or Java-like language?

    - by Jörg W Mittag
    There are some problems which are easily solved by Algebraic Data Types, for example a List type can be very succinctly expressed as: data ConsList a = Empty | ConsCell a (ConsList a) consmap f Empty = Empty consmap f (ConsCell a b) = ConsCell (f a) (consmap f b) l = ConsCell 1 (ConsCell 2 (ConsCell 3 Empty)) consmap (+1) l This particular example is in Haskell, but it would be similar in other languages with native support for Algebraic Data Types. It turns out that there is an obvious mapping to OO-style subtyping: the datatype becomes an abstract base class and every data constructor becomes a concrete subclass. Here's an example in Scala: sealed abstract class ConsList[+T] { def map[U](f: T => U): ConsList[U] } object Empty extends ConsList[Nothing] { override def map[U](f: Nothing => U) = this } final class ConsCell[T](first: T, rest: ConsList[T]) extends ConsList[T] { override def map[U](f: T => U) = new ConsCell(f(first), rest.map(f)) } val l = (new ConsCell(1, new ConsCell(2, new ConsCell(3, Empty))) l.map(1+) The only thing needed beyond naive subclassing is a way to seal classes, i.e. a way to make it impossible to add subclasses to a hierarchy. How would you approach this problem in a language like C# or Java? The two stumbling blocks I found when trying to use Algebraic Data Types in C# were: I couldn't figure out what the bottom type is called in C# (i.e. I couldn't figure out what to put into class Empty : ConsList< ??? >) I couldn't figure out a way to seal ConsList so that no subclasses can be added to the hierarchy What would be the most idiomatic way to implement Algebraic Data Types in C# and/or Java? Or, if it isn't possible, what would be the idiomatic replacement?

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  • Composing programs from small simple pieces: OOP vs Functional Programming

    - by Jay Godse
    I started programming when imperative programming languages such as C were virtually the only game in town for paid gigs. I'm not a computer scientist by training so I was only exposed to Assembler and Pascal in school, and not Lisp or Prolog. Over the 1990s, Object-Oriented Programming (OOP) became more popular because one of the marketing memes for OOP was that complex programs could be composed of loosely coupled but well-defined, well-tested, cohesive, and reusable classes and objects. And in many cases that is quite true. Once I learned object-oriented programming my C programs became better because I structured them more like classes and objects. In the last few years (2008-2014) I have programmed in Ruby, an OOP language. However, Ruby has many functional programming (FP) features such as lambdas and procs, which enable a different style of programming using recursion, currying, lazy evaluation and the like. (Through ignorance I am at a loss to explain why these techniques are so great). Very recently, I have written code to use methods from the Ruby Enumerable library, such as map(), reduce(), and select(). Apparently this is a functional style of programming. I have found that using these methods significantly reduce code volume, and make my code easier to debug. Upon reading more about FP, one of the marketing claims made by advocates is that FP enables developers to compose programs out of small well-defined, well-tested, and reusable functions, which leads to less buggy code, and low code volume. QUESTIONS: Is the composition of complex program by using FP techniques contradictory to or complementary to composition of a complex program by using OOP techniques? In which situations is OOP more effective, and when is FP more effective? Is it possible to use both techniques in the same complex program? Do the techniques overlap or contradict each other?

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  • How to REALLY start thinking in terms of objects?

    - by Mr Grieves
    I work with a team of developers who all have several years of experience with languages such as C# and Java. Most of them are young enough to have been shown OOP as a standard way to develop software in university and are very comfortable with concepts such as inheritance, abstraction, encapsulation and polymorphism. Yet, many of them, and I have to include myself, still tend to create classes which are meant to be used in a very functional fashion. The resulting software is often several smaller classes which correctly represent business objects which get passed through larger classes which only supply ways to modify and use those objects (functions). Large complex difficult-to-maintain classes named Manager are usually the result of such behaviour. I can see two theoretical reasons why people might write this type of code: It's easy to start thinking of everything in terms of the database Deep down, for me, a computer handling a web request feels more like a functional operation than an object oriented operation when you think about Request Handlers, Threads, Processes, CPU Cores and CPU operations... I want source code which is easy to read and easy to modify. I have seen excellent examples of OO code which meet these objectives. How can I start writing code like this? How I can I really start thinking in an object oriented fashion? How can I share such a mentality with my colleagues?

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  • FP for simulation and modelling

    - by heaptobesquare
    I'm about to start a simulation/modelling project. I already know that OOP is used for this kind of projects. However, studying Haskell made me consider using the FP paradigm for modelling a system of components. Let me elaborate: Let's say I have a component of type A, characterised by a set of data (a parameter like temperature or pressure,a PDE and some boundary conditions,etc.) and a component of type B, characterised by a different set of data(different or same parameter, different PDE and boundary conditions). Let's also assume that the functions/methods that are going to be applied on each component are the same (a Galerkin method for example). If I were to use an OOP approach, I would create two objects that would encapsulate each type's data, the methods for solving the PDE(inheritance would be used here for code reuse) and the solution to the PDE. On the other hand, if I were to use an FP approach, each component would be broken down to data parts and the functions that would act upon the data in order to get the solution for the PDE. This approach seems simpler to me assuming that linear operations on data would be trivial and that the parameters are constant. What if the parameters are not constant(for example, temperature increases suddenly and therefore cannot be immutable)? In OOP, the object's (mutable) state can be used. I know that Haskell has Monads for that. To conclude, would implementing the FP approach be actually simpler,less time consuming and easier to manage (add a different type of component or new method to solve the pde) compared to the OOP one? I come from a C++/Fortran background, plus I'm not a professional programmer, so correct me on anything that I've got wrong.

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  • Why is my ServiceOperation method missing from my WCF Data Services client proxy code?

    - by Kev
    I have a simple WCF Data Services service and I want to expose a Service Operation as follows: [System.ServiceModel.ServiceBehavior(IncludeExceptionDetailInFaults = true)] public class ConfigurationData : DataService<ProductRepository> { // This method is called only once to initialize service-wide policies. public static void InitializeService(IDataServiceConfiguration config) { config.SetEntitySetAccessRule("*", EntitySetRights.ReadMultiple | EntitySetRights.ReadSingle); config.SetServiceOperationAccessRule("*", ServiceOperationRights.All); config.UseVerboseErrors = true; } // This operation isn't getting generated client side [WebGet] public IQueryable<Product> GetProducts() { // Simple example for testing return (new ProductRepository()).Product; } Why isn't the GetProducts method visible when I add the service reference on the client?

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  • How to Convert multiple sets of Data going from left to right to top to bottom the Pythonic way?

    - by ThinkCode
    Following is a sample of sets of contacts for each company going from left to right. ID Company ContactFirst1 ContactLast1 Title1 Email1 ContactFirst2 ContactLast2 Title2 Email2 1 ABC John Doe CEO [email protected] Steve Bern CIO [email protected] How do I get them to go top to bottom as shown? ID Company Contactfirst ContactLast Title Email 1 ABC John Doe CEO [email protected] 1 ABC Steve Bern CIO [email protected] I am hoping there is a Pythonic way of solving this task. Any pointers or samples are really appreciated! p.s : In the actual file, there are 10 sets of contacts going from left to right and there are few thousand such records. It is a CSV file and I loaded into MySQL to manipulate the data.

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  • Object oriented design of game in Java: How to handle a party of NPCs?

    - by Arvanem
    Hi folks, I'm making a very simple 2D RPG in Java. My goal is to do this in as simple code as possible. Stripped down to basics, my class structure at the moment is like this: Physical objects have an x and y dimension. Roaming objects are physical objects that can move(). Humanoid objects are roaming objects that have inventories of GameItems. The Player is a singleton humanoid object that can hire up to 4 NPC Humanoids to join his or her party, and do other actions, such as fight non-humanoid objects. NPC Humanoids can be hired by the Player object to join his or her party, and once hired can fight for the Player. So far I have given the Player class a "party" ArrayList of NPC Humanoids, and the NPC Humanoids class a "hired" Boolean. However, my fight method is clunky, using an if to check the party size before implementing combat, e.g. public class Player extends Humanoids { private ArrayList<Humanoids> party; // GETTERS AND SETTERS for party here //... public void fightEnemy(Enemy eneObj) { if (this.getParty().size() == 0) // Do combat without party issues else if (this.getParty().size() == 1) // Do combat with party of 1 else if (this.getParty().size() == 2) // Do combat with party of 2 // etc. My question is, thinking in object oriented design, am I on the right track to do this in as simple code as possible? Is there a better way?

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  • How to add data manually in core data entity

    - by pankaj
    Hi I am working on core data for the first time. I have just created an entity and attributes for that entity. I want to add some data inside the entity(u can say i want to add data in a table), earlier i when i was using sqlite, i would add data using terminal. But here in core data i am not able to find a place where i can manually add data. I just want to add data in entity and display it in a UITableView. I have gone through the the documentation of core data but it does not explain how to add data manually although it explains how i can add it programmiticaly but i dont need to do it programically. I want to do it manually. Thanks in advance

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