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• Is functional GUI programming possible?

  - by eman

  I've recently caught the FP bug (trying to learn Haskell), and I've been really impressed with what I've seen so far (first-class functions, lazy evaluation, and all the other goodies). I'm no expert yet, but I've already begun to find it easier to reason "functionally" than imperatively for basic algorithms (and I'm having trouble going back where I have to). The one area where current FP seems to fall flat, however, is GUI programming. The Haskell approach seems to be to just wrap imperative GUI toolkits (such as GTK+ or wxWidgets) and to use "do" blocks to simulate an imperative style. I haven't used F#, but my understanding is that it does something similar using OOP with .NET classes. Obviously, there's a good reason for this--current GUI programming is all about IO and side effects, so purely functional programming isn't possible with most current frameworks. My question is, is it possible to have a functional approach to GUI programming? I'm having trouble imagining what this would look like in practice. Does anyone know of any frameworks, experimental or otherwise, that try this sort of thing (or even any frameworks that are designed from the ground up for a functional language)? Or is the solution to just use a hybrid approach, with OOP for the GUI parts and FP for the logic? (I'm just asking out of curiosity--I'd love to think that FP is "the future," but GUI programming seems like a pretty large hole to fill.)

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• partial entity loading and management in silverlight / wcf ria

  - by Dan Wray

  I have a Silverlight 4 app which pulls entities down from a database using WCF RIA services. These data objects are fairly simple, just a few fields but one of those fields contains binary data of an arbitrarily size. The application needs access to this data basically asap after a user has logged in, to display in a list, enable selection etc. My problem is because of the size of this data, the load times are not acceptable and can approach the default timeout of the RIA service. I'd like to somehow partially load the objects into my local data context so that I have the IDs, names etc but not the binary data. I could then at a later point (ie when it's actually needed) populate the binary fields of those objects I need to display. Any suggestions on how to accomplish this would be welcome. Another approach which has occurred to me whilst writing this question (how often does that happen?!) is that I could move the binary data into a seperate database table joined to the original record 1:1 which would allow me to make use of RIA's lazy loading on that binary data. again.. comments welcome! Thanks.

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• Valueurl Binding On Large Arrays Causes Sluggish User Interface

  - by Hooligancat

  I have a large data set (some 3500 objects) that returns from a remote server via HTTP. Currently the data is being presented in an NSCollectionView. One aspect of the data is a path pack to the server for a small image that represents the data (think thumbnail for simplicity). Bindings works fantastically for the data that is already returned, and binding the image via a valueurl binding is easy to do. However, the user interface is very sluggish when scrolling through the data set - which makes me think that the NSCollectionView is retrieving all the image data instead of just the image data used to display the currently viewable images. I was under the impression that Cocoa controls were smart enough to only retrieve data for the information that is actually being output to the user interface through lazy loading. This certainly seems to be the case with NSTableView - but I could be misguided on this thought. Should valueurl binding act lazily and, moreover, should it act lazily in an NSCollectionView? I could create a caching mechanism (in fact I already have such a thing in place for another application - see my post here if you are interested http://stackoverflow.com/questions/1740209/populating-nsimage-with-data-from-an-asynchronous-nsurlconnection) but I really don't want to go this route if I don't have to for this specific implementation as the user could potentially change data sets often and may only want small sub-sets of the data. Any suggested approaches? Thanks!

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• How to delay static initialization within a property

  - by Mystagogue

  I've made a class that is a cross between a singleton (fifth version) and a (dependency injectable) factory. Call this a "Mono-Factory?" It works, and looks like this: public static class Context { public static BaseLogger LogObject = null; public static BaseLogger Log { get { return LogFactory.instance; } } class LogFactory { static LogFactory() { } internal static readonly BaseLogger instance = LogObject ?? new BaseLogger(null, null, null); } } //USAGE EXAMPLE: //Optional initialization, done once when the application launches... Context.LogObject = new ConLogger(); //Example invocation used throughout the rest of code... Context.Log.Write("hello", LogSeverity.Information); The idea is for the mono-factory could be expanded to handle more than one item (e.g. more than a logger). But I would have liked to have made the mono-factory look like this: public static class Context { private static BaseLogger LogObject = null; public static BaseLogger Log { get { return LogFactory.instance; } set { LogObject = value; } } class LogFactory { static LogFactory() { } internal static readonly BaseLogger instance = LogObject ?? new BaseLogger(null, null, null); } } The above does not work, because the moment the Log property is touched (by a setter invocation) it causes the code path related to the getter to be executed...which means the internal LogFactory "instance" data is always set to the BaseLogger (setting the "LogObject" is always too late!). So is there a decoration or other trick I can use that would cause the "get" path of the Log property to be lazy while the set path is being invoked?

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• Web Hosting URL Length Limit?

  - by Isaac Waller

  Hello, I am designing a web application which is a tie in to my iPhone application. It sends massively large URLs to the web server (15000 about.) I was using NearlyFreeSpeech.net, but they only support URLS up to 2000 characters. I was wondering if anybody knows of web hosting that will support really large URLs? Thanks, Isaac Edit: My program needs to open a picture in Safari. I could do this 2 ways: send it base64 encoded in the URL and just echo the query parameters. first POST it to the server in my application, then the server would send back a unique ID after storing the photo in a database, which I would append to a URL which I would open in Safari which retrieved the photo from the database and delete it from the database. You see, I am lazy, and I know Mobile Safari can support URI's up to 80 000 characters, so I think this is a OK way to do it. If there is something really wrong with this, please tell me. Edit: I ended up doing it the proper POST way. Thanks.

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• [hibernate - jpa] @CollectionOfElements without create the apposite table

  - by blow

  Hi all. I have this: Municipality class @Entity public class Municipality implements Serializable { @Id @GeneratedValue(strategy=GenerationType.IDENTITY) private Long id; private String country; private String province; private String name; @Column(name="cod_catasto") private String codCatastale; private String cap; @CollectionOfElements private List<Address> addressList; public Municipality() { } ... Address class @Embeddable public class Address implements Serializable { @ManyToOne(fetch=FetchType.LAZY) @Cascade(CascadeType.SAVE_UPDATE) private Municipality municipality; @Column(length=45) private String address; public Address() { } ... Address is embedded in another class Person. When i save an instance of Person, hibernate create 3 tables: PERSON, MUNICIPALITY and MUNICIPALITY_ADDRESSLIST. MUNICIPALITY_ADDRESSLIST contains 2 fields: MUNICIPALITY_ID (FK) and STREET. I don't want this table, i only want the ID of table MUNICIPALITY into table PERSON(that embeds Address), what should i do? I tried to add @JoinTable in Municipality entity like this: @CollectionOfElements @JoinTable(name="person") private List<Address> addressList; It partially worked, but i cant choose the column name of table PERSON that contains ID of the table MUNICIPALITY, it is, by hibernate choose, simply "MUNICIPALITY_ID"... Thbaks.

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• how do I paste text to a line by line text filter like awk, without having stdin echo to the screen?

  - by Barton Chittenden

  I have a text in an email on a windows box that looks something like this: 100 some random text 101 some more random text 102 lots of random text, all different 103 lots of random text, all the same I want to extract the numbers, i.e. the first word on each line. I've got a terminal running bash open on my Linux box... If these were in a text file, I would do this: awk '{print $1}' mytextfile.txt I would like to paste these in, and get my numbers out, without creating a temp file. my naive first attempt looked like this: $ awk '{print $1}' 100 some random text 100 101 some more random text 101 102 lots of random text, all different 103 lots of random text, all the same 102 103 The buffering of stdin and stdout make a hash of this. I wouldn't mind if stdin all printed first, followed by all of stdout; this is what would happen if I were to paste into 'sort' for example, but awk and sed are a different story. a little more thought gave me this: open two terminals. Create a fifo file. Read from the fifo on one terminal, write to it on another. This does in fact work, but I'm lazy. I don't want to open a second terminal. Is there a way in the shell that I can hide the text echoed to the screen when I'm passing it in to a pipe, so that I paste this: 100 some random text 101 some more random text 102 lots of random text, all different 103 lots of random text, all the same but see this? $ awk '{print $1}' 100 101 102 103

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• Aggregate Pattern and Performance Issues

  - by Mosh

  Hello, I have read about the Aggregate Pattern but I'm confused about something here. The pattern states that all the objects belonging to the aggregate should be accessed via the Aggregate Root, and not directly. And I'm assuming that is the reason why they say you should have a single Repository per Aggregate. But I think this adds a noticeable overhead to the application. For example, in a typical Web-based application, what if I want to get an object belonging to an aggregate (which is NOT the aggregate root)? I'll have to call Repository.GetAggregateRootObject(), which loads the aggregate root and all its child objects, and then iterate through the child objects to find the one I'm looking for. In other words, I'm loading lots of data and throwing them out except the particular object I'm looking for. Is there something I'm missing here? PS: I know some of you may suggest that we can improve performance with Lazy Loading. But that's not what I'm asking here... The aggregate pattern requires that all objects belonging to the aggregate be loaded together, so we can enforce business rules.

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• Why put a DAO layer over a persistence layer (like JDO or Hibernate)

  - by Todd Owen

  Data Access Objects (DAOs) are a common design pattern, and recommended by Sun. But the earliest examples of Java DAOs interacted directly with relational databases -- they were, in essence, doing object-relational mapping (ORM). Nowadays, I see DAOs on top of mature ORM frameworks like JDO and Hibernate, and I wonder if that is really a good idea. I am developing a web service using JDO as the persistence layer, and am considering whether or not to introduce DAOs. I foresee a problem when dealing with a particular class which contains a map of other objects: public class Book { // Book description in various languages, indexed by ISO language codes private Map<String,BookDescription> descriptions; } JDO is clever enough to map this to a foreign key constraint between the "BOOKS" and "BOOKDESCRIPTIONS" tables. It transparently loads the BookDescription objects (using lazy loading, I believe), and persists them when the Book object is persisted. If I was to introduce a "data access layer" and write a class like BookDao, and encapsulate all the JDO code within this, then wouldn't this JDO's transparent loading of the child objects be circumventing the data access layer? For consistency, shouldn't all the BookDescription objects be loaded and persisted via some BookDescriptionDao object (or BookDao.loadDescription method)? Yet refactoring in that way would make manipulating the model needlessly complicated. So my question is, what's wrong with calling JDO (or Hibernate, or whatever ORM you fancy) directly in the business layer? Its syntax is already quite concise, and it is datastore-agnostic. What is the advantage, if any, of encapsulating it in Data Access Objects?

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• response.Text is undefined when returning variable

  - by George

  Not sure if the problem is related to Ajax or something silly about JavaScript that I'm overlooking in general, but I have the following script where fox.html is just plain text that reads, "The quick brown fox jumped over the lazy dog." : function loadXMLDoc() { if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp=new XMLHttpRequest(); } else {// code for IE6, IE5 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xmlhttp.open("GET","fox.html",true); xmlhttp.send(); xmlhttp.onreadystatechange=function() { if (xmlhttp.readyState==4 && xmlhttp.status==200) { fox = xmlhttp.responseText; alert(fox); } } } onload = loadXMLDoc; The above script alerts the contents of fox.html onload just fine. However if I change the script so that: { fox = xmlhttp.responseText; alert(fox); } becomes: { fox = xmlhttp.responseText; return fox; } and alert(loadXMLDoc()); onload I get 'undefined'. I'm wondering why this is so.

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• ConcurrentLinkedQueue$Node remains in heap after remove()

  - by action8

  I have a multithreaded app writing and reading a ConcurrentLinkedQueue, which is conceptually used to back entries in a list/table. I originally used a ConcurrentHashMap for this, which worked well. A new requirement required tracking the order entries came in, so they could be removed in oldest first order, depending on some conditions. ConcurrentLinkedQueue appeared to be a good choice, and functionally it works well. A configurable amount of entries are held in memory, and when a new entry is offered when the limit is reached, the queue is searched in oldest-first order for one that can be removed. Certain entries are not to be removed by the system and wait for client interaction. What appears to be happening is I have an entry at the front of the queue that occurred, say 100K entries ago. The queue appears to have the limited number of configured entries (size() == 100), but when profiling, I found that there were ~100K ConcurrentLinkedQueue$Node objects in memory. This appears to be by design, just glancing at the source for ConcurrentLinkedQueue, a remove merely removes the reference to the object being stored but leaves the linked list in place for iteration. Finally my question: Is there a "better" lazy way to handle a collection of this nature? I love the speed of the ConcurrentLinkedQueue, I just cant afford the unbounded leak that appears to be possible in this case. If not, it seems like I'd have to create a second structure to track order and may have the same issues, plus a synchronization concern.

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• Subsonic, child records, and collections

  - by Dane

  Hi, I've been working with subsonic for a few weeks now, and it is working really well. However, I've just run into an issue with child objects with additional partial properties. Some of it is probably me just not understanding the .Net object lifecycle. I have an object - search. This has a few properties like permissions and stuff, and it links to a child table called search_options. In my Asp.Net app, it loops through these search options and creates controls. Then on postback, it grabs the values and assigns it back to a "value" property on the search_option. This value property is a simple string that's defined in a partial class. I then want to create a method on the search object, called PerformSearch. This then loops through the child search_options, and performs a custom query based on the "value" property. However, even though I assign the "value" property to the child search_option, when I access it later via the search.search_options collection, it is null. I'm guessing that maybe because it's accessing it in two different places, it performs another lazy load from the DB and the value is lost? Is there a way to tell the class that it's already loaded or something? or a way to access it so it's not reloaded from the DB? Code is below (shitty pseudocode, not full version) : ASP.Net page, loading back the values from postback : dim obj_search as search = new subsonic.query.select().......' retrieves the search object for each opt as search_option in obj_search.search_options opt.Value = Ctype(FindControl("search_option_" + opt.search_option_id),Textbox).Text debug.print(opt.Value) ' value is correct next for each opt as search_option in obj_search.search_options debug.print(opt.Value) 'this is nothing next Now, the partial class : public partial class search_option private m_value as string public property Value() as string get return m_value end get set( byval value as string) m_value = value end set end property end class

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• .Net Entity objectcontext thread error

  - by Chris Klepeis

  I have an n-layered asp.net application which returns an object from my DAL to the BAL like so: public IEnumerable<SourceKey> Get(SourceKey sk) { var query = from SourceKey in _dataContext.SourceKeys select SourceKey; if (sk.sourceKey1 != null) { query = from SourceKey in query where SourceKey.sourceKey1 == sk.sourceKey1 select SourceKey; } return query.AsEnumerable(); } This result passes through my business layer and hits the UI layer to display to the end users. I do not lazy load to prevent query execution in other layers of my application. I created another function in my DAL to delete objects: public void Delete(SourceKey sk) { try { _dataContext.DeleteObject(sk); _dataContext.SaveChanges(); } catch (Exception ex) { Debug.WriteLine(ex.Message + " " + ex.StackTrace + " " + ex.InnerException); } } When I try to call "Delete" after calling the "Get" function, I receive this error: New transaction is not allowed because there are other threads running in the session This is an ASP.Net app. My DAL contains an entity data model. The class in which I have the above functions share the same _dataContext, which is instantiated in my constructor. My guess is that the reader is still open from the "Get" function and was not closed. How can I close it?

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• C# POCO T4 template, generate interfaces?

  - by Jonna

  Does anyone know of any tweaked version of POCO T4 template that generates interfaces along with classes? i.e. if I have Movie and Actor entities in .edmx file, I need to get the following classes and interfaces. interface IMovie { string MovieName { get; set; } ICollection<IActor> Actors { get; set; } //instead of ICollection<Actor> } class Movie : IMovie { string MovieName { get; set; } ICollection<IActor> Actors { get; set; } //instead of ICollection<Actor> } interface IActor { string ActorName { get; set; } } class Actor { string ActorName { get; set; } } Also, just in case I write my own entities, does POCO proxies(I need them for lazy loading) work with the interface declarations as shown above?

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• Why delete-orphan needs "cascade all" to run in JPA/Hibernate ?

  - by Jerome C.

  Hello, I try to map a one-to-many relation with cascade "remove" (jpa) and "delete-orphan", because I don't want children to be saved or persist when the parent is saved or persist (security reasons due to client to server (GWT, Gilead)) But this configuration doesn't work. When I try with cascade "all", it runs. Why the delete-orphan option needs a cascade "all" to run ? here is the code (without id or other fields for simplicity, the class Thread defines a simple many-to-one property without cascade): when using the removeThread function in a transactional function, it does not run but if I edit cascade.Remove into cascade.All, it runs. @Entity public class Forum { private List<ForumThread> threads; /** * @return the topics */ @OneToMany(mappedBy = "parent", cascade = CascadeType.REMOVE, fetch = FetchType.LAZY) @Cascade(org.hibernate.annotations.CascadeType.DELETE_ORPHAN) public List<ForumThread> getThreads() { return threads; } /** * @param topics the topics to set */ public void setThreads(List<ForumThread> threads) { this.threads = threads; } public void addThread(ForumThread thread) { getThreads().add(thread); thread.setParent(this); } public void removeThread(ForumThread thread) { getThreads().remove(thread); } } thanks.

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• 1k of Program Space, 64 bytes of RAM. Is assembly an absolute must?

  - by Earlz

  (If your lazy see bottom for TL;DR) Hello, I am planning to build a new (prototype) project dealing with physical computing. Basically, I have wires. These wires all need to have their voltage read at the same time. More than a few hundred microseconds difference between the readings of each wire will completely screw it up. The Arduino takes about 114 microseconds. So the most I could read is 2 or 3 wires before the latency would skew the accuracy of the readings. So my plan is to have an Arduino as the "master" of an array of ATTinys. The arduino is pretty cramped for space, but it's a massive playground compared to the tinys. An ATTiny13A has 1k of flash ROM(program space), 64 bytes of RAM, and 64 bytes of (not-durable and slow) EEPROM. (I'm choosing this for price as well as size) The ATTinys in my system will not do much. Basically, all they will do is wait for a signal from the Master, and then read the voltage of 1 or 2 wires and store it in RAM(or possibly EEPROM if it's that cramped). And then send it to the Master using only 1 wire for data.(no room for more than that!). So far then, all I should have to do is implement trivial voltage reading code (using built in ADC). But this communication bit I'm worried about. Do you think a communication protocol(using just 1 wire!) could even be implemented in such constraints? TL;DR: In less than 1k of program space and 64 bytes of RAM(and 64 bytes of EEPROM) do you think it is possible to implement a 1 wire communication protocol? Would I need to drop to assembly to make it fit? I know that currently my Arduino programs linking to the Wiring library are over 8k, so I'm a bit concerned.

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• tips for fixing bad coding/dev habits ?

  - by dfafa

  i want to become a better coder....so i have decided to sign up for computing science program...maybe a formal education can assist me. i started working on smaller projects to learn but currently i have really bad coding/dev habits which is hindering my productivity as the codebase increases.... i have highlighted them and perhaps someone could make suggestions (or redirect to resources) or a more efficient method. most stuff that i made in the past were web apps. i usually develop with putty + nano...i just love the minimalist feel i use winscp and develop directly on my private web server...too lazy to do it on localhost and upload it later. i dont use subversion control...which one do i need ? sometimes ctrl +z doesn't work well. when i run out of ideas for naming variable, i use swear words instead. i swear a lot when i get stuck....how to deal with anger issue ? my codes look ugly with comments everywhere. would rather use procedural coding finds "thinking" in OO difficult and time consuming i "write first think later". refactors code only if i am getting paid for it. dislikes configuring linux distro, Apache, MySQL, scaling, designing graphics and layouts. does not like writing tests likes working alone. does not like sharing codes. has an econ degree dislikes reading other people's code would rather write it on my own it seems my only true desire is to translate my ideas to a working prototype as fast as possible....it seems like i am very uninterested in the other details...could it be that i am not cut out to be a coder after all ? is going back to study comp sci a bad idea ?

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• Does O2Micro Oz776 Smartcard reader support SLE5528 cards?

  - by Proton

  Well, the title seems indicating I'm a lazy guy but it's not the truth... I'm messing with this weird circumstance a whole day. My laptop is a Dell Latitude D630 which has a Oz776 (usb idVendor == 0x0b97, idProduct == 0x7772) smartcard reader, but I'm not sure if it is functioning well. It can successfully recognize my Gemplus GPK4000 smartcard and my SIM card, but not SLE5528. This is my pcscd log when insert the GPK4000: 06039271 ifdhandler.c:1043:IFDHPowerICC() action: PowerUp, usb:0b97/7772:libhal:/org/freedesktop/Hal/devices/usb_device_b97_7772_noserial_if0 (lun: 0) 00000100 - 000000 62 00 00 00 00 00 14 01 00 00 00967744 <- 000000 80 0A 00 00 00 00 14 00 00 00 3B 27 00 80 65 A2 0C 01 01 37 00000048 ATR: 3B 27 00 80 65 A2 0C 01 01 37 00000013 atrhandler.c:102:ATRDecodeAtr() Conv: 01, Y1: 02, K: 07 00000011 atrhandler.c:120:ATRDecodeAtr() TA1: FFFFFFFF, TB1: 00, TC1: FFFFFFFF, TD1:FFFFFFFF 00000011 atrhandler.c:248:ATRDecodeAtr() CurrentProtocol: 1, AvailableProtocols: 1 00000062 eventhandler.c:429:EHStatusHandlerThread() Card inserted into O2 Micro Oz776 00 00 00000014 Card ATR: 3B 27 00 80 65 A2 0C 01 01 37 29016873 eventhandler.c:361:EHStatusHandlerThread() Card Removed From O2 Micro Oz776 00 00 This is the log when insert a SLE5528 card: 99999999 ifdhandler.c:1043:IFDHPowerICC() action: PowerUp, usb:0b97/7772:libhal:/org/freedesktop/Hal/devices/usb_device_b97_7772_noserial_if0 (lun: 0) 00000048 - 000000 62 00 00 00 00 00 11 01 00 00 ** Then it chokes here, when I remove the card, the log continues ** 04741980 <- 000000 80 00 00 00 00 00 11 42 FE 00 00000044 commands.c:225:CmdPowerOn Card absent or mute 00000017 ifdhandler.c:1096:IFDHPowerICC() PowerUp failed 00000082 eventhandler.c:429:EHStatusHandlerThread() Card inserted into O2 Micro Oz776 00 00 00000021 eventhandler.c:443:EHStatusHandlerThread() Error powering up card. 00402818 eventhandler.c:361:EHStatusHandlerThread() Card Removed From O2 Micro Oz776 00 00 I found that SLE5528 is ISO7816 compatible, and it should have ATR, but it just chokes at the PowerUp. When inserted any PVC card with no chip or AT24C01 card, it would not choke but report immediate PowerUp failure. When I tried it on Windows(Windows 7, "runas other user", smartcard login), it chokes too while PVC cards and AT24C01 report immediate failure.

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• Setting spring bean property value using ref-bean

  - by Apache Fan

  Hi, I am trying to set a property value using spring. <bean id="velocityPropsBean" class="com.test.CustomProperties" abstract="false" singleton="true" lazy-init="false" autowire="default" dependency-check="default"> <property name="properties"> <props> <prop key="resource.loader">file</prop> <prop key="file.resource.loader.cache">true</prop> <prop key="file.resource.loader.class">org.apache.velocity.runtime.resource.loader.FileResourceLoader</prop> <prop key="file.resource.loader.path">NEED TO INSERT VALUE AT STARTUP</prop> </props> </property> </bean> <bean id="velocityResourcePath" class="java.lang.String" factory-bean="velocityHelper" factory-method="getLoaderPath"/> Now what i need to do is insert the result from getLoaderPath into file.resource.loader.path. The value of getLoaderPath changes so it has to be loaded at server startup. Any thoughts how i can inset the velocityResourcePath value to the property?

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• Silverlight 3 data-binding child property doesn't update

  - by sonofpirate

  I have a Silverlight control that has my root ViewModel object as it's data source. The ViewModel exposes a list of Cards as well as a SelectedCard property which is bound to a drop-down list at the top of the view. I then have a form of sorts at the bottom that displays the properties of the SelectedCard. My XAML appears as (reduced for simplicity): <StackPanel Orientation="Vertical"> <ComboBox DisplayMemberPath="Name" ItemsSource="{Binding Path=Cards}" SelectedItem="{Binding Path=SelectedCard, Mode=TwoWay}" /> <TextBlock Text="{Binding Path=SelectedCard.Name}" /> <ListBox DisplayMemberPath="Name" ItemsSource="{Binding Path=SelectedCard.PendingTransactions}" /> </StackPanel> I would expect the TextBlock and ListBox to update whenever I select a new item in the ComboBox, but this is not the case. I'm sure it has to do with the fact that the TextBlock and ListBox are actually bound to properties of the SelectedCard so it is listening for property change notifications for the properties on that object. But, I would have thought that data-binding would be smart enough to recognize that the parent object in the binding expression had changed and update the entire binding. It bears noting that the PendingTransactions property (bound to the ListBox) is lazy-loaded. So, the first time I select an item in the ComboBox, I do make the async call and load the list and the UI updates to display the information corresponding to the selected item. However, when I reselect an item, the UI doesn't change! For example, if my original list contains three cards, I select the first card by default. Data-binding does attempt to access the PendingTransactions property on that Card object and updates the ListBox correctly. If I select the second card in the list, the same thing happens and I get the list of PendingTransactions for that card displayed. But, if I select the first card again, nothing changes in my UI! Setting a breakpoint, I am able to confirm that the SelectedCard property is being updated correctly. How can I make this work???

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• using EventToCommand & PassEventArgsToCommand :: how to get sender, or better metaphor?

  - by JoeBrockhaus

  The point of what I'm doing is that there are a lot of things that need to happen in the viewmodel, but when the view has been loaded, not on constructor. I could wire up event handlers and send messages, but that just seems kinda sloppy to me. I'm implementing a base view and base viewmodel where this logic is contained so all my views get it by default, hopefully. Perhaps I can't even get what I'm wanting: the sender. I just figured this is what RoutedEventArgs.OriginalSource was supposed to be? [Edit] In the meantime, I've hooked up an EventHandler in the xaml.cs, and sure enough, OriginalSource is null there as well. So I guess really I need to know if it's possible to get a reference to the view/sender in the Command as well? [/Edit] My implementation requires that a helper class to my viewmodels which is responsible for creating 'windows' knows of the 'host' control that all the windows get added to. i'm open to suggestions for accomplishing this outside the scope of using eventtocommand. :) (the code for Unloaded is the same) #region ViewLoadedCommand private RelayCommand<RoutedEventArgs> _viewLoadedCommand = null; /// <summary> /// Command to handle the control's Loaded event. /// </summary> public RelayCommand<RoutedEventArgs> ViewLoadedCommand { get { // lazy-instantiate the RelayCommand on first usage if (_viewLoadedCommand == null) { _viewLoadedCommand = new RelayCommand<RoutedEventArgs>( e => this.OnViewLoadedCommand(e)); } return _viewLoadedCommand; } } #endregion ViewLoadedCommand #region View EventHandlers protected virtual void OnViewLoadedCommand(RoutedEventArgs e) { EventHandler handler = ViewLoaded; if (handler != null) { handler(this, e); } } #endregion

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• Mac vs. Windows Browser Font Height Rendering Issue

  - by cdmckay

  I'm using a custom font and the @font-face tag. In Windows, everything looks great, regardless of whether it's Firefox, Chrome, or IE. On Mac, it's a different story. For some reason, the Mac font renderer thinks the font is a lot shorter than it is. For example, consider this test code (live example here): <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>Webble</title> <style type="text/css"> @font-face { font-family: "Bubbleboy 2"; src: url("bubbleboy-2.ttf") format('truetype'); } body { font-family: "Bubbleboy 2"; font-size: 30px; } div { background-color: maroon; color: yellow; height: 100px; line-height: 100px; } </style> </head> <body> <div>The quick brown fox jumped over the lazy dog.</div> </body> </html> Open it on Windows Firefox and on Mac Firefox. Use your mouse to select it. On Windows, you'll notice it fully selects the font. On Mac, it only selects about half the font. If you look at what it is selecting, you'll see that that part has been centered, instead of the full height of the font. Is there anyway to fix this rather large discrepancy?

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• Understanding Domain Driven Design

  - by Nihilist

  Hi I have been trying to understand DDD for few weeks now. Its very confusing. I dont understand how I organise my projects. I have lot of questions on UnitOfWork, Repository, Associations and the list goes on... Lets take a simple example. Album and Tracks. Album: AlbumId, Name, ListOf Tracks Tracks: TrackId, Name Question1: Should i expose Tracks as a IList/IEnumerabe property on Album ? If that how do i add an album ? OR should i expose a ReadOnlyCollection of Tracks and expose a AddTrack method? Question2: How do i load Tracks for Album [assuming lazy loading]? should the getter check for null and then use a repository to load the tracks if need be? Question3: How do we organise the assemblies. Like what does each assembly have? Model.dll - does it only have the domain entities? Where do the repositories go? Interfaces and implementations both. Can i define IAlbumRepository in Model.dll? Infrastructure.dll : what shold this have? Question4: Where is unit of work defined? How do repository and unit of work communicate? [ or should they ] for example. if i need to add multiple tracks to album, again should this be defined as AddTrack on Album OR should there a method in the repository? Regardless of where the method is, how do I implement unit of work here? Question5: Should the UI use Infrastructure..dll or should there be ServiceLayer? Do my quesitons make sense? Regards

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• conceptual question : what do performSelectorOnMainThread do?

  - by hib

  Hello all, I just come across this strange situation . I was using the technique of lazy image loading from apple examples . when I was used the class in my application it gave me topic to learn but don't what was actually happening there . So here goes the scenario : I think everybody has seen the apple lazytableimagesloading . I was reloading my table on finishing the parsing of data : - (void)didFinishParsing:(NSMutableArray *)appList { self.upcomingArray = [NSMutableArray arrayWithArray:loadedApps]; // we are finished with the queue and our ParseOperation [self.upcomingTableView reloadData]; self.queue = nil; // we are finished with the queue and our ParseOperation } but as a result the the connection was not starting and images were not loading . when I completely copy the lazyimageloading and I replaced the above code with the following code it works fine - (void)didFinishParsing:(NSMutableArray *)appList { [self performSelectorOnMainThread:@selector(handleLoadedApps:) withObject:appList waitUntilDone:NO]; self.queue = nil; // we are finished with the queue and our ParseOperation } So I want to know what is the concept behind this . Please let me know if you can not understand the question or details are not enough because I desperately want to know why it is like this ?

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• Good guidelines for developing an ecommerce application

  - by kaciula

  I'm making an ecommerce application on Android and, as it is my first serious project, I'm trying to figure out beforehand the best approach to do this. The application talks to a web service (magento api, meaning soap or xml rpc unfortunately) and gets all the content on the phone (product categories, product details, user credentials etc.). I think it should do lazy loading or something like that. So, I was thinking to keep the user credentials in a custom Object which will be kept in a SharedPreferences so that every Activity cand easily access it. I'll use a couple of ListViews to show the content and AsyncTask to fetch the data needed. Should I keep all the data in memory in objects or should I use some sort of cache or a local database? Also, I'm planning to use a HashMap with SoftReferences to hold the bitmaps I am downloading. But wouldn't this eat a lot of memory? How cand all the activities have access to all these objects (ecommerce basket etc.)? I'm thinking of passing them using Intents but this doesn't seem right to me. Can SharedPreferences be used for a lot of objects and are there any concurrency issues? Any pointers would be really appreciated. What are some good guidelines? What classes should I look into? Do you know of any resources on the Internet for me to check out?

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