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• Questions about "casting operation" in OOP

  - by rhapsodyn

  When programming, we usually use some type-casting operations. When the casting happens on the objects "on the same level", it feels ok. But when it happens on the ojects "on the different levels"(mainly between father and son), it feels weird. Considering this: Class Son extends Father WhenSon s = (Son)father;, it's absolutely unreasonable. Because a "Son" is not a "Father" anymore, "Son" may grow up with some new properties "Father" doesn't have, the casting operation makes these properties unknown. On the other hand, Father f = (Father)son seems reasonable, but according to LSP "An instance of a derived should be able to replace any instance of its superclass" A "Son" can do anything his "Father" can, so the casting operation seems useless. So can i say that these casting operations are agaisnt OO design principle but necessary?

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• Native arrays and computing hashvalues (VB, C#)

  - by Jeffrey Kern

  I feel bad asking this question but I am currently not able to program and test this as I'm writing this on my cell-phone and not on my dev machine :P (Easy rep points if someone answers! XD ) Anyway, I've had experience with using hashvalues from String objects. E.g., if I have StringA and StringB both equal to "foo", they'll both compute out the same hashvalue, because they're set to equal values. Now what if I have a List, with T being a native data type. If I tried to compute the hashvalue of ListA and ListB, assuming that they'd both be the same size and contain the same information, wouldn't they have equal hashvalues as well?

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• how to access jquery internal data?

  - by Unknown

  As you may or may not be aware as of jQuery 1.7 the whole event system was rewritten from the ground up. The codebase is much faster and with the new .on() method there is a lot of uniformity to wiring up event handlers. One used to be able to access the internal events data and investiate what events are registered on any given element, but recently this internal information has been hidden based on the following scenario... It seems that the "private" data is ALWAYS stored on the .data(jQuery.expando) - For "objects" where the deletion of the object should also delete its caches this makes some sense. In the realm of nodes however, I think we should store these "private" members in a separate (private) cache so that they don't pollute the object returned by $.fn.data()" Although I agree with the above change to hide the internal data, I have found having access to this information can be helpful for debugging and unit testing. What was the new way of getting the internal jquery event object in jQuery 1.7?

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• Realtime processing and callbacks with Python and C++

  - by Doughy

  I need to write code to do some realtime processing that is fairly computationally complex. I would like to create some Python classes to manage all my scripting, and leave the intensive parts of the algorithm coded in C++ so that they can run as fast as possible. I would like to instantiate the objects in Python, and have the C++ algorithms chime back into the script with callbacks in python. Something like: myObject = MyObject() myObject.setCallback(myCallback) myObject.run() def myCallback(val): """Do something with the value passed back to the python script.""" pass Will this be possible? How can I run a callback in python from a loop that is running in a C++ module? Anyone have a link or a tutorial to help me do this correctly?

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• Does anyone else think instance variables are problematic in database-backed applications?

  - by Ben Aston

  It occurs to me that state control in languages like C# is not well supported. By this, I mean, it is left upto the programmer to manage the state of in-memory objects. A common use-case is that instance variables in the domain-model are copies of information residing in persistent storage (i.e. the database). Clearly this violates the single point of authority principle, and "synchronisation" has to be managed by the developer. I envisage a system where instead of instance variables, we have simple public access/mutator methods marked with attributes that link them to the database, and where reads and writes are mediated by a framework that decides whether to hit the database. Does such a system exist? Am I completely missing the point, or is there some truth to this idea?

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• BeanUtils getPropertyOfMapBean

  - by dx-cp

  Hi, Im wondering if it is possible to get data from property which is map cotaining pairs Key-StringArray (Map) in BeanUtils library. I just simply need to access one of array elements by calling propertyName=string[0]. Current version (1.8.3) does not support indexed properties. If you look into their code you will find in class PropertyUtilsBean in method getPropertyOfMapBean: if (resolver.isIndexed(propertyName) || resolver.isMapped(propertyName)) { throw new IllegalArgumentException( "Indexed or mapped properties are not supported on" + " objects of type Map: " + propertyName); } way too bad:-( Have any of you any tip how to do it somehow differently?

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• Does std::multiset guarantee insertion order?

  - by Naveen

  I have a std::multiset which stores elements of class A. I have provided my own implementation of operator< for this class. My question is if I insert two equivalent objects into this multiset is their order guaranteed? For example, first I insert a object a1 into the set and then I insert an equivalent object a2 into this set. Can I expect the a1 to come before a2 when I iterate through the set? If no, is there any way to achieve this using multiset?

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• Covariant return types in Java enums

  - by Kelvin Chung

  As mentioned in another question on this site, something like this is not legal: public enum MyEnum { FOO { public Integer doSomething() { return (Integer) super.doSomething(); } }, BAR { public String doSomething() { return (String) super.doSomething(); } }; public Object doSomething(); } This is due to covariant return types apparently not working on enum constants (again breaking the illusion that enum constants are singleton subclasses of the enum type...) So, how about we add a bit of generics: is this legal? public enum MyEnum2 { FOO { public Class<Integer> doSomething() { return Integer.class; } }, BAR { public Class<String> doSomething() { return String.class; } }; public Class<?> doSomething(); } Here, all three return Class objects, yet the individual constants are "more specific" than the enum type as a whole...

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• Can I change the datsource of report model at runtime

  - by Manab De

  I've some adhoc reports developed on some report models which are published on Report Server (we're using SSRS 2008). Everything is running well. Now in our production environment we've near about forty (40) customers who have their own database (each have the same table structures and other database objects). Now the challenge is whenever a customer will log into the report server using windows authentication and trying to view those reports we need to get the SQL data from the proper database only. Reports are designed using the report model and each model has a valid data source which is connected to particular database. We can create forty separate data sources each will be connected to specific database. My question is, is there any way through which we can change the report model data source name dynamically or during runtime based on the customer name so that during execution of the report, SSRS would fetch the data from the correct database but not from any other database. Please help me.

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• Accessing items from a dictionary using pickle efficiently in Python

  - by user248237

  I have a large dictionary mapping keys (which are strings) to objects. I pickled this large dictionary and at certain times I want to pull out only a handful of entries from it. The dictionary has usually thousands of entries total. When I load the dictionary using pickle, as follows: from cPickle import * # my dictionary from pickle, containing thousands of entries mydict = open(load('mypickle.pickle')) # accessing only handful of entries here for entry in relevant_entries: # find relevant entry value = mydict[entry] I notice that it can take up to 3-4 seconds to load the entire pickle, which I don't need, since I access only a tiny subset of the dictionary entries later on (shown above.) How can I make it so pickle only loads those entries that I have from the dictionary, to make this faster? Thanks.

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• Substituting variables in a loop?

  - by jksl

  I am trying to write a loop in R but I think the nomenclature is not correct as it does not create the new objects, here is a simplified example of what I am trying to do: for i in (1:8) { List_i <-List colsToGrab_i <-grep(predefinedRegex_i, colnames(List_i$table)) List_i$table <- List_i$table[,predefinedRegex_i] } I have created 'predefinedRegex'es 1:8 which the grep should use to search The loop creates an object called "List_i" and then fails to find "predefinedRegex_i". I have tried putting quotes around the "i" and $ in front of the i but these do not work. Any help much appreciated. Thank you.

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• jQuery after show() assumes that display:inline is :hidden. Why?

  - by Janis Veinbergs

  With jQuery 1.4.2, :hidden filter is not filtering out elements that were hidden, but i've made then visible by calling show(). Filter assumes it is still hidden. Is this bug or am i missing something? Consider the following code: $("td.ms-authoringcontrols > span[id*='_ParallelApprovers']:hidden:first").css("display") "none" $("td.ms-authoringcontrols > span[id*='_ParallelApprovers']:hidden:first").show() Object $("td.ms-authoringcontrols > span[id*='_ParallelApprovers']:hidden:first").css("display") "inline" // ?? Let me scratch my head... $("td.ms-authoringcontrols > span[id*='_ParallelApprovers']:hidden:first").is(":hidden") true //element with "display:inline", visible in browser, but yet it is hidden Instead of "inline", you would expect "none", because :hidden filter was used. What it does is from an array of objects it selects first hidden element. Each time i call these lines of code, i expect them to select next hidden element (not the one i just showed).

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• C# Reflection - How can I tell if object o is of type KeyValuePair and then cast it?

  - by Logan

  Hi All I'm currently trying to write a Dump() method from LinqPad equivalent iin C# for my own amusment. I'm moving from Java to C# and this is an exercise rather than a business requirement. I've got almost everything working except for Dumping a Dictionary. The problem is that KeyValuePair is a Value type. For most other Value types I simply call the ToString method but this is insufficient as the KeyValuePair may contain Enumerables and other objects with undesirable ToString methods. So I need to work out if it's a KeyValuePair and then cast it. In Java I could use wildcard generics for this but I don't know the equivalent in C#. Your quest, given an object o, determine if it's a KeyValuePair and call Print on its key and value. Print(object o) { ... } Thanks!

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• What is the best to format messages for queueing?

  - by Tijmen

  I've been reading up on message queueing lately, and I'd like to implement a simple, extendable, system for my app. While there's a lot of good information on the subject of setting up a MQ system out there, I can't find a lot about the actual implementation. I'm looking for patterns and best practices on how to properly format messages for a queue, and ways to execute the jobs in PHP. Should I use JSON, serialized objects, text, URLs or XML? What information should I send? Is a worker with a switch($job['command']) {} (or something like that) the way to go, or are there any established patterns out there to implement a worker? Help greatly appreciated!

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• EGL initialized failed

  - by aquatear

  Hello Everybody, I used a SurfaceView and EGL to render my 3D contents. When I press BACK and return my activity, the activity's 3D objects become to white. The reason is when the original activity(3D activity) resume, EGL would initialize again. So EGL would initialize and destroy everytime when different activities switch. I am not sure if the problem is EGL initialize twice... but I did initialize and destroy EGL correctly. Anybody have this problem ? Have any solutions about this ?? Thank you so much

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• PropertyGrid + interface

  - by nilphilus

  public interface ITest { void Somethink(); } public class Test1 : ITest { public void Somethink() { /* do stuff */ } public int Test1Property { get; set; } } public class Test2 : ITest { public void Somethink() { /* do stuff */ } public float Test2Property { get; set; } } //Main class public class MainClass { [TypeConverter(ExpandableObjectConverter)] public ITest test { get; set; } } Ok, i have sth like this. Instance of MainClass is selected by PropertyGrid. How to make a DropDownList of objects of classes which implement ITest (here Test1 and Test2)

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• how to query list in powershell

  - by Varyanica

  add-type -Language CSharpVersion3 -TypeDefinition @" public class pack_code { public pack_code() {} public string code { get; set; } public string type { get; set; } } "@ $a = New-Object pack_code $a.code = "3" $a.type = "5" $b = New-Object pack_code $b.code = "2" $b.type = "5" $c = New-Object pack_code $c.code = "2" $c.type = "5" $d = New-Object pack_code $d.code = "1" $d.type = "1" $codes = New-Object 'System.Collections.Generic.List[object]' $codes.add($a) $codes.add($b) $codes.add($c) $codes.add($d) is there a way to select distinct from $codes and select the objects where type equals 1? How can i use linq with PowerShell?

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• How can I invoke the dialog to set printer options manually?

  - by FromTheMountain

  I'm using WPF and need to let users set some print related options like printer and printer properties (e.g. papertray, landscape/portrait, duplex, etc). I'm aware of the PrintDialog class to get a PrintQueue and PrintTicket object. However I need to create I custom solution and can not show the PrintDialog. I manage to get the available PrintQueue objects and let users select a printer. I'm struggling with the printer properties. My question is: how can I show the dialog in which a user can set the printer properties for the selected PrintQueue (the dialog that is shown when a user clicks on the Properties button in the WPF PrintDialog).

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• android exit application completely and go to main applications screen

  - by Totti

  i know that this question is asked many times, but really i can't understand the answer, i want to set button, when user click it i want to exit the application (also the carbage collector should remove the objects), and after exiting i want to go to the screen where the user found the application icon on mobile. for exit i don't know what to do for going to the screen where to find the application icon i tried like this Intent intent = new Intent(Intent.ACTION_MAIN); intent.addCategory(Intent.CATEGORY_HOME); intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); startActivity(intent); but doesn't work

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• getElementsByTagName() equivalent for textNodes

  - by levik

  Is there any way to get the collection of all textNode objects within a document? getElementsByTagName() works great for Elements, but textNodes are not Elements. Update: I realize this can be accomplished by walking the DOM - as many below suggest. I know how to write a DOM-walker function that looks at every node in the document. I was hoping there was some browser-native way to do it. After all it's a little strange that I can get all the <input>s with a single built-in call, but not all textNodes.

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• Subsonic foreign key returning collection?

  - by Shaul

  I'm just writing my first "Hello World" program using Subsonic, for which I've thrown together a simple little Customer/Invoice/InvoiceItem/Product database. The connection was successfully made to the DB, and it generated all the right ActiveRecord classes. But for some reason, the Invoice class has a property called Customers, which returns a collection of Customer objects, even though the Invoice table has a CustomerID field which has a foreign key to the Customer table. I would have expected a Customer property returning a single Customer object. I must be doing something wrong - but what?

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• C# Elegant way to handle checking for an item in a collection.

  - by JL

  I've posted a code sample below. Firstly let me explain termStore.Groups in the code below is a collection of Group Objects (The exact class is irrelevant). Checking for null : if (termStore.Groups[groupName] == null) seems like a logical (clean) approach, but if the Groups collection is empty then an exception is produced. using the termStore.Groups.Contains is not an option either because this expects a strong type i.e: .Contains(Group)... not .Contains(GroupName as string) Can someone recommend a clean / generic way I can check for if an item exists in collection . Thank you.... TermStore termStore = session.TermStores.Where(ts => ts.Name == termStoreName).FirstOrDefault(); if (termStore.Groups[groupName] == null) { termStore.CreateGroup(groupName); termStore.CommitAll(); } Update: The exact class Sharepoint Taxonomy Classes. http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.taxonomy.group.aspx

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• C# Event routing in code behind

  - by Nate

  I'm building a WPF MVVM-ish application. I want to be able to display an event log containing items in a collection that exists in my viewmodel. I want any of the objects in the model to be able to add data to the event log. Therefore every object needs to be able to pass data back to one central collection for databinding in the view. I could implement an event in every one of my data classes and manually pass the events up the object heirarchy but this seems super clumsy. On the visual tree a Routed Event would take care of this, is there some equivelent in the model scope? Any other ideas?

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• Is there a difference between `==` and `is` in python?

  - by Bernard

  My Google-fu has failed me. In Python, are these: n = 5 # Test one. if n == 5: print 'Yay!' # Test two. if n is 5: print 'Yay!' two tests for equality equivalent (ha!)? Does this hold true for objects where you would be comparing instances (a list say)? Okay, so this kind of answers my question: l = list() l.append(1) if l == [1]: print 'Yay!' # Holds true, but... if l is [1]: print 'Yay!' # Doesn't. So == tests value where is tests to see if they are the same object?

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• Linux program - reverse highlighted text

  - by Oren

  I want to develop a program that will run on the background of my Ubuntu 12.04 so when some text is selected in some textbox of any running program and some key-combination is pressed (like ctrl-F12), the text will be cut, reversed, and pasted in the same place. I know some programs that do it on windows. It is useful in some programs and web-pages that do not support right-to-left languages like arabic and hebrew - the letters are printed from left to right so the text becomes reversed. More specifically I need it in Prezi that has this kind of bug in their embedded flash editor (I thought about writing a chrome-plugin, but I don't think such plugin can manipulate the selected text inside a flash objects). Do you know if such a program exist? Where should I start reading in order to develop a program with such capabilities (manipulate selected text in other programs)? Thanks

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