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  • Can Spring.Net function as PostSharp?

    - by Alex K
    A few months back I've discovered PostSharp, and for a time, it was good. But then legal came back with an answer saying that they don't like the licence of the old versions. Then the department told me that 2.0's price was unacceptably high (for the number of seats we need)... I was extremely disapponted, but not disheartened. Can't be the only such framework, I thought. I kept looking for a replacement, but most of it was either dead, ill maintained (especially in documentation department), for academic use, or all of the above (I'm looking at you Aspect.Net) Then I've discovered Spring.Net, and for a time, it was good. I've been reading the documentation and it went on to paint what seemed to be a supperior picture of an AOP nirvana. No longer was I locked to attributes to mark where I wanted code interception to take place, but it could be configured in XML and changes to it didn't require re-compile. Great. Then I looked at the samples and saw the following, in every single usage scenario: // Create AOP proxy using Spring.NET IoC container. IApplicationContext ctx = ContextRegistry.GetContext(); ICommand command = (ICommand)ctx["myServiceCommand"]; command.Execute(); if (command.IsUndoCapable) { command.UnExecute(); } Why must the first two lines of code exist? It ruins everything. This means I cannot simply provide a user with a set of aspects and attributes or XML configs that they can use by sticking appropriate attributes on the appropriate methods/classes/etc or editing the match pattern in XML. They have to modify their program logic to make this work! Is there a way to make Spring.Net behave as PostSharp in this case? (i.e. user only needs to add attributes/XML config, not edit content of any methods. Alternatively, is there a worthy and functioning alternative to PostSharp? I've seen a few question titled like this on SO, but none of them were actually looking to replace PostSharp, they only wanted to supplement its functionality. I need full replacement.

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  • Revisiting .NET, but what should I focus on?

    - by Wayne M
    After about a two-year hiatus, I'm brushing up on my .NET skills to find a .NET job (my previous two positions have very little development, or development using legacy technologies, so apart from a few very minor apps I have not touched .NET in close to two years). I'm aware of things like ASP.NET MVC, and I have previously read on things like NHibernate and DI/IOC, albeit I have yet to use them apart from very trivial "Hello World" type applications. I have a subscription to Rob Conery's Tekpub website and occasionally watch these videos when I have free time. My concern is this: I don't live in a very technical area. I would be surprised if any but the most tech-savvy companies have heard of, let alone use, ASP.NET MVC, NHibernate (or even LINQ/EF), or know about IoC. I would be willing to bet a large sum of money that 95% of the possible jobs I could obtain will use the following: Visual Source Safe, if any VCS at all ASP.NET 2.0 Webforms (3.5 if lucky) Raw ADO.NET on top of a very thin implementation of the Gateway pattern Stored Procedures in the database for most CRUD operations Gratuitous use of code-behind, with a Service layer if I'm lucky If I were extremely lucky, I might find a shop that has heard of ORMs and either uses one, or has wrote their own data abstraction. Also if I were lucky, the company would be using Model-View-Presenter. In light of this I'm not sure what I should focus on learning. Personally, I would prefer to be using the latest stuff - ASP.NET MVC, NHibernate, jQuery, WCF etc. Reality says I should go back to the basics, since it looks like most potential opportunities aren't going to be anywhere near the cutting edge, or anywhere close to it. And, as much as I would like to find a position and start to show the other developers the benefits, in my past experience this has usually resulted in my being fired for "not being a team player" and doing things the bad old way. So, I am curious how you would approach a situation like this? What should I focus on, in order to A) Reaquaint myself with .NET, and B) Prepare myself to obtain a .NET job again that is more than likely going to use techniques that I and most other knowledgeable developers will scoff at?

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  • Hooking DirectX EndScene from an injected DLL

    - by Etan
    I want to detour EndScene from an arbitrary DirectX 9 application to create a small overlay. As an example, you could take the frame counter overlay of FRAPS, which is shown in games when activated. I know the following methods to do this: Creating a new d3d9.dll, which is then copied to the games path. Since the current folder is searched first, before going to system32 etc., my modified DLL gets loaded, executing my additional code. Downside: You have to put it there before you start the game. Same as the first method, but replacing the DLL in system32 directly. Downside: You cannot add game specific code. You cannot exclude applications where you don't want your DLL to be loaded. Getting the EndScene offset directly from the DLL using tools like IDA Pro 4.9 Free. Since the DLL gets loaded as is, you can just add this offset to the DLL starting address, when it is mapped to the game, to get the actual offset, and then hook it. Downside: The offset is not the same on every system. Hooking Direct3DCreate9 to get the D3D9, then hooking D3D9-CreateDevice to get the device pointer, and then hooking Device-EndScene through the virtual table. Downside: The DLL cannot be injected, when the process is already running. You have to start the process with the CREATE_SUSPENDED flag to hook the initial Direct3DCreate9. Creating a new Device in a new window, as soon as the DLL gets injected. Then, getting the EndScene offset from this device and hooking it, resulting in a hook for the device which is used by the game. Downside: as of some information I have read, creating a second device may interfere with the existing device, and it may bug with windowed vs. fullscreen mode etc. Same as the third method. However, you'll do a pattern scan to get EndScene. Downside: doesn't look that reliable. How can I hook EndScene from an injected DLL, which may be loaded when the game is already running, without having to deal with different d3d9.dll's on other systems, and with a method which is reliable? How does FRAPS for example perform it's DirectX hooks? The DLL should not apply to all games, just to specific processes where I inject it via CreateRemoteThread.

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  • Validate a string in a table in SQL Server - CLR function or T-SQL

    - by Ashish Gupta
    I need to check If a column value (string) in SQL server table starts with a small letter and can only contain '_', '-', numbers and alphabets. I know I can use a SQL server CLR function for that. However, I am trying to implement that validation using a scalar UDF and could make very little here...I can use 'NOT LIKE', but I am not sure how to make sure I validate the string irrespective of the order of characters or in other words write a pattern in SQL for this. Am I better off using a SQL CLR function? Any help will be appreciated.. Thanks in advance Thank you everyone for their comments. This morning, I chose to go CLR function way. For the purpose of what I was trying to achieve, I created one CLR function which does the validation of an input string and have that called from a SQL UDF and It works well. Just to measure the performance of t-SQL UDF using SQL CLR function vs t- SQL UDF, I created a SQL CLR function which will just check if the input string contains only small letters, it should return true else false and have that called from a UDF (IsLowerCaseCLR). After that I also created a regular t-SQL UDF(IsLowerCaseTSQL) which does the same thing using the 'NOT LIKE'. Then I created a table (Person) with columns Name(varchar) and IsValid(bit) columns and populate that with names to test. Data :- 1000 records with 'Ashish' as value for Name column 1000 records with 'ashish' as value for Name column then I ran the following :- UPDATE Person Set IsValid=1 WHERE dbo.IsLowerCaseTSQL (Name) Above updated 1000 records (with Isvalid=1) and took less than a second. I deleted all the data in the table and repopulated the same with same data. Then updated the same table using Sql CLR UDF (with Isvalid=1) and this took 3 seconds! If update happens for 5000 records, regular UDF takes 0 seconds compared to CLR UDF which takes 16 seconds! I am very less knowledgeable on t-SQL regular expression or I could have tested my actual more complex validation criteria. But I just wanted to know, even I could have written that, would that have been faster than the SQL CLR function considering the example above. Are we using SQL CLR because we can implement we can implement lot richer logic which would have been difficult otherwise If we write in regular SQL. Sorry for this long post. I just want to know from the experts. Please feel free to ask if you could not understand anything here. Thank you again for your time.

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  • How to arrange models, views, controllers in a Kohana 3 project

    - by Pekka
    I'm looking at how to set up a mid-sized web application with Kohana 3. I have implemented MVC patterns in the past but never worked against a "formalized" MVC framework so I'm still getting my head around the terminology - toying around with basic examples, building views and templates, and so on. I'm progressing fairly well but I want to set up a real-world web project (one of my own that I've been planning for quite some time now) as a learning object. I learn best by example, but example-based documentation is a bit sparse for Kohana 3 right now - they say so themselves on the site. While I'm not worried about getting into the framework soon enough, I'm a bit concerned about arranging a healthily structured code base from the start - i.e. how to split up controllers, how to name them, and how to separate the functionality into the appropriate models. My application could, in its core, be described as a business directory with a main businesses table. Businesses can be listed by category and by street name. Each business has a detail page. Business owners can log in and edit their business's entry. Businesses can post offers into an offers table. I know this is not very detailed, but I don't want to cram too much information into this question. I'll be more than happy to go into more detail if needed. Supposing I have all the basic functionality worked out and in place already - list all businesses, edit business, list businesses by street name, create offer logged in as business, and so on, and I'm just looking for how to fit the functionality into a MVC pattern and into a Kohana application structure that can be easily extended: Do you know real-life, publicly accessible examples of "database-heavy" applications like directories, online communities... with a log-in area built on Kohana 3 where I could take a peek how they do it? Are there conventions or best practices on how to structure an extendable login area for end users in a Kohana project that is not only able to handle a business directory page, but further products on separate pages as well? Do you know application structuring HOWTOs or best practices for Kohana 3 not mentioned in the user guide and the inofficial Wiki? Have you built something similar and could give me some recommendations?

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  • Entity Attribute Value Database vs. strict Relational Model Ecommerce question

    - by Dr. Zim
    It is safe to say that the EAV/CR database model is bad. That said, Question: What database model, technique, or pattern should be used to deal with "classes" of attributes describing e-commerce products which can be changed at run time? In a good E-commerce database, you will store classes of options (like TV resolution then have a resolution for each TV, but the next product may not be a TV and not have "TV resolution"). How do you store them, search efficiently, and allow your users to setup product types with variable fields describing their products? If the search engine finds that customers typically search for TVs based on console depth, you could add console depth to your fields, then add a single depth for each tv product type at run time. There is a nice common feature among good e-commerce apps where they show a set of products, then have "drill down" side menus where you can see "TV Resolution" as a header, and the top five most common TV Resolutions for the found set. You click one and it only shows TVs of that resolution, allowing you to further drill down by selecting other categories on the side menu. These options would be the dynamic product attributes added at run time. Further discussion: So long story short, are there any links out on the Internet or model descriptions that could "academically" fix the following setup? I thank Noel Kennedy for suggesting a category table, but the need may be greater than that. I describe it a different way below, trying to highlight the significance. I may need a viewpoint correction to solve the problem, or I may need to go deeper in to the EAV/CR. Love the positive response to the EAV/CR model. My fellow developers all say what Jeffrey Kemp touched on below: "new entities must be modeled and designed by a professional" (taken out of context, read his response below). The problem is: entities add and remove attributes weekly (search keywords dictate future attributes) new entities arrive weekly (products are assembled from parts) old entities go away weekly (archived, less popular, seasonal) The customer wants to add attributes to the products for two reasons: department / keyword search / comparison chart between like products consumer product configuration before checkout The attributes must have significance, not just a keyword search. If they want to compare all cakes that have a "whipped cream frosting", they can click cakes, click birthday theme, click whipped cream frosting, then check all cakes that are interesting knowing they all have whipped cream frosting. This is not specific to cakes, just an example.

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  • Defining InputBindings within a Style

    - by Brent
    I'm creating a WPF app using the MVVM design pattern, and I'm trying to extend the TabItem control so that it closes the tab when the user clicks the middle mouse button. I'm trying to achieve this using InputBindings, and it works very well until I try to define it within a style. I've learned that you cannot add InputBindings to a style unless you attach it using a DependencyProperty. So I followed this similar post here... and it works... almost. I can close one tab using the middle mouse button, but it won't work on any of the other tabs (all of the tabs are added at runtime and inherit the same style). So I need some help. Why would this only be working the first time, and not after? Obviously I could create a custom control that inherits from a TabItem and make it work, but I'd like to figure this out as I can see this being expanded in my projects. I'm no expert on DependencyProperties, so please help me out. Thanks! Style: <Style TargetType="{x:Type TabItem}"> <Setter Property="w:Attach.InputBindings"> <Setter.Value> <InputBindingCollection> <MouseBinding MouseAction="MiddleClick" Command="{Binding CloseCommand}"/> </InputBindingCollection> </Setter.Value> </Setter> ... </Style> Class public class Attach { public static readonly DependencyProperty InputBindingsProperty = DependencyProperty.RegisterAttached("InputBindings", typeof(InputBindingCollection), typeof(Attach), new FrameworkPropertyMetadata(new InputBindingCollection(), (sender, e) => { var element = sender as UIElement; if (element == null) return; element.InputBindings.Clear(); element.InputBindings.AddRange((InputBindingCollection)e.NewValue); })); public static InputBindingCollection GetInputBindings(UIElement element) { return (InputBindingCollection)element.GetValue(InputBindingsProperty); } public static void SetInputBindings(UIElement element, InputBindingCollection inputBindings) { element.SetValue(InputBindingsProperty, inputBindings); } }

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  • Rails - embedded polymorphic comment list + add comment form - example?

    - by odigity
    Hey, all. Working on my first Rails app. I've searched all around - read a bunch of tutorials, articles, and forum posts, watched some screencasts, and I've found a few examples that come close to what I'm trying to do (notably http://railscasts.com/episodes/154-polymorphic-association and ep 196 about nested model forms), but not exactly. I have two models (Podcast and BlogPost) that need to be commentable, and I have a Comment model that is polymorphically related to both. The railscasts above had a very similar example (ep 154), but Ryan used a full set of nested routes, so there were specific templates for adding and editing comments. What I want to do is show the list of comments right on the Podcast or BlogPost page, along with an Add Comment form at the bottom. I don't need a separate add template/route, and I don't need the ability to edit, only delete. This is a pretty common design on the web, but I can't find a Rails example specifically about this pattern. Here's my current understanding: I need routes for the create and delete actions, of course, but there are no templates associated with those. I'm also guessing that the right approach is to create a partial that can be included at the bottom of both the Podcast and BlogPost show template. The logical name for the partial seems to me to be something like _comments.html.haml. I know it's a common convention to have the object passed to the partial be named after the template, but calling the object 'comments' seems to not match my use case, since what I really need to pass is the commentable object (Podcast or BlogPost). So, I guess I'd use the locals option for the render partial call? (:commentable = @podcast). Inside the partial, I could call commentable.comments to get the comments collection, render that with a second partial (this time with the conventional use case, calling the partial _comment.html.haml), then create a form that submits to... what? REST-wise, it should be a POST to the collection, which would be /podcast|blogpost/:id/comments, and I think the helper for that is podcast_comments_path(podcast) if it were a podcast - not sure what to do though, since I'm using polymorphic comments. That would trigger the Comment.create action, which would then need to redirect back to the podcast|blogpost path /podcast|blogpost/:id. It's all a bit overwhelming, which is why I was really hoping to find a screencast or example that specifically implements this design.

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  • Best practices concerning view model and model updates with a subset of the fields

    - by Martin
    By picking MVC for developing our new site, I find myself in the midst of "best practices" being developed around me in apparent real time. Two weeks ago, NerdDinner was my guide but with the development of MVC 2, even it seems outdated. It's an thrilling experience and I feel privileged to be in close contact with intelligent programmers daily. Right now I've stumbled upon an issue I can't seem to get a straight answer on - from all the blogs anyway - and I'd like to get some insight from the community. It's about Editing (read: Edit action). The bulk of material out there, tutorials and blogs, deal with creating and view the model. So while this question may not spell out a question, I hope to get some discussion going, contributing to my decision about the path of development I'm to take. My model represents a user with several fields like name, address and email. All the names, in fact, on field each for first name, last name and middle name. The Details view displays all these fields but you can change only one set of fields at a time, for instance, your names. The user expands a form while the other fields are still visible above and below. So the form that is posted back contains a subset of the fields representing the model. While this is appealing to us and our layout concerns, for various reasons, it is to be shunned by serious MVC-developers. I've been reading about some patterns and best practices and it seems that this is not in key with the paradigm of viewmodel == view. Or have I got it wrong? Anyway, NerdDinner dictates using FormCollection och UpdateModel. All the null fields are happily ignored. Since then, the MVC-community has abandoned this approach to such a degree that a bug in MVC 2 was not discovered. UpdateModel does not work without a complete model in your formcollection. The view model pattern receiving most praise seems to be Dedicated view model that contains a custom view model entity and is the only one that my design issue could be made compatible with. It entails a tedious amount of mapping, albeit lightened by the use of AutoMapper and the ideas of Jimmy Bogard, that may or may not be worthwhile. He also proposes a 1:1 relationship between view and view model. In keeping with these design paradigms, I am to create a view and associated view for each of my expanding sets of fields. The view models would each be nearly identical, differing only in the fields which are read-only, the views also containing much repeated markup. This seems absurd to me. In future I may want to be able to display two, more or all sets of fields open simultaneously. I will most attentively read the discussion I hope to spark. Many thanks in advance.

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  • Arranging models, views, controllers in a Kohana 3 project

    - by Pekka
    I'm looking at how to set up a mid-sized web application with Kohana 3. I have implemented MVC patterns in the past but never worked against a "formalized" MVC framework so I'm still getting my head around the terminology - toying around with basic examples, building views and templates, and so on. I'm progressing fairly well but I want to set up a real-world web project (one of my own that I've been planning for quite some time now) as a learning object. I learn best by example, but example-based documentation is a bit sparse for Kohana 3 right now - they say so themselves on the site. While I'm not worried about getting into the framework soon enough, I'm a bit concerned about arranging a healthily structured code base from the start - i.e. how to split up controllers, how to name them, and how to separate the functionality into the appropriate models. My application could, in its core, be described as a business directory with a main businesses table. Businesses can be listed by category and by street name. Each business has a detail page. Business owners can log in and edit their business's entry. Businesses can post offers into an offers table. I know this is pretty vague, but I don't want to cram too much information into this question. I'll be more than happy to go into more detail if needed. Supposing I have all the basic functionality worked out and in place already - list all businesses, edit business, list businesses by street name, create offer, and so on, and I'm just looking for how to fit the functionality into a MVC pattern and into a Kohana application structure that can be easily extended: Do you know real-life, publicly accessible examples of "database-heavy" applications like directories, online communities... with a log-in area built on Kohana 3 where I could take a peek how they do it? Are there conventions or best practices on how to structure an extendable login area for end users in a Kohana project that is not only able to handle a business directory page, but further products on separate pages as well? Do you know application structuring HOWTOs or best practices for Kohana 3 not mentioned in the user guide and the inofficial Wiki? Have you built something similar and could give me some recommendations?

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  • Implement looped movement animation with tap to cancel

    - by Nader
    Hi All; My app is based around a grid and an image that moves within a grid that is contained within a scrollview. I have an imageview that I am animating from one cell to another in time with a slow finger movement and recentering the scrollview. That is rather straight forward. I have also implement the ability to detect a swipe and therefore move the image all the way to the end of the grid and the uiscrollview recentering. I have even implemented the ability to detect a subsequent tap and freeze the swiped movement. The issue with the swipe movement is that the UIScrollView will scroll all the way to the end before the Image reaches the end and so I have to wait for the image to arrive. Also, when I freeze the movement of the image, I have to re-align the image to a cell (which I can do). I have come to the realization that I have to animate the image one cell at a time for swipes and recentering the uiscrollview before moving the image to the next cell. I have attempted to implement this but I cannot come up with a solution that works or works properly. Can anyone suggest how I go about implementing this? Even if you are able to put up code from a different example or sudo code, it would help a lot as I cannot workout how this should be done, should I be using selectors, a listener in delegates, I just simply lack the experience to solve this design pattern. Here is some code: Note that the sprite is an UIImageView - (void)animateViewToPosition:(SpriteView *)sprite Position:(CGPoint)pos Duration:(CFTimeInterval)duration{ CGMutablePathRef traversePath = CGPathCreateMutable(); CGPathMoveToPoint(traversePath, NULL, sprite.center.x, sprite.center.y); CGPathAddLineToPoint(traversePath, NULL, pos.x, pos.y); CAKeyframeAnimation *traverseAnimation = [CAKeyframeAnimation animationWithKeyPath:kAnimatePosition]; traverseAnimation.duration = duration; traverseAnimation.removedOnCompletion = YES; traverseAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]; traverseAnimation.delegate = sprite; traverseAnimation.path = traversePath; CGPathRelease(traversePath); [sprite.layer addAnimation:traverseAnimation forKey:kAnimatePosition]; sprite.center = pos;

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  • Implement looped movement animation with tap to cancel

    - by Nader
    Hi All; My app is based around a grid and an image that moves within a grid that is contained within a scrollview. I have an imageview that I am animating from one cell to another in time with a slow finger movement and recentering the scrollview. That is rather straight forward. I have also implement the ability to detect a swipe and therefore move the image all the way to the end of the grid and the uiscrollview recentering. I have even implemented the ability to detect a subsequent tap and freeze the swiped movement. The issue with the swipe movement is that the UIScrollView will scroll all the way to the end before the Image reaches the end and so I have to wait for the image to arrive. Also, when I freeze the movement of the image, I have to re-align the image to a cell (which I can do). I have come to the realization that I have to animate the image one cell at a time for swipes and recentering the uiscrollview before moving the image to the next cell. I have attempted to implement this but I cannot come up with a solution that works or works properly. Can anyone suggest how I go about implementing this? Even if you are able to put up code from a different example or sudo code, it would help a lot as I cannot workout how this should be done, should I be using selectors, a listener in delegates, I just simply lack the experience to solve this design pattern. Here is some code: Note that the sprite is an UIImageView - (void)animateViewToPosition:(SpriteView *)sprite Position:(CGPoint)pos Duration:(CFTimeInterval)duration{ CGMutablePathRef traversePath = CGPathCreateMutable(); CGPathMoveToPoint(traversePath, NULL, sprite.center.x, sprite.center.y); CGPathAddLineToPoint(traversePath, NULL, pos.x, pos.y); CAKeyframeAnimation *traverseAnimation = [CAKeyframeAnimation animationWithKeyPath:kAnimatePosition]; traverseAnimation.duration = duration; traverseAnimation.removedOnCompletion = YES; traverseAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]; traverseAnimation.delegate = sprite; traverseAnimation.path = traversePath; CGPathRelease(traversePath); [sprite.layer addAnimation:traverseAnimation forKey:kAnimatePosition]; sprite.center = pos; }

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  • Haskell: how to get through 'no instance for' ?

    - by artemave
    I am learning Haskell. I am on the 8th chapter of this book. The main thing I've learned so far is that Haskell is very unfriendly to me and it bites my ass where possible. Moreover... Heck! Enough mourning, to business. Here is the code: module GlobRegex ( globToRegex, matchesGlob ) where import Text.Regex.Posix import Text.Regex.Posix.String import Text.Regex.Base.RegexLike data CaseOpt = Case | NoCase deriving (Eq) matchesGlob :: String -> String -> CaseOpt -> Bool matchesGlob name pat caseopt = match regex name where regex = case caseopt of NoCase -> makeRegexOpts (defaultCompOpt + compIgnoreCase) defaultExecOpt (globToRegex pat) Case -> makeRegex (globToRegex pat) globToRegex :: String -> String ... And here is how it fails to compile: Prelude Text.Regex.Posix Text.Regex.Base.RegexLike> :load globtoregex\GlobRegex. hs [1 of 1] Compiling GlobRegex ( globtoregex\GlobRegex.hs, interpreted ) globtoregex\GlobRegex.hs:14:31: No instance for (RegexLike regex [Char]) arising from a use of `match' at globtoregex\GlobRegex.hs:14:31-46 Possible fix: add an instance declaration for (RegexLike regex [Char]) In the expression: match regex name In the definition of `matchesGlob': matchesGlob name pat caseopt = match regex name where regex = case caseopt of { NoCase -> makeRegexOpts (defaultCompOpt + compIgnoreCase) defaultExecOpt (globToRegex pat) Case -> makeRegex (globToRegex pat) } globtoregex\GlobRegex.hs:17:23: No instance for (RegexMaker regex CompOption execOpt String) arising from a use of `makeRegex' at globtoregex\GlobRegex.hs:17:23-49 Possible fix: add an instance declaration for (RegexMaker regex CompOption execOpt String) In the expression: makeRegex (globToRegex pat) In a case alternative: Case -> makeRegex (globToRegex pat) In the expression: case caseopt of { NoCase -> makeRegexOpts (defaultCompOpt + compIgnoreCase) defaultExecOpt (globToRegex p at) Case -> makeRegex (globToRegex pat) } Failed, modules loaded: none. To my best understanding, Text.Regex.Posix.String provides instances for RegexLike Regex String and RegexMaker Regex CompOption ExecOption String, so it should work. On the other hand, I can see that regex in the error message is type variable, not a concrete type, so, perhaps not... Anyway, this is where I am stuck. May be there is a common pattern for resolving no instance for type of problems? Or, in Haskell terms, instance of SmartGuess typeclass for no instance for?

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  • My block is not retaining some of its objects

    - by Drew Crawford
    From the Blocks documentation: In a reference-counted environment, by default when you reference an Objective-C object within a block, it is retained. This is true even if you simply reference an instance variable of the object. I am trying to implement a completion handler pattern, where a block is given to an object before the work is performed and the block is executed by the receiver after the work is performed. Since I am being a good memory citizen, the block should own the objects it references in the completion handler and then they will be released when the block goes out of scope. I know enough to know that I must copy the block to move it to the heap since the block will survive the stack scope in which it was declared. However, one of my objects is getting deallocated unexpectedly. After some playing around, it appears that certain objects are not retained when the block is copied to the heap, while other objects are. I am not sure what I am doing wrong. Here's the smallest test case I can produce: typedef void (^ActionBlock)(UIView*); In the scope of some method: NSObject *o = [[[NSObject alloc] init] autorelease]; mailViewController = [[[MFMailComposeViewController alloc] init] autorelease]; NSLog(@"o's retain count is %d",[o retainCount]); NSLog(@"mailViewController's retain count is %d",[mailViewController retainCount]); ActionBlock myBlock = ^(UIView *view) { [mailViewController setCcRecipients:[NSArray arrayWithObjects:@"[email protected]",nil]]; [o class]; }; NSLog(@"mailViewController's retain count after the block is %d",[mailViewController retainCount]); NSLog(@"o's retain count after the block is %d",[o retainCount]); Block_copy(myBlock); NSLog(@"o's retain count after the copy is %d",[o retainCount]); NSLog(@"mailViewController's retain count after the copy is %d",[mailViewController retainCount]); I expect both objects to be retained by the block at some point, and I certainly expect their retain counts to be identical. Instead, I get this output: o's retain count is 1 mailViewController's retain count is 1 mailViewController's retain count after the block is 1 o's retain count after the block is 1 o's retain count after the copy is 2 mailViewController's retain count after the copy is 1 o (subclass of NSObject) is getting retained properly and will not go out of scope. However mailViewController is not retained and will be deallocated before the block is run, causing a crash.

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  • Validate a string in a table in SQL Server - CLR function or T-SQL (Question updated)

    - by Ashish Gupta
    I need to check If a column value (string) in SQL server table starts with a small letter and can only contain '_', '-', numbers and alphabets. I know I can use a SQL server CLR function for that. However, I am trying to implement that validation using a scalar UDF and could make very little here...I can use 'NOT LIKE', but I am not sure how to make sure I validate the string irrespective of the order of characters or in other words write a pattern in SQL for this. Am I better off using a SQL CLR function? Any help will be appreciated.. Thanks in advance Thank you everyone for their comments. This morning, I chose to go CLR function way. For the purpose of what I was trying to achieve, I created one CLR function which does the validation of an input string and have that called from a SQL UDF and It works well. Just to measure the performance of t-SQL UDF using SQL CLR function vs t- SQL UDF, I created a SQL CLR function which will just check if the input string contains only small letters, it should return true else false and have that called from a UDF (IsLowerCaseCLR). After that I also created a regular t-SQL UDF(IsLowerCaseTSQL) which does the same thing using the 'NOT LIKE'. Then I created a table (Person) with columns Name(varchar) and IsValid(bit) columns and populate that with names to test. Data :- 1000 records with 'Ashish' as value for Name column 1000 records with 'ashish' as value for Name column then I ran the following :- UPDATE Person Set IsValid=1 WHERE dbo.IsLowerCaseTSQL (Name) Above updated 1000 records (with Isvalid=1) and took less than a second. I deleted all the data in the table and repopulated the same with same data. Then updated the same table using Sql CLR UDF (with Isvalid=1) and this took 3 seconds! If update happens for 5000 records, regular UDF takes 0 seconds compared to CLR UDF which takes 16 seconds! I am very less knowledgeable on t-SQL regular expression or I could have tested my actual more complex validation criteria. But I just wanted to know, even I could have written that, would that have been faster than the SQL CLR function considering the example above. Are we using SQL CLR because we can implement we can implement lot richer logic which would have been difficult otherwise If we write in regular SQL. Sorry for this long post. I just want to know from the experts. Please feel free to ask if you could not understand anything here. Thank you again for your time.

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  • Succinct introduction to C++/CLI for C#/Haskell/F#/JS/C++/... programmer

    - by Henrik
    Hello everybody, I'm trying to write integrations with the operating system and with things like active directory and Ocropus. I know a bunch of programming languages, including those listed in the title. I'm trying to learn exactly how C++/CLI works, but can't find succinct, exact and accurate descriptions online from the searching that I have done. So I ask here. Could you tell me the pitfalls and features of C++/CLI? Assume I know all of C# and start from there. I'm not an expert in C++, so some of my questions' answers might be "just like C++", but could say that I am at C#. I would like to know things like: Converting C++ pointers to CLI pointers, Any differences in passing by value/doubly indirect pointers/CLI pointers from C#/C++ and what is 'recommended'. How do gcnew, __gc, __nogc work with Polymorphism Structs Inner classes Interfaces The "fixed" keyword; does that exist? Compiling DLLs loaded into the kernel with C++/CLI possible? Loaded as device drivers? Invoked by the kernel? What does this mean anyway (i.e. to load something into the kernel exactly; how do I know if it is?)? L"my string" versus "my string"? wchar_t? How many types of chars are there? Are we safe in treating chars as uint32s or what should one treat them as to guarantee language indifference in code? Finalizers (~ClassName() {}) are discouraged in C# because there are no garantuees they will run deterministically, but since in C++ I have to use "delete" or use copy-c'tors as to stack allocate memory, what are the recommendations between C#/C++ interactions? What are the pitfalls when using reflection in C++/CLI? How well does C++/CLI work with the IDisposable pattern and with SafeHandle, SafeHandleZeroOrMinusOneIsInvalid? I've read briefly about asynchronous exceptions when doing DMA-operations, what are these? Are there limitations you impose upon yourself when using C++ with CLI integration rather than just doing plain C++? Attributes in C++ similar to Attributes in C#? Can I use the full meta-programming patterns available in C++ through templates now and still have it compile like ordinary C++? Have you tried writing C++/CLI with boost? What are the optimal ways of interfacing the boost library with C++/CLI; can you give me an example of passing a lambda expression to an iterator/foldr function? What is the preferred way of exception handling? Can C++/CLI catch managed exceptions now? How well does dynamic IL generation work with C++/CLI? Does it run on Mono? Any other things I ought to know about?

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  • Succinct introduction to C++/CLI for C#/Haskell/F#/JS/C++/... programmer

    - by Henrik
    Hello everybody, I'm trying to write integrations with the operating system and with things like active directory and Ocropus. I know a bunch of programming languages, including those listed in the title. I'm trying to learn exactly how C++/CLI works, but can't find succinct, exact and accurate descriptions online from the searching that I have done. So I ask here. Could you tell me the pitfalls and features of C++/CLI? Assume I know all of C# and start from there. I'm not an expert in C++, so some of my questions' answers might be "just like C++", but could say that I am at C#. I would like to know things like: Converting C++ pointers to CLI pointers, Any differences in passing by value/doubly indirect pointers/CLI pointers from C#/C++ and what is 'recommended'. How do gcnew, __gc, __nogc work with Polymorphism Structs Inner classes Interfaces The "fixed" keyword; does that exist? Compiling DLLs loaded into the kernel with C++/CLI possible? Loaded as device drivers? Invoked by the kernel? What does this mean anyway (i.e. to load something into the kernel exactly; how do I know if it is?)? L"my string" versus "my string"? wchar_t? How many types of chars are there? Are we safe in treating chars as uint32s or what should one treat them as to guarantee language indifference in code? Finalizers (~ClassName() {}) are discouraged in C# because there are no garantuees they will run deterministically, but since in C++ I have to use "delete" or use copy-c'tors as to stack allocate memory, what are the recommendations between C#/C++ interactions? What are the pitfalls when using reflection in C++/CLI? How well does C++/CLI work with the IDisposable pattern and with SafeHandle, SafeHandleZeroOrMinusOneIsInvalid? I've read briefly about asynchronous exceptions when doing DMA-operations, what are these? Are there limitations you impose upon yourself when using C++ with CLI integration rather than just doing plain C++? Attributes in C++ similar to Attributes in C#? Can I use the full meta-programming patterns available in C++ through templates now and still have it compile like ordinary C++? Have you tried writing C++/CLI with boost? What are the optimal ways of interfacing the boost library with C++/CLI; can you give me an example of passing a lambda expression to an iterator/foldr function? What is the preferred way of exception handling? Can C++/CLI catch managed exceptions now? How well does dynamic IL generation work with C++/CLI? Does it run on Mono? Any other things I ought to know about?

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  • RegEx strip html tags problem

    - by Aleksandar Mirilovic
    Hi, I've tried to strip html tags using regex replace with pattern "<[^]*" from word generated html that looks like this: <html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:st1="urn:schemas-microsoft-com:office:smarttags" xmlns="http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv=Content-Type content="text/html; charset=iso-8859-2"> <meta name=Generator content="Microsoft Word 11 (filtered medium)"> <!--[if !mso]> <style> v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} </style> <![endif]--><o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place" downloadurl="http://www.5iantlavalamp.com/"/> <!--[if !mso]> <style> st1\:*{behavior:url(#default#ieooui) } </style> <![endif]--> <style> <!-- /* Font Definitions / @font-face {font-family:Tahoma; panose-1:2 11 6 4 3 5 4 4 2 4;} / Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0in; margin-bottom:.0001pt; font-size:12.0pt; font-family:"Times New Roman";} a:link, span.MsoHyperlink {color:blue; text-decoration:underline;} a:visited, span.MsoHyperlinkFollowed {color:purple; text-decoration:underline;} span.EmailStyle17 {mso-style-type:personal; font-family:Arial; color:windowtext;} span.EmailStyle18 {mso-style-type:personal-reply; font-family:Arial; color:navy;} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in;} div.Section1 {page:Section1;} --> </style> </head> Everything works fine except for the bolded lines above, anybody got ideas how to match the them to? Thanks, Aleksandar

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  • Regex slow on Windows Server 2008

    - by pjmyburg
    Hi I have a situation where my regular expressions compile extremely slowly on Windows Server 2008. I wrote a small console application to highlight this issue. The app generates its own input and builds up a Regex from words in an XML file. I built a release version of this app and ran it both on my personal laptop (running XP) and the Windows 2008 server. The regular expression took 0.21 seconds to compile on my laptop, but 23 seconds to compile on the server. Any ideas what could be causing this? The problem is only on first use of the Regex (when it is first compiled - thereafter it is fine) I have also found another problem - when using \s+ in the regular expression on the same Windows 2008 server, the memory balloons (uses 4GB+) and the compilation of the Regex never finishes. Is there a known issue with Regex and 64 bit .net? Is there a fix/patch available for this? I cannot really find any info on the net, but I have found a few articles about this same issues in Framework 2.0 - surely this has been fixed by now? More info: The server is running the 64 bit version of the .net framework (3.5 SP1) and on my laptop I have Visual Studio 2008 and the 3.5 framework installed. The regular expression is of the following pattern: ^word$|^word$|^word$ and is constructed with the following flags: RegexOptions.IgnoreCase | RegexOptions.Compiled Edit: Here is a code snippet: StringBuilder regexString = new StringBuilder(); if (!String.IsNullOrEmpty(fileLocation)) { XmlTextReader textReader = new XmlTextReader(fileLocation); textReader.Read(); while (textReader.Read()) { textReader.MoveToElement(); if (textReader.Name == "word") { regexString.Append("^" + textReader.GetAttribute(0) + "$|"); } } ProfanityFilter = new Regex(regexString.ToString(0, regexString.Length - 1), RegexOptions.IgnoreCase | RegexOptions.Compiled); } DateTime time = DateTime.Now; Console.WriteLine("\nIsProfane:\n" + ProfanityFilter.IsMatch("test")); Console.WriteLine("\nTime: " + (DateTime.Now - time).TotalSeconds); Console.ReadKey(); This results in a time of 0.21 seconds on my laptop and 23 seconds on the 2008 server. The XML file consists of 168 words in the following format: <word text="test" />

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  • imagick showing script url instead of image

    - by Raz
    Hi, currently i'm trying to use imagick to generate some images without saving them on the server and then outputting to the browser, my method of choice was image magic with the imagick extension for php. I read the documentation, and i'm sure the package is installed on my machine (windows xp, with xampp). the class is installed imagick module enabled imagick module version 2.0.0-alpha imagick classes Imagick, ImagickDraw, ImagickPixel, ImagickPixelIterator ImageMagick version ImageMagick 6.3.3 04/21/07 Q16 http://www.imagemagick.org ImageMagick release date 04/21/07 ImageMagick Number of supported formats: 164 ImageMagick Supported formats A, ART, AVI, AVS, B, BIE, BMP, BMP2, BMP3, C, CACHE, CAPTION, CIN, CIP, CLIP, CLIPBOARD, CMYK, CMYKA, CUR, CUT, DCM, DCX, DFONT, DPS, DPX, EMF, EPDF, EPI, EPS, EPS2, EPS3, EPSF, EPSI, EPT, EPT2, EPT3, FAX, FITS, FRACTAL, FTS, G, G3, GIF, GIF87, GRADIENT, GRAY, HISTOGRAM, HTM, HTML, ICB, ICO, ICON, INFO, JBG, JBIG, JNG, JP2, JPC, JPEG, JPG, JPX, K, LABEL, M, M2V, MAP, MAT, MATTE, MIFF, MNG, MONO, MPC, MPEG, MPG, MSL, MSVG, MTV, MVG, NULL, O, OTB, OTF, PAL, PALM, PAM, PATTERN, PBM, PCD, PCDS, PCL, PCT, PCX, PDB, PDF, PFA, PFB, PGM, PGX, PICON, PICT, PIX, PJPEG, PLASMA, PNG, PNG24, PNG32, PNG8, PNM, PPM, PREVIEW, PS, PS2, PS3, PSD, PTIF, PWP, R, RAS, RGB, RGBA, RGBO, RLA, RLE, SCR, SCT, SFW, SGI, SHTML, STEGANO, SUN, SVG, SVGZ, TEXT, TGA, THUMBNAIL, TIFF, TILE, TIM, TTC, TTF, TXT, UIL, UYVY, VDA, VICAR, VID, VIFF, VST, WBMP, WMF, WMFWIN32, WMZ, WPG, X, XBM, XC, XCF, XPM, XV, XWD, Y, YCbCr, YCbCrA, YUV this is from the phpinfo so i know i have it installed, the thing is when i try to generate an image and save it, it works flawlessly, but when i try to output the image directly, i get the script url as an image $draw = new ImagickDraw(); $draw->setFont('AnkeCalligraph.TTF'); $draw->setFontSize(52); $draw->annotation(110, 110, "Hello World!"); $draw->annotation(50, 220, "Hello World!"); $canvas = new Imagick('./pictures/test_live.PNG'); $canvas->drawImage($draw); $canvas->setImageFormat('png'); header("Content-Type: image/png"); echo $canvas; this is the code used. if i use writeimage, then the file on the server is created with no problems. does anyone have any ideas what i'm doing wrong ?

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  • Looking for efficient scaling patterns for Silverlight application with distributed text-file data s

    - by Edward Tanguay
    I'm designing a Silverlight software solution for students and teachers to record flashcards, e.g. words and phrases that students find while reading and errors that teachers notice while teaching. Requirements are: each person publishes his own flashcards in a file on a web server, e.g. http://:www.mywebserver.com/flashcards.txt other people subscribe to that person's flashcards by using a Silverlight flashcard reader that I have developed and entering the URLs of flashcard files they want to subscribe to, URLs and imported flashcards being saved in IsolatedStorage the flashcards.txt file has the following simple format: title, then blocks of question/answers: Jim Smith's flashcards from English class 53-222, winter semester 2009 ==fla Das kann nicht sein. That can't be. ==fla Es sei denn, er kommt nicht. Unless he doesn't come. The user then makes public the URL to his flashcard file and other readers begin reading in his flashcards. In order to lower the bar for non-technical users to contribute, it will even be possible for them to save this text in a Google Document, which they publish and distribute the URL. The flashcard readers will then recognize it is a google document and perform the necessary screen scraping to get at the raw text. I have two technical questions about this approach: What is a best way to plan now for scalability issues: e.g. if your reader is subscribed to 10 flashcard files that are each 200K, it will have to download 2MB of text just to find out if any new flashcards are available. Or can I somehow accurately and consistently get at the last update date/time of text files on servers and published google docs? Each reader will have the ability to allow the person to test himself on imported flashcards and add meta information to them, e.g. categorize them, edit them, etc. This information will be stored in IsolatedStorage along with the important flashcards themselves. What is a good pattern to allow these readers to share and synchronize this meta data, e.g. so when you are looking at a flashcard you can see that 5 other people have made corrections to it. The best solution I can think of now is that the Silverlight readers will have to republish their data to a central database, but then there is the problem of uniquely identifying each flashcard, the best approach seems to be URL + position-in-file, or even better URL + original text of both question and answer fields, but both of these have their obvious drawbacks. The main requirement is that the bar for participation is kept as low as possible, i.e. type text in a google document, publish it, distribute the URL, and you're publishing within the flashcard community. So I want to come up with the most efficient technical solutions in order to compensate for the lack of database, lack of unique ids, etc. For those who have designed or developed similar non-traditional, distributed database projects like this, what advice, experience or best-practice tips you can share on the above two points?

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  • How do I create a partial function with generics in scala?

    - by Matteo Caprari
    Hello. I'm trying to write a performance measurements library for Scala. My idea is to transparently 'mark' sections so that the execution time can be collected. Unfortunately I wasn't able to bend the compiler to my will. An admittedly contrived example of what I have in mind: // generate a timing function val myTimer = mkTimer('myTimer) // see how the timing function returns the right type depending on the // type of the function it is passed to it val act = actor { loop { receive { case 'Int => val calc = myTimer { (1 to 100000).sum } val result = calc + 10 // calc must be Int self reply (result) case 'String => val calc = myTimer { (1 to 100000).mkString } val result = calc + " String" // calc must be String self reply (result) } Now, this is the farthest I got: trait Timing { def time[T <: Any](name: Symbol)(op: => T) :T = { val start = System.nanoTime val result = op val elapsed = System.nanoTime - start println(name + ": " + elapsed) result } def mkTimer[T <: Any](name: Symbol) : (() => T) => () => T = { type c = () => T time(name)(_ : c) } } Using the time function directly works and the compiler correctly uses the return type of the anonymous function to type the 'time' function: val bigString = time('timerBigString) { (1 to 100000).mkString("-") } println (bigString) Great as it seems, this pattern has a number of shortcomings: forces the user to reuse the same symbol at each invocation makes it more difficult to do more advanced stuff like predefined project-level timers does not allow the library to initialize once a data structure for 'timerBigString So here it comes mkTimer, that would allow me to partially apply the time function and reuse it. I use mkTimer like this: val myTimer = mkTimer('aTimer) val myString= myTimer { (1 to 100000).mkString("-") } println (myString) But I get a compiler error: error: type mismatch; found : String required: () => Nothing (1 to 100000).mkString("-") I get the same error if I inline the currying: val timerBigString = time('timerBigString) _ val bigString = timerBigString { (1 to 100000).mkString("-") } println (bigString) This works if I do val timerBigString = time('timerBigString) (_: String), but this is not what I want. I'd like to defer typing of the partially applied function until application. I conclude that the compiler is deciding the return type of the partial function when I first create it, chosing "Nothing" because it can't make a better informed choice. So I guess what I'm looking for is a sort of late-binding of the partially applied function. Is there any way to do this? Or maybe is there a completely different path I could follow? Well, thanks for reading this far -teo

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  • With sqlalchemy how to dynamically bind to database engine on a per-request basis

    - by Peter Hansen
    I have a Pylons-based web application which connects via Sqlalchemy (v0.5) to a Postgres database. For security, rather than follow the typical pattern of simple web apps (as seen in just about all tutorials), I'm not using a generic Postgres user (e.g. "webapp") but am requiring that users enter their own Postgres userid and password, and am using that to establish the connection. That means we get the full benefit of Postgres security. Complicating things still further, there are two separate databases to connect to. Although they're currently in the same Postgres cluster, they need to be able to move to separate hosts at a later date. We're using sqlalchemy's declarative package, though I can't see that this has any bearing on the matter. Most examples of sqlalchemy show trivial approaches such as setting up the Metadata once, at application startup, with a generic database userid and password, which is used through the web application. This is usually done with Metadata.bind = create_engine(), sometimes even at module-level in the database model files. My question is, how can we defer establishing the connections until the user has logged in, and then (of course) re-use those connections, or re-establish them using the same credentials, for each subsequent request. We have this working -- we think -- but I'm not only not certain of the safety of it, I also think it looks incredibly heavy-weight for the situation. Inside the __call__ method of the BaseController we retrieve the userid and password from the web session, call sqlalchemy create_engine() once for each database, then call a routine which calls Session.bind_mapper() repeatedly, once for each table that may be referenced on each of those connections, even though any given request usually references only one or two tables. It looks something like this: # in lib/base.py on the BaseController class def __call__(self, environ, start_response): # note: web session contains {'username': XXX, 'password': YYY} url1 = 'postgres://%(username)s:%(password)s@server1/finance' % session url2 = 'postgres://%(username)s:%(password)s@server2/staff' % session finance = create_engine(url1) staff = create_engine(url2) db_configure(staff, finance) # see below ... etc # in another file Session = scoped_session(sessionmaker()) def db_configure(staff, finance): s = Session() from db.finance import Employee, Customer, Invoice for c in [ Employee, Customer, Invoice, ]: s.bind_mapper(c, finance) from db.staff import Project, Hour for c in [ Project, Hour, ]: s.bind_mapper(c, staff) s.close() # prevents leaking connections between sessions? So the create_engine() calls occur on every request... I can see that being needed, and the Connection Pool probably caches them and does things sensibly. But calling Session.bind_mapper() once for each table, on every request? Seems like there has to be a better way. Obviously, since a desire for strong security underlies all this, we don't want any chance that a connection established for a high-security user will inadvertently be used in a later request by a low-security user.

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  • redoing object model construction to fit with asynchronous data fetching

    - by Andrew Patterson
    I have a modeled a set of objects that correspond with some real world concepts. TradeDrug, GenericDrug, TradePackage, DrugForm Underlying the simple object model I am trying to provide is a complex medical terminology that uses numeric codes to represent relationships and concepts, all accessible via a REST service - I am trying to hide away some of that complexity with an object wrapper. To give a concrete example I can call TradeDrug d = Searcher.FindTradeDrug("Zoloft") or TradeDrug d = new TradeDrug(34) where 34 might be the code for Zoloft. This will consult a remote server to find out some details about Zoloft. I might then call GenericDrug generic = d.EquivalentGeneric() System.Out.WriteLine(generic.ActiveIngredient().Name) in order to get back the generic drug sertraline as an object (again via a background REST call to the remote server that has all these drug details), and then perhaps find its ingredient. This model works fine and is being used in some applications that involve data processing. Recently however I wanted to do a silverlight application that used and displayed these objects. The silverlight environment only allows asynchronous REST/web service calls. I have no problems with how to make the asychhronous calls - but I am having trouble with what the design should be for my object construction. Currently the constructors for my objects do some REST calls sychronously. public TradeDrug(int code) { form = restclient.FetchForm(code) name = restclient.FetchName(code) etc.. } If I have to use async 'events' or 'actions' in order to use the Silverlight web client (I know silverlight can be forced to be a synchronous client but I am interested in asychronous approaches), does anyone have an guidance or best practice for how to structure my objects. I can pass in an action callback to the constructor public TradeDrug(int code, Action<TradeDrug> constructCompleted) { } but this then allows the user to have a TradeDrug object instance before what I want to construct is actually finished. It also doesn't support an 'event' async pattern because the object doesn't exist to add the event to until it is constructed. Extending that approach might be a factory object that itself has an asynchronous interface to objects factory.GetTradeDrugAsync(code, completedaction) or with a GetTradeDrugCompleted event? Does anyone have any recommendations?

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  • How to efficiently save changes made in UI/main thread with Core Data?

    - by Jaanus
    So, there have been several posts here about importing and saving data from an external data source into Core Data. Apple documents a reasonable pattern for this: "import and save on background thread, merge saved objects to main thread." All fine and good. I have a related but different problem: the user is modifying data in the UI and main thread, and thus modifies state of some objects in the managed object context (MOC). I would like to save these changes from time to time. What is a good way to do that? Now, you could say that I could do the same: create a background thread with its own MOC and pass the changed objectID-s there. The catch-22 for me with this is that an object's ID changes when it is saved, and I cannot guarantee the order of things happening. I may end up passing a different objectID into the background thread for the same object, based on whether the object has been previously saved or not, and I don't know if Core Data can resolve this and see that different objectID-s are pointing to the same object and not create duplicates for me. (I could test this, but I'm lazywebbing with this question first.) One thought I had: I could always do MOC saves on a background thread, and queue them up with operationqueue, so that there is always only one save in progress. I would not create a new MOC, I would just use the same MOC as in main thread. Now, this is not thread safe and when someone modifies the MOC in main thread while it is being saved in background thread, the results will probably be catastrophic. But, minus the thread safety, you can see what kind of solution I'd wish for. To be clear, the problem I need to fix is that if I just do the save in main thread, it blocks the UI for an unacceptably long period of time, I want to move the save to background thread. So, questions: what about the reasoning of an object ID changing during saving, and Core Data being able to resolve them to the same object? Would this be the right way of addressing this problem? any other good ways of doing this?

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