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  • How to load entities into private collections using the entity framework

    - by Anton P
    I have a POCO domain model which is wired up to the entity framework using the new ObjectContext class. public class Product { private ICollection<Photo> _photos; public Product() { _photos = new Collection<Photo>(); } public int Id { get; set; } public string Name { get; set; } public virtual IEnumerable<Photo> Photos { get { return _photos; } } public void AddPhoto(Photo photo) { //Some biz logic //... _photos.Add(photo); } } In the above example i have set the Photos collection type to IEnumerable as this will make it read only. The only way to add/remove photos is through the public methods. The problem with this is that the Entity Framework cannot load the Photo entities into the IEnumerable collection as it's not of type ICollection. By changing the type to ICollection will allow callers to call the Add mentod on the collection itself which is not good. What are my options? Edit: I could refactor the code so it does not expose a public property for Photos: public class Product { public Product() { Photos = new Collection<Photo>(); } public int Id { get; set; } public string Name { get; set; } private Collection<Photo> Photos {get; set; } public IEnumerable<Photo> GetPhotos() { return Photos; } public void AddPhoto(Photo photo) { //Some biz logic //... Photos.Add(photo); } } And use the GetPhotos() to return the collection. The other problem with the approach is that I will loose the change tracking abilities as I cannot mark the collection as Virtual - It is not possible to mark a property as private virtual. In NHibernate I believe it's possible to map the proxy class to the private collection via configuration. I hope that this will become a feature of EF4. Currently i don't like the inability to have any control over the collection!

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  • Global Entity Framework Context in WPF Application

    - by OffApps Cory
    Good day, I am in the middle of development of a WPF application that is using Entity Framework (.NET 3.5). It accesses the entities in several places throughout. I am worried about consistency throughout the application in regard to the entities. Should I be instancing separate contexts in my different views, or should I (and is a a good way to do this) instance a single context that can be accessed globally? For instance, my entity model has three sections, Shipments (with child packages and further child contents), Companies/Contacts (with child addresses and telephones), and disk specs. The Shipments and EditShipment views access the DiskSpecs, and the OptionsView manages the DiskSpecs (Create, Edit, Delete). If I edit a DiskSpec, I have to have something in the ShipmentsView to retrieve the latest specs if I have separate contexts right? If it is safe to have one overall context from which the rest of the app retrieves it's objects, then I imagine that is the way to go. If so, where would that instance be put? I am using VB.NET, but I can translate from C# pretty good. Any help would be appreciated. I just don't want one of those applications where the user has to hit reload a dozen times in different parts of the app to get the new data. Update: OK so I have changed my app as follows: All contexts are created in Using Blocks to dispose of them after they are no longer needed. When loaded, all entities are detatched from context before it is disposed. A new property in the MainViewModel (ContextUpdated) raises an event that all of the other ViewModels subscribe to which runs that ViewModels RefreshEntities method. After implementing this, I started getting errors saying that an entity can only be referenced by one ChangeTracker at a time. Since I could not figure out which context was still referencing the entity (shouldn't be any context right?) I cast the object as IEntityWithChangeTracker, and set SetChangeTracker to nothing (Null). This has let to the current problem: When I Null the changeTracker on the Entity, and then attach it to a context, it loses it's changed state and does not get updated to the database. However if I do not null the change tracker, I can't attach. I have my own change tracking code, so that is not a problem. My new question is, how are you supposed to do this. A good example Entity query and entity save code snipped would go a long way, cause I am beating my head in trying to get what I once thought was a simple transaction to work. Any help would elevate you to near god-hood.

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  • Web Safe Area (optimal resolution) for web app design

    - by M.A.X
    I'm in the process of designing a new web app and I'm wondering for what 'web safe area' should I optimize the app layout and design. I did some investigation and thinking on my own but wanted to share this to see what the general opinion is. Here is what I found: Optimal Display Resolution: w3schools web stats seems to be the most referenced source (however they state that these are results from their site and is biased towards tech savvy users) http://www.w3counter.com/globalstats.php (aggregate data from something like 15,000 different sites that use their tracking services) StatCounter Global Stats Display Resolution (Stats are based on aggregate data collected by StatCounter on a sample exceeding 15 billion pageviews per month collected from across the StatCounter network of more than 3 million websites) NetMarketShare Screen Resolutions (marketshare.hitslink.com) (a web analytics consulting firm, they get data from browsers of site visitors to their on-demand network of live stats customers. The data is compiled from approximately 160 million visitors per month) Display Resolution Summary: There is a bit of variation between the above sources but in general as of Jan 2011 looks like 1024x768 is about 20%, while ~85% have a higher resolution of at least 1280x768 (1280x800 is the most common of these with 15-20% of total web, depending on the source; 1280x1024 and 1366x768 follow behind with 9-14% of the share). My guess would be that the higher resolution values will be even more common if we filter on North America, and even higher if we filter on N.American corporate users (unfortunately I couldn't find any free geographically filtered statistics). Another point to note is that the 1024x768 desktop user population is likely lower than the aforementioned 20%, seeing as the iPad (1024x768 native display) is likely propping up those number. My recommendation would be to optimize around the 1280x768 constraint (*note: 1280x768 is actually a relatively rare resolution, but I think it's a valid constraint range considering that 1366x768 is relatively common and 1280 is the most common horizontal resolution). Browser + OS Constraints: To further add to the constraints we have to subtract the space taken up by the browser (assuming IE, which is the most space consuming) and the OS (assuming WinXP-Win7): Win7 has the biggest taskbar footprint at a height of 40px (XP's and Vista's is 30px) The default IE8 view uses up 25px at the bottom of the screen with the status bar and a further 120px at the top of the screen with the windows title bar and the browser UI (assuming the default 'favorites' toolbar is present, it would instead be 91px without the favorites toolbar). Assuming no scrollbar, we also loose a total of 4px horizontally for the window outline. This means that we are left with 583px of vertical space and 1276px of horizontal. In other words, a Web Safe Area of 1276 x 583 Is this a correct line of thinking? I tried to Google some design best practices but most still talk about designing around 1024x768 which seems to be quickly disappearing. Any help on this would be greatly appreciated! Thanks.

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  • Perl Moose::Util::TypeConstraints bug ? what is this error about the name has invalid chars ?

    - by alex8657
    That has been hours i am tracking a Moose::Util::TypeConstraints exceptions, i don't understand where it gets to check a type and tells me that the name is incorrect. I tracked the error to a reduced example to try to locate the problem, and it just shows me that i do not get it. Did i get to a Moose::Util::TypeConstraints bug ? aoffice:new alex$ perl -c ../codesnippets/typeconstrainterror.pl ../codesnippets/typeconstrainterror.pl syntax OK aoffice:new alex$ perl -d ../codesnippets/typeconstrainterror.pl (...) DB<1> r Something::File::LocalFile=HASH(0x100d1bfa8) contains invalid characters for a type name. Names can contain alphanumeric character, ":", and "." at /opt/local/lib/perl5/vendor_perl/5.10.1/darwin-multi-2level/Moose/Util/TypeConstraints.pm line 508 Moose::Util::TypeConstraints::_create_type_constraint('Something::File::LocalFile=HASH(0x100d1bfa8)', undef, undef, undef, undef) called at /opt/local/lib/perl5/vendor_perl/5.10.1/darwin-multi-2level/Moose/Util/TypeConstraints.pm line 285 Moose::Util::TypeConstraints::type('Something::File::LocalFile=HASH(0x100d1bfa8)') called at ../codesnippets/typeconstrainterror.pl line 7 Something::File::is_slink('Something::File::LocalFile=HASH(0x100d1bfa8)') called at ../codesnippets/typeconstrainterror.pl line 33 Debugged program terminated. Use q to quit or R to restart, use o inhibit_exit to avoid stopping after program termination, h q, h R or h o to get additional info. Below, the code that crashes: package Something::File; use Moose; has 'type' =>(is=>'ro', isa=>'Str', writer=>'_set_type' ); sub is_slink { my $self = shift; return ( $self->type eq 'slink' ); } no Moose; __PACKAGE__->meta->make_immutable; 1; package Something::File::LocalFile; use Moose; use Moose::Util::TypeConstraints; extends 'Something::File'; subtype 'PositiveInt' => as 'Int' => where { $_ >0 } => message { 'Only positive greater than zero integers accepted' }; no Moose; __PACKAGE__->meta->make_immutable; 1; my $a = Something::File::LocalFile->new; # $a->_set_type('slink'); print $a->is_slink ." end\n";

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  • Custom NSView in NSMenuItem not receiving mouse events

    - by Dennis
    I have an NSMenu popping out of an NSStatusItem using popUpStatusItemMenu. These NSMenuItems show a bunch of different links, and each one is connected with setAction: to the openLink: method of a target. This arrangement has been working fine for a long time. The user chooses a link from the menu and the openLink: method then deals with it. Unfortunately, I recently decided to experiment with using NSMenuItem's setView: method to provide a nicer/slicker interface. Basically, I just stopped setting the title, created the NSMenuItem, and then used setView: to display a custom view. This works perfectly, the menu items look great and my custom view is displayed. However, when the user chooses a menu item and releases the mouse, the action no longer works (i.e., openLink: isn't called). If I just simply comment out the setView: call, then the actions work again (of course, the menu items are blank, but the action is executed properly). My first question, then, is why setting a view breaks the NSMenuItem's action. No problem, I thought, I'll fix it by detecting the mouseUp event in my custom view and calling my action method from there. I added this method to my custom view: - (void)mouseUp:(NSEvent *)theEvent { NSLog(@"in mouseUp"); } No dice! This method is never called. I can set tracking rects and receive mouseEntered: events, though. I put a few tests in my mouseEntered routine, as follows: if ([[self window] ignoresMouseEvents]) { NSLog(@"ignoring mouse events"); } else { NSLog(@"not ignoring mouse events"); } if ([[self window] canBecomeKeyWindow]) { dNSLog((@"canBecomeKeyWindow")); } else { NSLog(@"not canBecomeKeyWindow"); } if ([[self window] isKeyWindow]) { dNSLog((@"isKeyWindow")); } else { NSLog(@"not isKeyWindow"); } And got the following responses: not ignoring mouse events canBecomeKeyWindow not isKeyWindow Is this the problem? "not isKeyWindow"? Presumably this isn't good because Apple's docs say "If the user clicks a view that isn’t in the key window, by default the window is brought forward and made key, but the mouse event is not dispatched." But there must be a way do detect these events. HOW? Adding: [[self window] makeKeyWindow]; has no effect, despite the fact that canBecomeKeyWindow is YES.

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  • Questions related to writing your own file downloader using multiple threads java

    - by Shekhar
    Hello In my current company, i am doing a PoC on how we can write a file downloader utility. We have to use socket programming(TCP/IP) for downloading the files. One of the requirements of the client is that a file(which will be large in size) should be transfered in chunks for example if we have a file of 5Mb size then we can have 5 threads which transfer 1 Mb each. I have written a small application which downloads a file. You can download the eclipe project from http://www.fileflyer.com/view/QM1JSC0 A brief explanation of my classes FileSender.java This class provides the bytes of file. It has a method called sendBytesOfFile(long start,long end, long sequenceNo) which gives the number of bytes. import java.io.File; import java.io.IOException; import java.util.zip.CRC32; import org.apache.commons.io.FileUtils; public class FileSender { private static final String FILE_NAME = "C:\\shared\\test.pdf"; public ByteArrayWrapper sendBytesOfFile(long start,long end, long sequenceNo){ try { File file = new File(FILE_NAME); byte[] fileBytes = FileUtils.readFileToByteArray(file); System.out.println("Size of file is " +fileBytes.length); System.out.println(); System.out.println("Start "+start +" end "+end); byte[] bytes = getByteArray(fileBytes, start, end); ByteArrayWrapper wrapper = new ByteArrayWrapper(bytes, sequenceNo); return wrapper; } catch (IOException e) { throw new RuntimeException(e); } } private byte[] getByteArray(byte[] bytes, long start, long end){ long arrayLength = end-start; System.out.println("Start : "+start +" end : "+end + " Arraylength : "+arrayLength +" length of source array : "+bytes.length); byte[] arr = new byte[(int)arrayLength]; for(int i = (int)start, j =0; i < end;i++,j++){ arr[j] = bytes[i]; } return arr; } public static long fileSize(){ File file = new File(FILE_NAME); return file.length(); } } Second Class is FileReceiver.java - This class receives the file. Small Explanation what this file does This class finds the size of the file to be fetched from Sender Depending upon the size of the file it finds the start and end position till the bytes needs to be read. It starts n number of threads giving each thread start,end, sequence number and a list which all the threads share. Each thread reads the number of bytes and creates a ByteArrayWrapper. ByteArrayWrapper objects are added to the list Then i have while loop which basically make sure that all threads have done their work finally it sorts the list based on the sequence number. then the bytes are joined, and a complete byte array is formed which is converted to a file. Code of File Receiver package com.filedownloader; import java.io.File; import java.io.IOException; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.List; import java.util.zip.CRC32; import org.apache.commons.io.FileUtils; public class FileReceiver { public static void main(String[] args) { FileReceiver receiver = new FileReceiver(); receiver.receiveFile(); } public void receiveFile(){ long startTime = System.currentTimeMillis(); long numberOfThreads = 10; long filesize = FileSender.fileSize(); System.out.println("File size received "+filesize); long start = filesize/numberOfThreads; List<ByteArrayWrapper> list = new ArrayList<ByteArrayWrapper>(); for(long threadCount =0; threadCount<numberOfThreads ;threadCount++){ FileDownloaderTask task = new FileDownloaderTask(threadCount*start,(threadCount+1)*start,threadCount,list); new Thread(task).start(); } while(list.size() != numberOfThreads){ // this is done so that all the threads should complete their work before processing further. //System.out.println("Waiting for threads to complete. List size "+list.size()); } if(list.size() == numberOfThreads){ System.out.println("All bytes received "+list); Collections.sort(list, new Comparator<ByteArrayWrapper>() { @Override public int compare(ByteArrayWrapper o1, ByteArrayWrapper o2) { long sequence1 = o1.getSequence(); long sequence2 = o2.getSequence(); if(sequence1 < sequence2){ return -1; }else if(sequence1 > sequence2){ return 1; } else{ return 0; } } }); byte[] totalBytes = list.get(0).getBytes(); byte[] firstArr = null; byte[] secondArr = null; for(int i = 1;i<list.size();i++){ firstArr = totalBytes; secondArr = list.get(i).getBytes(); totalBytes = concat(firstArr, secondArr); } System.out.println(totalBytes.length); convertToFile(totalBytes,"c:\\tmp\\test.pdf"); long endTime = System.currentTimeMillis(); System.out.println("Total time taken with "+numberOfThreads +" threads is "+(endTime-startTime)+" ms" ); } } private byte[] concat(byte[] A, byte[] B) { byte[] C= new byte[A.length+B.length]; System.arraycopy(A, 0, C, 0, A.length); System.arraycopy(B, 0, C, A.length, B.length); return C; } private void convertToFile(byte[] totalBytes,String name) { try { FileUtils.writeByteArrayToFile(new File(name), totalBytes); } catch (IOException e) { throw new RuntimeException(e); } } } Code of ByteArrayWrapper package com.filedownloader; import java.io.Serializable; public class ByteArrayWrapper implements Serializable{ private static final long serialVersionUID = 3499562855188457886L; private byte[] bytes; private long sequence; public ByteArrayWrapper(byte[] bytes, long sequenceNo) { this.bytes = bytes; this.sequence = sequenceNo; } public byte[] getBytes() { return bytes; } public long getSequence() { return sequence; } } Code of FileDownloaderTask import java.util.List; public class FileDownloaderTask implements Runnable { private List<ByteArrayWrapper> list; private long start; private long end; private long sequenceNo; public FileDownloaderTask(long start,long end,long sequenceNo,List<ByteArrayWrapper> list) { this.list = list; this.start = start; this.end = end; this.sequenceNo = sequenceNo; } @Override public void run() { ByteArrayWrapper wrapper = new FileSender().sendBytesOfFile(start, end, sequenceNo); list.add(wrapper); } } Questions related to this code 1) Does file downloading becomes fast when multiple threads is used? In this code i am not able to see the benefit. 2) How should i decide how many threads should i create ? 3) Are their any opensource libraries which does that 4) The file which file receiver receives is valid and not corrupted but checksum (i used FileUtils of common-io) does not match. Whats the problem? 5) This code gives out of memory when used with large file(above 100 Mb) i.e. because byte array which is created. How can i avoid? I know this is a very bad code but i have to write this in one day -:). Please suggest any other good way to do this? Thanks Shekhar

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  • INSERT OR IGNORE in a trigger

    - by dan04
    I have a database (for tracking email statistics) that has grown to hundreds of megabytes, and I've been looking for ways to reduce it. It seems that the main reason for the large file size is that the same strings tend to be repeated in thousands of rows. To avoid this problem, I plan to create another table for a string pool, like so: CREATE TABLE AddressLookup ( ID INTEGER PRIMARY KEY AUTOINCREMENT, Address TEXT UNIQUE ); CREATE TABLE EmailInfo ( MessageID INTEGER PRIMARY KEY AUTOINCREMENT, ToAddrRef INTEGER REFERENCES AddressLookup(ID), FromAddrRef INTEGER REFERENCES AddressLookup(ID) /* Additional columns omitted for brevity. */ ); And for convenience, a view to join these tables: CREATE VIEW EmailView AS SELECT MessageID, A1.Address AS ToAddr, A2.Address AS FromAddr FROM EmailInfo LEFT JOIN AddressLookup A1 ON (ToAddrRef = A1.ID) LEFT JOIN AddressLookup A2 ON (FromAddrRef = A2.ID); In order to be able to use this view as if it were a regular table, I've made some triggers: CREATE TRIGGER trg_id_EmailView INSTEAD OF DELETE ON EmailView BEGIN DELETE FROM EmailInfo WHERE MessageID = OLD.MessageID; END; CREATE TRIGGER trg_ii_EmailView INSTEAD OF INSERT ON EmailView BEGIN INSERT OR IGNORE INTO AddressLookup(Address) VALUES (NEW.ToAddr); INSERT OR IGNORE INTO AddressLookup(Address) VALUES (NEW.FromAddr); INSERT INTO EmailInfo SELECT NEW.MessageID, A1.ID, A2.ID FROM AddressLookup A1, AddressLookup A2 WHERE A1.Address = NEW.ToAddr AND A2.Address = NEW.FromAddr; END; CREATE TRIGGER trg_iu_EmailView INSTEAD OF UPDATE ON EmailView BEGIN UPDATE EmailInfo SET MessageID = NEW.MessageID WHERE MessageID = OLD.MessageID; REPLACE INTO EmailView SELECT NEW.MessageID, NEW.ToAddr, NEW.FromAddr; END; The problem After: INSERT OR REPLACE INTO EmailView VALUES (1, '[email protected]', '[email protected]'); INSERT OR REPLACE INTO EmailView VALUES (2, '[email protected]', '[email protected]'); The updated rows contain: MessageID ToAddr FromAddr --------- ------ -------- 1 NULL [email protected] 2 [email protected] [email protected] There's a NULL that shouldn't be there. The corresponding cell in the EmailInfo table contains an orphaned ToAddrRef value. If you do the INSERTs one at a time, you'll see that Alice's ID in the AddressLookup table changes! It appears that this behavior is documented: An ON CONFLICT clause may be specified as part of an UPDATE or INSERT action within the body of the trigger. However if an ON CONFLICT clause is specified as part of the statement causing the trigger to fire, then conflict handling policy of the outer statement is used instead. So the "REPLACE" in the top-level "INSERT OR REPLACE" statement is overriding the critical "INSERT OR IGNORE" in the trigger program. Is there a way I can make it work the way that I wanted?

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  • how to read values from the remote OPC Server

    - by Shailesh Jaiswal
    I have created one asp.net web service. In this web service I am using the web method as follows. The web service is related to the OPC ( OLE for process control) public string ReadServerItems(string ServerName) { string txt = ""; ArrayList obj = new ArrayList(); XmlServer Srv = new XmlServer("XDAGW.CS.WCF.Eval.1"); RequestOptions opt = new RequestOptions(); ReadRequestItemList iList = new ReadRequestItemList(); iList.Items = new ReadRequestItem[3]; iList.Items[0] = new ReadRequestItem(); iList.Items[0].ItemName = "ServerInfo.ConnectedClients"; iList.Items[1] = new ReadRequestItem(); iList.Items[1].ItemName = "ServerInfo.TotalGroups"; iList.Items[2] = new ReadRequestItem(); iList.Items[2].ItemName = "EventSources.Area1.Tracking"; ReplyItemList rslt; OPCError[] err; ReplyBase reply = Srv.Read(opt, iList, out rslt, out err); if ((rslt == null)) txt += err[0].Text; else { foreach (xmldanet.xmlda.ItemValue iv in rslt.Items) { txt += iv.ItemName; if (iv.ResultID == null) // success { txt += " = " + iv.Value.ToString() + "\r\n"; obj.Add(txt); } else txt += " : Error: " + iv.ResultID.Name + "\r\n"; } } return txt; } I am using the namespaces as follows using xmldanet; using xmldanet.xmlda; I have installed XMLDA.NET client component evaluation. In this there is an in built Test client which successfully reads the values of these data items from the remote OPC server. I also provides the template through which we can build the OPC based applications. In the above code I am trying to read the values of the data items but i am not able to read the values. I have applied the breakpoint. In that I can see that the condition if (iv.ResultID == null) becomes false & also there is null values in the variable rslt. Please tell me where I am doing mistake ? how should I correct my mistake ? can provide me the correct code ?

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  • Dealing with external processes

    - by Jesse Aldridge
    I've been working on a gui app that needs to manage external processes. Working with external processes leads to a lot of issues that can make a programmer's life difficult. I feel like maintenence on this app is taking an unacceptably long time. I've been trying to list the things that make working with external processes difficult so that I can come up with ways of mitigating the pain. This kind of turned into a rant which I thought I'd post here in order to get some feedback and to provide some guidance to anybody thinking about sailing into these very murky waters. Here's what I've got so far: Output from the child can get mixed up with output from the parent. This can make both outputs misleading and hard to read. It can be hard to tell what came from where. It becomes harder to figure out what's going on when things are asynchronous. Here's a contrived example: import textwrap, os, time from subprocess import Popen test_path = 'test_file.py' with open(test_path, 'w') as file: file.write(textwrap.dedent(''' import time for i in range(3): print 'Hello %i' % i time.sleep(1)''')) proc = Popen('python -B "%s"' % test_path) for i in range(3): print 'Hello %i' % i time.sleep(1) os.remove(test_path) I guess I could have the child process write its output to a file. But it can be annoying to have to open up a file every time I want to see the result of a print statement. If I have code for the child process I could add a label, something like print 'child: Hello %i', but it can be annoying to do that for every print. And it adds some noise to the output. And of course I can't do it if I don't have access to the code. I could manually manage the process output. But then you open up a huge can of worms with threads and polling and stuff like that. A simple solution is to treat processes like synchronous functions, that is, no further code executes until the process completes. In other words, make the process block. But that doesn't work if you're building a gui app. Which brings me to the next problem... Blocking processes cause the gui to become unresponsive. import textwrap, sys, os from subprocess import Popen from PyQt4.QtGui import * from PyQt4.QtCore import * test_path = 'test_file.py' with open(test_path, 'w') as file: file.write(textwrap.dedent(''' import time for i in range(3): print 'Hello %i' % i time.sleep(1)''')) app = QApplication(sys.argv) button = QPushButton('Launch process') def launch_proc(): # Can't move the window until process completes proc = Popen('python -B "%s"' % test_path) proc.communicate() button.connect(button, SIGNAL('clicked()'), launch_proc) button.show() app.exec_() os.remove(test_path) Qt provides a process wrapper of its own called QProcess which can help with this. You can connect functions to signals to capture output relatively easily. This is what I'm currently using. But I'm finding that all these signals behave suspiciously like goto statements and can lead to spaghetti code. I think I want to get sort-of blocking behavior by having the 'finished' signal from QProcess call a function containing all the code that comes after the process call. I think that should work but I'm still a bit fuzzy on the details... Stack traces get interrupted when you go from the child process back to the parent process. If a normal function screws up, you get a nice complete stack trace with filenames and line numbers. If a subprocess screws up, you'll be lucky if you get any output at all. You end up having to do a lot more detective work everytime something goes wrong. Speaking of which, output has a way of disappearing when dealing external processes. Like if you run something via the windows 'cmd' command, the console will pop up, execute the code, and then disappear before you have a chance to see the output. You have to pass the /k flag to make it stick around. Similar issues seem to crop up all the time. I suppose both problems 3 and 4 have the same root cause: no exception handling. Exception handling is meant to be used with functions, it doesn't work with processes. Maybe there's some way to get something like exception handling for processes? I guess that's what stderr is for? But dealing with two different streams can be annoying in itself. Maybe I should look into this more... Processes can hang and stick around in the background without you realizing it. So you end up yelling at your computer cuz it's going so slow until you finally bring up your task manager and see 30 instances of the same process hanging out in the background. Also, hanging background processes can interefere with other instances of the process in various fun ways, such as causing permissions errors by holding a handle to a file or someting like that. It seems like an easy solution to this would be to have the parent process kill the child process on exit if the child process didn't close itself. But if the parent process crashes, cleanup code might not get called and the child can be left hanging. Also, if the parent waits for the child to complete, and the child is in an infinite loop or something, you can end up with two hanging processes. This problem can tie in to problem 2 for extra fun, causing your gui to stop responding entirely and force you to kill everything with the task manager. F***ing quotes Parameters often need to be passed to processes. This is a headache in itself. Especially if you're dealing with file paths. Say... 'C:/My Documents/whatever/'. If you don't have quotes, the string will often be split at the space and interpreted as two arguments. If you need nested quotes you can use ' and ". But if you need to use more than two layers of quotes, you have to do some nasty escaping, for example: "cmd /k 'python \'path 1\' \'path 2\''". A good solution to this problem is passing parameters as a list rather than as a single string. Subprocess allows you to do this. Can't easily return data from a subprocess. You can use stdout of course. But what if you want to throw a print in there for debugging purposes? That's gonna screw up the parent if it's expecting output formatted a certain way. In functions you can print one string and return another and everything works just fine. Obscure command-line flags and a crappy terminal based help system. These are problems I often run into when using os level apps. Like the /k flag I mentioned, for holding a cmd window open, who's idea was that? Unix apps don't tend to be much friendlier in this regard. Hopefully you can use google or StackOverflow to find the answer you need. But if not, you've got a lot of boring reading and frusterating trial and error to do. External factors. This one's kind of fuzzy. But when you leave the relatively sheltered harbor of your own scripts to deal with external processes you find yourself having to deal with the "outside world" to a much greater extent. And that's a scary place. All sorts of things can go wrong. Just to give a random example: the cwd in which a process is run can modify it's behavior. There are probably other issues, but those are the ones I've written down so far. Any other snags you'd like to add? Any suggestions for dealing with these problems?

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  • Can parser combination be made efficient?

    - by Jon Harrop
    Around 6 years ago, I benchmarked my own parser combinators in OCaml and found that they were ~5× slower than the parser generators on offer at the time. I recently revisited this subject and benchmarked Haskell's Parsec vs a simple hand-rolled precedence climbing parser written in F# and was surprised to find the F# to be 25× faster than the Haskell. Here's the Haskell code I used to read a large mathematical expression from file, parse and evaluate it: import Control.Applicative import Text.Parsec hiding ((<|>)) expr = chainl1 term ((+) <$ char '+' <|> (-) <$ char '-') term = chainl1 fact ((*) <$ char '*' <|> div <$ char '/') fact = read <$> many1 digit <|> char '(' *> expr <* char ')' eval :: String -> Int eval = either (error . show) id . parse expr "" . filter (/= ' ') main :: IO () main = do file <- readFile "expr" putStr $ show $ eval file putStr "\n" and here's my self-contained precedence climbing parser in F#: let rec (|Expr|) (P(f, xs)) = Expr(loop (' ', f, xs)) and shift oop f op (P(g, xs)) = let h, xs = loop (op, g, xs) loop (oop, f h, xs) and loop = function | ' ' as oop, f, ('+' | '-' as op)::P(g, xs) | (' ' | '+' | '-' as oop), f, ('*' | '/' as op)::P(g, xs) | oop, f, ('^' as op)::P(g, xs) -> let h, xs = loop (op, g, xs) let op = match op with | '+' -> (+) | '-' -> (-) | '*' -> (*) | '/' -> (/) | '^' -> pown loop (oop, op f h, xs) | _, f, xs -> f, xs and (|P|) = function | '-'::P(f, xs) -> let f, xs = loop ('~', f, xs) P(-f, xs) | '('::Expr(f, ')'::xs) -> P(f, xs) | c::xs when '0' <= c && c <= '9' -> P(int(string c), xs) My impression is that even state-of-the-art parser combinators waste a lot of time back tracking. Is that correct? If so, is it possible to write parser combinators that generate state machines to obtain competitive performance or is it necessary to use code generation?

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  • c++ exceptions and program execution logic

    - by Andrew
    Hello everyone, I have been thru a few questions but did not find an answer. I wonder how should the exception handling be implemented in a C++ software so it is centralized and it is tracking the software progress? For example, I want to process exceptions at four stages of the program and know that exception happened at that specific stage: 1. Initialization 2. Script processing 3. Computation 4. Wrap-up. At this point, I tried this: int main (...) { ... // start logging system try { ... } catch (exception &e) { cerr << "Error: " << e.what() << endl; cerr << "Could not start the logging system. Application terminated!\n"; return -1; } catch(...) { cerr << "Unknown error occured.\n"; cerr << "Could not start the logging system. Application terminated!\n"; return -2; } // open script file and acquire data try { ... } catch (exception &e) { cerr << "Error: " << e.what() << endl; cerr << "Could not acquire input parameters. Application terminated!\n"; return -1; } catch(...) { cerr << "Unknown error occured.\n"; cerr << "Could not acquire input parameters. Application terminated!\n"; return -2; } // computation try { ... } ... This is definitely not centralized and seems stupid. Or maybe it is not a good concept at all?

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  • Multiline editable textarea in SVG

    - by Timo
    I'm trying to implement multiline editable textfield in SVG. I have the following code in http://jsfiddle.net/ca4d3/ : <svg width="1000" height="1000" overflow="scroll"> <g transform="rotate(5)"> <rect width="300" height="400" fill="#22DD22" fill-opacity="0.5"/> </g> <foreignObject x="10" y="10" overflow="visible" width="10000" height="10000" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"> <p style="display:table-cell;padding:10px;border:1px solid red; background-color:white;opacity:0.5;font-family:Verdana; font-size:20px;white-space: pre; word-wrap: normal; overflow: visible; overflow-y: visible; overflow-x:visible;" contentEditable="true" xmlns="http://www.w3.org/1999/xhtml"> Write here some text. Be smart and select some word. If you wanna be really COOL, paste here something cool! </p> </foreignObject> </svg> In newest Chrome, Safari and Firefox the code works in some way, but in Opera and IE 9 not. The goal is that: 0) Works in newest Chrome, Safari, Firefox, Opera and IE and if ever possible in some pads. 1) White-spaces are preserved and text wraps only on newline char (works in Chrome, Safari and Firefox, but not in Opera and IE 9 *). 2) The textfield is editable (in the same reliable and stabile way as textareas and contenteditable p elements in html) and height and width is expanded to fit text (works in Chrome, Safari and Firefox, but not in Opera and IE 9 *). 3) Texfield can be transformed (rotated, skewed, translated) while maintaining text editability (Tested rotation, but not work in any browser *). EDIT: Foreignobject rotation works on Firefox 15.0.1, but not in Safari 5.1.7 (6534.57.2), Chrome 22.0.1229.79, Opera 12.02, IE 9. Tested on Mac OS X 10.6.8. 4) Textfield can be clipped and masked while not necessarily maintaining text editability (not yet tested). *) using above code These all can be achieved using Flash, but Flash has so severe problems that it is not suitable for my purposes (after every little change in code, all have to be compiled again using Flex, which is slow, font size has limits, tracking technique is pixeloriented, not relative to em size etc.) and there still are differences across platforms. And I want to give a try to SVG! GUESTION: Can I achieve my goals 0-4 with current SVG support in browsers? Is coming SVG 2.0 for some help in this case? EDIT: Changed display:table to display:table-cell (and added new jsfiddle), because display:table made the field to loses focus when pressed arrow-up on first text row.

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  • What is the most effective way to test for combined keyboard arrow direction in ActionScript 3.0?

    - by Relee
    I need to monitor the direction a user is indicating using the four directional arrow keys on a keyboard in ActionScript 3.0 and I want to know the most efficient and effective way to do this. I've got several ideas of how to do it, and I'm not sure which would be best. I've found that when tracking Keyboard.KEY_DOWN events, the event repeats as long as the key is down, so the event function is repeated as well. This broke the method I had originally chosen to use, and the methods I've been able to think of require a lot of comparison operators. The best way I've been able to think of would be to use bitwise operators on a uint variable. Here's what I'm thinking var _direction:uint = 0x0; // The Current Direction That's the current direction variable. In the Keyboard.KEY_DOWN event handler I'll have it check what key is down, and use a bitwise AND operation to see if it's already toggled on, and if it's not, I'll add it in using basic addition. So, up would be 0x1 and down would be 0x2 and both up and down would be 0x3, for example. It would look something like this: private function keyDownHandler(e:KeyboardEvent):void { switch(e.keyCode) { case Keyboard.UP: if(!(_direction & 0x1)) _direction += 0x1; break; case Keyboard.DOWN: if(!(_direction & 0x2)) _direction += 0x2; break; // And So On... } } The keyUpHandler wouldn't need the if operation since it only triggers once when the key goes up, instead of repeating. I'll be able to test the current direction by using a switch statement labeled with numbers from 0 to 15 for the sixteen possible combinations. That should work, but it doesn't seem terribly elegant to me, given all of the if statements in the repeating keyDown event handler, and the huge switch. private function checkDirection():void { switch(_direction) { case 0: // Center break; case 1: // Up break; case 2: // Down break; case 3: // Up and Down break; case 4: // Left break; // And So On... } } Is there a better way to do this?

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  • Moving a unit precisely along a path in x,y coordinates

    - by Adam Eberbach
    I am playing around with a strategy game where squads move around a map. Each turn a certain amount of movement is allocated to a squad and if the squad has a destination the points are applied each turn until the destination is reached. Actual distance is used so if a squad moves one position in the x or y direction it uses one point, but moving diagonally takes ~1.4 points. The squad maintains actual position as float which is then rounded to allow drawing the position on the map. The path is described by touching the squad and dragging to the end position then lifting the pen or finger. (I'm doing this on an iPhone now but Android/Qt/Windows Mobile would work the same) As the pointer moves x, y points are recorded so that the squad gains a list of intermediate destinations on the way to the final destination. I'm finding that the destinations are not evenly spaced but can be further apart depending on the speed of the pointer movement. Following the path is important because obstacles or terrain matter in this game. I'm not trying to remake Flight Control but that's a similar mechanic. Here's what I've been doing, but it just seems too complicated (pseudocode): getDestination() { - self.nextDestination = remove_from_array(destinations) - self.gradient = delta y to destination / delta x to destination - self.angle = atan(self.gradient) - self.cosAngle = cos(self.angle) - self.sinAngle = sin(self.angle) } move() { - get movement allocation for this turn - if self.nextDestination not valid - - getNextDestination() - while(nextDestination valid) && (movement allocation remains) { - - find xStep and yStep using movement allocation and sinAngle/cosAngle calculated for current self.nextDestination - - if current position + xStep crosses the destination - - - find x movement remaining after self.nextDestination reached - - - calculate remaining direct path movement allocation (xStep remaining / cosAngle) - - - make self.position equal to self.nextDestination - - else - - - apply xStep and yStep to current position - } - round squad's float coordinates to integer screen coordinates - draw squad image on map } That's simplified of course, stuff like sign needs to be tweaked to ensure movement is in the right direction. If trig is the best way to do it then lookup tables can be used or maybe it doesn't matter on modern devices like it used to. Suggestions for a better way to do it? an update - iPhone has zero issues with trig and tracking tens of positions and tracks implemented as described above and it draws in floats anyway. The Bresenham method is more efficient, trig is more precise. If I was to use integer Bresenham I would want to multiply by ten or so to maintain a little more positional accuracy to benefit collisions/terrain detection.

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  • How to fine tune FluentNHibernate's auto mapper?

    - by Venemo
    Okay, so yesterday I managed to get the latest trunk builds of NHibernate and FluentNHibernate to work with my latest little project. (I'm working on a bug tracking application.) I created a nice data access layer using the Repository pattern. I decided that my entities are nothing special, and also that with the current maturity of ORMs, I don't want to hand-craft the database. So, I chose to use FluentNHibernate's auto mapping feature with NHibernate's "hbm2ddl.auto" property set to "create". It really works like a charm. I put the NHibernate configuration in my app domain's config file, set it up, and started playing with it. (For the time being, I created some unit tests only.) It created all tables in the database, and everything I need for it. It even mapped my many-to-many relationships correctly. However, there are a few small glitches: All of the columns created in the DB allow null. I understand that it can't predict which properties should allow null and which shouldn't, but at least I'd like to tell it that it should allow null only for those types for which null makes sense in .NET (eg. non-nullable value types shouldn't allow null). All of the nvarchar and varbinary columns it created, have a default length of 255. I would prefer to have them on max instead of that. Is there a way to tell the auto mapper about the two simple rules above? If the answer is no, will it work correctly if I modify the tables it created? (So, if I set some columns not to allow null, and change the allowed length for some other, will it correctly work with them?) EDIT: I managed to achieve the above by using Fluent NHibernate's convention API. Thanks to everyone who helped! However, there is one more thing: after checking out the convention API, I really would like my IDs to be calld "ID", not "Id", but it seems to me that the PrimaryKey.Name.Is(x => "ID") is not working at all. If I add it to the conventions collection and rewrite my entities' properties to "ID" instead of "Id", it throws an exception that there is no primary key mapped. Any thoughts on this?

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  • Is there a recommended approach to handle saving data in response to within-site navigation without

    - by Carvell Fenton
    Hello all, Preamble to scope my question: I have a web app (or site, this is an internal LAN site) that uses jQuery and AJAX extensively to dynamically load the content section of the UI in the browser. A user navigates the app using a navigation menu. Clicking an item in the navigation menu makes an AJAX call to php, and php then returns the content that is used to populate the central content section. One of the pages served back by php has a table form, set up like a spreadsheet, that the user enters values into. This table is always kept in sync with data in the database. So, when the table is created, is it populated with the relevant database data. Then when the user makes a change in a "cell", that change immediately is written back to the database so the table and database are always in sync. This approach was take to reassure users that the data they entered has been saved (long story...), and to alleviate them from having to click a save button of some kind. So, this always in sync idea is great, except that a user can enter a value in a cell, not take focus out of the cell, and then take any number of actions that would cause that last value to be lost: e.g. navigate to another section of the site via the navigation menu, log out of the app, close the browser, etc. End of preamble, on to the issue: I initially thought that wasn't a problem, because I would just track what data was "dirty" or not saved, and then in the onunload event I would do a final write to the database. Herein lies the rub: because of my clever (or not so clever, not sure) use of AJAX and dynamically loading the content section, the user never actually leaves the original url, or page, when the above actions are taken, with the exception of closing the browser. Therefore, the onunload event does not fire, and I am back to losing the last data again. My question, is there a recommended way to handle figuring out if a person is navigating away from a "section" of your app when content is dynamically loaded this way? I can come up with a solution I think, that involves globals and tracking the currently viewed page, but I thought I would check if there might be a more elegant solution out there, or a change I could make in my design, that would make this work. Thanks in advance as always!

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  • Emulating Button Press Using Kinect/SimpleOpenNI + Processing Depth

    - by Alex Lu
    I am using Kinect with Simple OpenNI and Processing, and I was trying to use the Z position of a hand to emulate a button press. So far when I try it using one hand it works really well, however, when I try to get it to work with a second hand, only one of the hands work. (I know it can be more efficient by moving everything except the fill out of the if statements, but I kept those in there just in case I want to change the sizes or something.) irz and ilz are the initial Z positions of the hands when they are first recognized by onCreateHands and rz and lz are the current Z positions. As of now, the code works fine with one hand, but the other hand will either stay pressed or unpressed. If i comment one of the sections out, it works fine as well. if (rz - irz > 0) { pushStyle(); fill(60); ellipse(rx, ry, 10, 10); popStyle(); rpressed = true; } else { pushStyle(); noFill(); ellipse(rx, ry, 10, 10); popStyle(); rpressed = false; } if (lz - ilz > 0) { pushStyle(); fill(60); ellipse(lx, ly, 10, 10); popStyle(); lpressed = true; } else { pushStyle(); noFill(); ellipse(lx, ly, 10, 10); popStyle(); lpressed = false; } I tried outputting the values of rz - irz and lz - ilz and the numbers range from small negative values to small positive values (around -8 to 8) for lz - ilz. But rz - irz outputs numbers from around 8-30 depending on each time I run it and is never consistent. Also, when I comment out the code for the lz-ilz, the values for rz-irz look just fine and it operates as intended. Is there a reason tracking both Z positions throws off one hand? And is there a way to get it to work? Thanks!

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  • SQL Server architecture guidance

    - by Liam
    Hi, We are designing a new version of our existing product on a new schema. Its an internal web application with possibly 100 concurrent users (max)This will run on a SQL Server 2008 database. On of the discussion items recently is whether we should have a single database of split the database for performance reasons across 2 separate databases. The database could grow anywhere from 50-100GB over 5 years. We are Developers and not DBAs so it would be nice to get some general guidance. [I know the answer is not simple as it depends on the schema, archiving policy, amount of data etc. ] Option 1 Single Main Database [This is my preferred option]. The plan would be to have all the tables in a single database and possibly to use file groups and partitioning to separate the data if required across multiple disks. [Use schema if appropriate]. This should deal with the performance concerns One of the comments wrt this was that the a single server instance would still be processing this data so there would still be a processing bottle neck. For reporting we could have a separate reporting DB but this is still being discussed. Option 2 Split the database into 2 separate databases DB1 - Customers, Accounts, Customer resources etc DB2 - This would contain the bulk of the data [i.e. Vehicle tracking data, financial transaction tables etc]. These tables would typically contain a lot of data. [It could reside on a separate server if required] This plan would involve keeping the main data in a smaller database [DB1] and retaining the [mainly] read only transaction type data in a separate DB [DB2]. The UI would mainly read from DB1 and thus be more responsive. [I'm aware that this option makes it harder for Referential Integrity to be enforced.] Points for consideration As we are at the design stage we can at least make proper use of indexes to deal performance issues so thats why option 1 to me is attractive and its more of a standard approach. For both options we are considering implementing an archiving database. Apologies for the long Question. In summary the question is 1 DB or 2? Thanks in advance, Liam

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  • Bug in Safari: options.length = 0; not working as expected in Safari 4

    - by Stefan
    This is not a real question, but rather an answer to save some others the hassle of tracking this nasty bug down. I wasted hours finding this out. When using options.length = 0; to reset all options of a select element in safari, you can get mixed results depending on wether you have the Web Inspector open or not. If the web inspector is open you use myElement.options.length = 0; and after that query the options.length(), you might get back 1 instead of 0 (expected) but only if the Web Inspector is open (which is often the case when debugging problem like this). Workaround: Close the Web Inspector or call myElement.options.length = 0; twice like so: myElement.options.length = 0; myElement.options.length = 0; Testcase: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html> <head> <title>Testcase</title> <script type="text/javascript" language="javascript" charset="utf-8"> function test(el){ var el = document.getElementById("sel"); alert("Before calling options.length=" + el.options.length); el.options.length = 0; alert("After calling options.length=" + el.options.length); } </script> </head> <body onLoad="test();"> <p> Make note of the numbers displayed in the Alert Dialog, then open Web inspector, reload this page and compare the numbers. </p> <select id="sel" multiple> <option label="a----------" value="a"></option> <option label="b----------" value="b"></option> <option label="c----------" value="c"></option> </select> </body> </html>

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  • DataGridView live display of datatable using virtual mode

    - by Chris
    I have a DataGridView that will display records (log entries) from a database. The amount of records that can exist at a time is very large. I would like to use the virtual mode feature of the DataGridView to display a page of data, and to minimize the amount of data that has to be transferred across a network at a given time. Polling for data is out of the question. There will be several clients running at a time, all of which are on the same network and viewing the records. If they all poll for data, the network will run very slowly. The data is read-only to the user; they won't be able to edit any of it, just view it. I need to know when updates occur in the database, and I need to update the screen with those updates accordingly using virtual mode. If a page of data a user is viewing contains data that has change, he/she will see those updates on that page. If updates were made to data in the database, but not in the data the user is viewing, then not much really changes on the user screen (Maybe just the scroll bar if records were added or removed). My current approach is using SQL server change tracking with the sync framework. Each client has a local SQL Server CE instance and database file that is kept in sync with the main database server. I use the information from the synchronization event to see if any changes were made to the main database and were sync'ed to the client. I need to use the DataGridView virtual mode here because I can't have thousands of records loaded into the DataGridView at once, otherwise memory usage goes through the roof. The main challenge right now is knowing how to use virtual mode to provide a seamless experience to the user by allowing them to scroll up and down through the records, and also have records update on the fly without interfering with the user inappropriately. Has anybody dealt with this issue before, and if so, where I can see how they did it? I've gone through some of the MSDN documentation and examples on virtual mode. So far, I haven't found documentation and/or examples on their site that explains how to do what I am trying to accomplish.

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  • Inventory count in CakePHP

    - by metrobalderas
    We are developing an inventory tracking system. Basically we've got an order table in which orders are placed. When an order is payed, the status changes from 0 to 1. This table has multiple children in another table order_items. This is the main structure. CREATE TABLE order( id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY, user_id INT UNSIGNED, status INT(1), total INT UNSIGNED ); CREATE TABLE order_items( id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY, order_id INT UNSIGNED, article_id INT UNSIGNED, size enum('s', 'm', 'l', 'xl'), quantity INT UNSIGNED ); Now, we've got a stocks table with similar architecture for the acquisitions. This is the structure. CREATE TABLE stock( id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY, article_id INT UNSIGNED ); CREATE TABLE stock_items( id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY, stock_id INT UNSIGNED, size enum('s', 'm', 'l', 'xl'), quantity INT(2) ); The main difference is that stocks has no status field. What we are looking for is a way to sum each article size from stock_items, then sum each article size from order_items where Order.status = 1 and substract both these items to find our current inventory. This is the table we want to get from a single query: Size | Stocks | Sales | Available s | 10 | 3 | 7 m | 15 | 13 | 2 l | 7 | 4 | 3 Initially we thought abouth using complex find conditions, but perhaps that's the wrong approach. Also, since it's not a direct join, it turns out to be quite hard. This is the code we have to retrieve the stock's total for each item. function stocks_total($id){ $find = $this->StockItem->find('all', array( 'conditions' => array( 'StockItem.stock_id' => $this->find('list', array('conditions' => array('Stock.article_id' => $id))) ), 'fields' => array_merge( array( 'SUM(StockItem.cantidad) as total' ), array_keys($this->StockItem->_schema) ), 'group' => 'StockItem.size', 'order' => 'FIELD(StockItem.size, \'s\', \'m\' ,\'l\' ,\'xl\') ASC' )); return $find; } Thanks.

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  • Populating data in multiple cascading dropdown boxes in Access 2007

    - by miCRoSCoPiC_eaRthLinG
    Hello all, I've been assigned the task to design a temporary customer tracking system in MS Access 2007 (sheeeesh!). The tables and relationships have all been setup successfully. But I'm running into a minor problem while trying to design the data entry form for one table... Here's a bit of explanation first. The screen contains 3 dropdown boxes (apart from other fields). 1st dropdown The first dropdown (cboMarket) represents the Market lets users select between 2 options: Domestic International Since the first dropdown contains only 2 items I didn't bother making a table for it. I added them as pre-defined list items. 2nd dropdown Once the user makes a selection in this one, the second dropdown (cboLeadCategory) loads up a list of Lead Categories, namely, Fairs & Exhibitions, Agents, Press Ads, Online Ads etc. Different sets of lead categories are utilized for the 2 markets. Hence this box is dependent on the 1st one. Structure of the bound table, named Lead_Cateogries for the 2nd combo is: ID Autonumber Lead_Type TEXT <- actually a list that takes up Domestic or International Lead_Category_Name TEXT 3rd dropdown And based on the choice of category in the 2nd one, the third one (cboLeadSource) is supposed to display a pre-defined set of lead sources belonging to the particular category. Table is named Lead_Sources and the structure is: ID Autonumber Lead_Category NUMBER <- related to ID of Lead Categories table Lead_Source TEXT When I make the selection in the 1st dropdown, the AfterUpdate event of the combo is called, which instructs the 2nd dropdown to load contents: Private Sub cboMarket_AfterUpdate() Me![cboLead_Category].Requery End Sub The Row Source of the 2nd combo contains a query: SELECT Lead_Categories.ID, Lead_Categories.Lead_Category_Name FROM Lead_Categories WHERE Lead_Categories.Lead_Type=[cboMarket] ORDER BY Lead_Categories.Lead_Category_Name; The AfterUpdate event of 2nd combo is: Private Sub cboLeadCategory_AfterUpdate() Me![cboLeadSource].Requery End Sub The Row Source of 3rd combo contains: SELECT Leads_Sources.ID, Leads_Sources.Lead_Source FROM Leads_Sources WHERE [Lead_Sources].[Lead_Category]=[Lead_Categories].[ID] ORDER BY Leads_Sources.Lead_Source; Problem When I select Market type from cboMarket, the 2nd combo cboLeadCategory loads up the appropriate Categories without a hitch. But when I select a particular Category from it, instead of the 3rd combo loading the lead source names, a modal dialog is displayed asking me to Enter a Parameter. When I enter anything into this prompt (valid or invalid data), I get yet another prompt: Why is this happening? Why isn't the 3rd box loading the source names as desired. Can any one please shed some light on where I am going wrong? Thanks, m^e

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  • Windows MAchine Debugging

    - by PrettyFlower
    I've been learning how to program for Windows for some time now and am getting pretty comfy with COM. I had thought to go over to Linux and do some C++ programming there and I wished to run Rosetta Commons so I installed Fedora. I had tried installing Ubuntu a few months ago and things got messy. I had a glitch, maybe caused by one of the live cd creators, my video card or something I don't know. Who Crashed suggested it was my video card and I had regular messages about ntfs.sys and page file issues. At any rate I just installed Fedora and the same thing is happening again. I would like to think with the twenty five years of doing this that I might finally make some headway into debugging my system. I think I may have overlooked a lot of what could be done in favor of simply uninstalling, reinstalling and formatting and starting from scratch. I have opened up the folder windows debugging tools, quite accidentally and just before I was going to clean sweep again, and I found KD and WinDbg. I had never seen these before and I felt that maybe I should look into this. I am quite familiar with the modern machine that is known as the computer, I know what a Kernel is and am now pretty familiar with at the very least Windows Operating System Services. I wish to begin tracking my own machines errors. I understand that most kernel debugging is done on a second machine but I don't have one. And also I understand the goal of the debugger seems to be less about run of the mill errors and more about development time strategies but I'm sure there is more to this. This is my first go at this and I thought maybe I could get some suggestions on where to go from here. I would really like to learn ways to fix my machine and also maybe pick up some tricks on the dev side as well. I hope this isn't too broad a question or too generalized. I'm really just looking for the keywords and an overview of the more routine strategies used. thx

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  • How to save/retrieve words to/from SQlite database?

    - by user998032
    Sorry if I repeat my question but I have still had no clues of what to do and how to deal with the question. My app is a dictionary. I assume that users will need to add words that they want to memorise to a Favourite list. Thus, I created a Favorite button that works on two phases: short-click to save the currently-view word into the Favourite list; and long-click to view the Favourite list so that users can click on any words to look them up again. I go for using a SQlite database to store the favourite words but I wonder how I can do this task. Specifically, my questions are: Should I use the current dictionary SQLite database or create a new SQLite database to favorite words? In each case, what codes do I have to write to cope with the mentioned task? Could anyone there kindly help? Here is the dictionary code: package mydict.app; import java.util.ArrayList; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteException; import android.util.Log; public class DictionaryEngine { static final private String SQL_TAG = "[MyAppName - DictionaryEngine]"; private SQLiteDatabase mDB = null; private String mDBName; private String mDBPath; //private String mDBExtension; public ArrayList<String> lstCurrentWord = null; public ArrayList<String> lstCurrentContent = null; //public ArrayAdapter<String> adapter = null; public DictionaryEngine() { lstCurrentContent = new ArrayList<String>(); lstCurrentWord = new ArrayList<String>(); } public DictionaryEngine(String basePath, String dbName, String dbExtension) { //mDBExtension = getResources().getString(R.string.dbExtension); //mDBExtension = dbExtension; lstCurrentContent = new ArrayList<String>(); lstCurrentWord = new ArrayList<String>(); this.setDatabaseFile(basePath, dbName, dbExtension); } public boolean setDatabaseFile(String basePath, String dbName, String dbExtension) { if (mDB != null) { if (mDB.isOpen() == true) // Database is already opened { if (basePath.equals(mDBPath) && dbName.equals(mDBName)) // the opened database has the same name and path -> do nothing { Log.i(SQL_TAG, "Database is already opened!"); return true; } else { mDB.close(); } } } String fullDbPath=""; try { fullDbPath = basePath + dbName + "/" + dbName + dbExtension; mDB = SQLiteDatabase.openDatabase(fullDbPath, null, SQLiteDatabase.OPEN_READWRITE|SQLiteDatabase.NO_LOCALIZED_COLLATORS); } catch (SQLiteException ex) { ex.printStackTrace(); Log.i(SQL_TAG, "There is no valid dictionary database " + dbName +" at path " + basePath); return false; } if (mDB == null) { return false; } this.mDBName = dbName; this.mDBPath = basePath; Log.i(SQL_TAG,"Database " + dbName + " is opened!"); return true; } public void getWordList(String word) { String query; // encode input String wordEncode = Utility.encodeContent(word); if (word.equals("") || word == null) { query = "SELECT id,word FROM " + mDBName + " LIMIT 0,15" ; } else { query = "SELECT id,word FROM " + mDBName + " WHERE word >= '"+wordEncode+"' LIMIT 0,15"; } //Log.i(SQL_TAG, "query = " + query); Cursor result = mDB.rawQuery(query,null); int indexWordColumn = result.getColumnIndex("Word"); int indexContentColumn = result.getColumnIndex("Content"); if (result != null) { int countRow=result.getCount(); Log.i(SQL_TAG, "countRow = " + countRow); lstCurrentWord.clear(); lstCurrentContent.clear(); if (countRow >= 1) { result.moveToFirst(); String strWord = Utility.decodeContent(result.getString(indexWordColumn)); String strContent = Utility.decodeContent(result.getString(indexContentColumn)); lstCurrentWord.add(0,strWord); lstCurrentContent.add(0,strContent); int i = 0; while (result.moveToNext()) { strWord = Utility.decodeContent(result.getString(indexWordColumn)); strContent = Utility.decodeContent(result.getString(indexContentColumn)); lstCurrentWord.add(i,strWord); lstCurrentContent.add(i,strContent); i++; } } result.close(); } } public Cursor getCursorWordList(String word) { String query; // encode input String wordEncode = Utility.encodeContent(word); if (word.equals("") || word == null) { query = "SELECT id,word FROM " + mDBName + " LIMIT 0,15" ; } else { query = "SELECT id,content,word FROM " + mDBName + " WHERE word >= '"+wordEncode+"' LIMIT 0,15"; } //Log.i(SQL_TAG, "query = " + query); Cursor result = mDB.rawQuery(query,null); return result; } public Cursor getCursorContentFromId(int wordId) { String query; // encode input if (wordId <= 0) { return null; } else { query = "SELECT id,content,word FROM " + mDBName + " WHERE Id = " + wordId ; } //Log.i(SQL_TAG, "query = " + query); Cursor result = mDB.rawQuery(query,null); return result; } public Cursor getCursorContentFromWord(String word) { String query; // encode input if (word == null || word.equals("")) { return null; } else { query = "SELECT id,content,word FROM " + mDBName + " WHERE word = '" + word + "' LIMIT 0,1"; } //Log.i(SQL_TAG, "query = " + query); Cursor result = mDB.rawQuery(query,null); return result; } public void closeDatabase() { mDB.close(); } public boolean isOpen() { return mDB.isOpen(); } public boolean isReadOnly() { return mDB.isReadOnly(); } } And here is the code below the Favourite button to save to and load the Favourite list: btnAddFavourite = (ImageButton) findViewById(R.id.btnAddFavourite); btnAddFavourite.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // Add code here to save the favourite, e.g. in the db. Toast toast = Toast.makeText(ContentView.this, R.string.messageWordAddedToFarvourite, Toast.LENGTH_SHORT); toast.show(); } }); btnAddFavourite.setOnLongClickListener(new View.OnLongClickListener() { @Override public boolean onLongClick(View v) { // Open the favourite Activity, which in turn will fetch the saved favourites, to show them. Intent intent = new Intent(getApplicationContext(), FavViewFavourite.class); intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); getApplicationContext().startActivity(intent); return false; } }); }

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  • A Security (encryption) Dilemma

    - by TravisPUK
    I have an internal WPF client application that accesses a database. The application is a central resource for a Support team and as such includes Remote Access/Login information for clients. At the moment this database is not available via a web interface etc, but one day is likely to. The remote access information includes the username and passwords for the client's networks so that our client's software applications can be remotely supported by us. I need to store the usernames and passwords in the database and provide the support consultants access to them so that they can login to the client's system and then provide support. Hope this is making sense. So the dilemma is that I don't want to store the usernames and passwords in cleartext on the database to ensure that if the DB was ever compromised, I am not then providing access to our client's networks to whomever gets the database. I have looked at two-way encryption of the passwords, but as they say, two-way is not much different to cleartext as if you can decrypt it, so can an attacker... eventually. The problem here is that I have setup a method to use a salt and a passcode that are stored in the application, I have used a salt that is stored in the db, but all have their weaknesses, ie if the app was reflected it exposes the salts etc. How can I secure the usernames and passwords in my database, and yet still provide the ability for my support consultants to view the information in the application so they can use it to login? This is obviously different to storing user's passwords as these are one way because I don't need to know what they are. But I do need to know what the client's remote access passwords are as we need to enter them in at the time of remoting to them. Anybody have some theories on what would be the best approach here? update The function I am trying to build is for our CRM application that will store the remote access details for the client. The CRM system provides call/issue tracking functionality and during the course of investigating the issue, the support consultant will need to remote in. They will then view the client's remote access details and make the connection

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