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  • Why can't you call a non-static method from a static method?

    - by VoodooChild
    I have a static method [Method1] in my class, which calls another method [Method2] in the same class and is not a static method. But this is a no-no. I get this error: An object reference is required for the non-static field, method, or property "ClassName.MethodName()" Can someone please briefly describe why? including other things that might be related to this.

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  • Javascript - cannot make static reference to non-static function ....

    - by Ankur
    I am making a reference to the Javascript function splice() on an array and I get the error: "Cannot make a static reference to the non-static function splice()" What's going on - how is this a static reference, aren't I referencing an instance of an Array class and its method - how is that static? $(document).ready( function() { var queryPreds = new Array(); var queryObjs = new Array(); function remFromQuery(predicate) { for(var i=0; i<arrayName.length;i++ ) { if(queryPreds[i]==predicate) queryPreds.splice(i,1); queryObjs.splice(i,1); } } }

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  • No Method Error Undefined method 'save' for nil:NilClass

    - by BennyB
    I'm getting this error when i try to create a "Lecture" via my Lecture controller's create method. This used to work but i went on to work on other parts of the app & then of course i come back & something is now throwing this error when a user tries to create a Lecture in my app. I'm sure its something small i'm just overlooking (been at it a while & probably need to take a break)...but I'd appreciate if someone could let me know why this is happening...let me know if i need to post anything else...thx! The error I get NoMethodError in LecturesController#create undefined method `save' for nil:NilClass Rails.root: /Users/name/Sites/rails_projects/app_name Application Trace | Framework Trace | Full Trace app/controllers/lectures_controller.rb:13:in `create' My view to create a new Lecture views/lectures/new.html.erb <% provide(:title, 'Start a Lecture') %> <div class="container"> <div class="content-wrapper"> <h1>Create a Lecture</h1> <div class="row"> <div class="span 6 offset3"> <%= form_for(@lecture) do |f| %> <%= render 'shared/error_messages', :object => f.object %> <div class="field"> <%= f.text_field :title, :placeholder => "What will this Lecture be named?" %> <%= f.text_area :content, :placeholder => "Describe this Lecture & what will be learned..." %> </div> <%= f.submit "Create this Lecture", :class => "btn btn-large btn-primary" %> <% end %> </div> </div> </div> </div> Then my controller where its saying the error is coming from controllers/lectures_controller.rb class LecturesController < ApplicationController before_filter :signed_in_user, :only => [:create, :destroy] before_filter :correct_user, :only => :destroy def index end def new @lecture = current_user.lectures.build if signed_in? end def create if @lecture.save flash[:success] = "Lecture created!" redirect_to @lecture else @activity_items = [ ] render 'new' end end def show @lecture = Lecture.find(params[:id]) end def destroy @lecture.destroy redirect_to root_path end private def correct_user @lecture = current_user.lectures.find_by_id(params[:id]) redirect_to root_path if @lecture.nil? end

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  • Extension method question. Why do I need to use someObj = someObj.somemethod();

    - by Kettenbach
    Hi All, I have a simple extension method that I would like to use to add an item to an array of items. public static T[] addElement<T>(this T[] array, T elementToAdd) { var list = new List<T>(array) {elementToAdd}; return list.ToArray(); } this works ok, but when I use it, I am having to set the array equal to the return value. I see that I am returning an Array. I likely want this method to be void, but I would like the item added. Does anyone have any ideas on what I need to do , to make this work the way I am wanting? Instead of someArray = someArray.addElement(item), I just want to do someArray.addElement(item) and then someArray be ready to go. What am I missing here? Thanks, ~ck in San Diego

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  • How to use a method with more than one parameters to create custom buttons

    - by iphonix
    I am repeating my codes few times to create custom buttons, I am trying to create a method and create all my required buttons just by called that method and using two parameters, btnTitle and btnAction. My Codes for the method -(void) addnewButton:(NSString *) btnTitle withAction:UIAction btnAction; { // Add a custom edit navigation button editButton = [[[UIBarButtonItem alloc] initWithTitle:NSLocalizedString((btnTitle), @"") style:UIBarButtonItemStyleBordered target:self action:@selector(btnAction)] autorelease]; self.navigationItem.rightBarButtonItem = editButton; } Now how shall I call this method to create a button?

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  • How to call a method from another class that's been instantiated within the current class

    - by Pavan
    my screen has a few views like such __________________ | _____ | | | | | //viewX is a video screen | | | | | viewX | vY | | //viewY is a custom uiview i created. | |____| | //it contains a method which i would like to call that toggles |_________________| //the hidden property of this view. and when it hides, a little | | //button is replaced no the top right corner on top of viewX | viewZ | //the video layer | | |_________________| //viewZ is a view containing many square views - thumbnails. my question is, i dont know how to register for touch events so that it recognises any touch event on no matter which view the user touches the screen.. atm im handling the touch events for each view inside it. so all works well... however what im trying to do is that when the user taps anywhere else on the screen but on viewY, viewY should dissapear by calling that method in the viewY class. this viewY class is instantiated and has no xib file attached to it. the uiview is created progammatically in the viewY class. this whole class for viewY behviour is instantiated in viewX - the video view. my boss says add delegates.. although i have now clue how to do that... any help? is there anyway i can just make it really simple and be able to say REMOVE VIEW no matter which class im calling from? Also ive seen other people achieve this by using these funky arrows - ... <- etc.. although im not sure if thats what i need or how to implement such a thing. ah i think ive made my question quite complicated but i really mean it to be a simple one, and know it can be done in an easy way!

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  • How do I avoid boxing/unboxing when extending System.Object?

    - by Robert H.
    I'm working on an extension method that's only applicable to reference types. I think, however, it's currently boxing and unboxing the the value. How can I avoid this? namespace System { public static class SystemExtensions { public static TResult GetOrDefaultIfNull<T, TResult>(this T obj, Func<T, TResult> getValue, TResult defaultValue) { if (obj == null) return defaultValue; return getValue(obj); } } } Example usage: public class Foo { public int Bar { get; set; } } In some method: Foo aFooObject = new Foo { Bar = 1 }; Foo nullReference = null; Console.WriteLine(aFooObject.GetOrDefaultIfNull((o) => o.Bar, 0)); // results: 1 Console.WriteLine(nullReference.GetOrDefaultIfNull((o) => o.Bar, 0)); // results: 0

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  • Error message in XSLT with C# extension function

    - by iHeartGreek
    Hi! I am received the following error while trying to implement a C# extension function in XSLT. Extension function parameters or return values which have CLR type 'Char[]' are not supported.** code: <xsl:variable name="stringList"> <xsl:value-of select="extension:GetList('AAA BBB CCC', ' ')"/> </xsl:variable> <msxsl:script language="C#" implements-prefix="extension"> <![CDATA[ public string[] GetList(string str, char[] delimiter) { ... ... return str.Split(delimiter, StringSplitOptions.None); } ]]> </msxsl:script> Can someone explain this error message and how to get past it? Thanks!

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  • LINQ .Cast() extension method fails but (type)object works.

    - by Ben Robinson
    To convert between some LINQ to SQL objects and DTOs we have created explicit cast operators on the DTOs. That way we can do the following: DTOType MyDTO = (LinqToSQLType)MyLinq2SQLObj; This works well. However when you try to cast using the LINQ .Cast() extension method it trows an invalid cast exception saying cannot cast type Linq2SQLType to type DTOType. i.e. the below does not work List<DTO.Name> Names = dbContact.tNames.Cast<DTO.Name>() .ToList(); But the below works fine: DAL.tName MyDalName = new DAL.tName(); DTO.Name MyDTOName = (DTO.Name)MyDalName; and the below also works fine List<DTO.Name> Names = dbContact.tNames.Select(name => (DTO.Name)name) .ToList(); Why does the .Cast() extension method throw an invalid cast exception? I have used the .Cast() extension method in this way many times in the past and when you are casting something like a base type to a derived type it works fine, but falls over when the object has an explicit cast operator.

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  • C# Extension Method for String Data Type

    - by Jimbo
    My web application deals with strings that need to be converted to numbers alot - users often put commas, currency symbols etc. in these fields so what I want to do is create a string extension method that cleans the field up and converts it to a decimal. For example: decimal myNumber = "$1,250.85".ToDecimal(); Can anyone help with this? Thanks!

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  • Extension method not working if I set controller property in Action, works in OnExecuting

    - by Blankman
    I have a class MyController that inherits from Controller, so all my controllers inherit from MyController. I have a property in MyController: public class MyController : Controller { public string SomeProperty {get;set;} } if I set this property in MyController's OnExecuting method, my HtmlHelper extension method works fine: public static string SomeExtension(this HtmlHelper htmlHelper) { StringBuilder sb = new StringBuilder(); string result = ""; var controller = htmlHelper.ViewContext.Controller as MyController; if (controller != null) { result = controller.SomeProperty; } return result; } it doesn't work if I set 'SomeProperty' in my controllers action method. I guess because I am doing 'as MyController' in the extension method? is there a way for it to work in both situations? I am using the value of SomeProperty to be outputted on my view pages.

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  • Whats wrong with this method?

    - by David
    Here's the method: public static String CPUcolor () { System.out.println ("What color am I?") ; String s = getIns() ; System.out.println ("are you sure I'm "+s+"? (Y/N)") ; String a = getIns() ; while (!((a.equals ("y")) || (a.equals ("Y")) || (a.equals ("n")) || (a.equals ("N")))) { System.out.println ("try again") ; a = getIns () ; } if (a.equals ("n") || a.equals("N")) {CPUcolor() ;} System.out.println ("I am "+s) ; return s ; } here is a possible output of this method (y's and n's are user inputs): What color am I? red are you sure I'm red? (Y/N) N What color am I? blue are you sure I'm blue? (Y/N) N What color am I? Yellow are you sure I'm Yellow? (Y/N) y I am Yellow I am blue I am red Why is it that the line's "I am blue" and "I am Blue" printed? Why are they printed in reverse order with red, the first entered, printed last?

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  • loading method based on URL

    - by steeped
    I am trying to build a small mvc-based application. How do I call a method in a class based on a query string? For example, the $_GET query string is being set as load_master_form http://www.domain.com/settings/load_master_form And to call the method within the settings class, I am doing: function __construct(){ $this->{$_GET['method']}(); } But obviously that doesn't work - it just isn't possible to load a method like that. So how would it be done?

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  • c# passing method names as the argument in a method

    - by Alan Bennett
    hi guys, I have a recuring method which shows up many times in my code its basically checking to make sure that the connection to the odbc is ok and then connects but each time this method is called it calls another method and each instance of the main method this one is different, as each method is about 8 lines of code having it 8 times in the code isnt ideal. so basically i would like to have just one method which i can call passing the name of the new method as an arguement. so basically like: private void doSomething(methodToBeCalled) { if(somthingistrue) { methodToBeCalled(someArgument) } } is this possible? thanks in advance

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  • when to make a method static

    - by Don
    Hi, I'd like to know how people decide whether to define a method as static. I'm aware that a method can only be defined as static if it doesn't require access to instance fields. So lets say we have a method that does not access instance fields, do you always define such a method as static, or only if you need to call it statically (without a reference to an instance). Perhaps another way of asking the same question, is whether you use static or non-static as the default? Thanks, Don

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  • Does iPhone SDK Objective C support functions inside of functions?

    - by Moshe
    I know that javascript, for example supports functions inside of functions, like so: function doSomething(){ function doAnothingThing(){ //this function is redefined every time doSomething() is called and only exists inside doSomething() } //you can also stick it inside of conditions if(yes){ function doSomethingElse(){ //this function only exists if yes is true } } } Does objective-c support this? Theoretical example: -(void) doSomething:(id) sender{ -(void) respondToEvent: (id) sender{ //theoretically? ... please? } } BONUS: What is the proper term for a "local" function?

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  • Can fields of the class and arguments of the method interfere?

    - by Roman
    I have a class with a fields called "a". In the class I have a method and in the list of arguments of this method I also have "a". So, which "a" I will see inside of the method? Will it be the field or it will be the argument of the method? public class myClass { private String a; // Method which sets the value of the field "a". public void setA(String a) { a = a; } } By the way, there is a similar situation. A method has some local (for method) variables whose names coincide with the names of the fields. What will the "see" the method if I refer to such a method-local variable inside the method (the field or the local variable)?

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  • How do I show and position an Image initialized in the codebehind on my page?

    - by Andreas Strandfelt
    Hello. I have created a simple method to check if an image has been approved and finally returns it as an control. But how do i call and show it on the page? I've tried something like this in the aspx-file: <% SendImage("DKBygMiniLogo.gif", "True"); %> Here is the simple method: protected Image SendImage(object Image, object Approved) { bool approved = Convert.ToBoolean(Approved); Image img = new Image(); if (approved) { img.ImageUrl = "~/images/Ads/" + Image.ToString(); img.Visible = true; } else { img.ImageUrl = "~/images/Ads/" + Image.ToString(); img.Visible = false; } return img; } How do I actually show the image?

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  • Trouble calling a method from an external class

    - by Bradley Hobbs
    Here is my employee database program: import java.util.*; import java.io.*; import java.io.File; import java.io.FileReader; import java.util.ArrayList; public class P { //Instance Variables private static String empName; private static String wage; private static double wages; private static double salary; private static double numHours; private static double increase; // static ArrayList<String> ARempName = new ArrayList<String>(); // static ArrayList<Double> ARwages = new ArrayList<Double>(); // static ArrayList<Double> ARsalary = new ArrayList<Double>(); static ArrayList<Employee> emp = new ArrayList<Employee>(); public static void main(String[] args) throws Exception { clearScreen(); printMenu(); question(); exit(); } public static void printArrayList(ArrayList<Employee> emp) { for (int i = 0; i < emp.size(); i++){ System.out.println(emp.get(i)); } } public static void clearScreen() { System.out.println("\u001b[H\u001b[2J"); } private static void exit() { System.exit(0); } private static void printMenu() { System.out.println("\t------------------------------------"); System.out.println("\t|Commands: n - New employee |"); System.out.println("\t| c - Compute paychecks |"); System.out.println("\t| r - Raise wages |"); System.out.println("\t| p - Print records |"); System.out.println("\t| d - Download data |"); System.out.println("\t| u - Upload data |"); System.out.println("\t| q - Quit |"); System.out.println("\t------------------------------------"); System.out.println(""); } public static void question() { System.out.print("Enter command: "); Scanner q = new Scanner(System.in); String input = q.nextLine(); input.replaceAll("\\s","").toLowerCase(); boolean valid = (input.equals("n") || input.equals("c") || input.equals("r") || input.equals("p") || input.equals("d") || input.equals("u") || input.equals("q")); if (!valid){ System.out.println("Command was not recognized; please try again."); printMenu(); question(); } else if (input.equals("n")){ System.out.print("Enter the name of new employee: "); Scanner stdin = new Scanner(System.in); empName = stdin.nextLine(); System.out.print("Hourly (h) or salaried (s): "); Scanner stdin2 = new Scanner(System.in); wage = stdin2.nextLine(); wage.replaceAll("\\s","").toLowerCase(); if (!(wage.equals("h") || wage.equals("s"))){ System.out.println("Input was not h or s; please try again"); } else if (wage.equals("h")){ System.out.print("Enter hourly wage: "); Scanner stdin4 = new Scanner(System.in); wages = stdin4.nextDouble(); Employee emp1 = new HourlyEmployee(empName, wages); emp.add(emp1); printMenu(); question();} else if (wage.equals("s")){ System.out.print("Enter annual salary: "); Scanner stdin5 = new Scanner(System.in); salary = stdin5.nextDouble(); Employee emp1 = new SalariedEmployee(empName, salary); printMenu(); question();}} else if (input.equals("c")){ for (int i = 0; i < emp.size(); i++){ System.out.println("Enter number of hours worked by " + emp.get(i) + ":"); } Scanner stdin = new Scanner(System.in); numHours = stdin.nextInt(); System.out.println("Pay: " + emp1.computePay(numHours)); System.out.print("Enter number of hours worked by " + empName); Scanner stdin2 = new Scanner(System.in); numHours = stdin2.nextInt(); System.out.println("Pay: " + emp1.computePay(numHours)); printMenu(); question();} else if (input.equals("r")){ System.out.print("Enter percentage increase: "); Scanner stdin = new Scanner(System.in); increase = stdin.nextDouble(); System.out.println("\nNew Wages"); System.out.println("---------"); // System.out.println(Employee.toString()); printMenu(); question(); } else if (input.equals("p")){ printArrayList(emp); printMenu(); question(); } else if (input.equals("q")){ exit(); } } } Here is one of the class files: public abstract class Employee { private String name; private double wage; protected Employee(String name, double wage){ this.name = name; this.wage = wage; } public String getName() { return name; } public double getWage() { return wage; } public void setName(String name) { this.name = name; } public void setWage(double wage) { this.wage = wage; } public void percent(double wage, double percent) { wage *= percent; } } And here are the errors: P.java:108: cannot find symbol symbol : variable emp1 location: class P System.out.println("Pay: " + emp1.computePay(numHours)); ^ P.java:112: cannot find symbol symbol : variable emp1 location: class P System.out.println("Pay: " + emp1.computePay(numHours)); ^ 2 errors I'm trying to the get paycheck to print out but i'm having trouble with how to call the method. It should take the user inputed numHours and calculate it then print on the paycheck for each employee. Thanks!

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  • How to make a pause before continuing method

    - by user1766728
    Now, I know that this has been asked, but I need to know how to do this NOT on html or anything. Heres my code, not including all of the other java files. package rtype; import java.awt.Image; import java.awt.event.KeyEvent; import java.util.ArrayList; import javax.swing.ImageIcon; public class aa { private int xd; private int yd; private int dx; private int dy; private int x; private int y; private Image image; private ArrayList missiles; private final int CRAFT_SIZE = 70; public aa() { ImageIcon ii = new ImageIcon(this.getClass().getResource("/aa.png")); image = ii.getImage(); missiles = new ArrayList(); x = 10; y = 10; xd = -14; yd = 140; } public void move() { if(y >=xd) y += dx; else if(y < xd) y += 1; if(y <=yd) y += dy; else if(y > yd) y += -1; } public int getX() { return x; } public int getY() { return y; } public Image getImage() { return image; } public ArrayList getMissiles() { return missiles; } public void keyPressed(KeyEvent e) { int key = e.getKeyCode(); if (key == KeyEvent.VK_SPACE) { fire(); } if (key == KeyEvent.VK_UP) { dy = -1; } if (key == KeyEvent.VK_DOWN) { dy = 1; } if (key == KeyEvent.VK_RIGHT) { yd++; } if (key == KeyEvent.VK_LEFT) { yd--; } if (key == KeyEvent.VK_W) { xd++; } if (key == KeyEvent.VK_S) { xd--; } } public void fire() { try{ missiles.add(new Missle(x + CRAFT_SIZE, y + CRAFT_SIZE)); }catch(Exception e){} } public void keyReleased(KeyEvent e) { int key = e.getKeyCode(); if (key == KeyEvent.VK_UP) { dy = 0; } if (key == KeyEvent.VK_DOWN) { dy = 0; } } } So, at the method, fire(), I want to make it delay between shots. HOW? sorry if this is n00bish

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  • using empty on inaccessible object with __isset and __get

    - by David
    <?php class Magic_Methods { protected $meta; public function __construct() { $this->meta = (object) array( 'test' => 1 ); } public function __isset($name) { echo "pass isset {$name} \n"; return isset($this->$name); } public function __get($name) { echo "pass get {$name} \n"; return $this->$name; } } $mm = new Magic_Methods(); $meta = empty($mm->meta->notExisting); var_dump($meta); echo "||\n"; $meta = empty($mm->meta); var_dump($meta); The snippet above does not work as expected for me. Why would the first empty() ommit the __isset? I get this: pass get meta bool(true) || pass isset meta pass get meta bool(false) I would expected identical results or another pass at the __isset, but not a direct call to __get. Or am I missing something here?

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  • Cannot make a static reference to the non-static type MyRunnable

    - by kaiwii ho
    Here is the whole code : import java.util.ArrayList; public class Test{ ThreadLocal<ArrayList<E>>arraylist=new ThreadLocal<ArrayList<E>>(){ @Override protected ArrayList<E> initialValue() { // TODO Auto-generated method stub //return super.initialValue(); ArrayList<E>arraylist=new ArrayList<E>(); for(int i=0;i<=20;i++) arraylist.add((E) new Integer(i)); return arraylist; } }; class MyRunnable implements Runnable{ private Test mytest; public MyRunnable(Test test){ mytest=test; // TODO Auto-generated constructor stub } @Override public void run() { System.out.println("before"+mytest.arraylist.toString()); ArrayList<E>myarraylist=(ArrayList<E>) mytest.arraylist.get(); myarraylist.add((E) new Double(Math.random())); mytest.arraylist.set(myarraylist); System.out.println("after"+mytest.arraylist.toString()); } // TODO Auto-generated method stub } public static void main(String[] args){ Test test=new Test<Double>(); System.out.println(test.arraylist.toString()); new Thread(new MyRunnable(test)).start(); new Thread(new MyRunnable(test)).start(); System.out.println(arraylist.toString()); } } my questions are: 1\ why the new Thread(new MyRunnable(test)).start(); cause the error: Cannot make a static reference to the non-static type MyRunnable ? 2\ what is the static reference refer to right here? thx in advanced

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