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  • How to infer the type of a derived class in base class?

    - by enzi
    I want to create a method that allows me to change arbitrary properties of classes that derive from my base class, the result should look like this: SetPropertyValue("size.height", 50); – where size is a property of my derived class and height is a property of size. I'm almost done with my implementation but there's one final obstacle that I want to solve before moving on, to describe this I will first have to explain my implementation a bit: Properties that can be modified are decorated with an attribute There's a method in my base class that searches for all derived classes and their decorated properties For each property I generate a "property modifier", a class that contains 2 delegates: one to set and one to get the value of the property. Property Modifiers are stored in a dictionary, with the name of the property as key In my base class, there is another dictionary that contains all property-modifier-dictionaries, with the Type of the respective class as key. What the SetPropertyValue method does is this: Get the correct property-modifier-dictionary, using the concrete type of the derived class (<- yet to solve) Get the property modifier of the property to change (e.g. of the property size) Use the get or set delegate to modify the property's value Some example code to clarify further: private static Dictionary<RuntimeTypeHandle, object> EditableTypes; //property-modifier-dictionary protected void SetPropertyValue<T>(EditablePropertyMap<T> map, string property, object value) { var property = map[property]; // get the property modifier property.Set((T)this, value); // use the set delegate (encapsulated in a method) } In the above code, T is the Type of the actual (derived) class. I need this type for the get/set delegates. The problem is how to get the EditablePropertyMap<T> when I don't know what T is. My current (ugly) solution is to pass the map in an overriden virtual method in the derived class: public override void SetPropertyValue(string property, object value) { base.SetPropertyValue((EditablePropertyMap<ExampleType>)EditableTypes[typeof(ExampleType)], property, value); } What this does is: get the correct dictionary containing the property modifiers of this class using the class's type, cast it to the appropiate type and pass it to the SetPropertyValue method. I want to get rid of the SetPropertyValue method in my derived class (since there are a lot of derived classes), but don't know yet how to accomplish that. I cannot just make a virtual GetEditablePropertyMap<T> method because I cannot infer a concrete type for T then. I also cannot acces my dictionary directly with a type and retrieve an EditablePropertyMap<T> from it because I cannot cast to it from object in the base class, since again I do not know T. I found some neat tricks to infere types (e.g. by adding a dummy T parameter), but cannot apply them to my specific problem. I'd highly appreciate any suggestions you may have for me.

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  • ArrayList and Map problem in grails

    - by xain
    Hi, I have a service that contains a map: static Map cargosMap = ['1':'item1','2':'item 2','3':'item 3'] that is returned via a method in the service: static Map getCargos() { [cargosMap] } A controller calls it like this: def mform = { Map cargos = empService.getCargos() [cargos:cargos] } In the gsp, I have the select: <g:select name="cg1" from="${cargos}" /> But I'm getting the exception: Error 500: Executing action ....caused exception: org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object ... with class 'java.util.ArrayList' to class 'java.util.Map' Any clues ? Thanks

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  • ado.net data entity problem

    - by ognjenb
    I have this error Cannot implicitly convert type 'System.Linq.IQueryable' to 'Mvc.Models.engineer'. An explicit conversion exists (are you missing a cast?) after write this code engineer Ing = new engineer(); Ing = from j in testPersons.ibekoengineer select j.Name; What is wrong?

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  • Why is "int + string" possible in statically-typed C# but not in dynamically-typed Python?

    - by Salvador Dali
    While studying C# I found it really strange, that dynamically typed Python will rise an error in the following code: i = 5 print i + " " whereas statically typed C# will normally proceed the similar code: int i = 5; Console.Write(i + " "); I would expect other way around (in python I would be able to do this without any casting, but C# would require me to cast int to string or string to int). Just to highlight, I am not asking what language is better, I am curious what was the reason behind implementing the language this way.

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  • Hibernate Initial SessionFactory creation failed

    - by user364746
    Hello.. I'm trying to use hibernate to fill my jsf selectonemenu in ApplicationBean (in Liferay). The problem is that I got Initial SessionFactory creation failed problem. Before putting my functions in the applicationbean I was setting them in sessionbean and I got no error. For now the full error Initial SessionFactory creation failed.java.lang.ClassCastException: org.hibernate.type.StringType cannot be cast to org.hibernate.type.VersionType Thanks

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  • C# - Basic question: What is '?' ?

    - by Amokrane
    Hi, I'm wondering what ? means in C# ? I'm seeing things like: DateTime? or int?. I suppose this is C# specific to C# 4.0? I can't look for it in Google because I don't know the name of this thing. The problem is I'm using DateTime and I have a lot of cast errors (from DateTime to DateTime?). Thank you

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  • C# underlying types of enums

    - by Marlon
    What is the point of having enum SomeEnum : byte // <---- { SomeValue = 0x01, ... } when you have to make a cast just to assign it to the same type of variable as the enums underlying type? byte b = (byte)SomeEnum.SomeValue;

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  • Android pass a 2d int array from one activity to another ERROR

    - by user2189001
    ACTIVITY 1: Bundle bundle = new Bundle(); bundle.putSerializable("CustomLevelData", LevelCreator.LCLevelData); Intent i = new Intent(LevelCreatorPopout.this, GameView.class); i.putExtras(bundle); startActivity(i); ACTIVITY 2: LevelData=(int[][]) extras.getSerializable("CustomLevelData"); ERROR: E/AndroidRuntime(16220): FATAL EXCEPTION: main E/AndroidRuntime(16220): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.powerpoint45.maze/com.powerpoint45.maze.GameView}: java.lang.ClassCastException: java.lang.Object[] cannot be cast to int[][] I have searched but found nothing on 2d INT array passing

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  • Can you get a Func<T> (or similar) from a MethodInfo object?

    - by Dan Tao
    I realize that, generally speaking, there are performance implications of using reflection. (I myself am not a fan of reflection at all, actually; this is a purely academic question.) Suppose there exists some class that looks like this: public class MyClass { public string GetName() { return "My Name"; } } Bear with me here. I know that if I have an instance of MyClass called x, I can call x.GetName(). Furthermore, I could set a Func<string> variable to x.GetName. Now here's my question. Let's say I don't know the above class is called MyClass; I've got some object, x, but I have no idea what it is. I could check to see if that object has a GetName method by doing this: MethodInfo getName = x.GetType().GetMethod("GetName"); Suppose getName is not null. Then couldn't I furthermore check if getName.ReturnType == typeof(string) and getName.GetParameters().Length == 0, and at this point, wouldn't I be quite certain that the method represented by my getName object could definitely be cast to a Func<string>, somehow? I realize there's a MethodInfo.Invoke, and I also realize I could always create a Func<string> like: Func<string> getNameFunc = () => getName.Invoke(x, null); I guess what I'm asking is if there's any way to go from a MethodInfo object to the actual method it represents, incurring the performance cost of reflection in the process, but after that point being able to call the method directly (via, e.g., a Func<string> or something similar) without a performance penalty. What I'm envisioning might look something like this: // obviously this would throw an exception if GetActualInstanceMethod returned // something that couldn't be cast to a Func<string> Func<string> getNameFunc = (Func<string>)getName.GetActualInstanceMethod(x); (I realize that doesn't exist; I'm wondering if there's anything like it.) If what I'm asking doesn't make sense, or if I'm being unclear, I'll be happy to attempt to clarify.

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  • Problem getting size of Website Xcode

    - by Michael Amici
    When i try and compile I come up with a warning that reads initialization makes pointer from integer without a cast. No clue why. I am just trying to get the size of a website. #import "Lockerz_RedemptionViewController.h" @implementation Lockerz_RedemptionViewController -(IBAction)startLoop:(id) sender { NSData *dataNew = [NSData dataWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"http://www.google.com/"]]]; NSUInteger *len = [dataNew length]; //error is here NSLog(@"%@", len); }

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  • What does this C++ construct do?

    - by cambr
    Somewhere in lines of code, I came across this construct... //void* v = void* value from an iterator int i = (int)(long(v)) What possible purpose can this contruct serve? Why not simply use int(v) instead? Why the cast to long first?

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  • PHP - get MySQL query results as their native data type?

    - by redidas
    I've tried fetching MySQL query results using mysql_fetch_row() mysql_result() and numeric values are being returned as strings. Is there any way to fetch the data as its datatype stored in the table? The application will be querying many different queries so I will be unable to cast the values as the intended datatype on a 1 by 1 basis.

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  • T-SQL 2005 - Divide by zero error encountered

    - by Grant
    Hi, I am trying to get some percentage data from a stored procedure using code similar to the line below. Obviously this is going to cause a (Divide by zero error encountered) problem when base.[XXX_DataSetB] returns 0 which may happen some of the time. Does anyone know how i can deal with this in the most efficient manner? Note: There would be about 20+ lines looking like the one below... cast((base.[XXX_DataSetB] - base.[XXX_DataSetA]) as decimal) / base.[XXX_DataSetB] as [XXX_Percentage]

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  • SQL Server varchar to datetime

    - by Dezigo
    I have a field varchar(14) = 20090226115644 I need convert it to - 2009-02-26 11:56:44 (datetime format) My idea. use cast and convert.. but I always have errors. Conversion failed when converting datetime from character string. I made this, but don`t like it.. SELECT SUBSTRING(move,1,4) + '-' + SUBSTRING(move,5,2) + '-' + SUBSTRING(move,7,2) + ' ' + SUBSTRING(move,9,2) + ':' + SUBSTRING(move,11,2) + ':'+SUBSTRING(move,13,2) as new -- FROM [Test].[dbo].[container_events] where move IS not null Result :2009-02-26 11:56:44

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  • Copying an entire table with Postgres

    - by NudeCanalTroll
    Hello, I'm trying to copy the contents of one table into another in Postgres, however it appears some rows aren't being copied correctly: ActiveRecord::StatementInvalid: PGError: ERROR: column "email_date" is of type timestamp without time zone but expression is of type character varying HINT: You will need to rewrite or cast the expression. Is there any way I can have it automatically skip (or ignore) invalid rows? Here's the query I'm using: SET statement_timeout = 0; INSERT INTO emails3 SELECT * FROM emails

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  • how to use foreach loop to edit textboxes

    - by Ramakrishna
    foreach(textbox t in this.controls) { t.text=" "; } this is what i want to do. to clear all the textboxes in my page, at a time but it gives an error like Unable to cast object of type 'System.Web.UI.LiteralControl' to type 'System.Web.UI.WebControls.TextBox'. plz tell me how to do this

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