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  • Repository Pattern and Entity Framework.

    - by vitorcast
    Hi people, I want to make an implementation with repository pattern with ASP.NET MVC 2 and Entity Framework but I have had some issues in the process. First of all, I have 2 entities that has a relationship between them, like Order and Product. When I generate my dbml file it gaves me a class Order with a property that map a "ProductSet" and one class Product with a property that map wich Order that Product relates itself. So I create my Repository pattern like IReporitory with the basic CRUD operations and inside my controllers I implement the ProductRepository or OrderRepository. The problem occurs when I try to create Product and have to assign my Order on it, like ProductOne.Order = _orderRepository.Find(orderId); That operation gave me some strange behavior and I can't find out what is wrong with it. Thanks for the help.

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  • Repository Pattern with Entity Framework 3.5

    - by Ravi
    I am developing a Database File System. I am using - .Net framework 3.5 Entity Framework 3.5 WPF with MVVM pattern The project spans across multiple assemblies each using same model. One assembly,let's call it a "server", only adds data to the database using EF i.e. same model.Other assemblies (including the UI) both reads and writes the data.The changes made by server should immediately reflect in other assemblies. The database contains self referencing tables where each entity can have single OR no parent and (may be) some children. I want to use repository pattern which can also provide some mechanism to handle this hierarchical nature. I have already done reading on this on Code Project. It shares the same context(entities) everywhere. My question is - Should I share the same context everywhere? What are the advantages and disadvantages of doing that?

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  • Repository Pattern with Entity Framework 3.5

    - by Ravi
    I am developing a Database File System. I am using - .Net framework 3.5 Entity Framework 3.5 WPF with MVVM pattern The project spans across multiple assemblies each using same model. One assembly,let's call it a "server", only adds data to the database using EF i.e. same model.Other assemblies (including the UI) both reads and writes the data.The changes made by server should immediately reflect in other assemblies. The database contains self referencing tables where each entity can have single OR no parent and (may be) some children. I want to use repository pattern which can also provide some mechanism to handle this hierarchical nature. I have already done reading on this on Code Project. It shares the same context(entities) everywhere. My question is - Should I share the same context everywhere? What are the advantages and disadvantages of doing that?

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  • NULL value when using NSDateFormatter after setting NSDate property via XML parsing

    - by David A Gibson
    Hello, I am using the following code to try and display in a time in a table cell. TimeSlot *timeSlot = [timeSlots objectAtIndex:indexPath.row]; NSDateFormatter *timeFormat = [[NSDateFormatter alloc] init]; [timeFormat setDateFormat:@"HH:mm:ss"]; NSLog(@"Time: %@", timeSlot.time); NSDate *mydate = timeSlot.time; NSLog(@"Time: %@", mydate); NSString *theTime = [timeFormat stringFromDate:mydate]; NSLog(@"Time: %@", theTime); The log output is this: 2010-04-14 10:23:54.626 MyApp[1080:207] Time: 2010-04-14T10:23:54 2010-04-14 10:23:54.627 MyApp[1080:207] Time: 2010-04-14T10:23:54 2010-04-14 10:23:54.627 MyApp[1080:207] Time: (null) I am new to developing for the iPhone and as it all compiles with no errors or warnings I am at a loss as to why I am getting NULL in the log. Is there anything wrong with this code? Thanks Further Info I used the code exactly from your answer lugte098 just to check and I was getting dates which leads me to believe that my TimeSlot class can't have a date correctly set in it's NSDate property. So my question becomes - how from XML do I set a NSDate property? I have this code (abbreviated): -(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *) string { if ([currentElement isEqualToString:@"Time"]) { currentTimeSlot.time = string } } Thanks

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  • Null Reference Exception In LINQ DataContext

    - by Frank
    I have a Null Reference Exception Caused by this code: var recentOrderers = (from p in db.CMS where p.ODR_DATE > DateTime.Today - new TimeSpan(60, 0, 0, 0) select p.SOLDNUM).Distinct(); result = (from p in db.CMS where p.ORDER_ST2 == "SH" && p.ODR_DATE > DateTime.Today - new TimeSpan(365, 0, 0, 0) && p.ODR_DATE < DateTime.Today - new TimeSpan(60, 0, 0, 0) && !(recentOrderers.Contains(p.SOLDNUM))/**/ select p.SOLDNUM).Distinct().Count(); result is of double type. When I comment out: !(recentOrderers.Contains(p.SOLDNUM)) The code runs fine. I have verified that recentOrderers is not null, and when I run: if(recentOrderes.Contains(0)) return; Execution follows this path and returns. Not sure what is going on, since I use similar code above it: var m = (from p in db.CMS where p.ORDER_ST2 == "SH" select p.SOLDNUM).Distinct(); double result = (from p in db.CUST join r in db.DEMGRAPH on p.CUSTNUM equals r.CUSTNUM where p.CTYPE3 == "cmh" && !(m.Contains(p.CUSTNUM)) && r.ColNEWMEMBERDAT.Value.Year > 1900 select p.CUSTNUM).Distinct().Count(); which also runs flawlessly. After noting the similarity, can anyone help? Thanks in advance. -Frank GTP, Inc.

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  • Variable 'app' in url-pattern for servlet mapping

    - by Brian
    I'm learning Spring MVC (and servlets in general) and following springsource's mvc-ajax example, which uses annotated controller methods. It appears that there is only one url-pattern (in web.xml) mapped to a servlet in that example: /app/* I've deployed the app as a WAR file, and the actual, ugly URL I'm requesting is http://127.0.0.1:8080/org.springframework.samples.mvc.ajax-1.0.0-20100407.233245-1/account. So, it appears that 'app' in '/app/*' is a variable corresponding to 'org.springframework.samples.mvc.ajax-1.0.0-20100407.233245-1', however, it isn't universal because it isn't usable in my own app, and it contradicts my understanding that url-pattern contains the portion of the URL after the app name. So, what is 'app'? Where is it configured?

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  • when to use the abstract factory pattern?

    - by hguser
    Hi: I want to know when we need to use the abstract factory pattern. Here is an example,I want to know if it is necessary. The UML THe above is the abstract factory pattern, it is recommended by my classmate. THe following is myown implemention. I do not think it is necessary to use the pattern. And the following is some core codes: package net; import java.io.IOException; import java.util.HashMap; import java.util.Map; import java.util.Properties; public class Test { public static void main(String[] args) throws IOException, InstantiationException, IllegalAccessException, ClassNotFoundException { DaoRepository dr=new DaoRepository(); AbstractDao dao=dr.findDao("sql"); dao.insert(); } } class DaoRepository { Map<String, AbstractDao> daoMap=new HashMap<String, AbstractDao>(); public DaoRepository () throws IOException, InstantiationException, IllegalAccessException, ClassNotFoundException { Properties p=new Properties(); p.load(DaoRepository.class.getResourceAsStream("Test.properties")); initDaos(p); } public void initDaos(Properties p) throws InstantiationException, IllegalAccessException, ClassNotFoundException { String[] daoarray=p.getProperty("dao").split(","); for(String dao:daoarray) { AbstractDao ad=(AbstractDao)Class.forName(dao).newInstance(); daoMap.put(ad.getID(),ad); } } public AbstractDao findDao(String id) {return daoMap.get(id);} } abstract class AbstractDao { public abstract String getID(); public abstract void insert(); public abstract void update(); } class SqlDao extends AbstractDao { public SqlDao() {} public String getID() {return "sql";} public void insert() {System.out.println("sql insert");} public void update() {System.out.println("sql update");} } class AccessDao extends AbstractDao { public AccessDao() {} public String getID() {return "access";} public void insert() {System.out.println("access insert");} public void update() {System.out.println("access update");} } And the content of the Test.properties is just one line: dao=net.SqlDao,net.SqlDao So any ont can tell me if this suitation is necessary?

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  • MySQL - NULL value check and Dynamic SQL inside stored procedure

    - by Mithun P
    DROP PROCEDURE IF EXISTS HaveSomeFun; CREATE PROCEDURE HaveSomeFun(user_id CHAR(50),house_id CHAR(50),room_id CHAR(50),fun_text TEXT,video_url CHAR(100)) BEGIN DECLARE query_full TEXT; SET @fields_part = 'INSERT INTO fun(FunKey,UserKey,FunBody,LastModified'; SET @values_part = CONCAT(') VALUES( NewBinKey(), KeyToBin(\"', user_id, '\"), \"', fun_text, '\", NOW() '); IF (house_id) THEN SET @fields_part = CONCAT(@fields_part, ', HouseKey'); SET @values_part = CONCAT(@values_part, ', KeyToBin(\'', house_id, '\')'); END IF; IF (room_id) THEN SET @fields_part = CONCAT(@fields_part, ', RoomKey'); SET @values_part = CONCAT(@values_part, ', KeyToBin(\'', room_id, '\')'); END IF; IF (video_url IS NOT NULL) THEN SET @fields_part = CONCAT(@fields_part, ', VideoURL'); SET @values_part = CONCAT(@values_part, ', "', video_url, '"'); END IF; SET query_full = CONCAT(@fields_part, @values_part, ' );'); SET @query_full = query_full; PREPARE STMT FROM @query_full; EXECUTE STMT; SELECT query_full; END; And CALL HaveSomeFun('29B455DE-A9BC-102D-9C16-00163EEDFCFC', '', 'F82C47A8-64DE-11DF-9D7E-0026B9481364', 'Jokes apart', ''); will construct the below string in the variable query_full INSERT INTO fun(FunKey,UserKey,FunBody,LastModified, VideoURL) VALUES( NewBinKey(), KeyToBin("29B455DE-A9BC-102D-9C16-00163EEDFCFC"), "Jokes apart", NOW() , "" ); But I need to get INSERT INTO fun(FunKey,UserKey,FunBody,LastModified, RoomKey, VideoURL) VALUES( NewBinKey(), KeyToBin("29B455DE-A9BC-102D-9C16-00163EEDFCFC"), "Jokes apart", NOW() , KeyToBin('F82C47A8-64DE-11DF-9D7E-0026B9481364'), "" ); Something is missing in the check IF (room_id) THEN. But I cannot impose IF (room_id IS NOT NULL) THEN since it will create KeyToBin('') and RoomKey is foreign key , KeyToBin('') will produce an invalid RoomKey. Any Idea?

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  • Understanding pattern matching with cons operator

    - by Mathias
    In "Programming F#" I came across a pattern-matching like this one (I simplified a bit): let rec len list = match list with | [] -> 0 | [_] -> 1 | head :: tail -> 1 + len tail;; Practically, I understand that the last match recognizes the head and tail of the list. Conceptually, I don't get why it works. As far as I understand, :: is the cons operator, which appends a value in head position of a list, but it doesn't look to me like it is being used as an operator here. Should I understand this as a "special syntax" for lists, where :: is interpreted as an operator or a "match pattern" depending on context? Or can the same idea be extended for types other than lists, with other operators?

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  • Mimic property/list changes on an object on another object

    - by soundslike
    I need to mimic changes (property/list) changes on an object and then apply it to another object to keep the structure/property the same. In essence it's like cloning etc. the biz rules require certain properties to not be applied to the other object, so I can't just clone the object otherwise this would be easy. I've already walked the source object to get INotifyPropertyChanged and IListChanged events, so I have the "source" and the args (Property or List) changed event notifications. Given that I guess I could build a reflection "hierarchy path" starting from the top level of the source object to get to the Property or List changed "source" (which could be several levels deep). Ignoring for the moment that certain object properties should not propagate to the other object, what's a way to build this "path"? Is a brute force top level down to build the "path" (and discard on the way back up if we don't hit the original changed event "source") the only way to do it? Any clever ideas on how to mimic changes from one object to another object?

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  • When to use the Flyweight Pattern

    - by elmt
    So I've just gotten on the boost train and was checking out the flyweight pattern and was interested in implementing it in my project. Obviously, it doesn't make sense to use it on any class that has only has one instance of it. However, say I have 5 instances of an class. Should I be using the flyweight pattern or should it be only used for a class that has at least N instances. I realize that many factors will influence this answer (how many fields there are, the size of the fields, etc.).

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  • Problem with literal arguments in the PATTERN string for a python 2to3 fixer

    - by Zxaos
    Hi folks. I'm writing a fixer for the 2to3 tool in python. In my pattern string, I have a section where I'd like to match an empty string as an argument, or an empty unicode string. The relevant chunk of my pattern looks like: (args='""' | args='u""') My issue is the second option never matches. Even if it's alone, it won't match. However, if I simply say args=any and then output args, I can catch cases where args is exactly equal to the second option. Is there some weird unicode handling thing going on? Why won't the second literal option ever match?

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  • The maximum row size for the used table type, not counting BLOBs, is 65535. You have to change some columns to TEXT or BLOBs

    - by Matthew Chambers
    Hello I am getting the below message on a table i am trying to create The maximum row size for the used table type, not counting BLOBs, is 65535. You have to change some columns to TEXT or BLOBs Anyone know the answer to this please -- Table warrington_central.job -- ----------------------------------------------------- CREATE TABLE IF NOT EXISTS warrington_central.job ( id MEDIUMINT(8) UNSIGNED NOT NULL AUTO_INCREMENT , alias_title VARCHAR(255) NOT NULL , reference_number VARCHAR(100) NOT NULL , title VARCHAR(255) NOT NULL , primary_category SMALLINT(5) UNSIGNED NOT NULL , secondary_category SMALLINT(5) UNSIGNED NOT NULL , tertiary_category SMALLINT(5) UNSIGNED NULL , address_id BIGINT(20) UNSIGNED NOT NULL , geolocation_id BIGINT(20) UNSIGNED NULL , company VARCHAR(255) NOT NULL , description VARCHAR(10000) NOT NULL , skills_required VARCHAR(10000) NOT NULL , job_type TINYINT(2) UNSIGNED NOT NULL , experience_months_required TINYINT(2) UNSIGNED NOT NULL , experience_years_required TINYINT(2) UNSIGNED NOT NULL , salary_range VARCHAR(30) NOT NULL , extra_benefits_above_salary VARCHAR(500) NOT NULL , available_from DATE NULL , available_to DATE NULL , extra_location_details VARCHAR(1000) NOT NULL , contact_email VARCHAR(100) NOT NULL , contact_phone_number VARCHAR(20) NOT NULL , contact_mobile_number VARCHAR(20) NOT NULL , terms_conditions_application VARCHAR(5000) NOT NULL , link_to_profile ENUM('0','1') NOT NULL , created_on DATETIME NOT NULL , updated_on DATETIME NOT NULL , updated_by BIGINT(20) UNSIGNED NOT NULL , add_contact_form ENUM('0','1') NOT NULL , admin_package_id TINYINT(1) UNSIGNED NOT NULL , package_start_date DATETIME NOT NULL , package_end_date DATETIME NULL , package_comment VARCHAR(500) NOT NULL , viewable_to_members_only ENUM('0','1') NOT NULL , advertise_to DATETIME NULL , show_comment ENUM('0','1') NOT NULL , hits BIGINT(20) UNSIGNED NOT NULL DEFAULT 0 , visible ENUM('0','1') NOT NULL DEFAULT '0' , approved ENUM('I/* large SQL query (3.9 KB), snipped at 2,000 characters / / SQL Error (1118): Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. You have to change some columns to TEXT or BLOBs */ SHOW WARNINGS;

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  • Cannot pass null to server using jQuery AJAX. Value received at the server is the string "null".

    - by Tom
    I am converting a javascript/php/ajax application to use jQuery to ensure compatibility with browsers other than Firefox. I am having trouble passing true, false, and null values using jQuery's ajax function. Javascript code: $.ajax ( { url : <server_url>, dataType: 'json', type : 'POST', success : receiveAjaxMessage, data: { valueTrue : true, valueFalse : false, valueNull : null } } ); PHP code: var_dump($_POST); Server output: array(3) { ["valueTrue"]=> string(4) "true" ["valueFalse"]=> string(5) "false" ["valueNull"]=> string(4) "null" } The problem is that the null, true, and false values are being converted to strings. The Javascript AJAX code currently in use passes null, true, and false correctly but only works in Firefox. Does anyone know how to solve this problem using jQuery? Here is some working code (not using jQuery) to compare with the code not-working code given above. Javascript Code: ajaxPort.send ( <server_url>, { valueTrue : true, valueFalse : false, valueNull : null } ); PHP code: var_dump(json_decode(file_get_contents('php://input'), true)); Server output: array(3) { ["valueTrue"]=> bool(true) ["valueFalse"]=> bool(false) ["valueNull"]=> NULL } Note that the null, true, and false values are correctly received. Note also that in the second method the $_POST array is not used in the PHP code. I think this is the key to the problem, but I cannot find a way to replicate this behavior using jQuery.

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  • "Invalid use of Null" when using Str() with a Null Recordset field, but Str(Null) works fine

    - by Mike Spross
    I'm banging my head against the wall on this one. I was looking at some old database reporting code written in VB6 and case across this line (the code is moving data from a "source" database into a reporting database): rsTarget!VehYear = Trim(Str(rsSource!VehYear)) When rsSource!VehYear is Null, the above line generates an "Invalid use of Null" run-time error. If I break on the above line and type the following in the Immediate pane: ?rsSource!VehYear It outputs Null. Fine, that makes sense. Next, I try to reproduce the error: ?Str(rsSource!VehYear) I get an "Invalid use of Null" error. However, if I type the following into the Immediate window: ?Str(Null) I don't get an error. It simply outputs Null. If I repeat the same experiment with Trim() instead of Str(), everything works fine. ?Trim(rsSource!VehYear) returns Null, as does ?Trim(Null). No run-time errors. So, my question is, how can Str(rsSource!VehYear) possibly throw an "Invalid use of Null" error when Str(Null) does not, when I know that rsSource!VehYear is equal to Null?

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  • $_FILES is null, $_POST is not null

    - by Cory Dee
    When I am going to upload a file, my $_POST variable knows the file name, but the $_FILES variable is null. I've used this code before, so I'm really stumped. Here's what I'm using for input: <label for="importFile">Attach Resume:</label> <input type="hidden" name="MAX_FILE_SIZE" value="10000000"> <input type="file" name="importFile" id="importFile" class="validate['required']"> And for processing: $uploaddir = "E:/Sites/OPL/2008/assets/apps/newjobs/resumes/"; $uploadfile = $uploaddir . time() . '-' . urlencode(basename($_FILES['importFile']['name'])); if (!move_uploaded_file($_FILES['importFile']['tmp_name'], $uploadfile)) { echo 'Error uploading file. Error number: ' . $_FILES['importFile']['error']; var_dump($_FILES['importFile']); echo $_POST['importFile']; die(); } Which is giving me this result: Error uploading file. Error number: NULL Maintaining The OPL Website.doc Any help would be greatly appreciated.

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  • Are Promises/A a good event design pattern to implement even in synchronous languages like PHP?

    - by Xeoncross
    I have always kept an eye out for event systems when writing code in scripting languages. Web applications have a history of allowing the user to add plugins and modules whenever needed. In most PHP systems you have a global/singleton event object which all interested parties tie into and wait to be alerted to changes. Event::on('event_name', $callback); Recently more patterns like the observer have been used for things like jQuery. $(el).on('event', callback); Even PHP now has built in classes for it. class Blog extends SplSubject { public function save() { $this->notify(); } } Anyway, the Promises/A proposal has caught my eye. It is designed for asynchronous systems, but I'm wondering if it is also a good design to implement now that even synchronous languages like PHP are changing. Combining Dependency Injection with Promises/A seems it might be the best combination for handling events currently.

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  • Creating Entity Framework objects with Unity for Unit of Work/Repository pattern

    - by TobyEvans
    Hi there, I'm trying to implement the Unit of Work/Repository pattern, as described here: http://blogs.msdn.com/adonet/archive/2009/06/16/using-repository-and-unit-of-work-patterns-with-entity-framework-4-0.aspx This requires each Repository to accept an IUnitOfWork implementation, eg an EF datacontext extended with a partial class to add an IUnitOfWork interface. I'm actually using .net 3.5, not 4.0. My basic Data Access constructor looks like this: public DataAccessLayer(IUnitOfWork unitOfWork, IRealtimeRepository realTimeRepository) { this.unitOfWork = unitOfWork; this.realTimeRepository = realTimeRepository; } So far, so good. What I'm trying to do is add Dependency Injection using the Unity Framework. Getting the EF data context to be created with Unity was an adventure, as it had trouble resolving the constructor - what I did in the end was to create another constructor in my partial class with a new overloaded constructor, and marked that with [InjectionConstructor] [InjectionConstructor] public communergyEntities(string connectionString, string containerName) :this() { (I know I need to pass the connection string to the base object, that can wait until once I've got all the objects initialising correctly) So, using this technique, I can happily resolve my entity framework object as an IUnitOfWork instance thus: using (IUnityContainer container = new UnityContainer()) { container.RegisterType<IUnitOfWork, communergyEntities>(); container.Configure<InjectedMembers>() .ConfigureInjectionFor<communergyEntities>( new InjectionConstructor("a", "b")) DataAccessLayer target = container.Resolve<DataAccessLayer>(); Great. What I need to do now is create the reference to the repository object for the DataAccessLayer - the DAL only needs to know the interface, so I'm guessing that I need to instantiate it as part of the Unity Resolve statement, passing it the appropriate IUnitOfWork interface. In the past, I would have just passed the Repository constructor the db connection string, and it would have gone away, created a local Entity Framework object and used that just for the lifetime of the Repository method. This is different, in that I create an Entity Framework instance as an IUnitOfWork implementation during the Unity Resolve statement, and it's that instance I need to pass into the constructor of the Repository - is that possible, and if so, how? I'm wondering if I could make the Repository a property and mark it as a Dependency, but that still wouldn't solve the problem of how to create the Repository with the IUnitOfWork object that the DAL is being Resolved with I'm not sure if I've understood this pattern correctly, and will happily take advice on the best way to implement it - Entity Framework is staying, but Unity can be swapped out if not the best approach. If I've got the whole thing upside down, please tell me thanks

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  • MySQL "ERROR 1005 (HY000): Can't create table 'foo.#sql-12c_4' (errno: 150)"

    - by Ankur Banerjee
    Hi, I was working on creating some tables in database foo, but every time I end up with errno 150 regarding the foreign key. Firstly, here's my code for creating tables: CREATE TABLE Clients ( client_id CHAR(10) NOT NULL , client_name CHAR(50) NOT NULL , provisional_license_num CHAR(50) NOT NULL , client_address CHAR(50) NULL , client_city CHAR(50) NULL , client_county CHAR(50) NULL , client_zip CHAR(10) NULL , client_phone INT NULL , client_email CHAR(255) NULL , client_dob DATETIME NULL , test_attempts INT NULL ); CREATE TABLE Applications ( application_id CHAR(10) NOT NULL , office_id INT NOT NULL , client_id CHAR(10) NOT NULL , instructor_id CHAR(10) NOT NULL , car_id CHAR(10) NOT NULL , application_date DATETIME NULL ); CREATE TABLE Instructors ( instructor_id CHAR(10) NOT NULL , office_id INT NOT NULL , instructor_name CHAR(50) NOT NULL , instructor_address CHAR(50) NULL , instructor_city CHAR(50) NULL , instructor_county CHAR(50) NULL , instructor_zip CHAR(10) NULL , instructor_phone INT NULL , instructor_email CHAR(255) NULL , instructor_dob DATETIME NULL , lessons_given INT NULL ); CREATE TABLE Cars ( car_id CHAR(10) NOT NULL , office_id INT NOT NULL , engine_serial_num CHAR(10) NULL , registration_num CHAR(10) NULL , car_make CHAR(50) NULL , car_model CHAR(50) NULL ); CREATE TABLE Offices ( office_id INT NOT NULL , office_address CHAR(50) NULL , office_city CHAR(50) NULL , office_County CHAR(50) NULL , office_zip CHAR(10) NULL , office_phone INT NULL , office_email CHAR(255) NULL ); CREATE TABLE Lessons ( lesson_num INT NOT NULL , client_id CHAR(10) NOT NULL , date DATETIME NOT NULL , time DATETIME NOT NULL , milegage_used DECIMAL(5, 2) NULL , progress CHAR(50) NULL ); CREATE TABLE DrivingTests ( test_num INT NOT NULL , client_id CHAR(10) NOT NULL , test_date DATETIME NOT NULL , seat_num INT NOT NULL , score INT NULL , test_notes CHAR(255) NULL ); ALTER TABLE Clients ADD PRIMARY KEY (client_id); ALTER TABLE Applications ADD PRIMARY KEY (application_id); ALTER TABLE Instructors ADD PRIMARY KEY (instructor_id); ALTER TABLE Offices ADD PRIMARY KEY (office_id); ALTER TABLE Lessons ADD PRIMARY KEY (lesson_num); ALTER TABLE DrivingTests ADD PRIMARY KEY (test_num); ALTER TABLE Applications ADD CONSTRAINT FK_Applications_Offices FOREIGN KEY (office_id) REFERENCES Offices (office_id); ALTER TABLE Applications ADD CONSTRAINT FK_Applications_Clients FOREIGN KEY (client_id) REFERENCES Clients (client_id); ALTER TABLE Applications ADD CONSTRAINT FK_Applications_Instructors FOREIGN KEY (instructor_id) REFERENCES Instructors (instructor_id); ALTER TABLE Applications ADD CONSTRAINT FK_Applications_Cars FOREIGN KEY (car_id) REFERENCES Cars (car_id); ALTER TABLE Lessons ADD CONSTRAINT FK_Lessons_Clients FOREIGN KEY (client_id) REFERENCES Clients (client_id); ALTER TABLE Cars ADD CONSTRAINT FK_Cars_Offices FOREIGN KEY (office_id) REFERENCES Offices (office_id); ALTER TABLE Clients ADD CONSTRAINT FK_DrivingTests_Clients FOREIGN KEY (client_id) REFERENCES Clients (client_id); These are the errors that I get: mysql> ALTER TABLE Applications ADD CONSTRAINT FK_Applications_Cars FOREIGN KEY (car_id) REFERENCES Cars (car_id); ERROR 1005 (HY000): Can't create table 'foo.#sql-12c_4' (errno: 150) I ran SHOW ENGINE INNODB STATUS which gives a more detailed error description: ------------------------ LATEST FOREIGN KEY ERROR ------------------------ 100509 20:59:49 Error in foreign key constraint of table practice9/#sql-12c_4: FOREIGN KEY (car_id) REFERENCES Cars (car_id): Cannot find an index in the referenced table where the referenced columns appear as the first columns, or column types in the table and the referenced table do not match for constraint. Note that the internal storage type of ENUM and SET changed in tables created with >= InnoDB-4.1.12, and such columns in old tables cannot be referenced by such columns in new tables. See http://dev.mysql.com/doc/refman/5.1/en/innodb-foreign-key-constraints.html for correct foreign key definition. ------------ I searched around on StackOverflow and elsewhere online - came across a helpful blog post here with pointers on how to resolve this error - but I can't figure out what's going wrong. Any help would be appreciated!

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  • What is happening in Crockford's object creation technique?

    - by Chris Noe
    There are only 3 lines of code, and yet I'm having trouble fully grasping this: Object.create = function (o) { function F() {} F.prototype = o; return new F(); }; newObject = Object.create(oldObject); (from Prototypal Inheritance) 1) Object.create() starts out by creating an empty function called F. I'm thinking that a function is a kind of object. Where is this F object being stored? Globally I guess. 2) Next our oldObject, passed in as o, becomes the prototype of function F. Function (i.e., object) F now "inherits" from our oldObject, in the sense that name resolution will route through it. Good, but I'm curious what the default prototype is for an object, Object? Is that also true for a function-object? 3) Finally, F is instantiated and returned, becoming our newObject. Is the "new" operation strictly necessary here? Doesn't F already provide what we need, or is there a critical difference between function-objects and non-function-objects? Clearly it won't be possible to have a constructor function using this technique. What happens the next time Object.create() is called? Is global function F overwritten? Surely it is not reused, because that would alter previously configured objects. And what happens if multiple threads call Object.create(), is there any sort of synchronization to prevent race conditions on F?

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  • How to check for undefined or null variable in javascript

    - by Thomas Wanner
    We are frequently using the following code pattern in our javascript code if(typeof(some_variable) != 'undefined' && some_variable != null) { // do something with some_variable } and I'm wondering whether there is a less verbose way of checking that has the same effect. According to some forums and literature saying simply if(some_variable) { // do something with some_variable } should have the same effect. Unfortunately, Firebug evaluates such a statement as error on runtime when some_variable is undefined, whereas the first one is just fine for him. Is this only an (unwanted) behavior of Firebug or is there really some difference between those two ways ?

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