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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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  • 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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  • How should I deal with floating numbers that numbers that can get so small that the become zero

    - by Tristan Havelick
    So I just fixed an interesting bug in the following code, but I'm not sure the approach I took it the best: p = 1 probabilities = [ ... ] # a (possibly) long list of numbers between 0 and 1 for wp in probabilities: if (wp > 0): p *= wp # Take the natural log, this crashes when 'probabilites' is long enough that p ends up # being zero try: result = math.log(p) Because the result doesn't need to be exact, I solved this by simply keeping the smallest non-zero value, and using that if p ever becomes 0. p = 1 probabilities = [ ... ] # a long list of numbers between 0 and 1 for wp in probabilities: if (wp > 0): old_p = p p *= wp if p == 0: # we've gotten so small, its just 0, so go back to the smallest # non-zero we had p = old_p break # Take the natural log, this crashes when 'probabilites' is long enough that p ends up # being zero try: result = math.log(p) This works, but it seems a bit kludgy to me. I don't do a ton of this kind of numerical programming, and I'm not sure if this is the kind of fix people use, or if there is something better I can go for.

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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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  • Why isn't this simple test class's method inherited in Ruby?

    - by Kevin Bannister
    Consider this very simple logging class: class MockLog def self.log_stub_method(*args) args.each do |a| define_method "#{a}" do |msg| t = Time.now.strftime("%Y-%m-%d %H:%M:%S") $stderr.puts "[#{a.upcase}] \u00bb [#{t}] #{msg}" end end end log_stub_method :fatal, :error, :warn, :info, :debug end Let's add logging to all our classes: class Module def has_logging() class_eval { @log = MockLog.new def log self.class.instance_variable_get :@log end } end end Now, why doesn't this work? class Foo has_logging end Foo.new.log.nil? # => false, as expected class Bar < Foo end Bar.new.log.nil? # => true?! Why wasn't the `log` method inherited?

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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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  • File Segmentation when trying to write in a file

    - by user1286390
    I am trying in C language to use the method of bisection to find the roots of some equation, however when I try to write every step of this process in a file I get the problem "Segmentation fault". This might be an idiot fault that I did, however I have been trying to solve this for a long time. I am compiling using gcc and that is the code: #include <stdio.h> #include <stdlib.h> #include <math.h> #define R 1.0 #define h 1.0 double function(double a); void attractor(double *a1, double *a2, double *epsilon); void attractor(double *a1, double *a2, double *epsilon) { FILE* bisection; double a2_copia, a3, fa1, fa2; bisection = fopen("bisection-part1.txt", "w"); fa1 = function(*a1); fa2 = function(*a2); if(function(*a1) - function(*a2) > 0.0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); fprintf(bisection, "a1 a2 fa1 fa2 epsilon\n"); a2_copia = 0.0; if(function(*a1) * function(*a2) < 0.0 && *epsilon >= 0.00001) { a3 = *a2 - (*a2 - *a1); a2_copia = *a2; *a2 = a3; if(function(*a1) - function(*a2) > 0.0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); if(function(*a1) * function(*a2) < 0.0 && *epsilon >= 0.00001) { fprintf(bisection, "%.4f %.4f %.4f %.4f %.4f\n", *a1, *a2, function(*a1), function(*a1), *epsilon); attractor(a1, a2, epsilon); } else { *a2 = a2_copia; *a1 = a3; if(function(*a1) - function(*a2) > 0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); if(function(*a1) * function(*a2) < 0.0 && *epsilon >= 0.00001) { fprintf(bisection, "%.4f %.4f %.4f %.4f %.4f\n", *a1, *a2, function(*a1), function(*a1), *epsilon); attractor(a1, a2, epsilon); } } } fa1 = function(*a1); fa2 = function(*a2); if(function(*a1) - function(*a2) > 0.0) *epsilon = function(*a1) - function(*a2); else *epsilon = function(*a2) - function(*a1); fprintf(bisection, "%.4f %.4f %.4f %.4f %.4f\n", a1, a2, fa1, fa2, epsilon); } double function(double a) { double fa; fa = (a * cosh(h / (2 * a))) - R; return fa; } int main() { double a1, a2, fa1, fa2, epsilon; a1 = 0.1; a2 = 0.5; fa1 = function(a1); fa2 = function(a2); if(fa1 - fa2 > 0.0) epsilon = fa1 - fa2; else epsilon = fa2 - fa1; if(epsilon >= 0.00001) { fa1 = function(a1); fa2 = function(a2); attractor(&a1, &a2, &epsilon); fa1 = function(a1); fa2 = function(a2); if(fa1 - fa2 > 0.0) epsilon = fa1 - fa2; else epsilon = fa2 - fa1; } if(epsilon < 0.0001) printf("Vanish at %f", a2); else printf("ERROR"); return 0; } Thanks anyway and sorry if this question is not suitable.

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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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  • Design and Implementation with Prototyping Methodology

    - by Shahin
    I'm developing a game for my dissertation, and I'm using the spiral method approach. I'm having a bit of difficulty structuring my dissertation, specifically the design and implementation section. My solution was designed as much as possible initially, and then after each prototype implementation, the design was refined and extended and prototyped again (this was repeated a few times). My problem is how to structure this in my dissertation, my current idea is: Design Chapter Prototype 1 (Initial) Design Prototype 2 Design Prototype 3 Design Implementation Chapter Prototype 1 (Initial) Implementation Prototype 2 Implementation Prototype 3 Implementation Any suggestions?

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  • Understanding the singleton class when aliasing a instance method

    - by Backo
    I am using Ruby 1.9.2 and the Ruby on Rails v3.2.2 gem. I am trying to learn Metaprogramming "the right way" and at this time I am aliasing an instance method in the included do ... end block provided by the RoR ActiveSupport::Concern module: module MyModule extend ActiveSupport::Concern included do # Builds the instance method name. my_method_name = build_method_name.to_sym # => :my_method # Defines the :my_method instance method in the including class of MyModule. define_singleton_method(my_method_name) do |*args| # ... end # Aliases the :my_method instance method in the including class of MyModule. singleton_class = class << self; self end singleton_class.send(:alias_method, :my_new_method, my_method_name) end end "Newbiely" speaking, with a search on the Web I came up with the singleton_class = class << self; self end statement and I used that (instead of the class << self ... end block) in order to scope the my_method_name variable, making the aliasing generated dynamically. I would like to understand exactly why and how the singleton_class works in the above code and if there is a better way (maybe, a more maintainable and performant one) to implement the same (aliasing, defining the singleton method and so on), but "the right way" since I think it isn't so.

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  • how to access method variables from within an anonomous function in javascript

    - by Hussain
    I'm writing a small ajax class for personal use. In the class, I have a "post" method for sending post requests. The post method has a callback parameter. In the onreadystatechange propperty, I need to call the callback method. Something like this: this.requestObject.onreadystatechange = function() { callback(this.responseText); } However, I can't access the callback variable from within the anonomous function. How can I bring the callback variable into the scope of the onreadystatechange anonomous function?

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  • Memory management in iOS

    - by angrest
    Looks like I did not understand memory management in Objective C... sigh. I have the following code (note that in my case, placemark.thoroughfare and placemark.subThoroughfare are both filled with valid data, thus both if-conditions will be TRUE if (placemark.thoroughfare) { [item.place release]; item.place = [NSString stringWithFormat:@"%@ ", placemark.thoroughfare]; } else { [item.place release]; item.place = @"Unknown Place"; } if (placemark.thoroughfare && placemark.subThoroughfare) { // *** problem is here *** [item.place release]; item.place = [NSString stringWithFormat:@"%@ %@", placemark.thoroughfare , placemark.subThoroughfare]; } If I do not release item.place at the marked location in the code, Instruments finds a memory leak there. If I do, the program crashes as soon as I try to access item.place outside the offending method. Any ideas?

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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++. What is a subprogram and method?

    - by xbonez
    I have a CPP HW to be done. One question is: 1) Write a subprogram (not a method) void promptForMovie(Movie & myMovie) that ..... 2) Write a method void output(ostream & out); that .... My question is what exactly is a subprogram and a method? Which one of them means a function, and what does the other mean? Thank you

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  • How can I take any function as input for my Scala wrapper method?

    - by pr1001
    Let's say I want to make a little wrapper along the lines of: def wrapper(f: (Any) => Any): Any = { println("Executing now") val res = f println("Execution finished") res } wrapper { println("2") } Does this make sense? My wrapper method is obviously wrong, but I think the spirit of what I want to do is possible. Am I right in thinking so? If so, what's the solution? Thanks!

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  • Which kind of method signature do you prefer and why?

    - by devoured elysium
    Ok, this is probably highly subjective but here it comes: Let's assume I'm writing a method that will take a printscreen of some region of the screen. Which method signature would you prefer and why? Bitmap DoPrintScreen(int x, int y, int width, int height); Bitmap DoPrintScreen(Rectangle rect); Bitmap DoPrintScreen(Point point, Size size); Other Why? I keep seeing myself repeatedly implementing both 1) and 2) (redirecting one of them to the other) but I end up usually just using one of them, so there really is no point in having both. I can't decide which would be better. Maybe I should use the signature that looks the most with the method I'll be calling to make the printscreen?

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  • What elegant method callback design should be used ?

    - by ereOn
    Hi, I'm surprised this question wasn't asked before on SO (well, at least I couldn't find it). Have you ever designed a method-callback pattern (something like a "pointer" to a class method) in C++ and, if so, how did you do it ? I know a method is just a regular function with some hidden this parameter to serve as a context and I have a pretty simple design in mind. However, since things are often more complex than they seem to, I wonder how our C++ gurus would implement this, preferably in an elegant and standard way. All suggestions are welcome !

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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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  • 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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  • Implementing a kext that intercepts file system usage.

    - by UraN
    Hi, how do most of antivirus software block file system io in case of an infected file? I suppose all the magic resides in some custom kext to do that. Can anyone point me to some topics on this? Some working example would also be great. I've read apple docs about kext development, but mostly it's all about hardware drivers and i could not find what i need. Thanx.

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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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