how does this work?
in irb:
>> class A
>> b = [1, 2,3]
>> end
=> [1, 2, 3]
Is b an instance variable? class variable? how would I access b from
outside the class? Is it used for meta-programming?
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 ?
We are programming a new web application framework (Second WAF). I was wondering if we should support cookieless sessions or not.
Who use it and who needs it?
Hello everybody!
I've been wondering whether is possible or not to pass a function as parameter in PHP; I want something like when you're programming in JS:
object.exampleMethod(function(){
// some stuff to execute
});
What I want is to execute that function somewhere in exampleMethod. Is that possible in PHP?
Thank you so much.
hello I'm new to PHP programming and I migrated from ASP .net to PHP..
I have a div just like below
<div id="mydiv"></div>
what I wanted to do is just to change the text and html content(like some name or any data in it) in it.
What I imagine is just like
mydiv=innertext="some value";
Thanks,
GURU
Hi, I am learning the Opengl graphic programming at Eclipse. Can someone tell me the difference between GLUT application and SDL application, so that I can dig into either one of them? Tks.
Whatever it be, caffeine, tobacco, whatever, list your programming performance enhancing drug of choice.
Do you feel like you NEED it to be most effective at your work?
Vote up someone if they answered the same as you.
A friend of mine, who studies game development at an university, is currently learning programming in OpenCL. What would be a simple project that teaches the most important aspects of OpenCL and can be finished within about 50 - 100 hours?
For those of you who are into programming not just for the money. I would like to know which benefits you would like to have (or already have).
OK, maybe taking away the money factor will limit this question too much. I am surprised to see that most companies have a fixed set for their benefits package. Were you able to negotiate something new or just your salary? What things have you seen out there and/or value most?
"8,5,,1,4,7,,,,7,,1,9,3,6,,,8,6,3,9,,2,5,4,,,,,3,2,,,7,4,1,1,,4,,6,9,,5,,,,5,,,1,,6,3,,,6,5,,,,7,4,,1,7,6,,,,8,,5,,,7,1,,3,9,"
I'm doing a programming challenge where i need to parse this sequence into my sudoku script.
Need to get the above sequence into 8,5,0,1,4,7,0,0,0,7,0,1,9,3,6,0,0,8.........
I tried re but without success, help is appreciated, thanks.
Hi there
I'm programming against a Webservice that requires the amount of ticks (for the current time) (A single tick represents one hundred nanoseconds or one ten-millionth of a second) since 1.1.0001 (midnight).
what is the easiest way to get the amount of ticks from an NSDate Object?
thanks for your help
Is this considered good programming practise in C++:
try {
// some code
}
catch(someException) {
// do something
}
catch (...)
{
// left empty <-- Good Practise???
}
Hello,
I know it's not really a programming question but I don't know where to ask it.
Should i use a captcha in my sign up form ?
Facebook, twitter, foursquare, gowalla etc... don't use one (or not a visible one). Is there an invisible catpcha on theses sites ?
Thank you
Hello,
I'm new to PHP programming and I wanted to know that is it possible to handle PHP events as we do in ASP.NET
I mean I've got a img and I want to perform some task on click event of this img.
I know how to do it in ASP.NET but please help me in context of PHP
Thanks,
GURU
I'm trying to find out what a binormal is in the context of graphics programming but coming up short, I saw on a site that the binormal was being calculated as the corss between the normal and tangent (i.e. cross(normal, tangent)), is this the correct way to calculate a binormal?
This isn't a question about code, but it's programming related. We have a web app that's ready for beta testing. Has anyone noticed any difference between open beta vs. closed beta in terms of the quality or quantity of feedback the testers give or any other factors?
hello
i never worked with web programming and
i've been asked lately to write a web-based software to manage assets and tasks. to be used by more than 900 persons
what are the recommended modules , frameworks , libraries for this task.
and it will be highly appreciated if you guyz recommend some books and articles that might help me. thanks in advance
Hi,
My team and I are programming a sort of Document Manager and the idea is to store them completely on DB.
Is there a protocol or Extensions that allows us to show a "Virtual Directory" or files that are really non existent (only in DB). How does Sharepoint do this?
I understand that Sharepoint uses WebDav but it implies that the files do exist physically somewhere.
We intend to develop this application on .NET 4.0 and deploy it on IIS.
Any suggestions?
Thanks in advance
I need to programatically encrypt a directory of files, like in a .zip or whatever. Preferably password protected obviously.
How can I accomplish this, and WHAT IS the BEST encryption way to do it, if applicable?
Programming language doesn't matter. I am dictioned in all syntax.
I'm looking for web app frameworks and/or database administration tools, either popular and unpopular, written in any language, for any relational database.
In short, I'm looking for web accessible CRUD front-ends with minimal programming effort.
For example:
phpMyAdmin (MySQL administration tool)
Ruby on Rails (web app framework with scaffolding)
I am following the BigNerdRanch iOS Programming book and I am on this one chapter that deals with UITableViewController. I have been wondering however where UITableViewController finds out about its delegate and dataSource. Currently I have it as
@interface ItemsViewController : UITableViewController <UITableViewDataSource, UITableViewDelegate>
But there is nothing that looks like:
[self.tableView setDelegate:self]
I am just wondering how the UITableViewController finds out about its delegate and dataSource
I've been teaching myself object oriented programming and I'm thinking about a situation where I have an object "Transaction", that has quite a few properties to it like account, amount, date, currency, type, etc.
I never plan to mutate these data points, and calculation logic will live in other classes. My question is, is it poor Python design to instantiate thousands of objects just to hold data? I find the data far easier to work with embedded in a class rather than trying to cram it into some combination of data structures.
I am newbie to iPhone programming. I am not using Interface Builder in my programming. I have some doubt about memory management, @property topics in iPhone.
Consider the following code
@interface LoadFlag : UIViewController {
UIImage *flag;
UIImageView *preview;
}
@property (nonatomic, retain) UIImageView *preview;
@property (nonatomic, retain) UIImage *flag;
@implementation
@synthesize preview;
@synthesize flag;
- (void)viewDidLoad
{
flag = [UIImage imageNamed:@"myImage.png"]];
NSLog(@"Preview: %d\n",[preview retainCount]); //Count: 0 but shouldn't it be 1 as I am retaining it in @property in interface file
preview=[[UIImageView alloc]init];
NSLog(@"Count: %d\n",[preview retainCount]); //Count: 1
preview.frame=CGRectMake(0.0f, 0.0f, 100.0f, 100.0f);
preview.image = flag;
[self.view addSubview:preview];
NSLog(@"Count: %d\n",[preview retainCount]); //Count: 2
[preview release];
NSLog(@"Count: %d\n",[preview retainCount]); //Count: 1
}
When & Why(what is the need) do I have to set @property with retain (in above case for UIImage & UIImageView) ? I saw this statement in many sample programs but didn't understood the need of it.
When I declare @property (nonatomic, retain) UIImageView *preview; statement the retain Count is 0. Why doesn't it increase by 1 inspite of retaining it in @property.
Also when I declare [self.view addSubview:preview]; then retain Count increments by 1 again. In this case does the "Autorelease pool" releases for us later or we have to take care of releasing it. I am not sure but I think that the Autorelease should handle it as we didn't explicitly retained it so why should we worry of releasing it.
Now, after the [preview release]; statement my count is 1. Now I don't need UIImageView anymore in my program so when and where should I release it so that the count becomes 0 and the memory gets deallocated. Again, I am not sure but I think that the Autorelease should handle it as we didn't explicitly retained it so why should we worry of releasing it. What will happen if I release it in -(void) dealloc method
In the statement - flag = [UIImage imageNamed:@"myImage.png"]]; I haven't allocated any memory to flag but how can I still use it in my program. In this case if I do not allocate memory then who allocates & deallocates memory to it or is the "flag" just a reference pointing to - [UIImage imageNamed:@"myImage.png"]];. If it is a reference only then do i need to release it.
Thanks in advance.
Hi All,
I am programming C on cygwin windows. After having done a bit of C programming and getting comfortable with the language, I wanted to look under the hood and see what the compiler is doing for the code that I write.
So I wrote down a code block containing switch case statements and converted them into assembly using:
gcc -S foo.c
Here is the C source:
switch(i)
{
case 1:
{
printf("Case 1\n");
break;
}
case 2:
{ printf("Case 2\n");
break;
}
case 3:
{
printf("Case 3\n");
break;
}
case 4:
{
printf("Case 4\n");
break;
}
case 5:
{
printf("Case 5\n");
break;
}
case 6:
{
printf("Case 6\n");
break;
}
case 7:
{
printf("Case 7\n");
break;
}
case 8:
{
printf("Case 8\n");
break;
}
case 9:
{
printf("Case 9\n");
break;
}
case 10:
{
printf("Case 10\n");
break;
}
default:
{
printf("Nothing\n");
break;
}
}
Now the resultant assembly for the same is:
movl $5, -4(%ebp)
cmpl $10, -4(%ebp)
ja L13
movl -4(%ebp), %eax
sall $2, %eax
movl L14(%eax), %eax
jmp *%eax
.section .rdata,"dr"
.align 4
L14:
.long L13
.long L3
.long L4
.long L5
.long L6
.long L7
.long L8
.long L9
.long L10
.long L11
.long L12
.text
L3:
movl $LC0, (%esp)
call _printf
jmp L2
L4:
movl $LC1, (%esp)
call _printf
jmp L2
L5:
movl $LC2, (%esp)
call _printf
jmp L2
L6:
movl $LC3, (%esp)
call _printf
jmp L2
L7:
movl $LC4, (%esp)
call _printf
jmp L2
L8:
movl $LC5, (%esp)
call _printf
jmp L2
L9:
movl $LC6, (%esp)
call _printf
jmp L2
L10:
movl $LC7, (%esp)
call _printf
jmp L2
L11:
movl $LC8, (%esp)
call _printf
jmp L2
L12:
movl $LC9, (%esp)
call _printf
jmp L2
L13:
movl $LC10, (%esp)
call _printf
L2:
Now, in the assembly, the code is first checking the last case (i.e. case 10) first. This is very strange. And then it is copying 'i' into 'eax' and doing things that are beyond me.
I have heard that the compiler implements some jump table for switch..case. Is it what this code is doing? Or what is it doing and why? Because in case of less number of cases,
the code is pretty similar to that generated for if...else ladder, but when number of cases increases, this unusual-looking implementation is seen.
Thanks in advance.
Hello people,
I have three images,and , they are not square or rectangular in shape. They are just like face of anyone.
So,basically, my images are in the size 196x196 or anything like that, but complete square or rectangle with the face in the middle and transperant background in the rest of the portion.
Now, I want to remove the transperant background too and just keep the faces.
Don't know if this is possible and mind you, this isn't a programming question.