Search Results

Search found 9366 results on 375 pages for 'common lisp'.

Page 284/375 | < Previous Page | 280 281 282 283 284 285 286 287 288 289 290 291  | Next Page >

• Regressing panel data in SAS.

  - by John

  Hey Guys, thanks to your help I succesfully managed all my databases! I am now looking at a panel data set on which I have to regress. Since I only started my Phd this semester together with the econometrics courses I am still new to many statistic applications and regression methods. I want to do a simple regression as in Y = x1 x2 x3 etc, now I already browsed through some literature and found that for panel data it's common to do a fixed effects regression. Also, my Y variable only has positive values so I was thinking in the direction of a Tobit model? I'm doing some research concerning the coverage of analysts in the financial business. My independent variable is the coverage of analysts on a certain firm, so per observation i have 1 analyst and 1 firm, together with different characteristics(market cap and betas etc) of the firm. All this data is monthly. As coverage cannot become negative (only 0) I was thinking of a Tobit model? Do you guys have any ideas what would be a good regression method? Or have some good sources (e books, written books, through university I have access to almost anything concerning my field of work) of information (cause I do have to learn these things for future research)? Thanks!

  Read the article

• Design to distribute work when generating task oriented input for legacy dos application?

  - by TheDeeno

  I'm attempting to automate a really old dos application. I've decided the best way to do this is via input redirection. The legacy app (menu driven) has many tasks within tasks with branching logic. In order to easily understand and reuse the input for these tasks, I'd like to break them into bit size pieces. Since I'll need to start a fresh app on each run, repeating a context to consume a bit might be messy. I'd like to create an object model that: allows me to concentrate on the task at hand allows me to reuse common tasks from different start points prevents me from calling a task from the wrong start point To be more explicit, given I have the following task hierarchy: START A A1 A1a A1b A2 A2a B B1 B1a I'd like an object model that lets me generate an input file for task "A1b" buy using building blocks like: START -> do_A, do_A1, do_A1b but prevents me from: START -> do_A1 // because I'm assuming a different call chain from above This will help me write "do_A1b" because I can always assume the same starting context and will simplify writing "do_A1a" because it has THE SAME starting context. What patterns will help me out here? I'm using ruby at the moment so if dynamic language features can help, I'm game.

  Read the article

• Help me with DB design

  - by eugeneK

  Hi, i'm developing text ads system. Some small clone of Google Ads. Here is diagram with common tables. Basically make it short, advertiser can have up to 10 variant of same campaign with different text variations, can geo-target his ads and unique impressions count only for IP that haven't been on certain site for more than 24 hours. Pretty simple but the question is what i lack in here from your experience because later it would much harder to fix design flaws and some of you probably done something alike also many SQL gurus in here so maybe i did over normalized DB or did not normalized as needed ? Second question is. My end goal is to get ads for user from ie. Germany that haven't seen same ad on same site for 24 hours as long as ads fit country of user. Each impression is count same as each click if there is one. I need to get 5 "random" ads based on IP, Country and higher CPC (pay per click). How can i achieve this with current design or maybe to design database the way it would be easy to get ads and show stats for advirtisers... thanks for any help...

  Read the article

• Reference inherited class's <T>ype in a derived class

  - by DRapp

  I don't know if its possible or not, but here's what I need. I'm toying around with something and want to know if its possible since you can't create your own data type based on a sealed type such as int, Int32, Int64, etc. I want to create a top-level class that is defined of a given type with some common stuff. Then, derive this into two subclasses, but in this case, each class is based on either and int or Int64 type. From THAT instance, create an instance of either one and know its yped basis for parameter referenc / return settings. So when I need to create an instance of the "ThisClass", I don't have to know its type basis of either int or Int64, yet IT will know the type and be able to allow methods/functions to be called with the typed... This way, If I want to change my ThisClass definition from SubLevel1 to SubLevel2, I don't have to dance around all different data type definitions. Hope this makes sense.. public class TopLevel<T> { ... } pubic class SubLevel1 : TopLevel<int> { ... } public class SubLevel2 : TopLevel<Int64> { ... } public class ThisClass : SubLevel1 { ... public <based on the Int data type from SubLevel1> SomeFunc() { return <the Int value computed>; } }

  Read the article

• Why is an Add method required for { } initialization?

  - by Dan Tao

  To use initialization syntax like this: var contacts = new ContactList { { "Dan", "[email protected]" }, { "Eric", "[email protected]" } }; ...my understanding is that my ContactList type would need to define an Add method that takes two string parameters: public void Add(string name, string email); What's a bit confusing to me about this is that the { } initializer syntax seems most useful when creating read-only or fixed-size collections. After all it is meant to mimic the initialization syntax for an array, right? (OK, so arrays are not read-only; but they are fixed size.) And naturally it can only be used when the collection's contents are known (at least the number of elements) at compile-time. So it would almost seem that the main requirement for using this collection initializer syntax (having an Add method and therefore a mutable collection) is at odds with the typical case in which it would be most useful. I'm sure I haven't put as much thought into this matter as the C# design team; it just seems that there could have been different rules for this syntax that would have meshed better with its typical usage scenarios. Am I way off base here? Is the desire to use the { } syntax to initialize fixed-size collections not as common as I think? What other factors might have influenced the formulation of the requirements for this syntax that I'm simply not thinking of?

  Read the article

• How to implement Master-Detail with Multi-Selection in WPF?

  - by gehho

  Hi, I plan to create a typical Master-Detail scenario, i.e. a collection of items displayed in a ListView via DataBinding to an ICollectionView, and details about the selected item in a separate group of controls (TextBoxes, NumUpDowns...). No problem so far, actually I have already implemented a pretty similar scenario in an older project. However, it should be possible to select multiple items in the ListView and get the appropriate shared values displayed in the detail view. This means, if all selected items have the same value for a property, this value should be displayed in the detail view. If they do not share the same value, the corresponding control should provide some visual clue for the user indicating this, and no value should be displayed (or an "undefined" state in a CheckBox for example). Now, if the user edits the value, this change should be applied to all selected items. Further requirements are: MVVM compatibility (i.e. not too much code-behind) Extendability (new properties/types can be added later on) Does anyone have experience with such a scenario? Actually, I think this should be a very common scenario. However, I could not find any details on that topic anywhere. Thanks! gehho. PS: In the older project mentioned above, I had a solution using a subclass of the ViewModel which handles the special case of multi-selection. It checked all selected items for equality and returned the appropriate values. However, this approach had some drawbacks and somehow seemed like a hack because (besides other smelly things) it was necessary to break the synchronization between the ListView and the detail view and handle it manually.

  Read the article

• Pros/Cons of MySQL vs Postgresql for production Ruby on Rails environment?

  - by cakeforcerberus

  I will soon be switching from sqlite3 to either postgres or mysql. What should I consider when making this decision? Is mysql more suited for Rails than postgres in some areas and/or vice versa? Or, as I somewhat suspect, does it not really matter either way? Another factor that might play into my decision is the availability of tools to data pump my test data from the sqlite3 db to my new one. Is there anything that ActiveRecord provides natively to do this or any decent plugins/gems to help with this task? BONUS: How do I pronounce "Postgresql" and sound like I know what I'm talking about? :) Thanks Greg Smith for providing the following link that shows the most common pronunciations: http://www.postgresql.org/community/survey.33 UPDATE: Reference this question for more: http://stackoverflow.com/questions/110927/do-you-recommend-postgresql-over-mysql FYI: I ended up using MySQL. There is a neat plugin called yamldb that really saved me some time with the data transfer from my sqlite db to my new mysql one. Instructions on how to install and use it can be found here: http://accidentaltechnologist.com/ruby/change-databases-in-rails-with-yamldb/ Thanks Tom

  Read the article

• How to apply styles to all windows in WPF app?

  - by Brandon

  I have the following App.xaml file: <Application x:Class="MiniDeviceConfig.App" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" StartupUri="MiniDeviceConfig.xaml"> <Application.Resources> <ResourceDictionary> <ResourceDictionary.MergedDictionaries> <ResourceDictionary Source="Button.xaml"/> <ResourceDictionary Source="CheckBox.xaml"/> <ResourceDictionary Source="ComboBox.xaml"/> <ResourceDictionary Source="Common.xaml"/> <ResourceDictionary Source="GroupBox.xaml"/> <ResourceDictionary Source="Label.xaml"/> <ResourceDictionary Source="LinkButton.xaml"/> <ResourceDictionary Source="ListBox.xaml"/> <ResourceDictionary Source="ListView.xaml"/> <ResourceDictionary Source="RadioButton.xaml"/> <ResourceDictionary Source="Tooltip.xaml"/> <ResourceDictionary Source="Window.xaml"/> </ResourceDictionary.MergedDictionaries> </ResourceDictionary> </Application.Resources> In my application, my main window is MiniDeviceConfig.xaml (as seen above). In my Button.xaml file, I clearly set the button height to some obscene number. And, this size is reflected in my main window's buttons. However, some action on the main window triggers a modal window that has more buttons on it. I was expecting the same tall buttons but no such luck. How do I get the style to propagate into all windows in the application?

  Read the article

• Adding StyleSheets Programmatically in Asp.Net

  - by Braveyard

  I want to add StyleSheets programmatically in the head section but one of the examples I saw seemed to need to many lines of code to add just one style sheet even though I may need a lot: Example Code: HtmlLink css = new HtmlLink(); css.Href = "css/fancyforms.css"; css.Attributes["rel"] = "stylesheet"; css.Attributes["type"] = "text/css"; css.Attributes["media"] = "all"; Page.Header.Controls.Add(css); I also use Page.Header.RenderControl() method but it didn't work either. Object null something error was thrown. I also used Page.Header.InnerHtml and InnerText += "<link .... "/> things but they threw the Literal error which is I think common error. I used this code : List<Literal> cssFiles = new List<Literal>(); cssFiles.Add(new Literal() { Text = @"<link href=""" + ResolveUrl("~/Resources/Styles/MainMaster/MainDesign.css") + @""" type=""text/css"" rel=""stylesheet"" />" }); cssFiles.Add(new Literal() { Text = @"<link href=""" + ResolveUrl("~/Resources/Styles/MainMaster/MainLayout.css") + @""" type=""text/css"" rel=""stylesheet"" />" }); AddStyleRange(cssFiles); private void AddStyleRange(List<Literal> cssFiles) { foreach (Literal item in cssFiles) { this.Header.Controls.Add(item); } } It worked at first but when I change the pages it stopped working. I am using Master Page and I am writing these codes on Master.cs file and also some people recommended to use this.Header instead of Page.Header but when I built it throws an error which says I cannot declare that like this. It shouldn't be that hard to add many styles. It is getting complicated.

  Read the article

• What is the best way to attach static methods to classes rather than to instances of a class?

  - by John Gietzen

  If I have a method for calculating the greatest common divisor of two integers as: public static int GCD(int a, int b) { return b == 0 ? a : GCD(b, a % b); } What would be the best way to attach that to the System.Math class? Here are the three ways I have come up with: public static int GCD(this int a, int b) { return b == 0 ? a : b.GCD(a % b); } // Lame... var gcd = a.GCD(b); and: public static class RationalMath { public static int GCD(int a, int b) { return b == 0 ? a : GCD(b, a % b); } } // Lame... var gcd = RationalMath.GCD(a, b); and: public static int GCD(this Type math, int a, int b) { return b == 0 ? a : typeof(Math).GCD(b, a % b); } // Neat? var gcd = typeof(Math).GCD(a, b); The desired syntax is Math.GCD since that is the standard for all mathematical functions. Any suggestions? What should I do to get the desired syntax?

  Read the article

• mercurial: how to synchronize mq patches from a master repo as mq patches to a set of clone repos

  - by dim

  I have to run a dozen of different build tests on a code base maintained in a mercurial repository. I don't want to run serially these tests on same repository because they modify a set of common files and I want to run them in parallel on different machines. Also, after all tests are run I want to have access to latest test results from those test work areas. Currently I'm cloning the master repository a dozen of times and run in each clone one different test. Before each test execution I do a pull/update/purge preparation sequence in order to start the test on latest clean state. That's good for me. I'm also preparing new changes using mq extension that I would test on all clones as above before committing them. For testing some ready candidate mq patches I want somehow to deploy/synchronize them to be available in test clones and apply those ready for testing using some guard before running the test. Did anybody do this synchronization before? What's the most simple way to do it? Do I need to have versioned mq patches for that?

  Read the article

• Am I correctly extracting JPEG binary data from this mysqldump?

  - by Glenn

  I have a very old .sql backup of a vbulletin site that I ran around 8 years ago. I am trying to see the file attachments that are stored in the DB. The script below extracts them all and is verified to be JPEG by hex dumping and checking the SOI (start of image) and EOI (end of image) bytes (FFD8 and FFD9, respectively) according to the JPEG wiki page. But when I try to open them with evince, I get this message "Error interpreting JPEG image file (JPEG datastream contains no image)" What could be going on here? Some background info: sqldump is around 8 years old vbulletin 2.x was the software that stored the info most likely php 4 was used most likely mysql 4.0, possibly even 3.x the column datatype these attachments are stored in is mediumtext My Python 3.1 script: #!/usr/bin/env python3.1 import re trim_l = re.compile(b"""^INSERT INTO attachment VALUES\('\d+', '\d+', '\d+', '(.+)""") trim_r = re.compile(b"""(.+)', '\d+', '\d+'\);$""") extractor = re.compile(b"""^(.*(?:\.jpe?g|\.gif|\.bmp))', '(.+)$""") with open('attachments.sql', 'rb') as fh: for line in fh: data = trim_l.findall(line)[0] data = trim_r.findall(data)[0] data = extractor.findall(data) if data: name, data = data[0] try: filename = 'files/%s' % str(name, 'UTF-8') ah = open(filename, 'wb') ah.write(data) except UnicodeDecodeError: continue finally: ah.close() fh.close() update The JPEG wiki page says FF bytes are section markers, with the next byte indicating the section type. I see some that are not listed in the wiki page (specifically, I see a lot of 5C bytes, so FF5C). But the list is of "common markers" so I'm trying to find a more complete list. Any guidance here would also be appreciated.

  Read the article

• How do I unit test a finalizer?

  - by GraemeF

  I have the following class which is a decorator for an IDisposable object (I have omitted the stuff it adds) which itself implements IDisposable using a common pattern: public class DisposableDecorator : IDisposable { private readonly IDisposable _innerDisposable; public DisposableDecorator(IDisposable innerDisposable) { _innerDisposable = innerDisposable; } #region IDisposable Members public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } #endregion ~DisposableDecorator() { Dispose(false); } protected virtual void Dispose(bool disposing) { if (disposing) _innerDisposable.Dispose(); } } I can easily test that innerDisposable is disposed when Dispose() is called: [Test] public void Dispose__DisposesInnerDisposable() { var mockInnerDisposable = new Mock<IDisposable>(); new DisposableDecorator(mockInnerDisposable.Object).Dispose(); mockInnerDisposable.Verify(x => x.Dispose()); } But how do I write a test to make sure innerDisposable does not get disposed by the finalizer? I want to write something like this but it fails, presumably because the finalizer hasn't been called by the GC thread: [Test] public void Finalizer__DoesNotDisposeInnerDisposable() { var mockInnerDisposable = new Mock<IDisposable>(); new DisposableDecorator(mockInnerDisposable.Object); GC.Collect(); mockInnerDisposable.Verify(x => x.Dispose(), Times.Never()); }

  Read the article

• Simple grid layout question

  - by Matt H.

  I can't believe I'm back to this after working with WPF for 3 months :) Consider very common setup: How do I configure the rowheights so that the top and bottom rows (menu bar and status bar) size to fit the height of their content, and the middle row (main content), fills the remaining available space in the program? I can't fix the height of the top/bottom rows because the height of their content can vary. <Window> <Grid> <Grid.RowDefinitions> <RowDefinition/> <RowDefinition/> <RowDefinition/> </Grid.RowDefinitions> <Menu Grid.Row=0> ...menuitems </Menu> <Grid Grid.Row=1> ...main application content here (like most programs) </Grid> <StatusBar> ...statusbaritems </StatusBar> </Grid> </Window>

  Read the article

• Maven webapp with Eclipse and WTP plugin deploy files in stranges ways in Tomcat

  - by hokkos

  Hi, I use Eclipse J2EE 3.5 with Maven and tomcat. To deploy my maven webapp with WTP I added a Dynamic Web Module facet and changed the "org.eclipse.wst.common.component" file of the project because the webapp is not in a WebContent directory, here is the content of the file: <?xml version="1.0" encoding="UTF-8"?> <project-modules id="moduleCoreId" project-version="1.5.0"> <wb-module deploy-name="tkey-ca-web"> <wb-resource deploy-path="/" source-path="/src/main/webapp"/> <wb-resource deploy-path="/WEB-INF/classes" source-path="/src/main/java"/> <wb-resource deploy-path="/WEB-INF/classes" source-path="/src/main/resources"/> <property name="context-root" value="toto"/> <property name="java-output-path" value="/toto/target/classes"/> </wb-module> </project-modules> But it never deploy the content correctly, in "workspace.metadata.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps\toto\" the directory structure is correct with WEB-INF and META-INF but empty, the jsp, html, css files are in "workspace.metadata.plugins\org.eclipse.wst.server.core\tmp1\wtpwebapps\toto\WEB-INF\classes\" with another WEB-INF and META-INF structure but with the files. I don't understand this at all, thanks.

  Read the article

• How do I pass a const reference in C#?

  - by Maciek

  In C++, passing const references is a common practice - for instance : #include <iostream> using namespace std; class X { public : X() {m_x = 0; } X(const int & x) {m_x = x; } X(const X & other) { *this = other; } X & operator = (const X & other) { m_x = other.m_x; return *this; } void print() { cout << m_x << endl; } private : int m_x; }; void main() { X x1(5); X x2(4); X x3(x2); x2 = x1; x1.print(); x2.print(); x3.print(); } This very simple example illustrates how it's done - pretty much. However I've noticed that in C# this doesn't seem to be the case. Do I have to pass const references in C# ? what do I need the "ref" keyword for? Please note that I know and understand what C# reference and value types are.

  Read the article

• Matlab-Bisection-Newton-Secant , finding roots?

  - by i z

  Hello and thanks in advance for your possible help ! Here's my problem: I have 2 functions f1(x)=14.*x*exp(x-2)-12.*exp(x-2)-7.*x.^3+20.*x.^2-26.*x+12 f2(x)=54.*x.^6+45.*x.^5-102.*x.^4-69.*x.^3+35.*x.^2+16.*x-4 Make the graph for those 2, the first one in [0,3] and the 2nd one in [-2,2]. Find the 3 roots with accuracy of 6 decimal digits using a) bisection ,b) newton,c)secant.For each root find the number of iterations that have been made. For Newton-Raphson, find which roots have quadratic congruence and which don't. What is the main common thing that roots with no quadratic congruence (Newton's method)? Why ? Excuse me if i ask silly things, but i'm asked to do this with no Matlab courses and I'm trying to learn it myself. There are many issues i have with this exercise . Questions : 1.I only see 2 roots in the graph for the f1 function and 4-5 (?) roots for the function f2 and not 3 roots as the exercise says. Here's the 2 graphs : http://postimage.org/image/cltihi9kh/ http://postimage.org/image/gsn4sg97f/ Am i wrong ? Do both have only 3 roots in [0,3] and [-2,2] ? Concerning the Newton's method , how am i supposed to check out which roots have quadratic congruence and which not??? Accuracy means tolerance e=10^(-6), right ?

  Read the article

• Vertical-Align: A Full Explanation

  - by Livvy Jeffs

  I've been struggling with vertical alignments, a seemingly simple enough process that has a lot of idiosyncrasies throughout different languages and element types. I've done a lot of reading through stackexchange and can't seem to find a common thread of understanding. Here are the rules that I have been able to gather: 1) Vertical-align does not work in <\div>s, you have to set div {display: table-cell; vertical-align: middle} This seems like a big hassle, especially since table-cells override the height limitation even when overflow is set to hidden and expands to fit content, which means the vertical "center" is variable. I just read some source-code from Pinterest where button {vertical-align: middle}, but no other vertical-align commands seem to work. It seems as if button is by default aligned in the middle. Can someone provide a clear explanation for the vertical-align attribute? What html elements respond to vertical-align? Which html elements have default vertical-align attributes? Which html elements have non-overridable vertical-align attributes? And any clues as to understanding the idiosyncracies would help as well! Thanks in advance!

  Read the article

• Project Architecture For Enhancing Legacy project.

  - by vijay.shad

  I am working on legacy project. Now the situation demands project to be divided into parts. What strategy I should follow to do this task. Description: The legacy project (A) is fully functional web application with almost well defined layers. But now i need to extend the project to a further enhancement. This project usage maven as build tool. But it is used only for dependency managements only. (project exported to war form inside eclipse). The new enhancement needs me to add new data table, new UI(jsp, css, js and images). What should be my strategy to enhance to application. My proposed design. I am planing to create two new projects Project B : Main Enhancement works will done in this project. Will have all layers like service layer, dao layer and UI layer in itself. And will be a web application in itself. Project C : Extract some common model and service code form project-A and create this project. This project will be added as dependency to both the projects. If my this approach is okay! Then i presume there will be problem be problem in deployment. These two projects will demand to deploy separately(currently tomcat is used). But I must deploy these two projects as one war. So, i need to have a plan to change the web.xml entries to have configurations for both projects. This will comes with some more complexities with project. What should be my design for the project? Does my plan sounds good.

  Read the article

• HTML & CSS Horizontal menu with items on left & right

  - by Fabian Vilers

  Hi all, I'm building an horizontal menu in html+css. The current result is fine, except I want to have some items on the left, and others on the right. I couldn't find usefull result on Google with such common keywords so I'm asking on SO. Here's my code so far: #menu { background-color: #383838; height: 65px; margin-bottom: 20px; } #menu ul li { float: left; } <div id="menu"> <ul> <li>Link 1</li> <li>Link 2</li> <li>Link 3</li> </ul> </div> I'd like to have Link 3 on the right, so the space between link 2 and 3 should be filled at maximum. I don't want a filler <li> tag, but instead apply a class to the last <li> on the left, or the first <li> on the right. Don't want to adjust the width as I've a :hover background color changing effet on the links. I suppose margin or padding should do the trick but I can't manage to find how. Any clue? Thanks in advance, Fabian

  Read the article

• Viewstate in a .ashx Handler?

  - by Matt Dawdy

  I've got a handler (list.ashx for example) that has a method that retrieves a large dataset, then grabs only the records that will be shown on any given "page" of data. We are allowing the users to do sorting on these results. So, on any given page run, I will be retrieving a dataset that I just got a few seconds/minutes ago, but reordering them, or showing the next page of data, etc. My point is that my dataset really hasn't changed. Normally, the dataset would be stuck into the viewstate of a page, but since I'm using a handler, I don't have that convenience. At least I don't think so. So, what is a common way to store the viewstate associated with a current user's given page when using a handler? Is there a way to take the dataset, encode it somehow and send that back to the user, and then on the next call, pass it back and then rehydrate a dataset from those bits? I don't think Session would be a good place to store it since we might have 1000 users all viewing different datasets of different data, and that could bring the server to its knees. At least I think so. Does anyone have any experience with this kind of situation, and can you give me any advice?

  Read the article

• In SQL, if we rename INNER JOIN as INTERSECT JOIN, LEFT OUTER JOIN as LEFT UNION JOIN, and FULL OUTE

  - by Jian Lin

  In SQL, the name Join gives an idea of "merging" or a sense of "union", making something bigger. But in fact, as in the other post http://stackoverflow.com/questions/2706051/in-sql-a-join-is-actually-an-intersection-and-it-is-also-a-linkage-or-a-sidew it turns out that a Join (Inner Join) is actually an Intersection. So if we think of Join = Inner Join = Intersect Join Left Outer Join = Left Union Join Full Outer Join = Full Union Join = Union Join then we always get a feel of what's happening, and maybe never forget what they are easily. In a way, we can think of Intersect as "making it less", therefore it is excluding something. That's why the name "Join" won't go with the idea of "Intersect". But in fact, both Intersect and Union can be thought of as: Union: bringing something together and merge them unconditionally. Intersect: bringing something together and merge them based on some condition. so the "bringing something together" is probably what "Join" is all about. It is like, Intersection is a "half glass of water" -- we can thinking of it as "excluding something" or as "bringing something together and accepting the common ones". So if the word "Intersect Join" is used, maybe a clear picture is there, and "Union Join" can be a clear picture too. Maybe the word "Inner Join" and "Outer Join" is very clear when we use SQL a lot. Somehow, the word "Outer" tends to give a feeling that it is "outside" and excluding something rather than a "Union".

  Read the article

• How to make this OO?

  - by John

  Hello, Sorry for the poor title,I'm new to OOP so I don't know what is the term for what I need to do. I have, say, 10 different Objects that inherit one Object.They have different amount and type of class members,but all of them have one property in common - Visible. type TObj1=class(TObject) private a:integer; ...(More members) Visible:Boolean; end; TObj2=class(TObject) private b:String; ...(More members) Visible:Boolean; end; ...(Other 8 objects) For each of them I have a variable. var Obj1:TObj1; Obj2:TObj2; Obj3:TObj3; ....(Other 7 objects) Rule 1: Only one object can be initialized at a time(others have to be freed) to be visible. For this rule I have a global variable var CurrentVisibleObj:TObject; //Because they all inherit TObject Finally there is a procedure that changes visibility. procedure ChangeObjVisibility(newObj:TObject); begin CurrentVisibleObj.Free; //Free the old object CurrentVisibleObj:=newObj; //assign the new object CurrentVisibleObj:= ??? //Create new object CurrentVisibleObj.Visible:=true; //Set visibility to new object end; There is my problem,I don't know how to initialize it,because the derived class is unknown. How do I do this? I simplified the explanation,in the project there are TFrames each having different controls and I have to set visible/not visible the same way(By leaving only one frame initialized). Sorry again for the title,I'm very new to OOP.

  Read the article

• Duck type testing with C# 4 for dynamic objects.

  - by Tracker1

  I'm wanting to have a simple duck typing example in C# using dynamic objects. It would seem to me, that a dynamic object should have HasValue/HasProperty/HasMethod methods with a single string parameter for the name of the value, property, or method you are looking for before trying to run against it. I'm trying to avoid try/catch blocks, and deeper reflection if possible. It just seems to be a common practice for duck typing in dynamic languages (JS, Ruby, Python etc.) that is to test for a property/method before trying to use it, then falling back to a default, or throwing a controlled exception. The example below is basically what I want to accomplish. If the methods described above don't exist, does anyone have premade extension methods for dynamic that will do this? Example: In JavaScript I can test for a method on an object fairly easily. //JavaScript function quack(duck) { if (duck && typeof duck.quack === "function") { return duck.quack(); } return null; //nothing to return, not a duck } How would I do the same in C#? //C# 4 dynamic Quack(dynamic duck) { //how do I test that the duck is not null, //and has a quack method? //if it doesn't quack, return null }

  Read the article

• Abstract Methods in "Product" - Factory Method C#

  - by Regina Foo

  I have a simple class library (COM+ service) written in C# to consume 5 web services: Add, Minus, Divide, Multiply and Compare. I've created the abstract product and abstract factory classes. The abstract product named WS's code: public abstract class WS { public abstract double Calculate(double a, double b); public abstract string Compare(double a, double b); } As you see, when one of the subclasses inherits WS, both methods must be overridden which might not be useful in some subclasses. E.g. Compare doesn't need Calculate() method. To instantiate a new CompareWS object, the client class will call the CreateWS() method which returns a WS object type. public class CompareWSFactory : WSFactory { public override WS CreateWS() { return new CompareWS(); } } But if Compare() is not defined as abstract in WS, the Compare() method cannot be invoked. This is only an example with two methods, but what if there are more methods? Is it stupid to define all the methods as abstract in the WS class? My question is: I want to define abstract methods that are common to all subclasses of WS whereas when the factory creates a WS object type, all the methods of the subclasses can be invoked (overridden methods of WS and also the methods in subclasses). How should I do this?

  Read the article

< Previous Page | 280 281 282 283 284 285 286 287 288 289 290 291  | Next Page >