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  • How often do you implement the big three?

    - by Neil Butterworth
    I was just musing about the number of questions here that either are about the "big three" (copy constructor, assignment operator and destructor) or about problems caused by them not being implemented correctly, when it occurred to me that I could not remember the last time I had implemented them myself. A swift grep on my two most active projects indicate that I implement all three in only one class out of about 150. That's not to say I don't implement/declare one or more of them - obviously base classes need a virtual destructor, and a large number of my classes forbid copying using the private copy ctor & assignment op idiom. But fully implemented, there is this single lonely class, which does some reference counting. So I was wondering am I unusual in this? How often do you implement all three of these functions? Is there any pattern to the classes where you do implement them?

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  • Using Remote Web Server to Initialize iPhone App

    - by Chris_K
    My iPhone app relies on a vendor's XML feed to provide data. But that feed is not locked down. The vendor could change the format of the XML at any time, although so far they've promised not to. Since I might want to tell my app to use a different URL for its data source, I'd like to set up a single "Command Central" Web page, on my own server, to direct the app to the correct data source. In other words, each time my app starts, in the background and unseen by the user, it would visit "http://www.myserver.com/iphoneapp_data_sources.xml" to retrieve the URL for retrieving data from my vendor. That way, if my vendor suddenly changes the exact URL or the XML feed that the app needs, I can update that Web page and ensure that all installations of the app are using the correct XML feed. Does anyone have any advice or examples showing this kind of approach? It seems as if this must be a common problem, but so far I haven't found a well-established design pattern that fits it.

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  • Managing Data Prefetching and Dependencies with .NET Typed Datasets

    - by Derek Morrison
    I'm using .NET typed datasets on a project, and I often get into situations where I prefetch data from several tables into a dataset and then pass that dataset to several methods for processing. It seems cleaner to let each method decide exactly which data it needs and then load the data itself. However, several of the methods work with the same data, and I want the performance benefit of loading data in the beginning only once. My problem is that I don't know of a good way or pattern to use for managing dependencies (I want to be sure I load all the data that I'm going to need for each class/method that will use the dataset). Currently, I just end up looking through the code for the various classes that will use the dataset to make sure I'm loading everything appropriately. What are good approaches or patterns to use in this situation? Am I doing something fundamentally wrong? Although I'm using typed datasets, this seems like it would be a common situation where prefetching data is used. Thanks!

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  • bulk update/delete entities of different kind in db.run_in_transaction

    - by Ray Yun
    Here goes pseudo code of bulk update/delete entities of different kind in single transaction. Note that Album and Song entities have AlbumGroup as root entity. class AlbumGroup: pass class Album: group = db.ReferenceProperty(reference_class=AlbumGroup,collection_name="albums") class Song: album = db.ReferenceProperty(reference_class=Album,collection_name="songs") def bulk_update_album_group(album_group): updated = [album_group] deleted = [] for album in album_group.albums: updated.append(album) for song in album.songs: if song.is_updated: updated.append(song) if song.is_deleted: deleted.append(song) db.put(updated) db.delete(deleted) a = AlbumGroup.all().filter("...").get() # bulk update/delete album group. for simplicity, album cannot be deleted. db.run_in_transaction(bulk_update_album_group,a) But I met a famous "Only Ancestor Queries in Transactions" error at the iterating reference properties like album.songs or album_group.albums. I guess ancestor() filter does not help because those entities are modified in memory. Should I not to iterate reference property in transaction function and always provide them as function parameters like def bulk_update_album_group(updated,deleted): ??? Is there any good coding pattern for this situation?

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  • design patterns for hierarchical structures

    - by JLBarros
    Anyone knows some design patterns for hierarchical structures? For example, to manage inventory categories, accounting chart of accounts, divisions of human resources, etc.. Thank you very much in advance EDIT: Thanks for your interest. I am looking for a better way of dealing with hierarchical items to which they should apply operations depending on the level of hierarchy. I have been studying the patterns by Martin Fowler, for example Accounting, but I wonder if there are other more generic. The problem is that operations apply to the items must be possible to change even at run time and may depend on other external variables. I thought of a kind of strategy pattern but would like to combine it with the fact that it is a hierarchical scheme. I would appreciate any reference to hierarchical patterns and you'll take care of them in depth.

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  • How can I make this Dictionary TryGetValue code more readable?

    - by mafutrct
    I'd like to test if an id was not yet known or, if it is known, if the associated value has changed. I'm currently using code similar to this, but it is hard to understand for those not familiar with the pattern. Can you think of a way to make it more readable while keeping it short in LOC? string id; string actual; string stored; if (!someDictionary.TryGetValue (id, out stored) || stored != actual) { // id not known yet or associated value changed. }

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  • Avoiding Nested Blocks

    - by Helium3
    If there is a view controller that wants to execute a number of block based tasks one at a time, how can the control be given back to the view controller after a completion block has executed. Lets say ViewControllerOne wants to execute a number of tasks, each relying on the result of the previous one, how would this control be given back to the viewcontroller after each completion block has been executed? I started thinking about this and I was heading towards a deeply nested block pattern that will surely only cause confusion to whoever else reads or tests it. A task executes and the completion block returns the result or error which is needed by the next task, which has its own completion task, that the next task relies on and so forth. How can the control be managed in one place, the viewcontroller? Would the completion block just call the next function that handles the next task, using a pointer to the view controller?

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  • trying to prune down a list of files

    - by romunov
    I have a list of files and I'm trying to extract all layer1_*.grd files. Is there a way of doing this in one grep expression? lof <- c("layer1_1.grd", "layer1_1.gri", "layer1_2.grd", "layer1_2.gri", "layer1_3.grd", "layer1_3.gri", "layer1_4.grd", "layer1_4.gri", "layer1_5.grd", "layer1_5.gri", "layer2_1.grd", "layer2_1.gri", "layer2_2.grd", "layer2_2.gri", "layer2_3.grd", "layer2_3.gri", "layer2_4.grd", "layer2_4.gri", "layer2_5.grd", "layer2_5.gri", "layer3_1.grd", "layer3_1.gri", "layer3_2.grd", "layer3_2.gri", "layer3_3.grd", "layer3_3.gri", "layer3_4.grd", "layer3_4.gri", "layer3_5.grd", "layer3_5.gri", "layer4_1.grd", "layer4_1.gri", "layer4_2.grd", "layer4_2.gri", "layer4_3.grd", "layer4_3.gri", "layer4_4.grd", "layer4_4.gri", "layer4_5.grd", "layer4_5.gri" I tried doing this in two steps: list.of.files <- list.files(pattern = c("1_")) list.of.files <- list.of.files[grep(".grd", list.of.files)] Can someone enlighten me how to do this with grep in one step? I naively tried passing list() and c() to the grep but, as you can imagine, it doesn't work. list.of.files <- list.files() list.of.files <- list.of.files[grep(list("1_", ".grd"), list.of.files)]

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  • python processs complete list files matched

    - by thomytheyon
    Hi All, I'm trying to get a simple code working, unfortunatly im a python beginner. My script should return a list of files that doesn't match a pattern, more information here : http://stackoverflow.com/questions/2910106/python-grep-reverse-matching/2910288#2910288 My code is running but doesn't process the complete list of files found as it should : import sys,os filefilter = ['.xml','java','.jsp','lass'] path= "/home/patate/code/project" s = "helloworld" for path, subdirs, files in os.walk(path): for name in files: if name[-4:] in filefilter : f = str(os.path.join(path, name)) with open(f) as fp: if s in fp.read(): print "%s has the string" % f else: print "%s doesn't have the string" % f This code return : /home/patate/code/project/blabla/blabla/build.xml doesn't have the string None If i change f = str(os.path.join(path, name)) for print str(os.path.join(path, name)) I can see the whole list being printed. How can i process the whole list as i which to ? :( Thanks again.

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  • Routing Error in Chapter 7.1.2 of the Ruby on Rails Tutorial

    - by user2985910
    I've been working through the tutorial for the past few days, and finally hit a snag in chapter 7. It is in this step where the line in routes.rb: get "users/new" is replaced with resource :users After I do this, I get a routing error when visiting http://localhost:3000/users/1 - No route matches [GET] "/users/1" instead of the other "Unknown Action" error shown here. Per the instructions, my routes.db file looks like this: SampleApp::Application.routes.draw do resource :users root "static_pages#home" match '/signup', to: 'users#new', via: 'get' match '/help', to: 'static_pages#help', via: 'get' match '/about', to: 'static_pages#about', via: 'get' match '/contact', to: 'static_pages#contact', via: 'get' end Output from 'rake routes' shows: Prefix Verb URI Pattern Controller#Action users POST /users(.:format) users#create new_users GET /users/new(.:format) users#new edit_users GET /users/edit(.:format) users#edit GET /users(.:format) users#show PATCH /users(.:format) users#update PUT /users(.:format) users#update DELETE /users(.:format) users#destroy root GET / static_pages#home signup GET /signup(.:format) users#new help GET /help(.:format) static_pages#help about GET /about(.:format) static_pages#about contact GET /contact(.:format) static_pages#contact Does anyone have any insight to get past this? Many thanks.

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  • String Functions in IIS Url Rewrite Module

    - by Nariman
    The IIS URL Rewrite Module ships with 3 built-in functions: * ToLower - returns the input string converted to lower case. * UrlEncode - returns the input string converted to URL-encoded format. This function can be used if the substitution URL in rewrite rule contains special characters (for example non-ASCII or URI-unsafe characters). * UrlDecode - decodes the URL-encoded input string. This function can be used to decode a condition input before matching it against a pattern. The functions can be invoked by using the following syntax: {function_name:any_string} The question is: can this list be extended by introducing a Replace function that's available for changing values within a rewrite rule action or condition? Another way to frame the question: is there any way to do a global replace on a URL coming in using this module? It seems that you're limited to using regular expressions and back-references to construct strings, without a search/replace functionality to replace every X with Y in {REQUEST_URI} before issuing a redirect.

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  • How to organize architecture WPF project?

    - by Dmitriy
    Hello! In my WPF project i want to have only one Window - MainWindow and UserControls as working part. I have some little different applications in one, and want to make navigation on top of my MainWindow as buttons. And little applications as UserControl. In MainWindow - grid with Big Empty Zone - which use to keep and run work. But, i want to navigate to other userControl from another. (probably do not understand :() How organize architecture WPF project that: one main window and many usercontrols which places in mainwindow and replace each other in turn. and there is the possibility of navigating from another usercontrol to another. May be it's MVVM, but i don't understand how this pattern can help me.

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  • Setting up Matcher for String phrase match in file

    - by randomCoder
    Having trouble figuring out how to match a phrase string to a phrase in file stream. The file I'm dealing with contains random words such as: 3 little pigs built houses and 1 little pig went to the market etc. for many lines Using "little pig" as my pattern and matcher.find() I can locate 2 matches: "little pig" and "little pigs". However, I only want it to match "little pig". What can I do? I thought about using matcher.lookingAt() but I wouldn't know how to set a proper region when I can't rely on the file string phrases I'm matching being on separate lines.

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  • Django - Static content display based on URL

    - by Steven Potter
    I'm working on a Django site with a basic three column design. Left column navigation, center column content and right column URL specific content blocks. My question is about the best method of controlling the URL specific content blocks in the right column. I am thinking of something along the lines of the Flatpages app that will make the content available to the template context if the URL matches a pre-determined pattern (perhaps regex?). Does anyone know if such an app already exists? If not, I am looking for some advice about the best way to implement it. Particularly in relation to the matching of patterns to the current URL. Is there any good way to re-use parts of the Django URL dispatcher for this use?

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  • How do you make your Java application memory efficient?

    - by Boune
    How do you optimize the heap size usage of an application that has a lot (millions) of long-lived objects? (big cache, loading lots of records from a db) Use the right data type Avoid java.lang.String to represent other data types Avoid duplicated objects Use enums if the values are known in advance Use object pools String.intern() (good idea?) Load/keep only the objects you need I am looking for general programming or Java specific answers. No funky compiler switch. Edit: Optimize the memory representation of a POJO that can appear millions of times in the heap. Use cases Load a huge csv file in memory (converted into POJOs) Use hibernate to retrieve million of records from a database Resume of answers: Use flyweight pattern Copy on write Instead of loading 10M objects with 3 properties, is it more efficient to have 3 arrays (or other data structure) of size 10M? (Could be a pain to manipulate data but if you are really short on memory...)

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  • How to properly match the following message id format in a case statement

    - by hsatterwhite
    I'm trying to get this regex pattern working in a case statement to match a particular type of ID, which could be passed to the script. I need to match the exact number of alphanumeric characters with the dashes to differentiate this message id from anything else, which may be passed to this bash script. An example of the message id format: c7c3e910-c9d2-71e1-0999-0aec446b0000 #!/bin/bash until [ -z "$1" ] do case "$1" in "") echo "No value passed" ;; [a-z0-9]\{8\}-[a-z0-9]\{4\}-[a-z0-9]\{4\}-[a-z0-9]\{4\}-[a-z0-9]\{12\}) echo "Found message ID: $1" ;; *) echo "Server $1" ;; esac shift done

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  • ColdFusion - pass regex backreference to function call

    - by stubotnik
    Hi, I'm using ColdFusion's reReplace() function for regular expression pattern replacement. I'd like to use a function call for the replacement string, and pass a matched backreference to it. Something like this: <cfset s = "STARTDATE_2010-05-07 00:05:00.0_ENDDATE" /> <cfset s = reReplace(s, "STARTDATE_([\s-.:0-9]*)_ENDDATE", dateAdd("h", 1, "\1")) /> But that fails because "The value of parameter 3, which is currently \1, must be a class java.util.Date value." Is there any other way to achieve this? Thanks, Stu

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  • PHP validating integers

    - by Mikk
    Hi, I was wondering, what would be the best way to validate an integer. I'd like this to work with strings as well, so I could to something like (string)+00003 - (int)3 (valid) (string)-027 - (int)-27 (valid) (int)33 - (int)33 (valid) (string)'33a' - (FALSE) (invalid) That is what i've go so far: function parseInt($int){ //If $int already is integer, return it if(is_int($int)){return $int;} //If not, convert it to string $int=(string)$int; //If we have '+' or '-' at the beginning of the string, remove them $validate = ($int[0] === '-' || $int[0] === '+')?substr($int, 1):$int; //If $validate matches pattern 0-9 convert $int to integer and return it //otherwise return false return preg_match('/^[0-9]+$/', $validate)?(int)$int:FALSE; } As far as I tested, this function works, but it looks like a clumsy workaround. Is there any better way to write this kind of function. I've also tried filter_var($foo, FILTER_VALIDATE_INT); but it won't accept values like '0003', '-0' etc.

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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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  • filter log file by defining regexes

    - by fmpdmb
    I have some HUGE log files (50Mb; ~500K lines) I need to start filtering some of the crap out of. The log files are being produced using log4j and have the basic pattern of: [log-level] date-time class etc, etc log-message I'm looking for a way that I can identify a regex start and regex end (or something similar) that will filter out the matching entries from the file so I can more easily wade through these massive files. I'm sure I could write a java program to accomplish this task, but I thought I'd ask the community before going down that path. Thanks in advance.

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  • Buffering db inserts in multithreaded program

    - by Winter
    I have a system which breaks a large taks into small tasks using about 30 threads as a time. As each individual thread finishes it persists its calculated results to the database. What I want to achieve is to have each thread pass its results to a new persisance class that will perform a type of double buffering and data persistance while running in its own thread. For example, after 100 threads have moved their data to the buffer the persistance class then the persistance class swaps the buffers and persists all 100 entries to the database. This would allow utilization of prepared statements and thus cut way down on the I/O between the program and the database. Is there a pattern or good example of this type of multithreading double buffering?

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  • C#: Creating an editable object inside a PictureBox

    - by ET
    My goal is to let the user click on a specific location on a map to add a Placemark, and then edit the placemark by click its icon (change its name, move it around, etc). I am using a PictureBox to show the map, and by registering the MouseDoubleClick event I am drawing an Image on the map with GDI+ DrawImage() method. The problem is that after the placemark's Image was drawn, it does not editable: the user cant click the icon and move it around, change its name etc. Is there any other design pattern I can follow? maybe using other controls... ?

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  • How to get route "name" when in route controller

    - by Murph
    I'm using routing in asp.net to get nice URLs When I define routes in global.asax I create two distinct routes that use the same controller (c#): // Setup code for route a... routes.Add("routeb", routea); // Setup code for route b... routes.Add("routeb", routeb); (How) is it possible to determine from within the controller what the "key" value is that directed the user to this controller? Alternatively is the pattern of use wrong - it would be straightforward to subclass the Controller (again) to distinguish between the two and retain common code if that is a more appropriate solution.

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  • Injecting a dependancy into a base class

    - by Jamie Dixon
    Hey everyone, I'm on a roll today with questions. I'm starting out with Dependency Injection and am having some trouble injecting a dependency into a base class. I have a BaseController controller which my other controllers inherit from. Inside of this base controller I do a number of checks such as determining if the user has the right privileges to view the current page, checking for the existence of some session variables etc. I have a dependency inside of this base controller that I'd like to inject using Ninject however when I set this up as I would for my other dependencies I'm told by the compiler that: Error 1 'MyProject.Controllers.BaseController' does not contain a constructor that takes 0 argument This makes sense but I'm just not sure how to inject this dependency. Should I be using this pattern of using a base controller at all or should I be doing this in a more efficient/correct way?

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  • In the JSON spec, what does "Since the first two characters of a JSON text will always be ASCII characters" mean?

    - by dan gibson
    The spec is http://www.ietf.org/rfc/rfc4627.txt?number=4627 It contains this: Encoding JSON text SHALL be encoded in Unicode. The default encoding is UTF-8. Since the first two characters of a JSON text will always be ASCII characters [RFC0020], it is possible to determine whether an octet stream is UTF-8, UTF-16 (BE or LE), or UTF-32 (BE or LE) by looking at the pattern of nulls in the first four octets. What does it mean "Since the first two characters of a JSON text will always be ASCII characters [RFC0020]"? I've looked at RFC0020 but couldn't find anything about it. JSON could be {" or { " (ie whitespace before the quote.

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