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  • ruby class collections

    - by poseid
    how does this work? in irb: >> class A >> b = [1, 2,3] >> end => [1, 2, 3] Is b an instance variable? class variable? how would I access b from outside the class? Is it used for meta-programming?

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  • How to convert a table column to another data type

    - by holden
    I have a column with the type of Varchar in my Postgres database which I meant to be integers... and now I want to change them, unfortunately this doesn't seem to work using my rails migration. change_column :table1, :columnB, :integer So I tried doing this: execute 'ALTER TABLE "table1" ALTER COLUMN "columnB" TYPE integer USING CAST(columnB AS INTEGER)' but cast doesn't work in this instance because some of the column are null... any ideas?

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  • polymorphism, inheritance in c# - base class calling overridden method?

    - by Andrew Johns
    This code doesn't work, but hopefully you'll get what I'm trying to achieve here. I've got a Money class, which I've taken from http://www.noticeablydifferent.com/CodeSamples/Money.aspx, and extended it a little to include currency conversion. The implementation for the actual conversion rate could be different in each project, so I decided to move the actual method for retrieving a conversion rate (GetCurrencyConversionRate) into a derived class, but the ConvertTo method contains code that would work for any implementation assuming the derived class has overriden GetCurrencyConversionRate so it made sense to me to keep it in the parent class? So what I'm trying to do is get an instance of SubMoney, and be able to call the .ConvertTo() method, which would in turn use the overriden GetCurrencyConversionRate, and return a new instance of SubMoney. The problem is, I'm not really understanding some concepts of polymorphism and inheritance yet, so not quite sure what I'm trying to do is even possible in the way I think it is, as what is currently happening is that I end up with an Exception where it has used the base GetCurrencyConversionRate method instead of the derived one. Something tells me I need to move the ConvertTo method down to the derived class, but this seems like I'll be duplicating code in multiple implementations, so surely there's a better way? public class Money { public CurrencyConversionRate { get { return GetCurrencyConversionRate(_regionInfo.ISOCurrencySymbol); } } public static decimal GetCurrencyConversionRate(string isoCurrencySymbol) { throw new Exception("Must override this method if you wish to use it."); } public Money ConvertTo(string cultureName) { // convert to base USD first by dividing current amount by it's exchange rate. Money someMoney = this; decimal conversionRate = this.CurrencyConversionRate; decimal convertedUSDAmount = Money.Divide(someMoney, conversionRate).Amount; // now convert to new currency CultureInfo cultureInfo = new CultureInfo(cultureName); RegionInfo regionInfo = new RegionInfo(cultureInfo.LCID); conversionRate = GetCurrencyConversionRate(regionInfo.ISOCurrencySymbol); decimal convertedAmount = convertedUSDAmount * conversionRate; Money convertedMoney = new Money(convertedAmount, cultureName); return convertedMoney; } } public class SubMoney { public SubMoney(decimal amount, string cultureName) : base(amount, cultureName) {} public static new decimal GetCurrencyConversionRate(string isoCurrencySymbol) { // This would get the conversion rate from some web or database source decimal result = new Decimal(2); return result; } }

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  • Python: how to inherite and override

    - by Guy
    Consider this situation: I get an object of type A which has the function f. I.e: class A: def f(): print 'in f' def h(): print 'in h' and I get an instance of this class but I want to override the f function but save the rest of the functionality of A. So what I was thinking was something of the sort: class B(A): .... def f(): print 'in B->f' and the usage would be: def main(a): b = B(a) b.f() #prints "in B->f" b.h() #print "in h" How do you do such a thing?

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  • Best point to overwrite the navigationBar property of navigationController

    - by flohei
    Hi there, I'm overwriting UINavigationController to replace the default navigationBar property with an instance of my own subclass of UINavigationBar. So I tried something like _navigationBar = [[SBNavigationBar alloc] init]; in my -initWithRootViewController:. But that didn't work out as I expected it. There's still the default navigationBar being displayed. So what's the best point to overwrite the navigationBar? Thanks in advance –f

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  • how to add to dates in java??

    - by terrific
    I want to add days in a date to get a new date in java. How to achieve it using the Calender class. Gregorian calender. Calender dom = new GregorianCalender(d, m y); is the instance of my date of manufacture and I want to reach to Date of Expiry adding some 100 days to the current date and store it in doe but unable to do that. Any help would be appreciable.

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  • How many ways a java Program can end ?

    - by Frank
    I know use System.exit(0) can end a java program, for instance, if I have a JFrame window, it will close and end the program, but I wonder how many other ways, can it be closed and the program be ended ? Including when an error occurs, will the program be shut down and the JFrame be closed ?

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  • How to remove all comment tags from XmlDocument

    - by Filburt
    How would i go about to remove all comment tags from a XmlDocument instance? Is there a better way than retrieving a XmlNodeList and iterate over those? XmlNodeList list = xmlDoc.SelectNodes("//comment()"); foreach(XmlNode node in list) { node.ParentNode.RemoveChild(node); }

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  • NSMutableArray with only a particular type of objects

    - by Leo
    Hello, is it possible to specify that a NSMutableArray can only contain a certain type of objects. For example, if I want to store only this kind of objects : @interface MyObject : NSObject { UInt8 value; } In order to be able to use the instance variable like this : - (void)myMethod:(NSMutableArray *)myArray{ for (id myObject in myArray){ [self otherMethod:myObject.value]; } } because I'm getting this error : request for member 'value' in something not a structure or union Thank you for your help

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  • Default value of a type

    - by viky
    For any given type i want to know its default value. In C#, there is a keyword called default for doing this like object obj = default(Decimal); but I have an instance of Type (called myType) and if I say this, object obj = default(myType); it doesn't work Is there any good way of doing this? I know that a huge switch block will work but thats not a good choice.

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  • display one-to-many relationship for a model in Django admin (list mode)

    - by theactiveactor
    In Django admin site, when listing all the objects for a given model, I know we can customize which columns get displayed for a ModelA via list_display Say that ModelA has a one-to-many relationship with ModelB. I would like to add another column on the listing page for ModelA, where each entry is a URL pointing to all objects of ModelB having a foreign key relationship on corresponding instance of Model A in that row. How can I achieve this customization with the admin app?

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  • Finding partial substrings within a string

    - by Peter Chang
    I have two strings which must be compared for similarity. The algorithm must be designed to find the maximal similarity. In this instance, the ordering matters, but intervening (or missing) characters do not. Edit distance cannot be used in this case for various reasons. The situation is basically as follows: string 1: ABCDEFG string 2: AFENBCDGRDLFG the resulting algorithm would find the substrings A, BCD, FG I currently have a recursive solution, but because this must be run on massive amounts of data, any improvements would be greatly appreciated

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  • Move namespace declaration from payload to envelope on an axis created web service

    - by rmarimon
    I just created a web service client using axis and eclipse that does not work with my web service provider. The message created by the web service client looks like this: <?xml version="1.0" encoding="UTF-8"?> <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <soapenv:Body> <enviarMensajeRequest xmlns="http://www.springframework.org/spring-ws/Imk-Zenkiu-Services"> <usuario>someuser</usuario> <clave>somepassword</clave> <mensaje>somemessage</mensaje> <contacto> <buzonSMS>somenumber</buzonSMS> <primerNombre>somefirstname</primerNombre> <primerApellido>somelastname</primerApellido> </contacto> </enviarMensajeRequest> </soapenv:Body> </soapenv:Envelope> I see nothing wrong with the message but my provider insists the message should be: <?xml version="1.0" encoding="UTF-8"?> <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:imk="http://www.springframework.org/spring-ws/Imk-Zenkiu-Services"> <soapenv:Body> <imk:enviarMensajeRequest> <imk:usuario>someuser</imk:usuario> <imk:clave>somepassword</imk:clave> <imk:mensaje>somemessage</imk:mensaje> <imk:contacto> <imk:buzonSMS>somenumber</imk:buzonSMS> <imk:primerNombre>somefirstname</imk:primerNombre> <imk:primerApellido>somelastname</imk:primerApellido> </imk:contacto> </imk:enviarMensajeRequest> </soapenv:Body> </soapenv:Envelope> Notice the namespace declaration moving from the enviarMensajeRequest to the soapenv:Envelope and the qualification with imk: on the parameters. I've tried many combinations on the process but my web service, wsdl and xml knowledge is very limited. The provider says that they can't help beyond telling me this. Any ideas? Perhaps a different framework that I can use to create the correct client.

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  • Changing label color based on current label color in iPhone dev

    - by Matt Thomas
    I am having trouble figuring out the if statement code for changing the color of a UI label based on the current color of the label. For instance, if the label color is currently red and the correct button is pressed, I want the label color to change to black. If the label color is black I want the label color to change to blue. Many thanks for any tips.

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  • How to properly downcast in C# with a SWIG generated interface?

    - by JG
    I've got a very large and mature C++ code base that I'm trying to use SWIG on to generate a C# interface for. I cannot change the actual C++ code itself but we can use whatever SWIG offers in the way of extending/updating it. I'm facing an issue where a function C++ is written as such: A* SomeClass::next(A*) The caller might do something like: A* acurr = 0; while( (acurr = sc->next(acurr)) != 0 ){ if( acurr isoftype B ){ B* b = (B*)a; ...do some stuff with b.. } elseif( acurr isoftype C ) ... } Essentially, iterating through a container elements that depending on their true type, do something different. The SWIG generated C# layer for the "next" function unfortunately does the following: return new A(); So the calling code in C# land cannot determine if the returned object is actually a derived class or not, it actually appears to always be the base class (which does make sense). I've come across several solutions: Use the %extend SWIG keyword to add a method on an object and ultimately call dynamic_cast. The downside to this approach, as I see it, is that this requires you to know the inheritance hierarchy. In my case it is rather huge and I see this is as a maintenance issue. Use the %factory keyword to supply the method and the derived types and have SWIG automatically generate the dynamic_cast code. This appears to be a better solution that the first, however upon a deeper look it still requires you to hunt down all the methods and all the possible derived types it could return. Again, a huge maintenance issue. I wish I had a doc link for this but I can't find one. I found out about this functionality by looking through the example code that comes with SWIG. Create a C# method to create an instance of the derived object and transfer the cPtr to the new instance. While I consider this clumsy, it does work. See an example below. public static object castTo(object fromObj, Type toType) { object retval = null; BaseClass fromObj2 = fromObj as BaseClass; HandleRef hr = BaseClass.getCPtr(fromObj2); IntPtr cPtr = hr.Handle; object toObj = Activator.CreateInstance(toType, cPtr, false); // make sure it actually is what we think it is if (fromObj.GetType().IsInstanceOfType(toObj)) { return toObj; } return retval; } Are these really the options? And if I'm not willing to dig through all the existing functions and class derivations, then I'm left with #3? Any help would be appreciated.

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  • How can I use linq to initialize an array of repeated elements?

    - by Eric
    At present, I'm using something like this to build a list of 10 objects: myList = (from _ in Enumerable.Range(0, 9) select new MyObject {...}).toList() This is based off my python background, where I'd write: myList = [MyObject(...) for _ in range(10)] Note that I want my list to contain 10 instances of my object, not the same instance 10 times. Is this still a sensible way to do things in C#? Is there a cost to doing it this way over a simple for loop?

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  • Parent child class relationship design pattern

    - by Jeremy
    I have a class which has a list of child items. Is there a design pattern I can copy that I can apply to these classes so that I can access the parent instance from the child, and it enforces rules such as not being able to add the child to multiple parents, etc?

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  • Real-time Java graph / chart library?

    - by Joonas Pulakka
    There was an earlier thread on Java graph or chart library, where JFreeChart was found to be quite good, but, as stated in its FAQ, it's not meant for real-time rendering. Can anyone recommend a comparable library that supports real-time rendering? Just some basic xy-rendering - for instance, getting a voltage signal from data acquisition system and plotting it as it comes (time on x-axis, voltage on y-axis).

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  • Facebook-WordPress comment/feedback integration

    - by warren
    Currently I have my Facebook profile automatically republish blog posts from a WordPress instance. What I would like to be able to do, however, is to also have comments posted to either the blog of Facebook show up on the other in the appropriate location. Is there a way to do this with the Facebook API?

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  • How to iterate all query paths within an image header namespace in WIC?

    - by muruge
    Hello All, I am using Windows Imaging Component to read/write image metadata in my WPF application. I would like to know if there is an efficient way to know if any paths exist within a namespace. For instance I would like to know if any paths within IPTC namespace exist and if not I want to delete the namespace from the image header. Any pointers would be greatly appreciated. Thanks, Murugesh.

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