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  • Basic Custom String Class for C++

    - by wdow88
    Hey all, I'm working on building my own string class with very basic functionality. I am having difficulty understand what is going on with the basic class that I have define, and believe there is some sort of error dealing with the scope occurring. When I try to view the objects I created, all the fields are described as (obviously bad pointer). Also, if I make the data fields public or build an accessor method, the program crashes. For some reason the pointer for the object is 0xccccccccc which points to no where. How can a I fix this? Any help/comments are much appreciated. //This is a custom string class, so far the only functions are //constructing and appending #include<iostream> using namespace std; class MyString1 { public: MyString1() { //no arg constructor char *string; string = new char[0]; string[0] ='\0'; std::cout << string; size = 1; } //constructor receives pointer to character array MyString1(char* chars) { int index = 0; //Determine the length of the array while (chars[index] != NULL) index++; //Allocate dynamic memory on the heap char *string; string = new char[index+1]; //Copy the contents of the array pointed by chars into string, the char array of the object for (int ii = 0; ii < index; ii++) string[ii] = chars[ii]; string[index+1] = '\0'; size = index+1; } MyString1 append(MyString1 s) { //determine new size of the appended array and allocate memory int newsize = s.size + size; MyString1 MyString2; char *newstring; newstring = new char[newsize+1]; int index = 0; //load the first string into the array while (string[index] != NULL) { newstring[index] = string[index]; index++; } //load the second string while (s.string[index] != NULL) { newstring[index] = s.string[index]; index++; } //null terminate newstring[newsize+1] = '\0'; delete string; //generate the object for return MyString2.string=newstring; MyString2.size=newsize; return MyString2; } private: char *string; int size; }; int main() { MyString1 string1; MyString1 string2("Hello There"); MyString1 string3("Buddy"); string2.append(string3); return 0; }

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  • Should I call class destructor in this code?

    - by peterg
    I am using this sample to decode/encode some data I am retrieving/sending from/to a web server, and I want to use it like this: BOOL HandleMessage(UINT uMsg,WPARAM wParam,LPARAM lParam,LRESULT* r) { if(uMsg == WM_DESTROY) { PostQuitMessage(0); return TRUE; } else if(uMsg == WM_CREATE) { // Start timer StartTimer(); return TRUE; } else if(uMsg == WM_TIMER) { //get data from server char * test = "test data"; Base64 base64; char *temp = base64.decode(test); MessageBox(TEXT(temp), 0, 0); } } The timer is set every 5 minutes. Should I use delete base64 at the end? Does delete deallocates everything used by base64?

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  • Concurrency and Calendar classes

    - by fbielejec
    I have a thread (class implementing runnable, called AnalyzeTree) organised around a hash map (ConcurrentMap slicesMap). The class goes through the data (called trees here) in the large text file and parses the geographical coordinates from it to the HashMap. The idea is to process one tree at a time and add or grow the values according to the key (which is just a Double value representing time). The relevant part of code looks like this: // grow map entry if key exists if (slicesMap.containsKey(sliceTime)) { double[] imputedLocation = imputeValue( location, parentLocation, sliceHeight, nodeHeight, parentHeight, rate, useTrueNoise, currentTreeNormalization, precisionArray); slicesMap.get(sliceTime).add( new Coordinates(imputedLocation[1], imputedLocation[0], 0.0)); // start new entry if no such key in the map } else { List<Coordinates> coords = new ArrayList<Coordinates>(); double[] imputedLocation = imputeValue( location, parentLocation, sliceHeight, nodeHeight, parentHeight, rate, useTrueNoise, currentTreeNormalization, precisionArray); coords.add(new Coordinates(imputedLocation[1], imputedLocation[0], 0.0)); slicesMap.putIfAbsent(sliceTime, coords); // slicesMap.put(sliceTime, coords); }// END: key check And the class is called like this (executor is ExecutorService executor = Executors.newFixedThreadPool(NTHREDS) ): mrsd = new SpreadDate(mrsdString); int readTrees = 1; while (treesImporter.hasTree()) { currentTree = (RootedTree) treesImporter.importNextTree(); executor.submit(new AnalyzeTree(currentTree, precisionString, coordinatesName, rateString, numberOfIntervals, treeRootHeight, timescaler, mrsd, slicesMap, useTrueNoise)); // new AnalyzeTree(currentTree, precisionString, // coordinatesName, rateString, numberOfIntervals, // treeRootHeight, timescaler, mrsd, slicesMap, // useTrueNoise).run(); readTrees++; }// END: while has trees Now this is running into troubles when executed in parallel (the commented part running sequentially is fine), I thought it might throw a ConcurrentModificationException, but apparently the problem is in mrsd (instance of SpreadDate object, which is simply a class for date related calculations). The SpreadDate class looks like this: public class SpreadDate { private Calendar cal; private SimpleDateFormat formatter; private Date stringdate; public SpreadDate(String date) throws ParseException { // if no era specified assume current era String line[] = date.split(" "); if (line.length == 1) { StringBuilder properDateStringBuilder = new StringBuilder(); date = properDateStringBuilder.append(date).append(" AD") .toString(); } formatter = new SimpleDateFormat("yyyy-MM-dd G", Locale.US); stringdate = formatter.parse(date); cal = Calendar.getInstance(); } public long plus(int days) { cal.setTime(stringdate); cal.add(Calendar.DATE, days); return cal.getTimeInMillis(); }// END: plus public long minus(int days) { cal.setTime(stringdate); cal.add(Calendar.DATE, -days); //line 39 return cal.getTimeInMillis(); }// END: minus public long getTime() { cal.setTime(stringdate); return cal.getTimeInMillis(); }// END: getDate } And the stack trace from when exception is thrown: java.lang.ArrayIndexOutOfBoundsException: 58 at sun.util.calendar.BaseCalendar.getCalendarDateFromFixedDate(BaseCalendar.java:454) at java.util.GregorianCalendar.computeFields(GregorianCalendar.java:2098) at java.util.GregorianCalendar.computeFields(GregorianCalendar.java:2013) at java.util.Calendar.setTimeInMillis(Calendar.java:1126) at java.util.GregorianCalendar.add(GregorianCalendar.java:1020) at utils.SpreadDate.minus(SpreadDate.java:39) at templates.AnalyzeTree.run(AnalyzeTree.java:88) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) at java.util.concurrent.FutureTask.run(FutureTask.java:166) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) If a move the part initializing mrsd to the AnalyzeTree class it runs without any problems - however it is not very memory efficient to initialize class each time this thread is running, hence my concerns. How can it be remedied?

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  • Passing arguments to anonymous inner classes

    - by synic
    I'm trying to make an API library for our web services, and I'm wondering if it's possible to do something like this: abstract class UserRequest(val userId: Int) { def success(message: String) def error(error: ApiError) } api.invokeRequest(new UserRequest(121) { override def success(message: String) = { // handle success } override def error(error: ApiError) = { // handle the error } } I'm talking about passing parameters to the anonymous inner class, and also overriding the two methods. I'm extremely new to Scala, and I realize my syntax might be completely wrong. I'm just trying to come up with a good design for this library before I start coding it. I'm willing to take suggestions for this, if I'm doing it the completely wrong way, or if there's a better way. The idea is that the API will take some sort of request object, use it to make a request in a thread via http, and when the response has been made, somehow signal back to the caller if the request was a success or an error. The request/error functions have to be executed on the main thread.

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  • Is it possible to create a python iterator over pre-defined mutable data?

    - by Wilduck
    I might be doing this wrong, if I am, let me know, but I'm curious if the following is possible: I have a class that holds a number of dictionaries, each of which pairs names to a different set of objects of a given class. For example: items = {"ball" : ItemInstance1, "sword" : ItemInstance2} people = {"Jerry" : PersonInstance1, "Bob" : PersonInstance2, "Jill" : PersonInstance3} My class would then hold the current items and people that are availible, and these would be subject to change as the state changes: Class State: def __init__(self, items, people): self.items = items self.people = people I would like to define a iter() and next() method such that it iterates through all of the values in its attributes. My first question is whether or not this is possible. If it is, will it be able to support a situation as follows: I define items and people as above then: state = State(items, people) for names, thing in state: print name + " is " + thing.color items[cheese] = ItemInstance3 for names, thing in state: print name + " weighs " + thing.weight While I feel like this would be usefull in the code I have, I don't know if it's either possible or the right approach. Everything I've read about user defined iterators has suggested that each instance of them is one use only.

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  • Will this static class break in a multi user scenario ?

    - by Perpetualcoder
    Say I make a static class like following with an extension method: public static class MyStaticExtensionClass { private static readonly Dictionary<int, SomeClass> AlgoMgmtDict = new Dictionary<int, SomeClass>(); public static OutputClass ToOutput(this InputClass input) { // clears up the dict // does some kind of transform over the input class // return an OutputClass object } } In a multi user system, will the state management dictionary fail to provide correct values for the transform algorithm? Will a regular class be a better design or shoving the Dictionary inside the method a better design?

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  • Testing for the existence of a field in a class

    - by Brett
    Hi, i have a quick question. I have a 2D array that stores an instance of a class. The elements of the array are assigned a particular class based on a text file that is read earlier in the program. Since i do not know without looking in the file what class is stored at a particular element i could refer to a field that doesn't exist at that index (referring to appearance when an instance of temp is stored in that index). i have come up with a method of testing this, but it is long winded and requires a second matrix. Is there a function to test for the existence of a field in a class? class temp(): name = "default" class temp1(): appearance = "@"

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  • What classes should I map against with NHibernate?

    - by apollodude217
    Currently, we use NHibernate to map business objects to database tables. Said business objects enforce business rules: The set accessors will throw an exception on the spot if the contract for that property is violated. Also, the properties enforce relationships with other objects (sometimes bidirectional!). Well, whenever NHibernate loads an object from the database (e.g. when ISession.Get(id) is called), the set accessors of the mapped properties are used to put the data into the object. What's good is that the middle tier of the application enforces business logic. What's bad is that the database does not. Sometimes crap finds its way into the database. If crap is loaded into the application, it bails (throws an exception). Sometimes it clearly should bail because it cannot do anything, but what if it can continue working? E.g., an admin tool that gathers real-time reports runs a high risk of failing unnecessarily instead of allowing an admin to even fix a (potential) problem. I don't have an example on me right now, but in some instances, letting NHibernate use the "front door" properties that also enforce relationships (especially bidi) leads to bugs. What are the best solutions? Currently, I will, on a per-property basis, create a "back door" just for NHibernate: public virtual int Blah {get {return _Blah;} set {/*enforces BR's*/}} protected virtual int _Blah {get {return blah;} set {blah = value;}} private int blah; I showed the above in C# 2 (no default properties) to demonstrate how this gets us basically 3 layers of, or views, to blah!!! While this certainly works, it does not seem ideal as it requires the BL to provide one (public) interface for the app-at-large, and another (protected) interface for the data access layer. There is an additional problem: To my knowledge, NHibernate does not give you a way to distinguish between the name of the property in the BL and the name of the property in the entity model (i.e. the name you use when you query, e.g. via HQL--whenever you give NHibernate the name (string) of a property). This becomes a problem when, at first, the BR's for some property Blah are no problem, so you refer to it in your O/R mapping... but then later, you have to add some BR's that do become a problem, so then you have to change your O/R mapping to use a new _Blah property, which breaks all existing queries using "Blah" (common problem with programming against strings). Has anyone solved these problems?!

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  • Java/MySQL: Working with data in classes

    - by skiwi
    What is the best way to deal with accessing/modifying tables in a database? I have read about the Data Access Object approach, but none of the resources I have found so far indicate a clear implementation of it. So assume you have a database with a table called accounts that has columns id, name, password and email. How would you properly access it within Java? I mean most people know how to do SQL statements, but that is not really the point. I hope people here can be of help. Regards.

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  • Right way to return proxy model instance from a base model instance in Django ?

    - by sotangochips
    Say I have models: class Animal(models.Model): type = models.CharField(max_length=255) class Dog(Animal): def make_sound(self): print "Woof!" class Meta: proxy = True class Cat(Animal): def make_sound(self): print "Meow!" class Meta: proxy = True Let's say I want to do: animals = Animal.objects.all() for animal in animals: animal.make_sound() I want to get back a series of Woofs and Meows. Clearly, I could just define a make_sound in the original model that forks based on animal_type, but then every time I add a new animal type (imagine they're in different apps), I'd have to go in and edit that make_sound function. I'd rather just define proxy models and have them define the behavior themselves. From what I can tell, there's no way of returning mixed Cat or Dog instances, but I figured maybe I could define a "get_proxy_model" method on the main class that returns a cat or a dog model. Surely you could do this, and pass something like the primary key and then just do Cat.objects.get(pk = passed_in_primary_key). But that'd mean doing an extra query for data you already have which seems redundant. Is there any way to turn an animal into a cat or a dog instance in an efficient way? What's the right way to do what I want to achieve?

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  • Making Global Struct in C++ Program

    - by mosg
    Hello world! I am trying to make global structure, which will be seen from any part of the source code. I need it for my big Qt project, where some global variables needed. Here it is: 3 files (global.h, dialog.h & main.cpp). For compilation I use Visual Studio (Visual C++). global.h #ifndef GLOBAL_H_ #define GLOBAL_H_ typedef struct TNumber { int g_nNumber; } TNum; TNum Num; #endif dialog.h #ifndef DIALOG_H_ #define DIALOG_H_ #include <iostream> #include "global.h" using namespace std; class ClassB { public: ClassB() {}; void showNumber() { Num.g_nNumber = 82; cout << "[ClassB][Change Number]: " << Num.g_nNumber << endl; } }; #endif and main.cpp #include <iostream> #include "global.h" #include "dialog.h" using namespace std; class ClassA { public: ClassA() { cout << "Hello from class A!\n"; }; void showNumber() { cout << "[ClassA]: " << Num.g_nNumber << endl; } }; int main(int argc, char **argv) { ClassA ca; ClassB cb; ca.showNumber(); cb.showNumber(); ca.showNumber(); cout << "Exit.\n"; return 0; } When I`m trying to build this little application, compilation works fine, but the linker gives me back an error: 1>dialog.obj : error LNK2005: "struct TNumber Num" (?Num@@3UTNumber@@A) already defined in main.obj Is there exists any solution? Thanks.

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  • Dynamic Operator Overloading on dict classes in Python

    - by Ishpeck
    I have a class that dynamically overloads basic arithmetic operators like so... import operator class IshyNum: def __init__(self, n): self.num=n self.buildArith() def arithmetic(self, other, o): return o(self.num, other) def buildArith(self): map(lambda o: setattr(self, "__%s__"%o,lambda f: self.arithmetic(f, getattr(operator, o))), ["add", "sub", "mul", "div"]) if __name__=="__main__": number=IshyNum(5) print number+5 print number/2 print number*3 print number-3 But if I change the class to inherit from the dictionary (class IshyNum(dict):) it doesn't work. I need to explicitly def __add__(self, other) or whatever in order for this to work. Why?

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  • Help with psudo classes in CSS

    - by Anil Namde
    <a class="success" href="javascript:void(0)"></a> //CSS for setting background for above link a.success:hover{ //set background image } What my intent is to change the class of link on server side based on success/fail and set icon for the link accordingly. But above CSS is not working as expected. Can someone plz help with this.

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  • Eclipse outline of Prototype javascript classes

    - by Rob Agar
    Is there a way to show the structure of a javascript class declared using Prototype's Class.create function in the Eclipse outline view? The declarations look like: var Foo = Class.create({ bar: function() { ... }, baz: function() { ... }, }); At the moment all I get is "Foo:". (A google search turned up http://marketplace.eclipse.org/content/prototypewtp, but the link to the plugin homepage is dead)

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  • CakePHP: Interaction between different files/classes

    - by Alexx Hardt
    Hey, I'm cloning a commercial student management system. Students use the frontend to apply for lectures, uni staff can modify events (time, room, etc). The core of the app will be the algortihm which distributes the seats to students. I already asked about it here: How to implement a seat distribution algorithm for uni lectures Now, I found a class for that algorithm here: http://www.phpclasses.org/browse/file/10779.html I put the 'class GA' into app/vendors. I need to write a 'class Solution', which represents one object (a child, and later a parent for the evolutionary process). I'll also have to write functions mutate(), crossover() and fitness(). fitness calculates a score of a solution, based on if there are overbooked courses etc; crossover() is the crazy monkey sex function which produces a child from two parents, and mutate() modifies a child after crossover. Now, the fitness()-function needs to access a few related models, and their find()-functions. It evaluates a solution's fitness by checking e.g. if there are overbooked courses, or unfulfilled wishes, and penalizes that. Where would I put the ga.php, solution.php and the three functions? ga.php has to access the functions, but the functions have to access the models. I also don't want to call any App::import()'s from within the fitness()-function, because it gets called many thousand times when the algorithm runs. Hope someone can help me. Thanks in advance =)

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  • C++ converting back and forth from derived and base classes

    - by user127817
    I was wondering if there is a way in C++ to accomplish the following: I have a base class called ResultBase and two class that are Derived from it, Variable and Expression. I have a few methods that do work on vector<ResultBase> . I want to be able to pass in vectors of Variable and Expression into these methods. I can achieve this by creating a vector<ResultBase> and using static_cast to fill it with the members from my vector of Variable/Expression. However, once the vector has run through the methods, I want to be able to get it back as the vector of Result/Expression. I'll know for sure which one I want back. static_cast won't work here as there isn't a method to reconstruct a Variable/Expression from a ResultBase, and more importantly I wouldn't have the original properties of the Variables/Expressions The methods modify some of the properties of the ResultBase and I need those changes to be reflected in the original vectors. (i.e. ResultBase has a property called IsLive, and one of the methods will modify this property. I want this IsLive value to be reflected in the derived class used to create the ResultBase Whats the easiest way to accomplish this?

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  • Define the base class or base functionality of a dynamic proxy (e.g. Castle, LinFu)

    - by Graham
    Hi, I've asked this in the NHibernate forumns but I think this is more of a general question. NHibernate uses proxy generators (e.g. Castle) to create its proxy. What I'd like to do is to extend the proxy generated so that it implements some of my own custom behaviour (i.e. a comparer). I need this because the following standard .NET behaviour fails to produce the correct results: //object AC is a concrete class collection.Contains(AC) = true //object AP is a proxy with the SAME id and therefore represents the same instance as concrete AC collection.Contains(AP) = false If my comparer was implemented by AP (i.e. do id's match) then collection.Contains(AP) would return true, as I'd expect if proxies were implicit. (NB: For those who say NH inherits from your base class, then yes it does, but NH can also inherit from an interface - which is what we're doing) I'm not at all sure this is possible or where to start. Is this something that can be done in any of the common proxy generators that NH uses?

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  • get_by_id method on Model classes in Google App Engine Datastore

    - by tarn
    I'm unable to workout how you can get objects from the Google App Engine Datastore using get_by_id. Here is the model from google.appengine.ext import db class Address(db.Model): description = db.StringProperty(multiline=True) latitude = db.FloatProperty() longitdue = db.FloatProperty() date = db.DateTimeProperty(auto_now_add=True) I can create them, put them, and retrieve them with gql. address = Address() address.description = self.request.get('name') address.latitude = float(self.request.get('latitude')) address.longitude = float(self.request.get('longitude')) address.put() A saved address has values for >> address.key() aglndWVzdGJvb2tyDQsSB0FkZHJlc3MYDQw >> address.key().id() 14 I can find them using the key from google.appengine.ext import db address = db.get('aglndWVzdGJvb2tyDQsSB0FkZHJlc3MYDQw') But can't find them by id >> from google.appengine.ext import db >> address = db.Model.get_by_id(14) The address is None, when I try >> Address.get_by_id(14) AttributeError: type object 'Address' has no attribute 'get_by_id' How can I find by id? EDIT: It turns out I'm an idiot and was trying find an Address Model in a function called Address. Thanks for your answers, I've marked Brandon as the correct answer as he got in first and demonstrated it should all work.

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  • Continuing JavaScript "classes" - enums within

    - by espais
    From a previous question, I have the following: So I have implemented a resource class, now I'd like to continue extending it and add all my constants and enums (or as far as JS will allow...). This is what I currently have: var resources = { // images player : new c_resource("res/player.png"), enemies : new c_resource("res/enemies.png"), tilemap : new c_resource("res/tilemap.png") }; And this is what I would like to continue to extend it to: var resources = { // images player : new c_resource("res/player.png"), enemies : new c_resource("res/enemies.png"), tilemap : new c_resource("res/tilemap.png"), // enums directions : {up:0, right:1, down:2, left:3}, speeds : {slow: 1, medium: 3, fast: 5} }; ... function enemies() { this.dir = resources.directions.down; // initialize to down } When I attempt to access resources.directions.up, my JS script goes down in a flaming pile of burning code. Are enums allowed in this context, and if not, how can I properly insert them to be used outside of a normal function? I have also tried defining them as global to a similar effect. edits: fixed the comma...that was just an error in transcribing it. When I run it in Firefox and watch the console, I get an error that says resources is undefined. The resources 'class' is defined at the top of my script, and function enemies() directly follows...so from what I understand it should still be in scope...

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  • Am I trying to Implement Multiple Inheritance. How can I do this.

    - by Shantanu Gupta
    I have created a class say A which has some functions defined as protected. Now Class B inherits A and class C inherits B. Class A has private default constructor and protected parameterized constructor. I want Class B to be able to access all the protected functions defined in Class A but class C can have access on some of the functions only not all the functions and class C is inheriting class B. How can I restrict access to some of the functions of Class A from Class C ? EDIT: namespace Db { public Class A { private A(){} protected A(string con){assign this value} protected DataTable getTable(){return Table;} protected Sqlparameters setParameters(){return parameter;} } } namespace Data { public Class B:A { protected B():base("constring"){} protected DataTable output(){return getTable();} protected sqlparameter values(param IDataParameter[] parameter){} } } namespace Bsns { public Class C:B { protected C():base(){} protected DataTable show() {return values(setparameter());} } } EDIT I think what I am trying to do here is Multiple inheritance. Please check. Class A { //suppose 10 functions are declared } Class B:A { //5 functions declared which are using A's function in internal body } Class C:B { //using all functions of B but require only 4 functions of A to be accessible by C. }

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  • Implementing implicitly shared classes outside of Qt

    - by Timothy Baldridge
    I'm familiar with the way Qt uses D-pointers for managing data. How do I do this in my code? I tried this method: 1) move all data into a struct 2) add a QAtomicInt to the struct 3) implement a = operator and change my constructor/deconstructor to check-up on the reference count. The issue is, when I go to do a shallow copy of the object, I get an error about QObject declaring = as private. How then do I accomplish this? Here's an example of my copy operator: HttpRequest & HttpRequest::operator=(const HttpRequest &other) { other.d->ref.ref(); if (!d->ref.deref()) delete d; d = other.d; return *this; } Am I going about this the wrong way?

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  • XSD.exe question about include files and code generation

    - by Roger Willcocks
    If you have an XSD with an includes reference. Is it possible to generate 2 separate class files. 1 for the XSD, and 1 for the included XSD? My Scenario 4 XSDs, each of which share 15-20 element definitions in common. Rather than maintaining, I'd like to end up with the 4 XSDs all referencing a fifth file with the common definitions, and code generating 5 .cs files to use.

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