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  • Address calling class

    - by Samuel
    I have an abstract class Moveable with the method abstract void move() which is extended by the class Bullet and the abstract class Character, and Character is extended by the class Survivor and the class Zombie. In Survivor and Bullet the move() method doesnt require any parameters while in the class Zombie the move() method depends on the actual position of the survivor. The survivor and multiple zombies are created in the class Gui. I wanted to access the survivor in Zombie - what's the best way of doing this? In Gui i wrote a method getSurvivor() but i don't see how to access this method in Zombie? I am aware that as a workaround i could just pass a [Survivor survivor] as parameter in move() and ignore it in Bullet and Survivor, but that feels so ... bad practice.

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  • Exporting to CSV with dynamic field type handling

    - by serhio
    I have to do an export from DB to CSV. field; fileld; field... etc Have 3 types of fields: Alpha, Numeric and Bool respresented as "alphaValue",intValue and True/False. I try to encapsulate this in a fields collection, in order to export if alpha then set "", if Bool=True/False if numeric let as is. and try to build a CsvField class: Public Structure?Class CsvField(Of T As ???) End Structure Enum FieldType Alpha Bool Numeric End Enum any suggestions welcomed.

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  • Abstract Classes and ReadOnly Properties

    - by serhio
    Let's have three classes; Line PoliLine SuperPoliLine for all that three classes a Distance is defined. But only for the Line a Distance can be Set. Is there a possibility to build a common abstract (MustInherit) class Segment, having a Distance as (abstract +? ReadOnly) member? Question for VB.NET, but C# answers welcomed too. Business Background Imagine a Bus. It has a lot of Stations, MainStations, and 2 TerminalStations. So Line is between 2 Stations, PoliLine is between 2 MainStations, and SuperPoliLine is between 2 TerminalStations. All "lines" are "Segments", but only the distance A-B between 2 stations - Line can be defined.

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  • Help dealing with data dependency between two registration forms

    - by franko75
    I have a tricky issue here with a registration of both a user and his/her pet. Both the user and the pet are treated as separate entities and both require separate registration forms. However, the user's pet has to be linked to the user via a foreign key in the database. The process is basically that when a new user joins the site, firstly they register their pet, then they register themselves. The reason for this order is to check their pet's eligibility for the site (there are some criteria to be met) first, instead of getting the user to sign up only to then find out their pet is ineligible. It is this ordering of the form submissions which is causing me a bit of a headache, as follows... The site is being developed with an MVC framework, and the User registration process is managed via a method in a User_form controller, while the pet registration process is managed via a method in the Pet_form controller. The pet registration form happens first, and the pet data can be saved without the owner_id at this stage, with the user id possibly being added (e.g by retrieving pet's id from session) following user registration. However, doing it this way could potentially result in redundant data, where pet records would be created in the database, but if the user doesn't actually register themselves too, then the pets will be ownerless records in the DB. Other option is to serialize the new pet's data at the pet registration stage, don't save it to the DB until the user fills out their registration form. Once the user is created, i can pass serialised data AND the owner_id to a method in the Pet Model which can update the DB. However, I also need to set the newly created $pet to $this-pet which I then access for a sequence of other related forms. Should I just set the session variable in the model method? Then in the Pet controller constructor, do a check for pet stored in session, if yes, assign to $this-pet... If this makes any sense to anybody and you have some advice, i'd be grateful to hear it!

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  • How can I sync three classes?

    - by TheMachineCharmer
    class Foo { Bar b; List<Foo> Neighbours; } class Bar { Spam s; List<Bar> Neighbours; } class Spam { List<string> Neighbours; } Each of these classes have AddNeighbour,RemoveNeighbour methods. User can add/remove Neighbours from any of the class at random. I want these three objects to be in sync. How can I do this?

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  • Passing parameter to base class constructor or using instance variable?

    - by deamon
    All classes derived from a certain base class have to define an attribute called "path". In the sense of duck typing I could rely upon definition in the subclasses: class Base: pass # no "path" variable here def Sub(Base): def __init__(self): self.path = "something/" Another possiblity would be to use the base class constructor: class Base: def __init__(self, path): self.path = path def Sub(Base): def __init__(self): super().__init__("something/") What would you prefer and why? Is there a better way?

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  • What happens to a class in PHP once its been instantiated?

    - by Caylem
    Hi I'm just playing around with some PHP and was wondering what happens when an object from a class is created within another PHP script? I assume once its created and been processed their is no way of then going back and 'playing' around with it from another script? The idea is i'm trying to create a kind of deck of cards using a card class, each card has specific data that is added to each individual object to make it unique, suit, value etc. Once its created i need to be able to go back to specific cards to use them. In java i'd have an arraylist of card objects, i'm not sure how to approach the same area in PHP. Thanks.

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  • Where can i find exercises for familiarising OOPS

    - by CrazyBoy123
    Now that i have learned the theory of OOPS in good number of books , and practised a little. Still i am not comfortable when i look into OOPS being applied in some of the Open Source projs. Can someone suggest any problem / solution kind of book , or any resources , that covers OOPS end - end. (C# , Java preferably)

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  • can I put my sqlite connection and cursor in a function?

    - by steini
    I was thinking I'd try to make my sqlite db connection a function instead of copy/pasting the ~6 lines needed to connect and execute a query all over the place. I'd like to make it versatile so I can use the same function for create/select/insert/etc... Below is what I have tried. The 'INSERT' and 'CREATE TABLE' queries are working, but if I do a 'SELECT' query, how can I work with the values it fetches outside of the function? Usually I'd like to print the values it fetches and also do other things with them. When I do it like below I get an error Traceback (most recent call last): File "C:\Users\steini\Desktop\py\database\test3.py", line 15, in <module> for row in connection('testdb45.db', "select * from users"): ProgrammingError: Cannot operate on a closed database. So I guess the connection needs to be open so I can get the values from the cursor, but I need to close it so the file isn't always locked. Here's my testing code: import sqlite3 def connection (db, arg): conn = sqlite3.connect(db) conn.execute('pragma foreign_keys = on') cur = conn.cursor() cur.execute(arg) conn.commit() conn.close() return cur connection('testdb.db', "create table users ('user', 'email')") connection('testdb.db', "insert into users ('user', 'email') values ('joey', 'foo@bar')") for row in connection('testdb45.db', "select * from users"): print row How can I make this work?

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  • 'is instanceof' Interface bad design

    - by peterRit
    Say I have a class A class A { Z source; } Now, the context tells me that 'Z' can be an instance of different classes (say, B and C) which doesn't share any common class in their inheritance tree. I guess the naive approach is to make 'Z' an Interface class, and make classes B and C implement it. But something still doesn't convince me because every time an instance of class A is used, I need to know the type of 'source'. So all finishes in multiple 'ifs' making 'is instanceof' which doesn't sound quite nice. Maybe in the future some other class implements Z, and having hardcoded 'ifs' of this type definitely could break something. The escence of the problem is that I cannot resolve the issue by adding functions to Z, because the work done in each instance type of Z is different. I hope someone can give me and advice, maybe about some useful design pattern. Thanks

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  • How does one refer to the game1 class's variables in XNA

    - by user1149068
    I try to refer to an array in the Game1 class by creating an object of the Game1 class with its definition Game1 gameObject; , its declaration gameObject = new Game1(); in the constructor, and its usage gameObject.tileArray[xInt, yInt].treed = true;. The game1 class itself remains unchanged in its class code other than some methods and variables. When I try to use this code in the TreeRegion class it gives me "Object reference not set to an instance of an object," leading me to believe that the game1 class is null somehow. How might one change the class or object in order to refer to game1's variables? Mind you I am self-taught and still rather new to C#. The class that refers to game1: http://pastebin.com/0chEcKfq Game1 itself http://pastebin.com/zLDVzCca

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  • Override java methods without affecting parent behaviour

    - by Timmmm
    suppose I have this classes (sorry it's kind of hard to think of a simple example here; I don't want any "why would you want to do that?" answers!): class Squarer { public void setValue(int v) { mV = v; } public int getValue() { return mV; } private int mV; public void square() { setValue(getValue() * getValue()); } } class OnlyOddInputsSquarer extends Squarer { @Override public void setValue(int v) { if (v % 2 == 0) { print("Sorry, this class only lets you square odd numbers!") return; } super.setValue(v); } } auto s = new OnlyOddInputsSquarer(); s.setValue(3); s.square(); This won't work. When Squarer.square() calls setValue(), it will go to OnlyOddInputsSquarer.setValue() which will reject all its values (since all squares are even). Is there any way I can override setValue() so that all the functions in Squarer still use the method defined there? PS: Sorry, java doesn't have an auto keyword you haven't heard about! Wishful thinking on my part.

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  • Session State Anti-Pattern

    - by Curiosity
    I know the SOLID principles and other design patterns fairly well and have been programming for some time now - seeing many a bit of code throughout the years. Having said that, I'm having trouble coming up with a name to give the pattern, or lack thereof, to bits of code I've been dealing with at a current engagement. The application is an ASP.NET C# WebForms application, backed by a SQL Server/Mainframe backend (more mainframe than backend) and it's riddled with Session State properties being accessed/mutated from multiple pages/classes. Accessing/mutating global variables/application state was usually shunned upon while I was in school. Apparently the creators of this magnificent application didn't think it was such a bad idea. Question: Is there a name for such a pattern/anti-pattern that relies so heavily on Session State? I'd like to call the pig by its name ...

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  • java protected method accessibility

    - by JavaUser
    In the below code the Consumer class can access the protected method of Parent class.How is it possible since there is no relation between Parent and Consumer class.Please explain class Parent { public void method1(){ System.out.println("PUBLIC METHOD"); } private void method2(){ System.out.println("PRIVATE METHOD"); } protected void method3(){ System.out.println("PROTECTED METHOD"); } } public class Consumer { public static void main(String[] args){ Parent parentObj = new Parent(); parentObj.method1(); //parentObj.method2(); parentObj.method3(); } } Thanks

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  • Objects instead of global variables in Perl

    - by Gaurav Dadhania
    I don't know if this is the right thing to do. But I'm lookig for tutorials/articles on using objects instead of global variables to store state. For eg. package something # some code here... # that generates errors and uses # something::errors to track errors. package something::errors sub new { my ($this) = @_; bless $this; return $this; } sub setErrors{ my ($this, @errors) = @_; $this->{errors} = \@errors; } sub getErrors{ my ($this) = @_; return $this->{errors}; } Is this better than using global varibles? Any down-sides to this? Any approach which might be better? Thanks.

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  • Calling methods in super class constructor of subclass constructor?

    - by deamon
    Calling methods in super class constructor of subclass constructor? Passing configuration to the __init__ method which calls register implicitely: class Base: def __init__(self, *verbs=("get", "post")): self._register(verbs) def _register(self, *verbs): pass class Sub(Base): def __init__(self): super().__init__("get", "post", "put") Or calling register explicitely in the subclass' __init__ method: class Base: def __init__(self): self._register("get", "post") def _register(self, *verbs): pass class Sub(Base): def __init__(self): _register("get", "post", "put") What is better or more pythonic? Or is it only a matter of taste?

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  • php require class call from inside method

    - by jera
    from my understanding, require pastes code into the calling php file. what if you were requiring from inside a method...it would paste the entire code/class inside the method, blocking the next statement in the method. eg. function test() { require 'pathtosomeclasscode'; somestatement; // any code after the require is blocked. } how do i get around this, to be able to require code where-ever, without it being pasted in that exact spot? Thanks in advance for your help.

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  • What to call factory-like (java) methods used with immutable objects

    - by StaxMan
    When creating classes for "immutable objects" immutable meaning that state of instances can not be changed; all fields assigned in constructor) in Java (and similar languages), it is sometimes useful to still allow creation of modified instances. That is, using an instance as base, and creating a new instance that differs by just one property value; other values coming from the base instance. To give a simple example, one could have class like: public class Circle { final double x, y; // location final double radius; public Circle(double x, double y, double r) { this.x = x; this.y = y; this.r = r; } // method for creating a new instance, moved in x-axis by specified amount public Circle withOffset(double deltaX) { return new Circle(x+deltaX, y, radius); } } So: what should method "withOffset" be called? (note: NOT what its name ought to be -- but what is this class of methods called). Technically it is kind of a factory method, but somehow that does not seem quite right to me, since often factories are just given basic properties (and are either static methods, or are not members of the result type but factory type). So I am guessing there should be a better term for such methods. Since these methods can be used to implement "fluent interface", maybe they could be "fluent factory methods"? Better suggestions? EDIT: as suggested by one of answers, java.math.BigDecimal is a good example with its 'add', 'subtract' (etc) methods. Also: I noticed that there's this question (by Jon Skeet no less) that is sort of related (although it asks about specific name for method)

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  • Are protected constructors considered good practice?

    - by Álvaro G. Vicario
    I'm writing some little helper classes to handle trees. Basically, I have a node and a special root node that represents the tree. I want to keep it generic and simple. This is part of the code: <?php class Tree extends TreeNode{ public function addById($node_id, $parent_id, $generic_content){ if( $parent = $this->findNodeById($parent_id) ){ $parent->addChildById($node_id, $generic_content); } } } class TreeNode{ public function __construct($node_id, $parent_id, $generic_content){ // ... } protected function addChildById($node_id, $generic_content){ $this->children[] = new TreeNode($this->node_id, $node_id, $generic_content); } } $Categories = new Tree; $Categories->addById(1, NULL, $foo); $Categories->addById(2, NULL, $bar); $Categories->addById(3, 1, $gee); ?> My questions: Is it sensible to force TreeNode instances to be created through TreeNode::addById()? If it's so, would it be good practise to declare TreeNode::__construct() as private/protected?

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  • Object Design catalog and resources

    - by Tauren
    I'm looking for web sites, books, or other resources that provide a catalog of object designs used in common scenarios. I'm not looking for generic design patterns, but for samples of actual object designs that were used to solve real problems. For instance, I'm about to build an internal messaging system for a web application, similar to Facebook's messaging system. This system will allow administrators to send messages to all members, to selected groups of members, or to individuals. Members can send messages to other members or groups of members. Fairly common stuff and a feature that I'm sure thousands of web applications require. I know each situation is different and there are a million ways to design this solution. Although this scenario isn't really all that complex, I'm sure the basic design of the necessary objects and relationships for a system like this has already been done many times. It would be nice to review other similar designs before building my own. Is there a place where people can share their designs and others can browse/search through the catalog to review and provide feedback on them? StackOverflow could be used to a degree for this, but doesn't really provide a catalog of designs. Any other resources that would relate?

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  • Where do you put your dependencies?

    - by The All Foo
    If I use the dependency injection pattern to remove dependencies they end up some where else. For example, Snippet 1, or what I call Object Maker. I mean you have to instantiate your objects somewhere...so when you move dependency out of one object, you end up putting it another one. I see that this consolidates all my dependencies into one object. Is that the point, to reduce your dependencies so that they all reside in a single ( as close to as possible ) location? Snippet 1 - Object Maker <?php class ObjectMaker { public function makeSignUp() { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); $SignUpObject = new ControlSignUp(); $SignUpObject->setObjects($DatabaseObject, $TextObject, $MessageObject); return $SignUpObject; } public function makeSignIn() { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); $SignInObject = new ControlSignIn(); $SignInObject->setObjects($DatabaseObject, $TextObject, $MessageObject); return $SignInObject; } public function makeTweet( $DatabaseObject = NULL, $TextObject = NULL, $MessageObject = NULL ) { if( $DatabaseObject == 'small' ) { $DatabaseObject = new Database(); } else if( $DatabaseObject == NULL ) { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); } $TweetObject = new ControlTweet(); $TweetObject->setObjects($DatabaseObject, $TextObject, $MessageObject); return $TweetObject; } public function makeBookmark( $DatabaseObject = NULL, $TextObject = NULL, $MessageObject = NULL ) { if( $DatabaseObject == 'small' ) { $DatabaseObject = new Database(); } else if( $DatabaseObject == NULL ) { $DatabaseObject = new Database(); $TextObject = new Text(); $MessageObject = new Message(); } $BookmarkObject = new ControlBookmark(); $BookmarkObject->setObjects($DatabaseObject,$TextObject,$MessageObject); return $BookmarkObject; } }

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  • How do you determine how coarse or fine-grained a 'responsibility' should be when using the single r

    - by Mark Rogers
    In the SRP, a 'responsibility' is usually described as 'a reason to change', so that each class (or object?) should have only one reason someone should have to go in there and change it. But if you take this to the extreme fine-grain you could say that an object adding two numbers together is a responsibility and a possible reason to change. Therefore the object should contain no other logic, because it would produce another reason for change. I'm curious if there is anyone out there that has any strategies for 'scoping', the single-responsibility principle that's slightly less objective?

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