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  • Programming languages & proof of concepts

    - by Mike
    There are plenty of programming languages out there, as you all may know. I am primarily looking for a list of programming languages WITH some very neat proof of concepts. I would really like to learn a new language, but whenever I dive into something new and popular, it isn't what I expected. Any tutorial out there will give you code, small examples, but won't show you the true power of the language. I am looking for examples that run entirely on the language that it is exemplifying. For example, If I said C#, I could possibly show you a complete C# app with backend queries, reports, tables, all with a nice interface. It would be completely reliant on the language that is provided, so no supporting languages. I understand that most languages are integrated with other languages in order to provide a richer application. Any links, charts, websites that may reflect this request is appreciated.

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  • How can I modify my classes to use it's collections in WPF TreeView

    - by Victor
    Hello, i'am trying to modify my objects to make hierarchical collection model. I need help. My objects are Good and GoodCategory: public class Good { int _ID; int _GoodCategory; string _GoodtName; public int ID { get { return _ID; } } public int GoodCategory { get { return _GoodCategory; } set { _GoodCategory = value; } } public string GoodName { get { return _GoodName; } set { _GoodName = value; } } public Good(IDataRecord record) { _ID = (int)record["ID"]; _GoodtCategory = (int)record["GoodCategory"]; } } public class GoodCategory { int _ID; string _CategoryName; public int ID { get { return _ID; } } public string CategoryName { get { return _CategoryName; } set { _CategoryName = value; } } public GoodCategory(IDataRecord record) { _ID = (int)record["ID"]; _CategoryName = (string)record["CategoryName"]; } } And I have two Collections of these objects: public class GoodsList : ObservableCollection<Good> { public GoodsList() { string goodQuery = @"SELECT `ID`, `ProductCategory`, `ProductName`, `ProductFullName` FROM `products`;"; using (MySqlConnection conn = ConnectToDatabase.OpenDatabase()) { if (conn != null) { MySqlCommand cmd = conn.CreateCommand(); cmd.CommandText = productQuery; MySqlDataReader rdr = cmd.ExecuteReader(); while (rdr.Read()) { Add(new Good(rdr)); } } } } } public class GoodCategoryList : ObservableCollection<GoodCategory> { public GoodCategoryList () { string goodQuery = @"SELECT `ID`, `CategoryName` FROM `product_categoryes`;"; using (MySqlConnection conn = ConnectToDatabase.OpenDatabase()) { if (conn != null) { MySqlCommand cmd = conn.CreateCommand(); cmd.CommandText = productQuery; MySqlDataReader rdr = cmd.ExecuteReader(); while (rdr.Read()) { Add(new GoodCategory(rdr)); } } } } } So I have two collections which takes data from the database. But I want to use thats collections in the WPF TreeView with HierarchicalDataTemplate. I saw many post's with examples of Hierarlichal Objects, but I steel don't know how to make my objects hierarchicaly. Please help.

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  • jQuery's draggable grid

    - by Art
    It looks like that the 'grid' option in the constructor of Draggable is relatively bound to the original coordinates of the element being dragged - so simply put, if you have three draggable divs with their top set respectively to 100, 200, 254 pixels relative to their parent: <div class="parent-div" style="position: relative;"> <div id="div1" class="draggable" style="top: 100px; position: absolute;"></div> <div id="div2" class="draggable" style="top: 200px; position: absolute;"></div> <div id="div3" class="draggable" style="top: 254px; position: absolute;"></div> </div> Adn all of them are getting enabled for dragging with 'grid' set to [1, 100]: draggables = $('.draggable'); $.each(draggables, function(index, elem) { $(elem).draggable({ containment: $('#parent-div'), opacity: 0.7, revert: 'invalid', revertDuration: 300, grid: [1, 100], refreshPositions: true }); }); Problem here is that as soon as you drag div3, say, down, it's top is increased by 100, moving it to 354px instead of being increased by just mere 46px (254 + 46 = 300), which would get it to the next stop in the grid - 300px, if we are looking at the parent-div as a point of reference and "grid holder". I had a look at the draggable sources and it seem to be an in-built flaw - they just do all the calculations relative to the original position of the draggable element. I would like to avoid monkey-patching the code of draggable library and what I am really looking for here is the way how to make the Draggable calculate the grid positions relative to containing parent. However if monkey-patching is unavoidable, I guess I'll have to live with it. Thanks!

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  • Nullpointerexcption & abrupt IOStream closure with inheritence and subclasses

    - by user1401652
    A brief background before so we can communicate on the same wave length. I've had about 8-10 university courses on programming from data structure, to one on all languages, to specific ones such as java & c++. I'm a bit rusty because i usually take 2-3 month breaks from coding. This is a personal project that I started thinking of two years back. Okay down to the details, and a specific question, I'm having problems with my mutator functions. It seems to be that I am trying to access a private variable incorrectly. The question is, am I nesting my classes too much and trying to mutate a base class variable the incorrect way. If so point me in the way of the correct literature, or confirm this is my problem so I can restudy this information. Thanks package GroceryReceiptProgram; import java.io.*; import java.util.Vector; public class Date { private int hour, minute, day, month, year; Date() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What's the hour? (Use 1-24 military notation"); hour = Integer.parseInt(keyboard.readLine()); System.out.println("what's the minute? "); minute = Integer.parseInt(keyboard.readLine()); System.out.println("What's the day of the month?"); day = Integer.parseInt(keyboard.readLine()); System.out.println("Which month of the year is it, use an integer"); month = Integer.parseInt(keyboard.readLine()); System.out.println("What year is it?"); year = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (IOException e) { System.out.println("Yo houston we have a problem"); } } public void setHour(int hour) { this.hour = hour; } public void setHour() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What hour, use military notation?"); this.hour = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getHour() { return hour; } public void setMinute(int minute) { this.minute = minute; } public void setMinute() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What minute?"); this.minute = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ": doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": minute shall not cooperate"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in the setMinute function of the Date class"); } } public int getMinute() { return minute; } public void setDay(int day) { this.day = day; } public void setDay() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What day 0-6?"); this.day = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getDay() { return day; } public void setMonth(int month) { this.month = month; } public void setMonth() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What month 0-11?"); this.month = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getMonth() { return month; } public void setYear(int year) { this.year = year; } public void setYear() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What year?"); this.year = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getYear() { return year; } public void set() { setMinute(); setHour(); setDay(); setMonth(); setYear(); } public Vector<Integer> get() { Vector<Integer> holder = new Vector<Integer>(5); holder.add(hour); holder.add(minute); holder.add(month); holder.add(day); holder.add(year); return holder; } }; That is the Date class obviously, next is the other base class Location. package GroceryReceiptProgram; import java.io.*; import java.util.Vector; public class Location { String streetName, state, city, country; int zipCode, address; Location() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What is the street name"); streetName = keyboard.readLine(); System.out.println("Which state?"); state = keyboard.readLine(); System.out.println("Which city?"); city = keyboard.readLine(); System.out.println("Which country?"); country = keyboard.readLine(); System.out.println("Which zipcode?");//if not u.s. continue around this step zipCode = Integer.parseInt(keyboard.readLine()); System.out.println("What address?"); address = Integer.parseInt(keyboard.readLine()); } catch (IOException e) { System.out.println(e.toString()); } } public void setZipCode(int zipCode) { this.zipCode = zipCode; } public void setZipCode() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What zipCode?"); this.zipCode = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public void set() { setAddress(); setCity(); setCountry(); setState(); setStreetName(); setZipCode(); } public int getZipCode() { return zipCode; } public void setAddress(int address) { this.address = address; } public void setAddress() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.address = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getAddress() { return address; } public void setStreetName(String streetName) { this.streetName = streetName; } public void setStreetName() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.streetName = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getStreetName() { return streetName; } public void setState(String state) { this.state = state; } public void setState() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.state = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getState() { return state; } public void setCity(String city) { this.city = city; } public void setCity() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.city = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getCity() { return city; } public void setCountry(String country) { this.country = country; } public void setCountry() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.country = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getCountry() { return country; } }; their parent(What is the proper name?) class package GroceryReceiptProgram; import java.io.*; public class FoodGroup { private int price, count; private Date purchaseDate, expirationDate; private Location location; private String name; public FoodGroup() { try { setPrice(); setCount(); expirationDate.set(); purchaseDate.set(); location.set(); } catch (NullPointerException e) { System.out.println(e.toString() + ": in the constructor of the FoodGroup class"); } } public void setPrice(int price) { this.price = price; } public void setPrice() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What Price?"); price = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": in the FoodGroup class, setPrice function"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in FoodGroup class. SetPrice()"); } } public int getPrice() { return price; } public void setCount(int count) { this.count = count; } public void setCount() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What count?"); count = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": in the FoodGroup class, setCount()"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in FoodGroup class, setCount"); } } public int getCount() { return count; } public void setName(String name) { this.name = name; } public void setName() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.name = keyboard.readLine(); } catch (IOException e) { System.out.println(e.toString()); } } public String getName() { return name; } public void setLocation(Location location) { this.location = location; } public Location getLocation() { return location; } public void setPurchaseDate(Date purchaseDate) { this.purchaseDate = purchaseDate; } public void setPurchaseDate() { this.purchaseDate.set(); } public Date getPurchaseDate() { return purchaseDate; } public void setExpirationDate(Date expirationDate) { this.expirationDate = expirationDate; } public void setExpirationDate() { this.expirationDate.set(); } public Date getExpirationDate() { return expirationDate; } } and finally the main class, so I can get access to all of this work. package GroceryReceiptProgram; public class NewMain { public static void main(String[] args) { FoodGroup test = new FoodGroup(); } } If anyone is further interested, here is a link the UML for this. https://www.dropbox.com/s/1weigjnxih70tbv/GRP.dia

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  • How to best propagate changes upwards a hierarchical structure for binding?

    - by H.B.
    If i have a folder-like structure that uses the composite design pattern and i bind the root folder to a TreeView. It would be quite useful if i can display certain properties that are being accumulated from the folder's contents. The question is, how do i best inform the folder that changes occurred in a child-element so that the accumulative properties get updated? The context in which i need this is a small RSS-FeedReader i am trying to make. This are the most important objects and aspects of my model: Composite interface: public interface IFeedComposite : INotifyPropertyChanged { string Title { get; set; } int UnreadFeedItemsCount { get; } ObservableCollection<FeedItem> FeedItems { get; } } FeedComposite (aka Folder) public class FeedComposite : BindableObject, IFeedComposite { private string title = ""; public string Title { get { return title; } set { title = value; NotifyPropertyChanged("Title"); } } private ObservableCollection<IFeedComposite> children = new ObservableCollection<IFeedComposite>(); public ObservableCollection<IFeedComposite> Children { get { return children; } set { children.Clear(); foreach (IFeedComposite item in value) { children.Add(item); } NotifyPropertyChanged("Children"); } } public FeedComposite() { } public FeedComposite(string title) { Title = title; } public ObservableCollection<FeedItem> FeedItems { get { ObservableCollection<FeedItem> feedItems = new ObservableCollection<FeedItem>(); foreach (IFeedComposite child in Children) { foreach (FeedItem item in child.FeedItems) { feedItems.Add(item); } } return feedItems; } } public int UnreadFeedItemsCount { get { return (from i in FeedItems where i.IsUnread select i).Count(); } } Feed: public class Feed : BindableObject, IFeedComposite { private string url = ""; public string Url { get { return url; } set { url = value; NotifyPropertyChanged("Url"); } } ... private ObservableCollection<FeedItem> feedItems = new ObservableCollection<FeedItem>(); public ObservableCollection<FeedItem> FeedItems { get { return feedItems; } set { feedItems.Clear(); foreach (FeedItem item in value) { AddFeedItem(item); } NotifyPropertyChanged("Items"); } } public int UnreadFeedItemsCount { get { return (from i in FeedItems where i.IsUnread select i).Count(); } } public Feed() { } public Feed(string url) { Url = url; } Ok, so here's the thing, if i bind a TextBlock.Text to the UnreadFeedItemsCount there won't be simple notifications when an item is marked unread, so one of my approaches has been to handle the PropertyChanged event of every FeedItem and if the IsUnread-Property is changed i have my Feed make a notification that the property UnreadFeedItemsCount has been changed. With this approach i also need to handle all PropertyChanged events of all Feeds and FeedComposites in Children of FeedComposite, from the sound of it, it should be obvious that this is not such a very good idea, you need to be very careful that items never get added or removed to any collection without having attached the PropertyChanged event handler first and things like that. Also: What do i do with the CollectionChanged-Events which necessarily also cause a change in the sum of the unread items count? Sounds like more event handling fun. It is such a mess, it would be great if anyone has an elegant solution to this since i don't want the feed-reader to end up as awful as my first attempt years ago when i didn't even know about DataBinding...

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  • Dataset and Hierarchial Data How to Sort

    - by mdjtlj
    This is probably a dumb question, but I've hit a wall with this one at this current time. I have some data which is hierarchial in nature which is in an ADO.NEt dataset. The first field is the ID, the second is the Name, the third is the Parent ID. ID NAME Parent ID 1 Air Handling NULL 2 Compressor 1 3 Motor 4 4 Compressor 1 5 Motor 2 6 Controller 4 7 Controller 2 So the tree would look like the following: 1- Air Handling 4- Compressor 6 - Controller 3 - Motor 2- Compressor 7- Controller 5 - Motor What I'm trying to figure our is how to get the dataset in the same order that ths would be viewed in a treeview, which in this case is the levels at the appropriate levels for the nodes and then the children at the appropriate levels sorted by the name. It would be like binding this to a treeview and then simply working your way down the nodes to get the right order. Any links or direction would be greatly appreciated.

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  • Security question

    - by Syom
    in my cms i have index.php, where client must enter username and password. if they are correct, he'll moove to admin.php, where the cms is. but now hacker can enter to cms/admin.php, so my security now is awful. i know, that i can use $_SESSION variable. index.php - i can give some value to $_SESSION['success']: $_SESSION['success'] = TRUE, and in admin.php just verify it admin.php if($_SESSION['success'] == TRUE) { my script here... } else header("Location: index.php"); but i want to rich this effect without SESSION. could you give me an idea, how can i do it? thanks

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  • SQL 2008 HierarchyID - Select X descendants down

    - by NTulip
    How can I query a table which has a column of data type HIERARCHYID and get a list of descendants X levels deep under an employee? Here is the current structure: CREATE TABLE [dbo].[Employees]( [NodeId] [hierarchyid] NOT NULL, [EmployeeId] [int] IDENTITY(1,1) NOT NULL, [FirstName] [varchar](120) NULL, [MiddleInitial] [varchar](1) NULL, [LastName] [varchar](120) NULL, [DepartmentId] [int] NULL, [Title] [varchar](120) NULL, [PhoneNumber] [varchar](20) NULL, [IM] [varchar](120) NULL, [Photo] [varbinary](max) NULL, [Bio] [varchar](400) NULL, [Active] [bit] NULL, [ManagerId] [int] NULL )

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  • Macros in C.... please give the solution

    - by Jungle_hacker
    suppose i declared a macro name anything, xyz() and now i am creating another macro xyz1() and referencing the 1st macro i.e xyz() in 2nd. finally i'll create another macro xyz2() and referencing 2nd macro in 3rd... now my question is is this correct(its executing without any problem)..? and macro xyz() is defined twice.... why its not giving error ? what is the solution..?

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  • Should I worry about running out of HierarchyIDs?

    - by Bruno Martinez
    When you ask for a new HierarchyID between two others, the result gets progressively longer. For example, between 2/5.6 and 2/5.7 there's only 2/5.6.1 and other 4 component paths. The HierarchyID data type is limited to 800 some bytes, so you can't repeat this forever. Then again, integer types are also limited, but it isn't a problem in practice. Should I periodically defragment my table so that height doesn't grow unbounded?

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  • Getting HIERARCHY_REQUEST_ERR when using Javascript to recursively generate a nested list

    - by Mark
    I have a method that is trying to take in a list. This list can contain data and other lists. The end goal is to try to convert something like this ["a", "b", ["c", "d"]] into <ol> <li> <b>a</a> </li> <li> <b>b</a> </li> <ol> <li> <b>c</a> </li> <li> <b>d</a> </li> </ol> </ol> The code is: function $(tagName) { return document.createElement(tagName); } //returns an html element representing data //data should be an array or some sort of value function tagMaker(data) { tag = null; if(data instanceof Array) { //data is an array, represent using <ol> tag = $("ol"); for(i=0; i<data.length; i++) { //construct one <li> for each item in the array listItem = $("li"); //get the html element representing this particular item in the array child = tagMaker(data[i]); //<li>*html for child*</li> listItem.appendChild(child); //add this item to the list tag.appendChild(listItem); } } else { //data is not an array, represent using <b>data</b> tag = $("b"); tag.innerHTML = data.toString(); } return tag; } Calling tagMaker throws HIERARCHY_REQUEST_ERR: DOM Exception 3, rather than generating a helpful HTML element object which I was planning to append to document.body.

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  • Sorting nested set by name while keep depth integrity

    - by wb
    I'm using the nested set model that'll later be used to build a sitemap for my web site. This is my table structure. create table departments ( id int identity(0, 1) primary key , lft int , rgt int , name nvarchar(60) ); insert into departments (lft, rgt, name) values (1, 10, 'departments'); insert into departments (lft, rgt, name) values (2, 3, 'd'); insert into departments (lft, rgt, name) values (4, 9, 'a'); insert into departments (lft, rgt, name) values (5, 6, 'b'); insert into departments (lft, rgt, name) values (7, 8, 'c'); How can I sort by depth as well as name? I can do select replicate('----', count(parent.name) - 1) + ' ' + node.name , count(parent.name) - 1 as depth , node.lft from departments node , departments parent where node.lft between parent.lft and parent.rgt group by node.name, node.lft order by depth asc, node.name asc; However, that does not match children with their parent for some reason. department lft rgt --------------------------- departments 0 1 ---- a 1 4 ---- d 1 2 -------- b 2 5 -------- c 2 7 As you can see, department 'd' has department 'a's children! Thank you.

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  • Flattening out a lib directory using jarjar

    - by voodoogiant
    I'm trying to flatten out the lib directory of a project using jarjar, where it will produce a jar file with my main code and all my required libraries inside of it. I can get the project code into the jar, but I need to find a way to get every jar in the './lib/' directory extracted to the base directory of the final output jar. I don't want it flattened in the sense that I still want the package hiearchy preserved. I could manually list every jar file using zipfileset, but I was hoping to do it dynamically. I would also like to include any *.so files flattened into the base directory of the output jar so I can extract them into a temp dir easily without having to search through the jar. For example my lib directory... ./lib/library1.jar ./lib/library2.jar ./lib/foo/library3.jar ./lib/foo/bar.so would look like this when cracked open in the output jar file... /..library1_package_hierarchy../lib1.class /..library1_package_heirarchy../lib2.class ... (and so on) /..library2_package_hierarchy../lib1.class /..library2_package_heirarchy../lib2.class ... (and so on) /..library3_package_hierarchy../lib1.class <-- foo gone /..library3_package_heirarchy../lib2.class <-- foo gone /bar.so <-- foo gone

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  • frame variable cannot be found

    - by Umzz Mo
    I am making 3 board games, and I have started my coding off in one class. Now that i wanted to move around it is giving me problems. In my view class I just want to have the main frame where users can pick from the games. And in the other views, i.e the childrens of view class i want to have the interface for the actual games. Now that the Jframe frame = new frame was created in the parent class, it cannot find the variable frame in the children classes.

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  • Learning a new concept - write from scratch or use frameworks?

    - by Stu
    I have recently been trying to learn about MVVM and all of the associated concepts such as repositories, mediators, data access. I made a decision that I would not use any frameworks for this so that I could gain a better understanding of how everything worked. I’m beginning to wonder if that was the best idea because I have hit some problems which I am not able to solve, even with the help of Stack Overflow! Writing from scratch I still feel that you have a much better understanding of something when you have been in the guts of it than if you were at a higher level. The other side of that coin is that you are in the guts of something that you don't fully understand which will lead to bad design decisions. This then makes it hard to get help because you will create unusual scenarios which are less likely to occur when you working within the confines of a framework. I have found that there are plenty of tutorials on the basics of a concept but very few that take you all the way from novice to expert. Maybe I should be looking at a book for this? Using frameworks The biggest motivation for me to use frameworks is that they are much more likely to be used in the workplace than a custom rolled solution. This can be quite a benefit when starting a new job if it's one less thing you have to learn. I feel that there is much better support for a framework than a custom solution which makes sense; many more people are using the framework than the solution that you created. The level of help is much wider as well, from basic questions to really specific, detailed questions. I would be interested to hear other people's views on this. When you are learning something new, should you/do you use frameworks or not? Why? If it's a combination of both, when do you stop one and move on to the other?

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  • Is there a language or design pattern that allows the *removal* of object behavior or properties in a class hierarchy?

    - by Sebastien Diot
    A well-know shortcoming of traditional class hierarchies is that they are bad when it comes to model the real world. As an example, trying to represent animals species with classes. There are actually several problems when doing that, but one that I never saw a solution to is when a sub-class "looses" a behavior or properties that was defined in a super-class, like a penguin not being able to fly (there are probably better examples, but that's the first one that comes to my mind, having seen "Madagascar 2" recently). On the one hand, you don't want to define for every property and behavior some flag that specifies if it is at all present, and check it every time before accessing that behavior or property. You would just like to say that birds can fly, simply and clearly, in the Bird class. But then it would be nice if one could define "exceptions" afterward, without having to use some horrible hacks everywhere. This often happens when a system has been productive for a while. You suddenly find an "exception" that doesn't fit in the original design at all, and you don't want to change a large portion of your code to accommodate it. So, is there some language or design patterns that can cleanly handle this problem, without requiring major changes to the "super-class", and all the code that uses it? Even if a solution only handle a specific case, several solutions might together form a complete strategy. [EDIT] Forgot about the Liskov Substitution Principle. That is why you can't do it. Assuming you define "traits/interfaces" for all major "feature groups", you can freely implement traits in different branches of the hierarchy, like the Flying trait could be implemented by Birds, and some special kind of squirrels and fish. So my question could amount to "How could I un-implement a trait?" If your super-class is a Java Serializable, you have to be one too, even if there is no way for you to serialize your state, for example if you contained a "Socket". So one way to do it is to always define all your traits in pair from the start: Flying and NotFlying (which would throw UnsupportedOperationExceiption, if not checked against). The Not-trait would not define any new interface, and could be simply checked for. Sounds like a "cheap" solution, in particular if used from the start.

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  • Why is my class worse than the hierarchy of classes in the book (beginner OOP)?

    - by aditya menon
    I am reading this book. The author is trying to model a lesson in a college. The goal is to output the Lesson Type (Lecture or Seminar), and the Charges for the lesson depending on whether it is a hourly or fixed price lesson. So the output should be: lesson charge 20. Charge type: hourly rate. lesson type seminar. lesson charge 30. Charge type: fixed rate. lesson type lecture. When the input is as follows: $lessons[] = new Lesson('hourly rate', 4, 'seminar'); $lessons[] = new Lesson('fixed rate', null, 'lecture'); I wrote this: class Lesson { private $chargeType; private $duration; private $lessonType; public function __construct($chargeType, $duration, $lessonType) { $this->chargeType = $chargeType; $this->duration = $duration; $this->lessonType = $lessonType; } public function getChargeType() { return $this->getChargeType; } public function getLessonType() { return $this->getLessonType; } public function cost() { if($this->chargeType == 'fixed rate') { return "30"; } else { return $this->duration * 5; } } } $lessons[] = new Lesson('hourly rate', 4, 'seminar'); $lessons[] = new Lesson('fixed rate', null, 'lecture'); foreach($lessons as $lesson) { print "lesson charge {$lesson->cost()}."; print " Charge type: {$lesson->getChargeType()}."; print " lesson type {$lesson->getLessonType()}."; print "<br />"; } But according to the book, I am wrong (I am pretty sure I am, too). The author gave a large hierarchy of classes as the solution instead. In a previous chapter, the author stated the following 'four signposts' as the time when I should consider changing my class structure: Code Duplication The Class Who Knew Too Much About His Context The Jack of All Trades - Classes that try to do many things Conditional Statements The only problem I can see is Conditional Statements, and that too in a vague manner - so why refactor this? What problems do you think might arise in the future that I have not foreseen?

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  • What arguments can I use to "sell" the BDD concept to a team reluctant to adopt it?

    - by S.Robins
    I am a bit of a vocal proponent of the BDD methodology. I've been applying BDD for a couple of years now, and have adopted StoryQ as my framework of choice when developing DotNet applications. Even though I have been unit testing for many years, and had previously shifted to a test-first approach, I've found that I get much more value out of using a BDD framework, because my tests capture the intent of the requirements in relatively clear English within my code, and because my tests can execute multiple assertions without ending the test halfway through - meaning I can see which specific assertions pass/fail at a glance without debugging to prove it. This has really been the tip of the iceberg for me, as I've also noticed that I am able to debug both test and implementation code in a more targeted manner, with the result that my productivity has grown significantly, and that I can more easily determine where a failure occurs if a problem happens to make it all the way to the integration build due to the output that makes its way into the build logs. Further, the StoryQ api has a lovely fluent syntax that is easy to learn and which can be applied in an extraordinary number of ways, requiring no external dependencies in order to use it. So with all of these benefits, you would think it an easy to introduce the concept to the rest of the team. Unfortunately, the other team members are reluctant to even look at StoryQ to evaluate it properly (let alone entertain the idea of applying BDD), and have convinced each other to try and remove a number of StoryQ elements from our own core testing framework, even though they originally supported the use of StoryQ, and that it doesn't impact on any other part of our testing system. Doing so would end up increasing my workload significantly overall and really goes against the grain, as I am convinced through practical experience that it is a better way to work in a test-first manner in our particular working environment, and can only lead to greater improvements in the quality of our software, given I've found it easier to stick with test first using BDD. So the question really comes down to the following: What arguments can I use to really drive the point home that it would be better to use StoryQ, or at the very least apply the BDD methodology? Can you point me to any anecdotal evidence that I can use to support my argument to adopt BDD as our standard method of choice? What counter arguments can you think of that could suggest that my wish to convert the team efforts to BDD might be in error? Yes, I'm happy to be proven wrong provided the argument is a sound one. NOTE: I am not advocating that we rewrite our tests in their entirety, but rather to simply start working in a different manner for all future testing work.

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  • How to generate an ASCII representation of a Unix file hierarchy?

    - by Jenn D.
    Hi, all. I'm looking for a quick and dirty way to generate some diagrams of some directories that have almost, but not exactly, the same hierarchy, so I can show them around at a meeting and we can decide which flavor we like best. I'm not interested in the "leaf" nodes, just the directories. The catch: I don't want to mess with X. This is a server system I deal with entirely through SSH. So I'm looking for something that will do ASCII layout, maybe with simple pipes-and-hyphens for lines or something. Does anyone know of such a utility? I'm sure I could write something myself, but it's such a fiddly little sort of project, with handling spacing and layout and such; I'd really like to discover that someone's done it for me. Alas, Google doesn't seem to know of such a thing...or if it does, it's hidden beneath heaps of excellent visual explications of the standard general Unix file hierarchy. Thanks!

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  • Name of the concept of designing an interface to allow expert users to become more efficient?

    - by Grundlefleck
    I'm searching for sources and further information on a particular concept in user experience design. It's not a particularly complicated concept, just that when designing user interfaces, you should both make it intuitive and simple for new users, but also provide way for users to become more efficient as they become more familiar with the application. An example could be including a prominent button for a common action for new users, but also providing a keyboard shortcut / mnemonic for expert users. However, that's just an example, another example could be providing full functionality through a GUI, but allow expert users to script the same actions. The point is it's more difficult to learn, but it makes them more efficient. I'm pretty sure there's a name for that which I can't recall, and I'm having trouble searching for sources and references on it. Name of the concept of designing an interface to allow expert users to become more efficient?

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  • Isn't it better to create the subview hierarchy in -viewDidLoad rather than in -loadView?

    - by dontWatchMyProfile
    The docs say that the whole subview hierarchy can be created in -loadView. But there's also this -viewDidLoad method which sounds nice to ovewrite for actually building the hierarchy, when the view loaded. I guess it's a matter of taste only. But maybe doing so in -viewDidLoad hast the advantage that the view controller already adjusted the frame of the view correctly to accomodate for the status bar or any other kind of bar like tab bar or tool bar?

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  • [C#] How do I make hierarchy of objects from two alternating classes?

    - by Millicent
    Here's the scenario: I have two classes ("Page" and "Field"), that are descended from a common class ("Pield"). They represent tags in an XML file and are in the following hierarchy: <page> <field> <page> ... </page> ... </field> ... </page> I.e.: Page and Field objects are in a hierarchy of alternating type (there may be more than one Page or Field to each rung of the hierarchy). Every Field and Page object has a parent property, which points to the respective parent object of the other type. This is not a problem unless the parent-child mechanism is controlled by the base class (Pield), which is shared by the two descended classes (Page and Field). Here is one try, that fails at the line "Pield child = new Pield(pchild, this);": class Pield<T> { private T _pield_parent; ... private void get_children() { ... Pield<Page> child = new Pield<Page>(pchild, this); ... } ... } class Page : Pield<Field> { ... } class Field : Pield<Page> { ... } Any ideas about how to solve this elegantly? Best, Millicent

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