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  • Application Design: Single vs. Multiple Hits to the DB

    - by shyneman
    I'm building a service that performs a set of configured activities based on the type of request that it receives. Each activity involves going to the database and retrieving/updating some kind of information. The logic for each activity can be generalized and re-used across different request types. The activities may need to participate in a transaction for the duration of the servicing the request. One option, I'm considering is having each activity maintain its own access to DAL/database. This fully encapsulates the activity into a stand-alone re-usable piece, but hitting the database multiple times for one request doesn't seem like a viable option. I don't really know how to easily implement the concept of a transaction across the multiple activities here either. The second option is to encapsulate ALL the activities into one big activity and hit the database once. But this does not allow re-use and configuration of these activities for different requests. Does anyone have any suggestions and input about what should be the best way to approach my problem? Thanks for any help.

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  • C system calls open / read / write / close problem.

    - by Andrei Ciobanu
    Hello, given the following code (it's supposed to write "hellowolrd" in a "helloworld" file, and then read the text): #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #define FNAME "helloworld" int main(){ int filedes, nbytes; char buf[128]; /* Creates a file */ if((filedes=open(FNAME, O_CREAT | O_EXCL | O_WRONLY | O_APPEND, S_IRUSR | S_IWUSR)) == -1){ write(2, "Error1\n", 7); } /* Writes hellow world to file */ if(write(filedes, FNAME, 10) != 10) write(2, "Error2\n", 7); /* Close file */ close(filedes); if((filedes = open(FNAME, O_RDONLY))==-1) write(2, "Error3\n", 7); /* Prints file contents on screen */ if((nbytes=read(filedes, buf, 128)) == -1) write(2, "Error4\n", 7); if(write(1, buf, nbytes) != nbytes) write(2, "Error5\n", 7); /* Close rile afte read */ close(filedes); return (0); } The first time i run the program, the output is: helloworld After that every time I to run the program, the output is: Error1 Error2 helloworld I don't understand why the text isn't appended, as I've specified the O_APPEND file. Is it because I've included O_CREAT ? It the file is already created, shouldn't O_CREAT be ignored ?

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  • Reordering methods in ComImport interfaces throws COMException (0x80041001)

    - by Ohad Schneider
    Consider the following code for COM interop with internet shortcuts: [ComImport] [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)] [Guid("CABB0DA0-DA57-11CF-9974-0020AFD79762")] public interface IUniformResourceLocatorW { void SetUrl([MarshalAs(UnmanagedType.LPWStr)] string pcszUrl, int dwInFlags); void GetUrl([MarshalAs(UnmanagedType.LPWStr)] out StringBuilder ppszUrl); void InvokeCommand(IntPtr purlici); } [ComImport] [Guid("FBF23B40-E3F0-101B-8488-00AA003E56F8")] public class InternetShortcut { } The following works as expected: var ishort = new InternetShortcut(); ((IPersistFile)ishort).Load("MyLink.url", 0); ((IUniformResourceLocatorW)ishort).GetUrl(out url); However: If I comment out IUniformResourceLocatorW.SetUrl (which I am not using), IUniformResourceLocatorW.GetUrl throws a COMException (HResult 0x80041001). If I switch between IUniformResourceLocatorW.SetUrl and IUniformResourceLocatorW.GetUrl (that is place the former below the latter) the same exception is thrown If I comment out IUniformResourceLocatorW.InvokeCommand the code runs fine. It's as if the order has to be preserved "up to" the invoked method. Is this behavior by design? documented somewhere? I'm asking because some COM interfaces are composed of many methods with possibly many supporting types and I'd rather avoid defining what I don't need if possible.

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  • Static files in (Java) App Engine not accessible.

    - by fiXedd
    The example documentation says that you simply need to place your files in war/ (or a subdirectory) and they should be accessible from the host (as long as they aren't JSPs or in WEB-INF). For example, if you place foo.css in war/ then you should be able to access it at http://localhost:8080/foo.css. However, this isn't working for me at all. NONE of my static files are accessible. The docs on appengine-web.xml say that you can also specifically denote certain types as static. I've tried this as well and it makes no difference. Am I missing something obvious? UPDATE: Turns out one of the mappings in my web.xml was a little too aggressive. The following was the culprit: <servlet> <servlet-name>Main</servlet-name> <servlet-class>MainServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>Main</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> It seems that it was grabbing everything that wasn't grabbed be one of the other rules, which I don't understand because there was no * on the end of the url-pattern. It also seems to be directly contradictory to the documentation that says: Note: Static files, files that are served verbatim to users such as images, CSS or JavaScript, are handled separately from paths mentioned in the deployment descriptor. A request for a URL path that matches a path to a file in the WAR that's considered a static file will serve the file, regardless of servlet and filter mappings in the deployment descriptor. You can exclude files from those treated as static files using the appengine-web.xml file. So, how can I have a rule that matches the base of my domain (eg. http://www.example.com/) and still allows the static files to filter through?

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  • Dynamically compose ASP MVC view based on context

    - by robertFall
    I have several views that are composed of several partial views based on context. For example, we have a Project view that shows all the details of a project, which includes the scalar values, name etc, and also all the assigned employees, tasks and/or clients. The problem I have is that certain types of project have all of the above sections while others have only two or even on section, ie. details only. What is the best way to compose the Projects master view? I don't want to have logic to check the project in the view. Is there a way to compose a view in code by programatically rendering the relevant partials and ignoring the rest? Otherwise are there any other ideas how to do this in a maintainable way? I could of course just render the partials using if statements to check if they apply, but that way the view contains VERY important logic. In another situation we want to use this method to display content based on the type of subscription a user has. Thanks!

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  • How do you pass a generic delegate argument to a method in .NET 2.0 - UPDATED

    - by Seth Spearman
    Hello, I have a class with a delegate declaration as follows... Public Class MyClass Public Delegate Function Getter(Of TResult)() As TResult ''#the following code works. Public Shared Sub MyMethod(ByVal g As Getter(Of Boolean)) ''#do stuff End Sub End Class However, I do not want to explicitly type the Getter delegate in the Method call. Why can I not declare the parameter as follows... ... (ByVal g As Getter(Of TResult)) Is there a way to do it? My end goal was to be able to set a delegate for property setters and getters in the called class. But my reading indicates you can't do that. So I put setter and getter methods in that class and then I want the calling class to set the delegate argument and then invoke. Is there a best practice for doing this. I realize in the above example that I can set set the delegate variable from the calling class...but I am trying to create a singleton with tight encapsulation. For the record, I can't use any of the new delegate types declared in .net35. Answers in C# are welcome. Any thoughts? Seth

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  • Why does first call to java.io.File.createTempFile(String,String,File) take 5 seconds on Citrix?

    - by Ben Roling
    While debugging slow startup of an Eclipse RCP app on a Citrix server, I came to find out that java.io.createTempFile(String,String,File) is taking 5 seconds. It does this only on the first execution and only for certain user accounts. Specifically, I am noticing it Citrix anonymous user accounts. I have not tried many other types of accounts, but this behavior is not exhibited with an administrator account. Also, it does not matter if the user has access to write to the given directory or not. If the user does not have access, the call will take 5 seconds to fail. If they do have access, the call with take 5 seconds to succeed. This is on a Windows 2003 Server. I've tried Sun's 1.6.0_16 and 1.6.0_19 JREs and see the same behavior. I googled a bit expecting this to be some sort of known issue, but didn't find anything. It seems like someone else would have had to have run into this before. The Eclipse Platform uses File.createTempFile() to test various directories to see if they are writeable during initialization and this issue adds 5 seconds to the startup time of our application. I imagine somebody has run into this before and might have some insight. Here is sample code I executed to see that it is indeed this call that is consuming the time. I also tried it with a second call to createTempFile and notice that subsequent calls return nearly instantaneously. public static void main(final String[] args) throws IOException { final File directory = new File(args[0]); final long startTime = System.currentTimeMillis(); File file = null; try { file = File.createTempFile("prefix", "suffix", directory); System.out.println(file.getAbsolutePath()); } finally { System.out.println(System.currentTimeMillis() - startTime); if (file != null) { file.delete(); } } } Sample output of this program is the following: C:\java.exe -jar filetest.jar C:/Temp C:\Temp\prefix8098550723198856667suffix 5093

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  • Can't create new "enterprise" project in netbeans

    - by Danny
    I'm running netbeans 6.7.1 on Ubuntu Karmic. On the services tab I added a new glassfish v3 prelude server, I installed it to my home directory using the download button. I started the server and opened localhost:4848 to verify I can get into the admin panel. Then I did file-new projct and created a new java web-web application. On the configuration step of the wizard it preselected glassfish v3 prelude and java ee 5. I accepted and did a test run. I ran the project just fine. So now I did file-new projecct and attempted to create a Java EE-ejb module. When I arrive to the server configuration stage of the wizard, it doesn't show any servers on the server dropdown list (so it's empty), it also doesn't see any version of java on the "java ee version" dropdown list. This also happens for the other "Java EE" project types. I can't seem to get my head around why I can make a new web application but not an ejb module. Can anyone provide any insight to why it might not be seeing that I have java or glassfish installed when I try to make a new java ee project but I see it when I try to make a java web project?

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  • Emptying the datastore in GAE

    - by colwilson
    I know what you're thinking, 'O not that again!', but here we are since Google have not yet provided a simpler method. I have been using a queue based solution which worked fine: import datetime from models import * DELETABLE_MODELS = [Alpha, Beta, AlphaBeta] def initiate_purge(): for e in config.DELETABLE_MODELS: deferred.defer(delete_entities, e, 'purging', _queue = 'purging') class NotEmptyException(Exception): pass def delete_entities(e, queue): try: q = e.all(keys_only=True) db.delete(q.fetch(200)) ct = q.count(1) if ct > 0: raise NotEmptyException('there are still entities to be deleted') else: logging.info('processing %s completed' % queue) except Exception, err: deferred.defer(delete_entities, e, then, queue, _queue = queue) logging.info('processing %s deferred: %s' % (queue, err)) All this does is queue a request to delete some data (once for each class) and then if the queued process either fails or knows there is still some stuff to delete, it re-queues itself. This beats the heck out of hitting the refresh on a browser for 10 minutes. However, I'm having trouble deleting AlphaBeta entities, there are always a few left at the end. I think because it contains Reference Properties: class AlphaBeta(db.Model): alpha = db.ReferenceProperty(Alpha, required=True, collection_name='betas') beta = db.ReferenceProperty(Beta, required=True, collection_name='alphas') I have tried deleting the indexes relating to these entity types, but that did not make any difference. Any advice would be appreciated please.

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  • Retrieving license type (linux/windows/windows+sqlserver) for an Amazon EC2 instance via the API?

    - by Geir
    I need to calculate the hourly running costs for my Amazon EC2 instances. This varies even between instances with same hardware configs (instance types) because I use different amazon images (AMIs): some plain windows server and some windows server with sql server (both of them have additional costs compared with plain linux instances) The EC2 Java API has a describeInstances() method which returns Instance objects with metadata such as instance id, instance type (m1.small/large...), state (running,stopped..) public ip, etc. This Instance object also has a .getLicense().getPool() which according to the Java API should return "The license pool from which this license was used (ex: 'windows')." I thought this is were it may also give 'windows+sqlserver' or something to that effect. The getLicense() method does however return null.. I've navigated around the EC2 web console, not being able to find this information, but I'm hoping that it is possible - otherwise it would mean that you cannot identify the true hourly cost of an particular instance unless you know which AMI was used to create it in the first place (plain windows server or windows server with sql server). Anyone? Thanks :) /Geir

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  • Using JAXB to customise the generation of java enums

    - by belltower
    I'm using an external bindings file when using jaxb against an XML schema. I'm mostly using the bindings file to map from the XML schema primitives to my own types. This is a snippet of the bindings file <jxb:bindings version="1.0" xmlns:jxb="http://java.sun.com/xml/ns/jaxb" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:ai="http://java.sun.com/xml/ns/jaxb/xjc" extensionBindingPrefixes="ai"> <jxb:bindings schemaLocation="xsdurl" node="xs:schema"> <jxb:globalBindings> <jxb:javaType name="com.companyname.StringType" xmlType="xs:string" parseMethod="parse" printMethod="print" hasNsContext="true"> </jxb:javaType> </jxb:globalBindings> </jxb:bindings> </jxb:bindings> So whenever a xs:string is encountered, the com.companyname.StringType the methods print / parse are called for marshalling/unmarshalling etc. Now if JAXB encounters an xs:enumeration it will generate a java enum. For example: <xs:simpleType name="Address"> <xs:restriction base="xs:string"> <xs:enumeration value="ADDR"/> <xs:enumeration value="PBOX"/> </xs:restriction> </xs:simpleType> public enum Address { ADDR, PBOX, public String value() { return name(); } public static Address fromValue(String v) { return valueOf(v); } } Does anyone know if it is possible to customise the creation of an enum like it is for a primitive? I would like to be able to: Add a standard member variable / other methods to every enum generated by jaxb. Specify the static method used to create the enum.

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  • How can I use a single-table inheritance and single controller to make this more DRY?

    - by Angela
    I have three models, Calls, Emails, and Letters and those are basically templates of what gets sent to individuals, modeled as Contacts. When a Call is made, a row in model in ContactCalls gets created. If an Email is sent, an entry in ContactEmails is made. Each has its own controller: contact_calls_controller.rb and contact_emails_controller.rb. I would like to create a single table inheritance called ContactEvents which has types Calls, Emails, and Letters. But I'm not clear how I pass the type information or how to consolidate the controllers. Here's the two controllers I have, as you can see, there's alot of duplication, but some differences that needs to be preserved. In the case of letter and postcards (another Model), it's even more so. class ContactEmailsController < ApplicationController def new @contact_email = ContactEmail.new @contact_email.contact_id = params[:contact] @contact_email.email_id = params[:email] @contact = Contact.find(params[:contact]) @company = Company.find(@contact.company_id) contacts = @company.contacts.collect(&:full_name) contacts.each do |contact| @colleagues = contacts.reject{ |c| [email protected]_name } end @email = Email.find(@contact_email.email_id) @contact_email.subject = @email.subject @contact_email.body = @email.message @email.message.gsub!("{FirstName}", @contact.first_name) @email.message.gsub!("{Company}", @contact.company_name) @email.message.gsub!("{Colleagues}", @colleagues.to_sentence) @email.message.gsub!("{NextWeek}", (Date.today + 7.days).strftime("%A, %B %d")) @contact_email.status = "sent" end def create @contact_email = ContactEmail.new(params[:contact_email]) @contact = Contact.find_by_id(@contact_email.contact_id) @email = Email.find_by_id(@contact_email.email_id) if @contact_email.save flash[:notice] = "Successfully created contact email." # send email using class in outbound_mailer.rb OutboundMailer.deliver_campaign_email(@contact,@contact_email) redirect_to todo_url else render :action => 'new' end end AND: class ContactCallsController < ApplicationController def new @contact_call = ContactCall.new @contact_call.contact_id = params[:contact] @contact_call.call_id = params[:call] @contact_call.status = params[:status] @contact = Contact.find(params[:contact]) @company = Company.find(@contact.company_id) @contact = Contact.find(@contact_call.contact_id) @call = Call.find(@contact_call.call_id) @contact_call.title = @call.title contacts = @company.contacts.collect(&:full_name) contacts.each do |contact| @colleagues = contacts.reject{ |c| [email protected]_name } end @contact_call.script = @call.script @call.script.gsub!("{FirstName}", @contact.first_name) @call.script.gsub!("{Company}", @contact.company_name ) @call.script.gsub!("{Colleagues}", @colleagues.to_sentence) end def create @contact_call = ContactCall.new(params[:contact_call]) if @contact_call.save flash[:notice] = "Successfully created contact call." redirect_to contact_path(@contact_call.contact_id) else render :action => 'new' end end

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  • How to create a generic C free function .

    - by nomemory
    I have some C structures related to a 'list' data structure. They look like this. struct nmlist_element_s { void *data; struct nmlist_element_s *next; }; typedef struct nmlist_element_s nmlist_element; struct nmlist_s { void (*destructor)(void *data); int (*cmp)(const void *e1, const void *e2); unsigned int size; nmlist_element *head; nmlist_element *tail; }; typedef struct nmlist_s nmlist; This way I can have different data types being hold in "nmlist_element-data" . The "constructor" (in terms of OOP) has the following signature: nmlist *nmlist_alloc(void (*destructor)(void *data)); Where "destructor" is specific function that de-allocated "data" (being hold by the nmlist_element). If I want to have a list containing integers as data, my "destructor" would like this: void int_destructor(void *data) { free((int*)data); } Still i find it rather "unfriendly" for me to write a destructor functions for every simple primitive data type. So is there a trick to write something like this ? (for primitives): void "x"_destructor(void *data, "x") { free(("x" *)data); } PS: I am not a macro fan myself, and in my short experience regarding C, i don't use them, unless necessary.

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  • Type-safe mapping from Class<T> to Thing<T>

    - by Joonas Pulakka
    I want to make a map-kind of container that has the following interface: public <T> Thing<T> get(Class<T> clazz); public <T> void put(Class<T> clazz, Thing<T> thing); The interesting point is that the Ts in each Class<T><- Thing<T> pair is the same T, but the container should be able to hold many different types of pairs. Initially I tried a (Hash)Map. But, for instance, Map<Class<T>, Thing<T>> is not right, because then T would be same T for all pairs in that map. Of course, Map<Class<?>, Thing<?>> works, but then I don't have type-safety guarantees so that when I get(String.class), I can't be sure that I get a Thing<String> instance back. Is there a way to accomplish the kind of type safety that I'm looking for?

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  • Help me clean up this crazy lambda with the out keyword

    - by Sarah Vessels
    My code looks ugly, and I know there's got to be a better way of doing what I'm doing: private delegate string doStuff( PasswordEncrypter encrypter, RSAPublicKey publicKey, string privateKey, out string salt ); private bool tryEncryptPassword( doStuff encryptPassword, out string errorMessage ) { ...get some variables... string encryptedPassword = encryptPassword(encrypter, publicKey, privateKey, out salt); ... } This stuff so far doesn't bother me. It's how I'm calling tryEncryptPassword that looks so ugly, and has duplication because I call it from two methods: public bool method1(out string errorMessage) { string rawPassword = "foo"; return tryEncryptPassword( (PasswordEncrypter encrypter, RSAPublicKey publicKey, string privateKey, out string salt) => encrypter.EncryptPasswordAndDoStuff( // Overload 1 rawPassword, publicKey, privateKey, out salt ), out errorMessage ); } public bool method2(SecureString unencryptedPassword, out string errorMessage) { return tryEncryptPassword( (PasswordEncrypter encrypter, RSAPublicKey publicKey, string privateKey, out string salt) => encrypter.EncryptPasswordAndDoStuff( // Overload 2 unencryptedPassword, publicKey, privateKey, out salt ), out errorMessage ); } Two parts to the ugliness: I have to explicitly list all the parameter types in the lambda expression because of the single out parameter. The two overloads of EncryptPasswordAndDoStuff take all the same parameters except for the first parameter, which can either be a string or a SecureString. So method1 and method2 are pretty much identical, they just call different overloads of EncryptPasswordAndDoStuff. Any suggestions? Edit: if I apply Jeff's suggestions, I do the following call in method1: return tryEncryptPassword( (encrypter, publicKey, privateKey) => { var result = new EncryptionResult(); string salt; result.EncryptedValue = encrypter.EncryptPasswordAndDoStuff( rawPassword, publicKey, privateKey, out salt ); result.Salt = salt; return result; }, out errorMessage ); Much the same call is made in method2, just with a different first value to EncryptPasswordAndDoStuff. This is an improvement, but it still seems like a lot of duplicated code.

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  • Strongly Typed DataSet column requires custom type to implement IXmlSerializable?

    - by Phil
    I have a strongly typed Dataset with a single table with three columns. These columns all contain custom types. DataColumn1 is of type Parent DataColumn2 is of type Child1 DataColumn3 is of type Child2 Here is what these classes look like: [Serializable] [XmlInclude(typeof(Child1)), XmlInclude(typeof(Child2))] public abstract class Parent { public int p1; } [Serializable] public class Child1 :Parent { public int c1; } [Serializable] public class Child2 : Parent { public int c1; } now, if I add a row with DataColumn1 being null, and DataColumns 2 and 3 populated and try to serialize it, it works: DataSet1 ds = new DataSet1(); ds.DataTable1.AddDataTable1Row(null, new Child1(), new Child2()); StringBuilder sb = new StringBuilder(); using (StringWriter writer = new StringWriter(sb)) { ds.WriteXml(writer);//Works! } However, if I try to add a value to DataColumn1, it fails: DataSet1 ds = new DataSet1(); ds.DataTable1.AddDataTable1Row(new Child1(), new Child1(), new Child2()); StringBuilder sb = new StringBuilder(); using (StringWriter writer = new StringWriter(sb)) { ds.WriteXml(writer);//Fails! } Here is the Exception: "Type 'WindowsFormsApplication4.Child1, WindowsFormsApplication4, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' does not implement IXmlSerializable interface therefore can not proceed with serialization." I have also tried using the XmlSerializer to serialize the dataset, but I get the same exception. Does anyone know of a way to get around this where I don't have to implement IXmlSerializable on all the Child classes? Alternatively, is there a way to implement IXmlSerializable keeping all default behavior the same (ie not having any class specific code in the ReadXml and WriteXml methods)

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  • Entity Framework: Auto-updating foreign key when setting a new object reference

    - by Adrian Grigore
    Hi, I am porting an existing application from Linq to SQL to Entity Framework 4 (default code generation). One difference I noticed between the two is that a foreign key property are not updated when resetting the object reference. Now I need to decide how to deal with this. For example supposing you have two entity types, Company and Employee. One Company has many Employees. In Linq To SQL, setting the company also sets the company id: var company=new Company(ID=1); var employee=new Employee(); Debug.Assert(employee.CompanyID==0); employee.Company=company; Debug.Assert(employee.CompanyID==1); //Works fine! In Entity Framework (and without using any code template customization) this does not work: var company=new Company(ID=1); var employee=new Employee(); Debug.Assert(employee.CompanyID==0); employee.Company=company; Debug.Assert(employee.CompanyID==1); //Throws, since CompanyID was not updated! How can I make EF behave the same way as LinqToSQL? I had a look at the default code generation T4 template, but I could not figure out how to make the necessary changes.

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  • Compiling a Windows C++ program in g++

    - by Phenom
    I'm trying to compile a Windows C++ program in g++. This is what I get. /usr/include/c++/4.4/backward/backward_warning.h:28:2: warning: #warning This file includes at least one deprecated or antiquated header which may be removed without further notice at a future date. Please use a non-deprecated interface with equivalent functionality instead. For a listing of replacement headers and interfaces, consult the file backward_warning.h. To disable this warning use -Wno-deprecated. btree.cpp:1204: error: ‘_TCHAR’ has not been declared btree.cpp: In function ‘int _tmain(int, int**)’: btree.cpp:1218: error: ‘__int64’ was not declared in this scope btree.cpp:1218: error: expected ‘;’ before ‘frequency’ btree.cpp:1220: error: ‘LARGE_INTEGER’ was not declared in this scope btree.cpp:1220: error: expected primary-expression before ‘)’ token btree.cpp:1220: error: ‘frequency’ was not declared in this scope btree.cpp:1220: error: ‘QueryPerformanceFrequency’ was not declared in this scope btree.cpp:1262: error: expected primary-expression before ‘)’ token btree.cpp:1262: error: ‘start’ was not declared in this scope btree.cpp:1262: error: ‘QueryPerformanceCounter’ was not declared in this scope btree.cpp:1264: error: name lookup of ‘i’ changed for ISO ‘for’ scoping btree.cpp:1264: note: (if you use ‘-fpermissive’ G++ will accept your code) btree.cpp:1304: error: expected primary-expression before ‘)’ token btree.cpp:1304: error: ‘end’ was not declared in this scope btree.cpp:1306: error: ‘total’ was not declared in this scope btree.cpp:1316: error: ‘getchar’ was not declared in this scope The first thing I noticed is that there are these variable types called _TCHAR, _int64, and LARGE_INTEGER, which is probably a Windows thing. What can these be changed to so that they will work in g++? Also, if there's anything else in here that you know can be converted to g++, that would be helpful. I got the code from here: http://touc.org/btree.html

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  • Constructor Overloading

    - by Mark Baker
    Normally when I want to create a class constructor that accepts different types of parameters, I'll use a kludgy overloading principle of not defining any args in the constructor definition: e.g. for an ECEF coordinate class constructor, I want it to accept either $x, $y and $z arguments, or to accept a single array argument containg x, y and z values, or to accept a single LatLong object I'd create a constructor looking something like: function __construct() { // Identify if any arguments have been passed to the constructor if (func_num_args() > 0) { $args = func_get_args(); // Identify the overload constructor required, based on the datatype of the first argument $argType = gettype($args[0]); switch($argType) { case 'array' : // Array of Cartesian co-ordinate values $overloadConstructor = 'setCoordinatesFromArray'; break; case 'object' : // A LatLong object that needs converting to Cartesian co-ordinate values $overloadConstructor = 'setCoordinatesFromLatLong'; break; default : // Individual Cartesian co-ordinate values $overloadConstructor = 'setCoordinatesFromXYZ'; break; } // Call the appropriate overload constructor call_user_func_array(array($this,$overloadConstructor),$args); } } // function __construct() I'm looking at an alternative: to provide a straight constructor with $x, $y and $z as defined arguments, and to provide static methods of createECEFfromArray() and createECEFfromLatLong() that handle all the necessary extraction of x, y and z; then create a new ECEF object using the standard constructor, and return that Which option is cleaner from an OO purists perspective?

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  • What OOP pattern to use when only adding new methods, not data?

    - by Jonathon Reinhart
    Hello eveyone... In my app, I have deal with several different "parameters", which derive from IParameter interface, and also ParamBase abstract base class. I currently have two different parameter types, call them FooParameter and BarParameter, which both derive from ParamBase. Obviously, I can treat them both as IParameters when I need to deal with them generically, or detect their specific type when I need to handle their specific functionality. My question lies in specific FooParameters. I currently have a few specific ones with their own classes which derive from FooParameter, we'll call them FP12, FP13, FP14, etc. These all have certain characteristics, which make me treat them differently in the UI. (Most have names associated with the individual bits, or ranges of bits). Note that these specific, derived FP's have no additional data associated with them, only properties (which refer to the same data in different ways) or methods. Now, I'd like to keep all of these parameters in a Dictionary<String, IParameter> for easy generic access. The problem is, if I want to refer to a specific one with the special GUI functions, I can't write: FP12 fp12 = (FP12)paramList["FP12"] because you can't downcast to a derived type (rightfully so). But in my case, I didn't add any data, so the cast would theoretically work. What type of programming model should I be using instead? Thanks!

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  • Expand chaining hashtable. Errors on code.

    - by FILIaS
    Expanding a hashtable with linked lists there are some errors and warnings. I wanna make sure that the following code is right (expand method) and find out what happens that raise these warnings/errors typedef struct { int length; struct List *head; struct List *tail; } HashTable; //resolving collisions using linked lists - chaining typedef struct { char *number; char *name; int time; struct List *next; }List; //on the insert method i wanna check hashtable's size, //if it seems appropriate there is the following code: //Note: hashtable variable is: Hashtable * ...... hashtable = expand(hashtable,number,name,time); /**WARNING**:assignment makes pointer from integer without a cast*/ HashTable* expand( HashTable* h ,char number[10],char* name,int time) /**error**: conflicting types for ‘expand’ previous implicit declaration of ‘expand’ was here*/ { HashTable* new; int n; clientsList *node,*next; PrimesIndex++; int new_size= primes[PrimesIndex]; /* double the size,odd length */ if (!(new=malloc((sizeof( List*))*new_size))) return NULL; for(n=0; n< h->length; ++n) { for(node=h[n].head; node; node=next) { add (&new, node->number, node->name,node->time); next=node->next;//// free(node); } } free(h); return new; }

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  • How to update GUI thread/class from worker thread/class?

    - by user315182
    First question here so hello everyone. The requirement I'm working on is a small test application that communicates with an external device over a serial port. The communication can take a long time, and the device can return all sorts of errors. The device is nicely abstracted in its own class that the GUI thread starts to run in its own thread and has the usual open/close/read data/write data basic functions. The GUI is also pretty simple - choose COM port, open, close, show data read or errors from device, allow modification and write back etc. The question is simply how to update the GUI from the device class? There are several distinct types of data the device deals with so I need a relatively generic bridge between the GUI form/thread class and the working device class/thread. In the GUI to device direction everything works fine with [Begin]Invoke calls for open/close/read/write etc. on various GUI generated events. I've read the thread here (How to update GUI from another thread in C#?) where the assumption is made that the GUI and worker thread are in the same class. Google searches throw up how to create a delegate or how to create the classic background worker but that's not at all what I need, although they may be part of the solution. So, is there a simple but generic structure that can be used? My level of C# is moderate and I've been programming all my working life, given a clue I'll figure it out (and post back)... Thanks in advance for any help.

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  • Good data structure for efficient insert/querying on arbitrary properties

    - by Juliet
    I'm working on a project where Arrays are the default data structure for everything, and every query is a linear search in the form of: Need a customer with a particular name? customer.Find(x => x.Name == name) Need a customer with a particular unique id? customer.Find(x => x.Id == id) Need a customer of a particular type and age? customer.Find(x => x is PreferredCustomer && x.Age >= age) Need a customer of a particular name and age? customer.Find(x => x.Name == name && x.Age == age) In almost all instances, the criteria for lookups is well-defined. For example, we only search for customers by one or more of the properties Id, Type, Name, or Age. We rarely search by anything else. Is a good data structure to support arbitrary queries of these types with lookup better than O(n)? Any out-of-the-box implementations for .NET?

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  • switching C compiler causes: Error Initializer cannot be specified for a flexible array member

    - by user1054210
    I am trying to convert our code from one IDE to be used in a different one. The current one uses gcc which allows for this structure to be initialized from a variable array. The new tool does not use gcc gives me an error "Initializer cannot be specified for a flexible array member". So can someone help me understand how to set this up? Should I set up a blank array of variable size and then somewhere assign the #define array as seen below? Here would be an example of the code…(this is current implementation current IDE) In one header file that is Build switchable so we can build this on different hardware platforms we have the following #define #define GPIOS \ /* BANK, PIN, SPD, MODE,… */ GPIOINIT( A, 0, 2, AIN, …) \ GPIOINIT( A, 1, 2, AIN, …) \ GPIOINTINIT(A, 2, 2, AIN, …) \ . . . Then in a different header file that is used in all builds we have PLATFORM_CONFIG_T g_platformConfig = { .name = {PLATFORM_NAME}, (bunch of other stuff), .allGpios = { GPIOS /* here I get the error */ }, }; So I am thinking I can make the error line a variable array and assign to it later in some other way? The problem is the actual array "GPIO" is of different types and pin orders on different designs are different.

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  • Java Scanner newline parsing with regex (Bug?)

    - by SEK
    I'm developing a syntax analyzer by hand in Java, and I'd like to use regex's to parse the various token types. The problem is that I'd also like to be able to accurately report the current line number, if the input doesn't conform to the syntax. Long story short, I've run into a problem when I try to actually match a newline with the Scanner class. To be specific, when I try to match a newline with a pattern using the Scanner class, it fails. Almost always. But when I perform the same matching using a Matcher and the same source string, it retrieves the newline exactly as you'd expect it too. Is there a reason for this, that I can't seem to discover, or is this a bug, as I suspect? FYI: I was unable to find a bug in the Sun database that describes this issue, so if it is a bug, it hasn't been reported. Example Code: Pattern newLinePattern = Pattern.compile("(\\r\\n?|\\n)", Pattern.MULTILINE); String sourceString = "\r\n\n\r\r\n\n"; Scanner scan = new Scanner(sourceString); scan.useDelimiter(""); int count = 0; while (scan.hasNext(newLinePattern)) { scan.next(newLinePattern); count++; } System.out.println("found "+count+" newlines"); // finds 7 newlines Matcher match = newLinePattern.matcher(sourceString); count = 0; while (match.find()) { count++; } System.out.println("found "+count+" newlines"); // finds 5 newlines

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