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  • Nested luabind classes declared in Lua

    - by Matt Fichman
    I am trying to declare a class B in a namespace A using Luabind (from the Lua side). I figure that if Luabind has a clean way to do this, it would look something like this: class 'A.B' (Super) function A.B:__init() Super.__init(self) end Notice that the B class is defined in the A table. I know the following hackish way of doing this: class 'A.B' (Super) A = {} A.B = _G['A.B'] However, I would really like to know if Luabind provides this feature explicitly.

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  • Adding DataAnnontations to Generated Partial Classes

    - by Naz
    Hi I have a Subsonic3 Active Record generated partial User class which I've extended on with some methods in a separate partial class. I would like to know if it is possible to add Data Annotations to the member properties on one partial class where it's declared on the other Subsonic Generated one I tried this. public partial class User { [DataType(DataType.EmailAddress, ErrorMessage = "Please enter an email address")] public string Email { get; set; } ... } That examples gives the "Member is already defined" error. I think I might have seen an example a while ago of what I'm trying to do with Dynamic Data and Linq2Sql.

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  • How to restrict an access to some of the functions at third level in Classes (OOPs)

    - by Shantanu Gupta
    I have created a class say A which has some functions defined as protected. Now Class B inherits A and class C inherits B. Class A has private default constructor and protected parameterized constructor. I want Class B to be able to access all the protected functions defined in Class A but class C can have access on some of the functions only not all the functions and class C is inheriting class B. How can I restrict access to some of the functions of Class A from Class C ? Class A { private A(){} protected A(int ){} } Class B : A {} CLass C:B { }

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  • PHP classes totally forgotten something today - sorry

    - by russp
    Hi guys, really sorry about being "totally thick today" but I have forgotten how to do something simple - too much time not in php recently. Want to use the OS phpapi How do I print out the individual rows - see told you I was being thick today // The fields we will be fetching. if (isset($_GET['test']) && $_GET['test'] == 'plaxo') { // plaxo is a PortableContacts end-point so doesn't know about the OpenSocial specific fields $profile_fields = array(); } else { $profile_fields = array( 'aboutMe', 'displayName', 'bodyType', 'currentLocation', 'drinker', 'happiestWhen', 'lookingFor' ); } // The number of friends to fetch. $friend_count = 2; $batch = $osapi->newBatch(); // Fetch the current user. $self_request_params = array( 'userId' => $userId, // Person we are fetching. 'groupId' => '@self', // @self for one person. 'fields' => $profile_fields // Which profile fields to request. ); $batch->add($osapi->people->get($self_request_params), 'self'); // Fetch the friends of the user $friends_request_params = array( 'userId' => $userId, // Person whose friends we are fetching. 'groupId' => '@friends', // @friends for the Friends group. 'fields' => $profile_fields, // Which profile fields to request. 'count' => $friend_count // Max friends to fetch. ); $batch->add($osapi->people->get($friends_request_params), 'friends'); // Get supportedFields Request $batch->add($osapi->people->getSupportedFields(), 'supportedFields'); // Send the batch request. $result = $batch->execute(); Say I wanted to print out "aboutMe", whats the echo? cos echo $result['aboutMe'] doesn't work.

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  • iPhone: Helpful Classes or extended Subclasses which should have been in the SDK

    - by disp
    This is more a community sharing post than a real question. In my iPhone OS projects I'm always importing a helper class with helpful methods which I can use for about every project. So I thought it might be a good idea, if everyone shares some of their favorite methods, which should have been in everyones toolcase. I'll start with an extension of the NSString class, so I can make strings with dates on the fly providing format and locale. Maybe someone can find some need in this. @implementation NSString (DateHelper) +(NSString *) stringWithDate:(NSDate*)date withFormat:(NSString *)format withLocaleIdent:(NSString*)localeString{ NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; //For example @"de-DE", or @"en-US" NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:localeString]; [dateFormatter setLocale:locale]; // For example @"HH:mm" [dateFormatter setDateFormat:format]; NSString *string = [dateFormatter stringFromDate:date]; [dateFormatter release]; [locale release]; return string; } @end I'd love to see some of your tools.

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  • FindBugs and CheckForNull on classes vs. interfaces

    - by ndn
    Is there any way to let FindBugs check and warn me if a CheckForNull annotation is present on the implementation of a method in a class, but not on the declaration of the method in the interface? import javax.annotation.CheckForNull; interface Foo { public String getBar(); } class FooImpl implements Foo { @CheckForNull @Override public String getBar() { return null; } } public class FindBugsDemo { public static void main(String[] args) { Foo foo = new FooImpl(); System.out.println(foo.getBar().length()); } } I just discovered a bug in my application due to a missing null check that was not spotted by FindBugs because CheckForNull was only present on FooImpl, but not on Foo, and I don't want to spot all other locations of this problem manually.

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  • Difficulty creating classes and arrays of those classes C#

    - by Lucifer Fayte
    I'm trying to implement a Discrete Fourier Transformation algorithm for a project I'm doing in school. But creating a class is seeming to be difficult(which it shouldn't be). I'm using Visual Studio 2012. Basically I need a class called Complex to store the two values I get from a DFT; The real portion and the imaginary portion. This is what I have so far for that: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace SoundEditor_V3 { public class Complex { public double real; public double im; public Complex() { real = 0; im = 0; } } } The problem is that it doesn't recognize the constructor as a constructor, now I'm just learning C#, but I looked it up online and this is how it's supposed to look apparently. It recognizes my constructor as a method. Why is that? Am I creating the class wrong? It's doing the same thing for my Fourier class as well. So each time I try to create a Fourier object and then use it's method...there is no such thing. example, I do this: Fourier fou = new Fourier(); fou.DFT(s, N, amp, 0); and it tells me fou is a 'field' but is used like a 'type' why is it saying that? Here is the code for my Fourier class as well: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace SoundEditor_V3 { public class Fourier { //FOURIER //N = number of samples //s is the array of samples(data) //amp is the array where the complex result will be written to //start is the where in the array to start public void DFT(byte[] s, int N, ref Complex[] amp, int start) { Complex tem = new Complex(); int f; int t; for (f = 0; f < N; f++) { tem.real = 0; tem.im = 0; for (t = 0; t < N; t++) { tem.real += s[t + start] * Math.Cos(2 * Math.PI * t * f / N); tem.im -= s[t + start] * Math.Sin(2 * Math.PI * t * f / N); } amp[f].real = tem.real; amp[f].im = tem.im; } } //INVERSE FOURIER public void IDFT(Complex[] A, ref int[] s) { int N = A.Length; int t, f; double result; for (t = 0; t < N; t++) { result = 0; for (f = 0; f < N; f++) { result += A[f].real * Math.Cos(2 * Math.PI * t * f / N) - A[f].im * Math.Sin(2 * Math.PI * t * f / N); } s[t] = (int)Math.Round(result); } } } } I'm very much stuck at the moment, any and all help would be appreciated. Thank you.

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  • Classes within classes in PHP

    - by Matt
    Can you do this in PHP? I've heard conflicting opinions: Something like: Class bar { function a_function () { echo "hi!"; } } Class foo { public $bar; function __construct() { $this->bar = new bar(); } } $x = new foo(); $x->bar->a_function(); Will this echo "hi!" or not?

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  • MySQL inner join different results

    - by Darryl at NetHosted
    I am trying to work out why the following two queries return different results: SELECT DISTINCT i.id, i.date FROM `tblinvoices` i INNER JOIN `tblinvoiceitems` it ON it.userid=i.userid INNER JOIN `tblcustomfieldsvalues` cf ON it.relid=cf.relid WHERE i.`tax` = 0 AND i.`date` BETWEEN '2012-07-01' AND '2012-09-31' and SELECT DISTINCT i.id, i.date FROM `tblinvoices` i WHERE i.`tax` = 0 AND i.`date` BETWEEN '2012-07-01' AND '2012-09-31' Obviously the difference is the inner join here, but I don't understand why the one with the inner join is returning less results than the one without it, I would have thought since I didn't do any cross table references they should return the same results. The final query I am working towards is SELECT DISTINCT i.id, i.date FROM `tblinvoices` i INNER JOIN `tblinvoiceitems` it ON it.userid=i.userid INNER JOIN `tblcustomfieldsvalues` cf ON it.relid=cf.relid WHERE cf.`fieldid` =5 AND cf.`value` REGEXP '[A-Za-z]' AND i.`tax` = 0 AND i.`date` BETWEEN '2012-07-01' AND '2012-09-31' But because of the different results that seem incorrect when I add the inner join (it removes some results that should be valid) it's not working at present, thanks.

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  • Reflective discovery of an inner class in an API

    - by wassup
    Let me ask you, as this bothers me for quite a while but appears to be subjectively the best solution for my problem, if reflective discovery of an inner class for API purposes is that bad idea? First, let me explain what I mean by saying "reflective discovery" and all that stuff. I am sketching an API for a Java database system, that'll be centered around block-based entities (don't ask me what that means - that's a long story), and those entities can be read and returned to the Java code as objects subclassed from the Entity class. I have an Entity.Factory class, that, by means of fluent interfaces, takes a Class<? extends Entity> argument and then, uses an instance of Section.Builder, Property.Builder, or whatever builder the entity has, to put it into the back-end storage. The idea about registering all entity types and their builders just doesn't appeal to me, so I thought that the closest solution to the problem that'd suffice my design needs would be to discover, using reflection, all inner classes of Entity classes and find one that's called Builder. Looking for some expert insight :) And if I missed some important design details (which could happen as I tried to make this question as concise as possible), just tell me and I'll add them.

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  • How to simulate inner join on very large files in java (without running out of memory)

    - by Constantin
    I am trying to simulate SQL joins using java and very large text files (INNER, RIGHT OUTER and LEFT OUTER). The files have already been sorted using an external sort routine. The issue I have is I am trying to find the most efficient way to deal with the INNER join part of the algorithm. Right now I am using two Lists to store the lines that have the same key and iterate through the set of lines in the right file once for every line in the left file (provided the keys still match). In other words, the join key is not unique in each file so would need to account for the Cartesian product situations ... left_01, 1 left_02, 1 right_01, 1 right_02, 1 right_03, 1 left_01 joins to right_01 using key 1 left_01 joins to right_02 using key 1 left_01 joins to right_03 using key 1 left_02 joins to right_01 using key 1 left_02 joins to right_02 using key 1 left_02 joins to right_03 using key 1 My concern is one of memory. I will run out of memory if i use the approach below but still want the inner join part to work fairly quickly. What is the best approach to deal with the INNER join part keeping in mind that these files may potentially be huge public class Joiner { private void join(BufferedReader left, BufferedReader right, BufferedWriter output) throws Throwable { BufferedReader _left = left; BufferedReader _right = right; BufferedWriter _output = output; Record _leftRecord; Record _rightRecord; _leftRecord = read(_left); _rightRecord = read(_right); while( _leftRecord != null && _rightRecord != null ) { if( _leftRecord.getKey() < _rightRecord.getKey() ) { write(_output, _leftRecord, null); _leftRecord = read(_left); } else if( _leftRecord.getKey() > _rightRecord.getKey() ) { write(_output, null, _rightRecord); _rightRecord = read(_right); } else { List<Record> leftList = new ArrayList<Record>(); List<Record> rightList = new ArrayList<Record>(); _leftRecord = readRecords(leftList, _leftRecord, _left); _rightRecord = readRecords(rightList, _rightRecord, _right); for( Record equalKeyLeftRecord : leftList ){ for( Record equalKeyRightRecord : rightList ){ write(_output, equalKeyLeftRecord, equalKeyRightRecord); } } } } if( _leftRecord != null ) { write(_output, _leftRecord, null); _leftRecord = read(_left); while(_leftRecord != null) { write(_output, _leftRecord, null); _leftRecord = read(_left); } } else { if( _rightRecord != null ) { write(_output, null, _rightRecord); _rightRecord = read(_right); while(_rightRecord != null) { write(_output, null, _rightRecord); _rightRecord = read(_right); } } } _left.close(); _right.close(); _output.flush(); _output.close(); } private Record read(BufferedReader reader) throws Throwable { Record record = null; String data = reader.readLine(); if( data != null ) { record = new Record(data.split("\t")); } return record; } private Record readRecords(List<Record> list, Record record, BufferedReader reader) throws Throwable { int key = record.getKey(); list.add(record); record = read(reader); while( record != null && record.getKey() == key) { list.add(record); record = read(reader); } return record; } private void write(BufferedWriter writer, Record left, Record right) throws Throwable { String leftKey = (left == null ? "null" : Integer.toString(left.getKey())); String leftData = (left == null ? "null" : left.getData()); String rightKey = (right == null ? "null" : Integer.toString(right.getKey())); String rightData = (right == null ? "null" : right.getData()); writer.write("[" + leftKey + "][" + leftData + "][" + rightKey + "][" + rightData + "]\n"); } public static void main(String[] args) { try { BufferedReader leftReader = new BufferedReader(new FileReader("LEFT.DAT")); BufferedReader rightReader = new BufferedReader(new FileReader("RIGHT.DAT")); BufferedWriter output = new BufferedWriter(new FileWriter("OUTPUT.DAT")); Joiner joiner = new Joiner(); joiner.join(leftReader, rightReader, output); } catch (Throwable e) { e.printStackTrace(); } } } After applying the ideas from the proposed answer, I changed the loop to this private void join(RandomAccessFile left, RandomAccessFile right, BufferedWriter output) throws Throwable { long _pointer = 0; RandomAccessFile _left = left; RandomAccessFile _right = right; BufferedWriter _output = output; Record _leftRecord; Record _rightRecord; _leftRecord = read(_left); _rightRecord = read(_right); while( _leftRecord != null && _rightRecord != null ) { if( _leftRecord.getKey() < _rightRecord.getKey() ) { write(_output, _leftRecord, null); _leftRecord = read(_left); } else if( _leftRecord.getKey() > _rightRecord.getKey() ) { write(_output, null, _rightRecord); _pointer = _right.getFilePointer(); _rightRecord = read(_right); } else { long _tempPointer = 0; int key = _leftRecord.getKey(); while( _leftRecord != null && _leftRecord.getKey() == key ) { _right.seek(_pointer); _rightRecord = read(_right); while( _rightRecord != null && _rightRecord.getKey() == key ) { write(_output, _leftRecord, _rightRecord ); _tempPointer = _right.getFilePointer(); _rightRecord = read(_right); } _leftRecord = read(_left); } _pointer = _tempPointer; } } if( _leftRecord != null ) { write(_output, _leftRecord, null); _leftRecord = read(_left); while(_leftRecord != null) { write(_output, _leftRecord, null); _leftRecord = read(_left); } } else { if( _rightRecord != null ) { write(_output, null, _rightRecord); _rightRecord = read(_right); while(_rightRecord != null) { write(_output, null, _rightRecord); _rightRecord = read(_right); } } } _left.close(); _right.close(); _output.flush(); _output.close(); } UPDATE While this approach worked, it was terribly slow and so I have modified this to create files as buffers and this works very well. Here is the update ... private long getMaxBufferedLines(File file) throws Throwable { long freeBytes = Runtime.getRuntime().freeMemory() / 2; return (freeBytes / (file.length() / getLineCount(file))); } private void join(File left, File right, File output, JoinType joinType) throws Throwable { BufferedReader leftFile = new BufferedReader(new FileReader(left)); BufferedReader rightFile = new BufferedReader(new FileReader(right)); BufferedWriter outputFile = new BufferedWriter(new FileWriter(output)); long maxBufferedLines = getMaxBufferedLines(right); Record leftRecord; Record rightRecord; leftRecord = read(leftFile); rightRecord = read(rightFile); while( leftRecord != null && rightRecord != null ) { if( leftRecord.getKey().compareTo(rightRecord.getKey()) < 0) { if( joinType == JoinType.LeftOuterJoin || joinType == JoinType.LeftExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, leftRecord, null); } leftRecord = read(leftFile); } else if( leftRecord.getKey().compareTo(rightRecord.getKey()) > 0 ) { if( joinType == JoinType.RightOuterJoin || joinType == JoinType.RightExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, null, rightRecord); } rightRecord = read(rightFile); } else if( leftRecord.getKey().compareTo(rightRecord.getKey()) == 0 ) { String key = leftRecord.getKey(); List<File> rightRecordFileList = new ArrayList<File>(); List<Record> rightRecordList = new ArrayList<Record>(); rightRecordList.add(rightRecord); rightRecord = consume(key, rightFile, rightRecordList, rightRecordFileList, maxBufferedLines); while( leftRecord != null && leftRecord.getKey().compareTo(key) == 0 ) { processRightRecords(outputFile, leftRecord, rightRecordFileList, rightRecordList, joinType); leftRecord = read(leftFile); } // need a dispose for deleting files in list } else { throw new Exception("DATA IS NOT SORTED"); } } if( leftRecord != null ) { if( joinType == JoinType.LeftOuterJoin || joinType == JoinType.LeftExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, leftRecord, null); } leftRecord = read(leftFile); while(leftRecord != null) { if( joinType == JoinType.LeftOuterJoin || joinType == JoinType.LeftExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, leftRecord, null); } leftRecord = read(leftFile); } } else { if( rightRecord != null ) { if( joinType == JoinType.RightOuterJoin || joinType == JoinType.RightExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, null, rightRecord); } rightRecord = read(rightFile); while(rightRecord != null) { if( joinType == JoinType.RightOuterJoin || joinType == JoinType.RightExclusiveJoin || joinType == JoinType.FullExclusiveJoin || joinType == JoinType.FullOuterJoin ) { write(outputFile, null, rightRecord); } rightRecord = read(rightFile); } } } leftFile.close(); rightFile.close(); outputFile.flush(); outputFile.close(); } public void processRightRecords(BufferedWriter outputFile, Record leftRecord, List<File> rightFiles, List<Record> rightRecords, JoinType joinType) throws Throwable { for(File rightFile : rightFiles) { BufferedReader rightReader = new BufferedReader(new FileReader(rightFile)); Record rightRecord = read(rightReader); while(rightRecord != null){ if( joinType == JoinType.LeftOuterJoin || joinType == JoinType.RightOuterJoin || joinType == JoinType.FullOuterJoin || joinType == JoinType.InnerJoin ) { write(outputFile, leftRecord, rightRecord); } rightRecord = read(rightReader); } rightReader.close(); } for(Record rightRecord : rightRecords) { if( joinType == JoinType.LeftOuterJoin || joinType == JoinType.RightOuterJoin || joinType == JoinType.FullOuterJoin || joinType == JoinType.InnerJoin ) { write(outputFile, leftRecord, rightRecord); } } } /** * consume all records having key (either to a single list or multiple files) each file will * store a buffer full of data. The right record returned represents the outside flow (key is * already positioned to next one or null) so we can't use this record in below while loop or * within this block in general when comparing current key. The trick is to keep consuming * from a List. When it becomes empty, re-fill it from the next file until all files have * been consumed (and the last node in the list is read). The next outside iteration will be * ready to be processed (either it will be null or it points to the next biggest key * @throws Throwable * */ private Record consume(String key, BufferedReader reader, List<Record> records, List<File> files, long bufferMaxRecordLines ) throws Throwable { boolean processComplete = false; Record record = records.get(records.size() - 1); while(!processComplete){ long recordCount = records.size(); if( record.getKey().compareTo(key) == 0 ){ record = read(reader); while( record != null && record.getKey().compareTo(key) == 0 && recordCount < bufferMaxRecordLines ) { records.add(record); recordCount++; record = read(reader); } } processComplete = true; // if record is null, we are done if( record != null ) { // if the key has changed, we are done if( record.getKey().compareTo(key) == 0 ) { // Same key means we have exhausted the buffer. // Dump entire buffer into a file. The list of file // pointers will keep track of the files ... processComplete = false; dumpBufferToFile(records, files); records.clear(); records.add(record); } } } return record; } /** * Dump all records in List of Record objects to a file. Then, add that * file to List of File objects * * NEED TO PLACE A LIMIT ON NUMBER OF FILE POINTERS (check size of file list) * * @param records * @param files * @throws Throwable */ private void dumpBufferToFile(List<Record> records, List<File> files) throws Throwable { String prefix = "joiner_" + files.size() + 1; String suffix = ".dat"; File file = File.createTempFile(prefix, suffix, new File("cache")); BufferedWriter writer = new BufferedWriter(new FileWriter(file)); for( Record record : records ) { writer.write( record.dump() ); } files.add(file); writer.flush(); writer.close(); }

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  • Why my inner class DO see a NON static variable?

    - by Roman
    Earlier I had a problem when an inner anonymous class did not see a field of the "outer" class. I needed to make a final variable to make it visible to the inner class. Now I have an opposite situation. In the "outer" class "ClientListener" I use an inner class "Thread" and the "Thread" class I have the "run" method and does see the "earPort" from the "outer" class! Why? import java.io.IOException; import java.net.*; import java.io.BufferedReader; import java.io.InputStreamReader; public class ClientsListener { private int earPort; // Constructor. public ClientsListener(int earPort) { this.earPort = earPort; } public void starListening() { Thread inputStreamsGenerator = new Thread() { public void run() { System.out.println(earPort); try { System.out.println(earPort); ServerSocket listeningSocket = new ServerSocket(earPort); Socket serverSideSocket = listeningSocket.accept(); BufferedReader in = new BufferedReader(new InputStreamReader(serverSideSocket.getInputStream())); } catch (IOException e) { System.out.println(""); } } }; inputStreamsGenerator.start(); } }

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  • SQL Outer Join on a bunch of Inner Joined results

    - by Matthew Frederick
    I received some great help on joining a table to itself and am trying to take it to the next level. The SQL below is from the help but with my addition of the select line beginning with COUNT, the inner join to the Recipient table, and the Group By. SELECT Event.EventID AS EventID, Event.EventDate AS EventDateUTC, Participant2.ParticipantID AS AwayID, Participant1.ParticipantID AS HostID, COUNT(Recipient.ChallengeID) AS AllChallenges FROM Event INNER JOIN Matchup Matchup1 ON (Event.EventID = Matchup1.EventID) INNER JOIN Matchup Matchup2 ON (Event.EventID = Matchup2.EventID) INNER JOIN Participant Participant1 ON (Matchup1.Host = 1 AND Matchup1.ParticipantID = Participant1.ParticipantID) INNER JOIN Participant Participant2 ON (Matchup2.Host != 1 AND Matchup2.ParticipantID = Participant2.ParticipantID) INNER JOIN Recipient ON (Event.EventID = Recipient.EventID) WHERE Event.CategoryID = 1 AND Event.Resolved = 0 AND Event.Type = 1 GROUP BY Recipient.ChallengeID ORDER BY EventDateUTC ASC My goal is to get a count of how many rows in the Recipient table match the EventID in Event. This code works fine except that I also want to get results where there are 0 matching rows in Recipient. I want 15 rows (= the number of events) but I get 2 rows, one with a count of 1 and one with a count of 2 (which is appropriate for an inner join as there are 3 rows in the sample Recipient table, one for one EventID and two for another EventID). I thought that either a LEFT join or an OUTER join was what I was looking for, but I know that I'm not quite getting how the tables are actually joined. A LEFT join there gives me one more row with 0, which happens to be EventID 1 (first thing in the table), but that's all. Errors advise me that I can't just change that INNER join to an OUTER. I tried some parenthesizing and some subselects and such but can't seem to make it work.

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  • Generating EF Code First model classes from an existing database

    - by Jon Galloway
    Entity Framework Code First is a lightweight way to "turn on" data access for a simple CLR class. As the name implies, the intended use is that you're writing the code first and thinking about the database later. However, I really like the Entity Framework Code First works, and I want to use it in existing projects and projects with pre-existing databases. For example, MVC Music Store comes with a SQL Express database that's pre-loaded with a catalog of music (including genres, artists, and songs), and while it may eventually make sense to load that seed data from a different source, for the MVC 3 release we wanted to keep using the existing database. While I'm not getting the full benefit of Code First - writing code which drives the database schema - I can still benefit from the simplicity of the lightweight code approach. Scott Guthrie blogged about how to use entity framework with an existing database, looking at how you can override the Entity Framework Code First conventions so that it can work with a database which was created following other conventions. That gives you the information you need to create the model classes manually. However, it turns out that with Entity Framework 4 CTP 5, there's a way to generate the model classes from the database schema. Once the grunt work is done, of course, you can go in and modify the model classes as you'd like, but you can save the time and frustration of figuring out things like mapping SQL database types to .NET types. Note that this template requires Entity Framework 4 CTP 5 or later. You can install EF 4 CTP 5 here. Step One: Generate an EF Model from your existing database The code generation system in Entity Framework works from a model. You can add a model to your existing project and delete it when you're done, but I think it's simpler to just spin up a separate project to generate the model classes. When you're done, you can delete the project without affecting your application, or you may choose to keep it around in case you have other database schema updates which require model changes. I chose to add the Model classes to the Models folder of a new MVC 3 application. Right-click the folder and select "Add / New Item..."   Next, select ADO.NET Entity Data Model from the Data Templates list, and name it whatever you want (the name is unimportant).   Next, select "Generate from database." This is important - it's what kicks off the next few steps, which read your database's schema.   Now it's time to point the Entity Data Model Wizard at your existing database. I'll assume you know how to find your database - if not, I covered that a bit in the MVC Music Store tutorial section on Models and Data. Select your database, uncheck the "Save entity connection settings in Web.config" (since we won't be using them within the application), and click Next.   Now you can select the database objects you'd like modeled. I just selected all tables and clicked Finish.   And there's your model. If you want, you can make additional changes here before going on to generate the code.   Step Two: Add the DbContext Generator Like most code generation systems in Visual Studio lately, Entity Framework uses T4 templates which allow for some control over how the code is generated. K Scott Allen wrote a detailed article on T4 Templates and the Entity Framework on MSDN recently, if you'd like to know more. Fortunately for us, there's already a template that does just what we need without any customization. Right-click a blank space in the Entity Framework model surface and select "Add Code Generation Item..." Select the Code groupt in the Installed Templates section and pick the ADO.NET DbContext Generator. If you don't see this listed, make sure you've got EF 4 CTP 5 installed and that you're looking at the Code templates group. Note that the DbContext Generator template is similar to the EF POCO template which came out last year, but with "fix up" code (unnecessary in EF Code First) removed.   As soon as you do this, you'll two terrifying Security Warnings - unless you click the "Do not show this message again" checkbox the first time. It will also be displayed (twice) every time you rebuild the project, so I checked the box and no immediate harm befell my computer (fingers crossed!).   Here's the payoff: two templates (filenames ending with .tt) have been added to the project, and they've generated the code I needed.   The "MusicStoreEntities.Context.tt" template built a DbContext class which holds the entity collections, and the "MusicStoreEntities.tt" template build a separate class for each table I selected earlier. We'll customize them in the next step. I recommend copying all the generated .cs files into your application at this point, since accidentally rebuilding the generation project will overwrite your changes if you leave them there. Step Three: Modify and use your POCO entity classes Note: I made a bunch of tweaks to my POCO classes after they were generated. You don't have to do any of this, but I think it's important that you can - they're your classes, and EF Code First respects that. Modify them as you need for your application, or don't. The Context class derives from DbContext, which is what turns on the EF Code First features. It holds a DbSet for each entity. Think of DbSet as a simple List, but with Entity Framework features turned on.   //------------------------------------------------------------------------------ // <auto-generated> // This code was generated from a template. // // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. // </auto-generated> //------------------------------------------------------------------------------ namespace EF_CodeFirst_From_Existing_Database.Models { using System; using System.Data.Entity; public partial class Entities : DbContext { public Entities() : base("name=Entities") { } public DbSet<Album> Albums { get; set; } public DbSet<Artist> Artists { get; set; } public DbSet<Cart> Carts { get; set; } public DbSet<Genre> Genres { get; set; } public DbSet<OrderDetail> OrderDetails { get; set; } public DbSet<Order> Orders { get; set; } } } It's a pretty lightweight class as generated, so I just took out the comments, set the namespace, removed the constructor, and formatted it a bit. Done. If I wanted, though, I could have added or removed DbSets, overridden conventions, etc. using System.Data.Entity; namespace MvcMusicStore.Models { public class MusicStoreEntities : DbContext { public DbSet Albums { get; set; } public DbSet Genres { get; set; } public DbSet Artists { get; set; } public DbSet Carts { get; set; } public DbSet Orders { get; set; } public DbSet OrderDetails { get; set; } } } Next, it's time to look at the individual classes. Some of mine were pretty simple - for the Cart class, I just need to remove the header and clean up the namespace. //------------------------------------------------------------------------------ // // This code was generated from a template. // // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. // //------------------------------------------------------------------------------ namespace EF_CodeFirst_From_Existing_Database.Models { using System; using System.Collections.Generic; public partial class Cart { // Primitive properties public int RecordId { get; set; } public string CartId { get; set; } public int AlbumId { get; set; } public int Count { get; set; } public System.DateTime DateCreated { get; set; } // Navigation properties public virtual Album Album { get; set; } } } I did a bit more customization on the Album class. Here's what was generated: //------------------------------------------------------------------------------ // // This code was generated from a template. // // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. // //------------------------------------------------------------------------------ namespace EF_CodeFirst_From_Existing_Database.Models { using System; using System.Collections.Generic; public partial class Album { public Album() { this.Carts = new HashSet(); this.OrderDetails = new HashSet(); } // Primitive properties public int AlbumId { get; set; } public int GenreId { get; set; } public int ArtistId { get; set; } public string Title { get; set; } public decimal Price { get; set; } public string AlbumArtUrl { get; set; } // Navigation properties public virtual Artist Artist { get; set; } public virtual Genre Genre { get; set; } public virtual ICollection Carts { get; set; } public virtual ICollection OrderDetails { get; set; } } } I removed the header, changed the namespace, and removed some of the navigation properties. One nice thing about EF Code First is that you don't have to have a property for each database column or foreign key. In the Music Store sample, for instance, we build the app up using code first and start with just a few columns, adding in fields and navigation properties as the application needs them. EF Code First handles the columsn we've told it about and doesn't complain about the others. Here's the basic class: using System.ComponentModel; using System.ComponentModel.DataAnnotations; using System.Web.Mvc; using System.Collections.Generic; namespace MvcMusicStore.Models { public class Album { public int AlbumId { get; set; } public int GenreId { get; set; } public int ArtistId { get; set; } public string Title { get; set; } public decimal Price { get; set; } public string AlbumArtUrl { get; set; } public virtual Genre Genre { get; set; } public virtual Artist Artist { get; set; } public virtual List OrderDetails { get; set; } } } It's my class, not Entity Framework's, so I'm free to do what I want with it. I added a bunch of MVC 3 annotations for scaffolding and validation support, as shown below: using System.ComponentModel; using System.ComponentModel.DataAnnotations; using System.Web.Mvc; using System.Collections.Generic; namespace MvcMusicStore.Models { [Bind(Exclude = "AlbumId")] public class Album { [ScaffoldColumn(false)] public int AlbumId { get; set; } [DisplayName("Genre")] public int GenreId { get; set; } [DisplayName("Artist")] public int ArtistId { get; set; } [Required(ErrorMessage = "An Album Title is required")] [StringLength(160)] public string Title { get; set; } [Required(ErrorMessage = "Price is required")] [Range(0.01, 100.00, ErrorMessage = "Price must be between 0.01 and 100.00")] public decimal Price { get; set; } [DisplayName("Album Art URL")] [StringLength(1024)] public string AlbumArtUrl { get; set; } public virtual Genre Genre { get; set; } public virtual Artist Artist { get; set; } public virtual List<OrderDetail> OrderDetails { get; set; } } } The end result was that I had working EF Code First model code for the finished application. You can follow along through the tutorial to see how I built up to the finished model classes, starting with simple 2-3 property classes and building up to the full working schema. Thanks to Diego Vega (on the Entity Framework team) for pointing me to the DbContext template.

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  • CSS and HTML incoherences when declaring multiple classes

    - by Cesco
    I'm learning CSS "seriously" for the first time, but I found the way you deal with multiple CSS classes in CSS and HTML quite incoherent. For example I learned that if I want to declare multiple CSS classes with a common style applied to them, I have to write: .style1, .style2, .style3 { color: red; } Then, if I have to declare an HTML tag that has multiple classes applied to it, I have to write: <div class="style1 style2 style3"></div> And I'm asking why? From my personal point of view it would be more coherent if both could be declared by using a comma to separate each class, or if both could be declared using a space; after all IMHO we're still talking about multiple classes, in both CSS and HTML. I think that it would make more sense if I could write this to declare a div with multiple classes applied: <div class="style1, style2, style3"></div> Am I'm missing something important? Could you explain me if there's a valid reason behind these two different syntaxes?

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  • Présentation de ClassObject.js : un framework JavaScript de construction de classes, par Abraham Tewa

    Bonjour, Je vous propose de découvrir un article sur ClassObject, un framework javascript de construction de classes, développé par votre serviteur. Ce framework permet de créer simplement des classes avec des attributs et des méthodes publiques, protégées et privées, statiques (ou non), constantes (ou non), tout en prenant en charge l'héritage. Vous pouvez poster dans cette discussion vos commentaires concernant l'article ClassObject.js : un framework JavaScript de construction de classes Merci à tous....

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  • What are the consequences of immutable classes with references to mutable classes?

    - by glenviewjeff
    I've recently begun adopting the best practice of designing my classes to be immutable per Effective Java [Bloch2008]. I have a series of interrelated questions about degrees of mutability and their consequences. I have run into situations where a (Java) class I implemented is only "internally immutable" because it uses references to other mutable classes. In this case, the class under development appears from the external environment to have state. Do any of the benefits (see below) of immutable classes hold true even by only "internally immutable" classes? Is there an accepted term for the aforementioned "internal mutability"? Wikipedia's immutable object page uses the unsourced term "deep immutability" to describe an object whose references are also immutable. Is the distinction between mutability and side-effect-ness/state important? Josh Bloch lists the following benefits of immutable classes: are simple to construct, test, and use are automatically thread-safe and have no synchronization issues do not need a copy constructor do not need an implementation of clone allow hashCode to use lazy initialization, and to cache its return value do not need to be copied defensively when used as a field make good Map keys and Set elements (these objects must not change state while in the collection) have their class invariant established once upon construction, and it never needs to be checked again always have "failure atomicity" (a term used by Joshua Bloch) : if an immutable object throws an exception, it's never left in an undesirable or indeterminate state

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  • embedding LEFT OUTER JOIN within INNER JOIN

    - by user3424954
    I am having some problems with one of the question's answered in the book "SQL FOR MERE MORTALS". Here is the problem statement Here is the Database Structure Here is the answer which I am unable to comprehend Here is an answer which looks perfect to me Now the problem with the first answer I am having is: We first use LEFT OUTER JOIN for recipe class and recipes. So it selects all recipe class rows but only matching recipes. Perfecty fine as the question is demanding. Lets call this result set R. Now in the next step when we use INNER JOIN to join RecipieIngridients, it should filter out the rows from R in which Recipie ID doesn't match with the Recipe Id in Recipie Ingredients and hence filtering out the related Recipe class and recipe description also(Since it filters out the entire row of R). So this contradicts with the problem which demands all recipieID and RecipieDescription to be displayed from Recipe_Classes Table in this very step only. How can it be correct. Or Am i Missing some concept.

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  • Unit-Testing functions which have parameters of classes where source code is not accessible

    - by McMannus
    Relating to this question, I have another question regarding unit testing functions in the utility classes: Assume you have function signatures like this: public function void doSomething(InternalClass obj, InternalElement element) where InternalClass and InternalElement are both Classes which source code are not available, because they are hidden in the API. Additionally, doSomething only operates on obj and element. I thought about mocking those classes away but this option is not possible due to the fact that they do not implement an interface at all which I could use for my Mocking classes. However, I need to fill obj with defined data to test doSomething. How can this problem be solved?

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  • Best Practices in .NET XML Serialization of Complex Classes

    This article will show you XML serialization, so simply added in code, is not a magical stick. Serialization must be planned in full detail when working with complex classes, rather than expected to work by itself. Loss of planning work leads to redesign work later on, when maintaining serialization of original classes becomes too expensive or even hits the limit after which serialization of original classes is not possible without loss of data.

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