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  • Trying to understand the usage of class_eval

    - by eMxyzptlk
    Hello everyone, I'm using the rails-settings gem, and I'm trying to understand how you add functions to ActiveRecord classes (I'm building my own library for card games), and I noticed that this gem uses one of the Meta-programming techniques to add the function to the ActiveRecord::Base class (I'm far from Meta-programming master in ruby, but I'm trying to learn it) module RailsSettings class Railtie < Rails::Railtie initializer 'rails_settings.initialize', :after => :after_initialize do Railtie.extend_active_record end end class Railtie def self.extend_active_record ActiveRecord::Base.class_eval do def self.has_settings class_eval do def settings RailsSettings::ScopedSettings.for_thing(self) end scope :with_settings, :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :select => "DISTINCT #{self.table_name}.*" scope :with_settings_for, lambda { |var| { :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'" } } scope :without_settings, :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :conditions => 'settings.id IS NULL' scope :without_settings_for, lambda { |var| { :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'", :conditions => 'settings.id IS NULL' } } end end end end end end What I don't understand is why he uses class_eval on ActiveRecord::Base, wasn't it easier if he just open the ActiveRecord::Base class and define the functions? Specially that there's nothing dynamic in the block (What I mean by dynamic is when you do class_eval or instance_eval on a string containing variables) something like this: module ActiveRecord class Base def self.has_settings class_eval do def settings RailsSettings::ScopedSettings.for_thing(self) end scope :with_settings, :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :select => "DISTINCT #{self.table_name}.*" scope :with_settings_for, lambda { |var| { :joins => "JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'" } } scope :without_settings, :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}')", :conditions => 'settings.id IS NULL' scope :without_settings_for, lambda { |var| { :joins => "LEFT JOIN settings ON (settings.thing_id = #{self.table_name}.#{self.primary_key} AND settings.thing_type = '#{self.base_class.name}') AND settings.var = '#{var}'", :conditions => 'settings.id IS NULL' } } end end end end I understand the second class_eval (before the def settings) is to define functions on the fly on every class that 'has_settings' right ? Same question here, I think he could use "def self.settings" instead of "class_eval.... def settings", no ?

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  • An agenda in Korn Shell: New / Edit / Delete / View appointment

    - by Abaco
    As stated in the title, I have to write a simple script which should perform some typical agenda's functions. The script must use crontab. The functions are: Creating a new appointment Edit an existent appointment Delete an appointment List the appointment I really don't have a clue how to do this, can you help me with some hint? Maybe a bit of sweet code? Thank you very much, Abaco EDIT: To be more specific on my question Point 1: how can I edit a crontab thorugh ksh? How can I insert a new line? Can you link me some documentation or a bit of code about this?

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  • Query to return internal details about stored function in MS-SQL database

    - by Anthony
    I have been given access to a ms-sql database that is currently used by 3rd party app. As such, I don't have any documentation on how that application stores the data or how it retrieves it. I can figure a few things out based on the names of various tables and the parameters that the user-defined functions takes and returns, but I'm still getting errors at every other turn. I was thinking that it would be really helpful if I could see what the stored functions were doing with the parameters given to return the output. Right now all I've been able to figure out is how to query for the input parameters and the output columns. Is there any built-in information_schema table that will expose what the function is doing between input and output?

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  • Should i use HttpResponse.End() for a fast webapp?

    - by acidzombie24
    HttpResponse.End() seems to throw an exception according to msdn. Right now i have the choice of returning a value to say end thread (it only goes 2 functions deep) or i can call end(). I know that throwing exceptions is significantly slower (read the comment for a C#/.NET test) so if i want a fast webapp should i consider not calling it when it is trivially easy to not call it? -edit- I do have a function call in certain functions and in the constructor in classes to ensure the user is logged in. So i call HttpResponse.End() in enough places although hopefully in regular site usage it doesn't occur too often.

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  • Need help with homework(very short code)

    - by b3y4z1d
    I have a code, and I need to have it done until friday or so.I'd say 95% of it is finished,but the functions and the function-calling could use some grooming. It is really simple for anyone who knows C++ pretty well, but I'm a newbie and I just can't seem to get through this with the functions so if anyone could take a look and correct the few mistakes or add a line or two if needed I'd be very grateful. Here is the link to the full code, you'll understand the purpose of the code once you see it. I use Borland C++ by the way if it helps. Thanks in advance!

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  • python iterators and thread-safety

    - by Igor
    I have a class which is being operated on by two functions. One function creates a list of widgets and writes it into the class: def updateWidgets(self): widgets = self.generateWidgetList() self.widgets = widgets the other function deals with the widgets in some way: def workOnWidgets(self): for widget in self.widgets: self.workOnWidget(widget) each of these functions runs in it's own thread. the question is, what happens if the updateWidgets() thread executes while the workOnWidgets() thread is running? I am assuming that the iterator created as part of the for...in loop will keep some kind of reference to the old self.widgets object? So I will finish iterating over the old list... but I'd love to know for sure.

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  • The most elegant way to encapsulate WinAPI callbacks inside a class

    - by FractalizeR
    Hello. I am thinking about elegant way to encapsulate WinAPI callbacks inside a class. Suppose I am making a class handling asynchronous I/O. All Windows callbacks should be stdcall functions, not class methods (I need to pass their addresses to ReadFileEx WinAPI function for example). So, I cannot just pass method addresses as a callback routines to WinAPI functions. What is the most elegant way to encapsulate functionality of this type inside a class so that the class have events OnReadCompleted and OnWriteCompleted (I am using Delphi as a primary language, but I guess the situation must be the same in C++ because class methods are different from simple methods by the fact, that the first hidden parameter of them is this link. Of course this class is not a singleton and there can be many of them created by app at the same time. What do you think would be the good way to implement this?

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  • Image processing on bifurcation diagram to get small eps size

    - by yCalleecharan
    Hello, I'm producing bifurcation diagrams (which are normally used in nonlinear dynamics). These diagrams identify abrupt changes in topologies due to stability changes. These abrupt changes occur as one or more parameters pass through some critical value(s). An example is here: http://en.wikipedia.org/wiki/File:LogisticMap_BifurcationDiagram.png On the above figure, some image processing has been done so as to make the plot more visually pleasant. A bifurcation diagram usually contains hundreds of thousands of points and the resulting eps file can become very big. Journal submission in the LaTeX format require that figures are to be submitted in the eps format. In my case one of such figures can result in about 6 MB in Matlab and even much more in Gnuplot. For the example in the above figure, 100,000 x values are calculated for each r and one can imagine that the resulting eps file would be huge. The site however explains some image processing that makes the plot more visually pleasing. Can anyone explain to me stepwise how go about? I can't understand the explanation provided in the "summary" section. Will the resulting image processing also reduce the figure size? Furthermore, any tips on reducing the file size of such a huge eps figure? Thanks a lot...

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  • Is there any valid reason radians are used as the inputs to trig function in many modern languages?

    - by johnmortal
    Is there any pressing reason trig functions should use radian inputs in modern programming languages? As far as I know radians are typically ugly to deal with except in three cases: (1) You want to compute an arc length and you know the angle of the arc and (2) You need to do symbolic calculus with trig functions (3) certain infinite series expansion look prettier if the input is in radians. None of these scenarios seem like a worthy justification for every programming language I am familiar with using radian inputs for Sin, Cos, Tangent, etc... The third one sounds good because it might mean one gets faster computations using radians (very slightly faster- the cost of one additional floating point multiplication ) , but I am dubious even of that because most commonly the developer had to take an extra step to put the angle in radians in the first place. The other two are ridiculous justifications for all the added obscurity.

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  • Why doesn't MySQL support millisecond precision?

    - by Byron Whitlock
    So I just found the most frustrating bug ever in MySQL. Apparently the TIMESTAMP field, and supporting functions do not support any greater precision than seconds!? So I am using PHP and Doctrine, and I really need those microseconds (I am using the actAs: [Timestampable] property). I found a that I can use a BIGINT field to store the values. But will doctrine add the milliseconds? I think it just assigns NOW() to the field. I am also worried the date manipulation functions (in SQL) sprinkled through the code will break. I also saw something about compiling a UDF extension. This is not an acceptable workaround because I or a future maintainer will upgrade and poof, change gone. Has anyone found a suitable workaround?

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  • Php wrapper class for XML

    - by gms8994
    I'm working on a new class to wrap XML handling. I want my class to use simplexml if it's installed, and the built in XML functions if it's not. Can anyone give me some suggestions on a skeleton class to do this? It seems "wrong" to litter each method with a bunch of if statements, and that also seems like it would make it nearly impossible to correctly test. Any upfront suggestions would be great! EDIT: I'm talking about these built-in xml functions.

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  • BDD / TDD with JSpec - Removing code duplication

    - by Chetan
    How do I refactor to remove the code duplication in this spec: describe 'TestPlugins' describe '.MovieScanner(document)' before_each MoviePage_loggedIn = fixture("movie_logged_in.html") // Get logged-in movie page MoviePage_notloggedIn = fixture("movie_not_logged_in.html") // Get non logged-in movie page scanner = new MovieScanner() // Get movie scanner end it 'should scan logged-in movie page for movie data' doc = MoviePage_loggedIn // Get document to scan // Unit Tests // ------------------------------------------------------------ // Test movie scanner's functions scanner.getMovieTitle(doc).should.eql "The Jacket" scanner.getMovieYear(doc).should.eql "2005" // Test movie scanner's main scan function scannedData = scanner.scan(doc) scannedData.title.should.eql "The Jacket" scannedData.year.should.eql "2005" end it 'should scan non logged-in movie page for movie data' doc = MoviePage_notloggedIn // Get document to scan // Unit Tests // ------------------------------------------------------------ // Test movie scanner's functions scanner.getMovieTitle(doc).should.eql "The Jacket" scanner.getMovieYear(doc).should.eql "2005" // Test movie scanner's main scan function scannedData = scanner.scan(doc) scannedData.title.should.eql "The Jacket" scannedData.year.should.eql "2005" end end end

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  • Hashing a python method to regenerate output when method is modified

    - by Seth Johnson
    I have a python method that has a deterministic result. It takes a long time to run and generates a large output: def time_consuming_method(): # lots_of_computing_time to come up with the_result return the_result I modify time_consuming_method from time to time, but I would like to avoid having it run again while it's unchanged. [Time_consuming_method only depends on functions that are immutable for the purposes considered here; i.e. it might have functions from Python libraries but not from other pieces of my code that I'd change.] The solution that suggests itself to me is to cache the output and also cache some "hash" of the function. If the hash changes, the function will have been modified, and we have to re-generate the output. Is this possible or a ridiculous idea? If this isn't a terrible idea, is the best implementation to write f = """ def ridiculous_method(): a = # # lots_of_computing_time return a """ , use the hashlib module to compute a hash for f, and use compile or eval to run it as code?

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  • Outputting variable values in x86?

    - by Airjoe
    Hello All- I'm working on a homework assignment in x86 and it isn't working as I expect (surprise surprise!). I'd like to be able to output values of variables in x86 functions to ensure that the values are what I expect them to be. Is there a simple way to do this, or is it very complex? For what it's worth, the x86 functions are being used by a C file and compiled with gcc, so if that makes it simpler that is how I'm going about it. Thanks for the help.

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  • Compare values in each column of two Oracle Types

    - by colinjameswebb
    I've been playing around with the pluto-test-framework today, and I'd like to get some existing functions into a test harness with it. I have lots of functions with this type of specification. FUNCTION DO_SOME_STUFF (pOldSchedule IN SCHEDULE_OBJ, pNewSchedule OUT SCHEDULE_OBJ, pLoggerContext IN OUT LOGGER_CONTEXT_OBJ) RETURN NUMBER; It takes pOldSchedule, does some stuff to it, and then returns pNewSchedule. The logger_context just does logging. As part of a test, I'd like to be able to compare the values in each of the columns of the type, without having to write individual IF statements. It'll need to return boolean to signify whether or not pOldSchedule and pNewSchedule match. Any ideas?

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  • How to override event on a UserControl

    - by Vadim
    Hello! I have a WinForms application (OwnerForm) with some UserControl. When textbox of UserControl is changed, I want to filter content of a OwnerForm. But how can I make it? I don't want to specify OwnerForm inside the user control. I know a solution to add manually handlers for MyUserControl.tb.TextChanged to some functions on a owner form, but I think it's bad way. I'll prefer to have overridable functions, but I can't imagine how to do it. Any suggestions? Thanks in advance,

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  • How to reference an anonymous JavaScript function?

    - by ProfK
    I'm trying to call a Page Method using a jQuery 'attached' event function, in which I like to use the closure to keep the event target local, as below, but page method calls declare several 'error' functions, and I would like to use one function for all of them. If, in the below code, I was handling an error and not success, how could I use my single, anonymous handler for all 3 error functions? $(":button").click(function () { var button = this; PageMethods.DoIt( function (a, b, c) { alert(button); }); }); This example passes an anonymous function for the success callback. There is only one of these. If I was passing an error callback, how could I use 'function (e, c, t)' for all 3 error callbacks?

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  • The ultimate .NET file and directory utility library?

    - by Serge van den Oever
    I find myself writing file and directory utility functions all the time, and I was wondering if there is good file and directory library that already implements a more extensive set than available by default in System.IO. The kind of functions I'm looking for is things like: public static void GetTemporaryDirectory() { string tempDirectory = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName()); Directory.CreateDirectory(tempDirectory); return tempDirectory; } public static void CreateEmptyFile(string filename) { File.Create(filename).Dispose(); } public static void CreateEmptyFile(string path, string filename) { File.Create(Path.Combine(path, filename)).Dispose(); } public static void CreateDirectory(string path) { Directory.CreateDirectory(path); } public static void CreateDirectory(string path, string childpath) { Directory.CreateDirectory(Path.Combine(path, childpath)); }

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  • A smoother alternative to jQuery show() and hide()

    - by David B
    I have a page setup with a hidden column using the jQuery show() and hide() functions to slide the column in and out. However it's kind of "clunky" and does not look very smooth when showing/hiding; in contrast I also have a section of the page using jquery UI accordion. When switching between these sections the transition looks very nice and smooth... Is there a better function than show()/hide() which looks as nice as the accordion does? (maybe the "easing" parameter can be used in the show/hide functions, but i'm not sure how to use this properly?)

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  • Jquery Delay Function Calls

    - by fizgig07
    I'm trying to find a way to delay all code that takes place after I make a service call. The reason for this delay is that my service returns code necesarry for the following functions and the result I pass is to these following functions is undefined. I have tried attaching the setTimeout() to the function that is called directly after the service call, but then it just skips the function I set the timeout on and jumps to the next function...My web method that I am calling is not that big and is not doing anything that is too intensive public bool GetSpreadsheetStatusForAdmin(string cacId) { SpreadSheetStatus result = new SpreadSheetStatus(); List<Data.Spreadsheet> spreadsheets = SpreadsheetManager.GetUserSpreadsheets(GetCurrent.Identity); if (spreadsheets.Count != 0) { foreach (Data.Spreadsheet spreadsheet in spreadsheets) { if (spreadsheet.Status == SpreadsheetStatus.Pending) { return true; } } } return false; } I had found the delay() and thought that might work, but I don't have jquery 1.4 and can't use it as of yet. is there anything that can help..?

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  • What's the purpose of having a separate "operator new[]" ?

    - by sharptooth
    Looks like operator new and operator new[] have exactly the same signature: void* operator new( size_t size ); void* operator new[]( size_t size ); and do exactly the same: either return a pointer to a big enough block of raw (not initialized in any way) memory or throw an exception. Also operator new is called internally when I create an object with new and operator new[] - when I create an array of objects with new[]. Still the above two special functions are called by C++ internally in exactly the same manner and I don't se how the two calls can have different meanings. What's the purpose of having two different functions with exactly the same signatures and exactly the same behavior?

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  • Python list as *args?

    - by Cap
    I have two Python functions, both of which take variable arguments in their function definitions. To give a simple example: def func1(*args): for arg in args: print arg def func2(*args): return [2 * arg for arg in args] I'd like to compose them -- as in func1(func2(3, 4, 5)) -- but I don't want args in func1 to be ([6, 7, 8],), I want it to be (6, 7, 8), as if it was called as func1(6, 7, 8) rather than func1([6, 7, 8]). Normally, I would just use func1(*func2(3, 4, 5)) or have func1 check to see if args[0] was a list. Unfortunately, I can't use the first solution in this particular instance and to apply the second would require doing such a check in many places (there are a lot of functions in the role of func1). Does anybody have an idea how to do this? I imagine some sort of introspection could be used, but I could be wrong.

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  • Class template specializations with shared functionality

    - by Thomas
    I'm writing a simple maths library with a template vector type: template<typename T, size_t N> class Vector { public: Vector<T, N> &operator+=(Vector<T, N> const &other); // ... more operators, functions ... }; Now I want some additional functionality specifically for some of these. Let's say I want functions x() and y() on Vector<T, 2> to access particular coordinates. I could create a partial specialization for this: template<typename T> class Vector<T, 3> { public: Vector<T, 3> &operator+=(Vector<T, 3> const &other); // ... and again all the operators and functions ... T x() const; T y() const; }; But now I'm repeating everything that already existed in the generic template. I could also use inheritance. Renaming the generic template to VectorBase, I could do this: template<typename T, size_t N> class Vector : public VectorBase<T, N> { }; template<typename T> class Vector<T, 3> : public VectorBase<T, 3> { public: T x() const; T y() const; }; However, now the problem is that all operators are defined on VectorBase, so they return VectorBase instances. These cannot be assigned to Vector variables: Vector<float, 3> v; Vector<float, 3> w; w = 5 * v; // error: no conversion from VectorBase<float, 3> to Vector<float, 3> I could give Vector an implicit conversion constructor to make this possible: template<typename T, size_t N> class Vector : public VectorBase<T, N> { public: Vector(VectorBase<T, N> const &other); }; However, now I'm converting from Vector to VectorBase and back again. Even though the types are the same in memory, and the compiler might optimize all this away, it feels clunky and I don't really like to have potential run-time overhead for what is essentially a compile-time problem. Is there any other way to solve this?

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  • JavaScript array to PHP array then process in PHP and return

    - by Constructor
    Example: javascript: var mycourses=new Array(); mycourses[0]="History"; mycourses[1]="Math"; mycourses[1][0]="Introduction to math"; mycourses[1][1]="Math 2"; mycourses[1][2]="Math 3"; PHP will then run these values through functions (please note values are mostly not strings as in the example above but rather numbers), the functions will return some text which will than be displayed in a form How should I go about doing this? p.s.: I found some similar stuff, but nothing quite like this... as far as I see I will have to use JSON (is there a way to code it from JS automatically - saw this for strings) and AJAX

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