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  • Is "If a method is re-used without changes, put the method in a base class, else create an interface" a good rule-of-thumb?

    - by exizt
    A colleague of mine came up with a rule-of-thumb for choosing between creating a base class or an interface. He says: Imagine every new method that you are about to implement. For each of them, consider this: will this method be implemented by more than one class in exactly this form, without any change? If the answer is "yes", create a base class. In every other situation, create an interface. For example: Consider the classes cat and dog, which extend the class mammal and have a single method pet(). We then add the class alligator, which doesn't extend anything and has a single method slither(). Now, we want to add an eat() method to all of them. If the implementation of eat() method will be exactly the same for cat, dog and alligator, we should create a base class (let's say, animal), which implements this method. However, if it's implementation in alligator differs in the slightest way, we should create an IEat interface and make mammal and alligator implement it. He insists that this method covers all cases, but it seems like over-simplification to me. Is it worth following this rule-of-thumb?

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  • It's not just “Single Sign-on” by Steve Knott (aurionPro SENA)

    - by Greg Jensen
    It is true that Oracle Enterprise Single Sign-on (Oracle ESSO) started out as purely an application single sign-on tool but as we have seen in the previous articles in this series the product has matured into a suite of tools that can do more than just automated single sign-on and can also provide rapidly deployed, cost effective solution to many demanding password management problems. In the last article of this series I would like to discuss three cases where customers faced password scenarios that required more than just single sign-on and how some of the less well known tools in the Oracle ESSO suite “kitbag” helped solve these challenges. Case #1 One of the issues often faced by our customers is how to keep their applications compliant. I had a client who liked the idea of automated single sign-on for most of his applications but had a key requirement to actually increase the security for one specific SOX application. For the SOX application he wanted to secure access by using two-factor authentication with a smartcard. The problem was that the application did not support two-factor authentication. The solution was to use a feature from the Oracle ESSO suite called authentication manager. This feature enables you to have multiple authentication methods for the same user which in this case was a smartcard and the Windows password.  Within authentication manager each authenticator can be configured with a security grade so we gave the smartcard a high grade and the Windows password a normal grade. Security grading in Oracle ESSO can be configured on a per application basis so we set the SOX application to require the higher grade smartcard authenticator. The end result for the user was that they enjoyed automated single sign-on for most of the applications apart from the SOX application. When the SOX application was launched, the user was required by ESSO to present their smartcard before being given access to the application. Case #2 Another example solving compliance issues was in the case of a large energy company who had a number of core billing applications. New regulations required that users change their password regularly and use a complex password. The problem facing the customer was that the core billing applications did not have any native user password change functionality. The customer could not replace the core applications because of the cost and time required to re-develop them. With a reputation for innovation aurionPro SENA were approached to provide a solution to this problem using Oracle ESSO. Oracle ESSO has a password expiry feature that can be triggered periodically based on the timestamp of the users’ last password creation therefore our strategy here was to leverage this feature to provide the password change experience. The trigger can launch an application change password event however in this scenario there was no native change password feature that could be launched therefore a “dummy” change password screen was created that could imitate the missing change password function and connect to the application database on behalf of the user. Oracle ESSO was configured to trigger a change password event every 60 days. After this period if the user launched the application Oracle ESSO would detect the logon screen and invoke the password expiry feature. Oracle ESSO would trigger the “dummy screen,” detect it automatically as the application change password screen and insert a complex password on behalf of the user. After the password event had completed the user was logged on to the application with their new password. All this was provided at a fraction of the cost of re-developing the core applications. Case #3 Recent popular initiatives such as the BYOD and working from home schemes bring with them many challenges in administering “unmanaged machines” and sometimes “unmanageable users.” In a recent case, a client had a dispersed community of casual contractors who worked for the business using their own laptops to access applications. To improve security the around password management the security goal was to provision the passwords directly to these contractors. In a previous article we saw how Oracle ESSO has the capability to provision passwords through Provisioning Gateway but the challenge in this scenario was how to get the Oracle ESSO agent to the casual contractor on an unmanaged machine. The answer was to use another tool in the suite, Oracle ESSO Anywhere. This component can compile the normal Oracle ESSO functionality into a deployment package that can be made available from a website in a similar way to a streamed application. The ESSO Anywhere agent does not actually install into the registry or program files but runs in a folder within the user’s profile therefore no local administrator rights are required for installation. The ESSO Anywhere package can also be configured to stay persistent or disable itself at the end of the user’s session. In this case the user just needed to be told where the website package was located and download the package. Once the download was complete the agent started automatically and the user was provided with single sign-on to their applications without ever knowing the application passwords. Finally, as we have seen in these series Oracle ESSO not only has great utilities in its own tool box but also has direct integration with Oracle Privileged Account Manager, Oracle Identity Manager and Oracle Access Manager. Integrated together with these tools provides a complete and complementary platform to address even the most complex identity and access management requirements. So what next for Oracle ESSO? “Agentless ESSO available in the cloud” – but that will be a subject for a future Oracle ESSO series!                                                                                                                               

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  • Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

    - by mortezam
    This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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  • how to update child records when updating the Master table using Linq [closed]

    - by user20358
    I currently use a general repositry class that can update only a single table like so public abstract class MyRepository<T> : IRepository<T> where T : class { protected IObjectSet<T> _objectSet; protected ObjectContext _context; public MyRepository(ObjectContext Context) { _objectSet = Context.CreateObjectSet<T>(); _context = Context; } public IQueryable<T> GetAll() { return _objectSet.AsQueryable(); } public IQueryable<T> Find(Expression<Func<T, bool>> filter) { return _objectSet.Where(filter); } public void Add(T entity) { _objectSet.AddObject(entity); _context.ObjectStateManager.ChangeObjectState(entity, System.Data.EntityState.Added); _context.SaveChanges(); } public void Update(T entity) { _context.ObjectStateManager.ChangeObjectState(entity, System.Data.EntityState.Modified); _context.SaveChanges(); } public void Delete(T entity) { _objectSet.Attach(entity); _context.ObjectStateManager.ChangeObjectState(entity, System.Data.EntityState.Deleted); _objectSet.DeleteObject(entity); _context.SaveChanges(); } } For every table class generated by my EDMX designer I create another class like this public class CustomerRepo : MyRepository<Customer> { public CustomerRepo (ObjectContext context) : base(context) { } } for any updates that I need to make to a particular table I do this: Customer CustomerObj = new Customer(); CustomerObj.Prop1 = ... CustomerObj.Prop2 = ... CustomerObj.Prop3 = ... CustomerRepo.Update(CustomerObj); This works perfectly well when I am updating just to the specific table called Customer. Now if I need to also update each row of another table which is a child of Customer called Orders what changes do I need to make to the class MyRepository. Orders table will have multiple records for a Customer record and multiple fields too, say for example Field1, Field2, Field3. So my questions are: 1.) If I only need to update Field1 of the Orders table for some rows based on a condition and Field2 for some other rows based on a different condition then what changes I need to do? 2.) If there is no such condition and all child rows need to be updated with the same value for all rows then what changes do I need to do? Thanks for taking the time. Look forward to your inputs...

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  • Getting a Temporary Table Returned from from Dynamic SQL in SQL Server 05, and parsing

    - by gloomy.penguin
    So I was requested to make a few things.... (it is Monday morning and for some reason this whole thing is turning out to be really hard for me to explain so I am just going to try and post a lot of my code; sorry) First, I needed a table: CREATE TABLE TICKET_INFORMATION ( TICKET_INFO_ID INT IDENTITY(1,1) NOT NULL, TICKET_TYPE INT, TARGET_ID INT, TARGET_NAME VARCHAR(100), INFORMATION VARCHAR(MAX), TIME_STAMP DATETIME DEFAULT GETUTCDATE() ) -- insert this row for testing... INSERT INTO TICKET_INFORMATION (TICKET_TYPE, TARGET_ID, TARGET_NAME, INFORMATION) VALUES (1,1,'RT_ID','IF_ID,int=1&IF_ID,int=2&OTHER,varchar(10)=val,ue3&OTHER,varchar(10)=val,ue4') The Information column holds data that needs to be parsed into a table. This is where I am having problems. In the resulting table, Target_Name needs to become a column that holds Target_ID as a value for each row in the resulting table. The string that needs to be parsed is in this format: @var_name1,@var_datatype1=@var_value1&@var_name2,@var_datatype2=@var_value2&@var_name3,@var_datatype3=@var_value3 And what I ultimately need as a result (in a table or table variable): RT_ID IF_ID OTHER 1 1 val,ue3 1 2 val,ue3 1 1 val,ue4 1 2 val,ue4 And I need to be able to join on the result. Initially, I was just going to make this a function that returns a table variable but for some reason I can't figure out how to get it into an actual table variable. Whatever parses the string needs to be able to be used directly in queries so I don't think a stored procedure is really the right thing to be using. This is the code that parses the Information string... it returns in a temporary table. -- create/empty temp table for var_name, var_type and var_value fields if OBJECT_ID('tempdb..#temp') is not null drop table #temp create table #temp (row int identity(1,1), var_name varchar(max), var_type varchar(30), var_value varchar(max)) -- just setting stuff up declare @target_name varchar(max), @target_id varchar(max), @info varchar(max) set @target_name = (select target_name from ticket_information where ticket_info_id = 1) set @target_id = (select target_id from ticket_information where ticket_info_id = 1) set @info = (select information from ticket_information where ticket_info_id = 1) --print @info -- some of these variables are re-used later declare @col_type varchar(20), @query varchar(max), @select as varchar(max) set @query = 'select ' + @target_id + ' as ' + @target_name + ' into #target; ' set @select = 'select * into ##global_temp from #target' declare @var_name varchar(100), @var_type varchar(100), @var_value varchar(100) declare @comma_pos int, @equal_pos int, @amp_pos int set @comma_pos = 1 set @equal_pos = 1 set @amp_pos = 0 -- while loop to parse the string into a table while @amp_pos < len(@info) begin -- get new comma position set @comma_pos = charindex(',',@info,@amp_pos+1) -- get new equal position set @equal_pos = charindex('=',@info,@amp_pos+1) -- set stuff that is going into the table set @var_name = substring(@info,@amp_pos+1,@comma_pos-@amp_pos-1) set @var_type = substring(@info,@comma_pos+1,@equal_pos-@comma_pos-1) -- get new ampersand position set @amp_pos = charindex('&',@info,@amp_pos+1) if @amp_pos=0 or @amp_pos<@equal_pos set @amp_pos = len(@info)+1 -- set last variable for insert into table set @var_value = substring(@info,@equal_pos+1,@amp_pos-@equal_pos-1) -- put stuff into the temp table insert into #temp (var_name, var_type, var_value) values (@var_name, @var_type, @var_value) -- is this a new field? if ((select count(*) from #temp where var_name = (@var_name)) = 1) begin set @query = @query + ' create table #' + @var_name + '_temp (' + @var_name + ' ' + @var_type + '); ' set @select = @select + ', #' + @var_name + '_temp ' end set @query = @query + ' insert into #' + @var_name + '_temp values (''' + @var_value + '''); ' end if OBJECT_ID('tempdb..##global_temp') is not null drop table ##global_temp exec (@query + @select) --select @query --select @select select * from ##global_temp Okay. So, the result I want and need is now in ##global_temp. How do I put all of that into something that can be returned from a function (or something)? Or can I get something more useful returned from the exec statement? In the end, the results of the parsed string need to be in a table that can be joined on and used... Ideally this would have been a view but I guess it can't with all the processing that needs to be done on that information string. Ideas? Thanks!

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  • LaTeX table too wide. How to make it fit?

    - by Erik B
    I just started to learn latex and now I'm trying to create a table. This is my code: \begin{table} \caption{Top Scorers} \begin{tabular}{ l l } \hline \bf Goals & \bf Players\\ \hline 4 & First Last, First Last, First Last, First Last\\ 3 & First Last\\ 2 & First Last\\ 1 & First Last, First Last, First Last, First Last, First Last, First Last, First Last, First Last, First Last, First Last, First Last, First Last, First Last\\ \hline \end{tabular} \end{table} The problem is that the table is wider than the page. I was hoping that it would automatically fit to the page like normal text does, but it didn't. How do I tell latex to make the table fit to the page?

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  • How to make a table, which is wider than screen size, scrollable?

    - by understack
    I've a table with 2 columns and each column is 800px wide. I want to show this table in 800x50 window. So there should be horizontal and vertical scrollbar to view complete table. While I've found few related solutions (this and this) on SO, they only work if table width is smaller than screen size. In my case screen size is 1200px and total table width is 1600px. How could I do this? i want to achieve something like this.

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  • How to make last line of each table's part unfinished in latex longtable?

    - by diver_ru
    I have a table that automatically stretched over several pages by longtable package. \begin{longtable}{| l | l |} \hline A & B \\ \hline \endfirsthead \multicolumn{3}{l}{Table \thetable{} -- finishing} \\ \hline \endhead a1 & b1 \\ \hline a1 & b2 \\ hline ........ \end{longtable} Suppose that table broken (automatically) between first and second lines. Now i have this: ------- |A | B| ------- |a1|b1| ------- <page break> Table 1 -- finishing. ------- |a2|b2| ------- I want the following effect: ------- |A | B| ------- |a1|b1| <page break> Table 1 -- finishing. ------- |a2|b2| ------- I.e. last line of broken part should be unfinished.

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  • SQL SERVER – Single Wait Time Introduction with Simple Example – Wait Type – Day 2 of 28

    - by pinaldave
    In this post, let’s delve a bit more in depth regarding wait stats. The very first question: when do the wait stats occur? Here is the simple answer. When SQL Server is executing any task, and if for any reason it has to wait for resources to execute the task, this wait is recorded by SQL Server with the reason for the delay. Later on we can analyze these wait stats to understand the reason the task was delayed and maybe we can eliminate the wait for SQL Server. It is not always possible to remove the wait type 100%, but there are few suggestions that can help. Before we continue learning about wait types and wait stats, we need to understand three important milestones of the query life-cycle. Running - a query which is being executed on a CPU is called a running query. This query is responsible for CPU time. Runnable – a query which is ready to execute and waiting for its turn to run is called a runnable query. This query is responsible for Single Wait time. (In other words, the query is ready to run but CPU is servicing another query). Suspended – a query which is waiting due to any reason (to know the reason, we are learning wait stats) to be converted to runnable is suspended query. This query is responsible for wait time. (In other words, this is the time we are trying to reduce). In simple words, query execution time is a summation of the query Executing CPU Time (Running) + Query Wait Time (Suspended) + Query Single Wait Time (Runnable). Again, it may be possible a query goes to all these stats multiple times. Let us try to understand the whole thing with a simple analogy of a taxi and a passenger. Two friends, Tom and Danny, go to the mall together. When they leave the mall, they decide to take a taxi. Tom and Danny both stand in the line waiting for their turn to get into the taxi. This is the Signal Wait Time as they are ready to get into the taxi but the taxis are currently serving other customer and they have to wait for their turn. In other word they are in a runnable state. Now when it is their turn to get into the taxi, the taxi driver informs them he does not take credit cards and only cash is accepted. Neither Tom nor Danny have enough cash, they both cannot get into the vehicle. Tom waits outside in the queue and Danny goes to ATM to fetch the cash. During this time the taxi cannot wait, they have to let other passengers get into the taxi. As Tom and Danny both are outside in the queue, this is the Query Wait Time and they are in the suspended state. They cannot do anything till they get the cash. Once Danny gets the cash, they are both standing in the line again, creating one more Single Wait Time. This time when their turn comes they can pay the taxi driver in cash and reach their destination. The time taken for the taxi to get from the mall to the destination is running time (CPU time) and the taxi is running. I hope this analogy is bit clear with the wait stats. You can check the single wait stats using following query of Glenn Berry. -- Signal Waits for instance SELECT CAST(100.0 * SUM(signal_wait_time_ms) / SUM (wait_time_ms) AS NUMERIC(20,2)) AS [%signal (cpu) waits], CAST(100.0 * SUM(wait_time_ms - signal_wait_time_ms) / SUM (wait_time_ms) AS NUMERIC(20,2)) AS [%resource waits] FROM sys.dm_os_wait_stats OPTION (RECOMPILE); Higher the single wait stats are not good for the system. Very high value indicates CPU pressure. In my experience, when systems are running smooth and without any glitch the single wait stat is lower than 20%. Again, this number can be debated (and it is from my experience and is not documented anywhere). In other words, lower is better and higher is not good for the system. In future articles we will discuss in detail the various wait types and wait stats and their resolution. Read all the post in the Wait Types and Queue series. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL DMV, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • Joins in single-table queries

    - by Rob Farley
    Tables are only metadata. They don’t store data. I’ve written something about this before, but I want to take a viewpoint of this idea around the topic of joins, especially since it’s the topic for T-SQL Tuesday this month. Hosted this time by Sebastian Meine (@sqlity), who has a whole series on joins this month. Good for him – it’s a great topic. In that last post I discussed the fact that we write queries against tables, but that the engine turns it into a plan against indexes. My point wasn’t simply that a table is actually just a Clustered Index (or heap, which I consider just a special type of index), but that data access always happens against indexes – never tables – and we should be thinking about the indexes (specifically the non-clustered ones) when we write our queries. I described the scenario of looking up phone numbers, and how it never really occurs to us that there is a master list of phone numbers, because we think in terms of the useful non-clustered indexes that the phone companies provide us, but anyway – that’s not the point of this post. So a table is metadata. It stores information about the names of columns and their data types. Nullability, default values, constraints, triggers – these are all things that define the table, but the data isn’t stored in the table. The data that a table describes is stored in a heap or clustered index, but it goes further than this. All the useful data is going to live in non-clustered indexes. Remember this. It’s important. Stop thinking about tables, and start thinking about indexes. So let’s think about tables as indexes. This applies even in a world created by someone else, who doesn’t have the best indexes in mind for you. I’m sure you don’t need me to explain Covering Index bit – the fact that if you don’t have sufficient columns “included” in your index, your query plan will either have to do a Lookup, or else it’ll give up using your index and use one that does have everything it needs (even if that means scanning it). If you haven’t seen that before, drop me a line and I’ll run through it with you. Or go and read a post I did a long while ago about the maths involved in that decision. So – what I’m going to tell you is that a Lookup is a join. When I run SELECT CustomerID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 285; against the AdventureWorks2012 get the following plan: I’m sure you can see the join. Don’t look in the query, it’s not there. But you should be able to see the join in the plan. It’s an Inner Join, implemented by a Nested Loop. It’s pulling data in from the Index Seek, and joining that to the results of a Key Lookup. It clearly is – the QO wouldn’t call it that if it wasn’t really one. It behaves exactly like any other Nested Loop (Inner Join) operator, pulling rows from one side and putting a request in from the other. You wouldn’t have a problem accepting it as a join if the query were slightly different, such as SELECT sod.OrderQty FROM Sales.SalesOrderHeader AS soh JOIN Sales.SalesOrderDetail as sod on sod.SalesOrderID = soh.SalesOrderID WHERE soh.SalesPersonID = 285; Amazingly similar, of course. This one is an explicit join, the first example was just as much a join, even thought you didn’t actually ask for one. You need to consider this when you’re thinking about your queries. But it gets more interesting. Consider this query: SELECT SalesOrderID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 276 AND CustomerID = 29522; It doesn’t look like there’s a join here either, but look at the plan. That’s not some Lookup in action – that’s a proper Merge Join. The Query Optimizer has worked out that it can get the data it needs by looking in two separate indexes and then doing a Merge Join on the data that it gets. Both indexes used are ordered by the column that’s indexed (one on SalesPersonID, one on CustomerID), and then by the CIX key SalesOrderID. Just like when you seek in the phone book to Farley, the Farleys you have are ordered by FirstName, these seek operations return the data ordered by the next field. This order is SalesOrderID, even though you didn’t explicitly put that column in the index definition. The result is two datasets that are ordered by SalesOrderID, making them very mergeable. Another example is the simple query SELECT CustomerID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 276; This one prefers a Hash Match to a standard lookup even! This isn’t just ordinary index intersection, this is something else again! Just like before, we could imagine it better with two whole tables, but we shouldn’t try to distinguish between joining two tables and joining two indexes. The Query Optimizer can see (using basic maths) that it’s worth doing these particular operations using these two less-than-ideal indexes (because of course, the best indexese would be on both columns – a composite such as (SalesPersonID, CustomerID – and it would have the SalesOrderID column as part of it as the CIX key still). You need to think like this too. Not in terms of excusing single-column indexes like the ones in AdventureWorks2012, but in terms of having a picture about how you’d like your queries to run. If you start to think about what data you need, where it’s coming from, and how it’s going to be used, then you will almost certainly write better queries. …and yes, this would include when you’re dealing with regular joins across multiples, not just against joins within single table queries.

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  • OOP concept: is it possible to update the class of an instantiated object?

    - by Federico
    I am trying to write a simple program that should allow a user to save and display sets of heterogeneous, but somehow related data. For clarity sake, I will use a representative example of vehicles. The program flow is like this: The program creates a Garage object, which is basically a class that can contain a list of vehicles objects Then the users creates Vehicles objects, these Vehicles each have a property, lets say License Plate Nr. Once created, the Vehicle object get added to a list within the Garage object --Later on--, the user can specify that a given Vehicle object is in fact a Car object or a Truck object (thus giving access to some specific attributes such as Number of seats for the Car, or Cargo weight for the truck) At first sight, this might look like an OOP textbook question involving a base class and inheritance, but the problem is more subtle because at the object creation time (and until the user decides to give more info), the computer doesn't know the exact Vehicle type. Hence my question: how would you proceed to implement this program flow? Is OOP the way to go? Just to give an initial answer, here is what I've came up until now. There is only one Vehicle class and the various properties/values are handled by the main program (not the class) through a dictionary. However, I'm pretty sure that there must be a more elegant solution (I'm developing using VB.net): Public Class Garage Public GarageAdress As String Private _ListGarageVehicles As New List(Of Vehicles) Public Sub AddVehicle(Vehicle As Vehicles) _ListGarageVehicles.Add(Vehicle) End Sub End Class Public Class Vehicles Public LicensePlateNumber As String Public Enum VehicleTypes Generic = 0 Car = 1 Truck = 2 End Enum Public VehicleType As VehicleTypes Public DictVehicleProperties As New Dictionary(Of String, String) End Class NOTE that in the example above the public/private modifiers do not necessarily reflect the original code

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  • Solution with multiple projects and (GitHub) single issue tracker and repository

    - by Luiz Damim
    I have a Visual Studio solution with multiple projects: Acme.Core Acme.Core.Tests Acme.UI.MvcSite1 Acme.UI.MvcSite2 Acme.UI.WinformsApp1 Acme.UI.WinformsApp2 ... The entire solution is checked-in in a single GitHub (private) repo. Acme.Core contains our business logic and all UI projects are deployables. UI projects have different requirements and features, but some of them are implemented in more than one project. All issues are opened in a single issue tracker and classified using labels ([MvcSite1], [WinformsApp1], etc) but I'm thinking it's starting to get messy. Is it ok to use a single repository and issue tracker to track multiple projects in one solution?

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  • Backup a Single Table in SQL Server using SSMS

    - by Greg Low
    Our buddy Buck Woody made an interesting post about a common question: "How do I back up a single table in SQL Server?" That got me thinking about what a backup of a table really is. BCP is often used to get the data but you want the schema as well. For reasonable-sized tables, the easiest way to do this now is to create a script using SQL Server Management Studio. To do this, you: 1. Right-click the database (note not the table) 2. Choose Tasks > Generate Scripts 3. In the Choose Objects pane,...(read more)

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  • Recommend an open source CMS for single page web site

    - by RedMan
    Hi I want to create a single page web site like http://kiskolabs.com/ or http://www.carat.se to display my portfolio. I want to add new products after launching the site without having to edit the entire site. I've looked at opencart (too much for single page site), Magneto (more for ecommerce), Wordpress (couldn't find open source / free templates which i can start from). Can you suggest a CMS which will support the creation of a single page site and allow insertion of new products without having to edit the entire page? I would prefer a CMS which also has open source / free templates which I can tweak for my use. I can do php and mysql, xml. If it is an easier option I can do PSD to site (but don't know much about this at all).

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  • What OO Design to use ( is there a Design Pattern )?

    - by Blundell
    I have two objects that represent a 'Bar/Club' ( a place where you drink/socialise). In one scenario I need the bar name, address, distance, slogon In another scenario I need the bar name, address, website url, logo So I've got two objects representing the same thing but with different fields. I like to use immutable objects, so all the fields are set from the constructor. One option is to have two constructors and null the other fields i.e: class Bar { private final String name; private final Distance distance; private final Url url; public Bar(String name, Distance distance){ this.name = name; this.distance = distance; this.url = null; } public Bar(String name, Url url){ this.name = name; this.distance = null; this.url = url; } // getters } I don't like this as you would have to null check when you use the getters In my real example the first scenario has 3 fields and the second scenario has about 10, so it would be a real pain having two constructors, the amount of fields I would have to declare null and then when the object are in use you wouldn't know which Bar you where using and so what fields would be null and what wouldn't. What other options do I have? Two classes called BarPreview and Bar? Some type of inheritance / interface? Something else that is awesome?

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  • $.fadeTo/fadeOut() operations on Table Rows in IE fail

    - by Rick Strahl
    Here’s a a small problem that one of customers ran into a few days ago: He was playing around with some of the sample code I’ve put out for one of my simple jQuery demos which deals with providing a simple pulse behavior plug-in: $.fn.pulse = function(time) { if (!time) time = 2000; // *** this == jQuery object that contains selections $(this).fadeTo(time, 0.20, function() { $(this).fadeTo(time, 1); }); return this; } it’s a very simplistic plug-in and it works fine for simple pulse animations. However he ran into a problem where it didn’t work when working with tables – specifically pulsing a table row in Internet Explorer. Works fine in FireFox and Chrome, but IE not so much. It also works just fine in IE as long as you don’t try it on tables or table rows specifically. Applying against something like this (an ASP.NET GridView): var sel = $("#gdEntries>tbody>tr") .not(":first-child") // no header .not(":last-child") // no footer .filter(":even") .addClass("gridalternate"); // *** Demonstrate simple plugin sel.pulse(2000); fails in IE. No pulsing happens in any version of IE. After some additional experimentation with single rows and various ways of selecting each and still failing, I’ve come to the conclusion that the various fade operations in jQuery simply won’t work correctly in IE (any version). So even something as ‘elemental’ as this: var el = $("#gdEntries>tbody>tr").get(0);$(el).fadeOut(2000); is not working correctly. The item will stick around for 2 seconds and then magically disappear. Likewise: sel.hide().fadeIn(5000); also doesn’t fade in although the items become immediately visible in IE. Go figure that behavior out. Thanks to a tweet from red_square and a link he provided here is a grid that explains what works and doesn’t in IE (and most last gen browsers) regarding opacity: http://www.quirksmode.org/js/opacity.html It appears from this link that table and row elements can’t be made opaque, but td elements can. This means for the row selections I can force each of the td elements to be selected and then pulse all of those. Once you have the rows it’s easy to explicitly select all the columns in those rows with .find(“td”). Aha the following actually works: var sel = $("#gdEntries>tbody>tr") .not(":first-child") // no header .not(":last-child") // no footer .filter(":even") .addClass("gridalternate"); // *** Demonstrate simple plugin sel.find("td").pulse(2000); A little unintuitive that, but it works. Stay away from <table> and <tr> Fades The moral of the story is – stay away from TR, TH and TABLE fades and opacity. If you have to do it on tables use the columns instead and if necessary use .find(“td”) on your row(s) selector to grab all the columns. I’ve been surprised by this uhm relevation, since I use fadeOut in almost every one of my applications for deletion of items and row deletions from grids are not uncommon especially in older apps. But it turns out that fadeOut actually works in terms of behavior: It removes the item when the timeout’s done and because the fade is relatively short lived and I don’t extensively test IE code any more I just never noticed that the fade wasn’t happening. Note – this behavior or rather lack thereof appears to be specific to table table,tr,th elements. I see no problems with other elements like <div> and <li> items. Chalk this one up to another of IE’s shortcomings. Incidentally I’m not the only one who has failed to address this in my simplistic plug-in: The jquery-ui pulsate effect also fails on the table rows in the same way. sel.effect("pulsate", { times: 3 }, 2000); and it also works with the same workaround. If you’re already using jquery-ui definitely use this version of the plugin which provides a few more options… Bottom line: be careful with table based fade operations and remember that if you do need to fade – fade on columns.© Rick Strahl, West Wind Technologies, 2005-2010Posted in jQuery  

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  • How to maintain encapsulation with composition in C++?

    - by iFreilicht
    I am designing a class Master that is composed from multiple other classes, A, Base, C and D. These four classes have absolutely no use outside of Master and are meant to split up its functionality into manageable and logically divided packages. They also provide extensible functionality as in the case of Base, which can be inherited from by clients. But, how do I maintain encapsulation of Master with this design? So far, I've got two approaches, which are both far from perfect: 1. Replicate all accessors: Just write accessor-methods for all accessor-methods of all classes that Master is composed of. This leads to perfect encapsulation, because no implementation detail of Master is visible, but is extremely tedious and makes the class definition monstrous, which is exactly what the composition should prevent. Also, adding functionality to one of the composees (is that even a word?) would require to re-write all those methods in Master. An additional problem is that inheritors of Base could only alter, but not add functionality. 2. Use non-assignable, non-copyable member-accessors: Having a class accessor<T> that can not be copied, moved or assigned to, but overrides the operator-> to access an underlying shared_ptr, so that calls like Master->A()->niceFunction(); are made possible. My problem with this is that it kind of breaks encapsulation as I would now be unable to change my implementation of Master to use a different class for the functionality of niceFunction(). Still, it is the closest I've gotten without using the ugly first approach. It also fixes the inheritance issue quite nicely. A small side question would be if such a class already existed in std or boost. EDIT: Wall of code I will now post the code of the header files of the classes discussed. It may be a bit hard to understand, but I'll give my best in explaining all of it. 1. GameTree.h The foundation of it all. This basically is a doubly-linked tree, holding GameObject-instances, which we'll later get to. It also has it's own custom iterator GTIterator, but I left that out for brevity. WResult is an enum with the values SUCCESS and FAILED, but it's not really important. class GameTree { public: //Static methods for the root. Only one root is allowed to exist at a time! static void ConstructRoot(seed_type seed, unsigned int depth); inline static bool rootExists(){ return static_cast<bool>(rootObject_); } inline static weak_ptr<GameTree> root(){ return rootObject_; } //delta is in ms, this is used for velocity, collision and such void tick(unsigned int delta); //Interaction with the tree inline weak_ptr<GameTree> parent() const { return parent_; } inline unsigned int numChildren() const{ return static_cast<unsigned int>(children_.size()); } weak_ptr<GameTree> getChild(unsigned int index) const; template<typename GOType> weak_ptr<GameTree> addChild(seed_type seed, unsigned int depth = 9001){ GOType object{ new GOType(seed) }; return addChildObject(unique_ptr<GameTree>(new GameTree(std::move(object), depth))); } WResult moveTo(weak_ptr<GameTree> newParent); WResult erase(); //Iterators for for( : ) loop GTIterator& begin(){ return *(beginIter_ = std::move(make_unique<GTIterator>(children_.begin()))); } GTIterator& end(){ return *(endIter_ = std::move(make_unique<GTIterator>(children_.end()))); } //unloading should be used when objects are far away WResult unloadChildren(unsigned int newDepth = 0); WResult loadChildren(unsigned int newDepth = 1); inline const RenderObject& renderObject() const{ return gameObject_->renderObject(); } //Getter for the underlying GameObject (I have not tested the template version) weak_ptr<GameObject> gameObject(){ return gameObject_; } template<typename GOType> weak_ptr<GOType> gameObject(){ return dynamic_cast<weak_ptr<GOType>>(gameObject_); } weak_ptr<PhysicsObject> physicsObject() { return gameObject_->physicsObject(); } private: GameTree(const GameTree&); //copying is only allowed internally GameTree(shared_ptr<GameObject> object, unsigned int depth = 9001); //pointer to root static shared_ptr<GameTree> rootObject_; //internal management of a child weak_ptr<GameTree> addChildObject(shared_ptr<GameTree>); WResult removeChild(unsigned int index); //private members shared_ptr<GameObject> gameObject_; shared_ptr<GTIterator> beginIter_; shared_ptr<GTIterator> endIter_; //tree stuff vector<shared_ptr<GameTree>> children_; weak_ptr<GameTree> parent_; unsigned int selfIndex_; //used for deletion, this isn't necessary void initChildren(unsigned int depth); //constructs children }; 2. GameObject.h This is a bit hard to grasp, but GameObject basically works like this: When constructing a GameObject, you construct its basic attributes and a CResult-instance, which contains a vector<unique_ptr<Construction>>. The Construction-struct contains all information that is needed to construct a GameObject, which is a seed and a function-object that is applied at construction by a factory. This enables dynamic loading and unloading of GameObjects as done by GameTree. It also means that you have to define that factory if you inherit GameObject. This inheritance is also the reason why GameTree has a template-function gameObject<GOType>. GameObject can contain a RenderObject and a PhysicsObject, which we'll later get to. Anyway, here's the code. class GameObject; typedef unsigned long seed_type; //this declaration magic means that all GameObjectFactorys inherit from GameObjectFactory<GameObject> template<typename GOType> struct GameObjectFactory; template<> struct GameObjectFactory<GameObject>{ virtual unique_ptr<GameObject> construct(seed_type seed) const = 0; }; template<typename GOType> struct GameObjectFactory : GameObjectFactory<GameObject>{ GameObjectFactory() : GameObjectFactory<GameObject>(){} unique_ptr<GameObject> construct(seed_type seed) const{ return unique_ptr<GOType>(new GOType(seed)); } }; //same as with the factories. this is important for storing them in vectors template<typename GOType> struct Construction; template<> struct Construction<GameObject>{ virtual unique_ptr<GameObject> construct() const = 0; }; template<typename GOType> struct Construction : Construction<GameObject>{ Construction(seed_type seed, function<void(GOType*)> func = [](GOType* null){}) : Construction<GameObject>(), seed_(seed), func_(func) {} unique_ptr<GameObject> construct() const{ unique_ptr<GameObject> gameObject{ GOType::factory.construct(seed_) }; func_(dynamic_cast<GOType*>(gameObject.get())); return std::move(gameObject); } seed_type seed_; function<void(GOType*)> func_; }; typedef struct CResult { CResult() : constructions{} {} CResult(CResult && o) : constructions(std::move(o.constructions)) {} CResult& operator= (CResult& other){ if (this != &other){ for (unique_ptr<Construction<GameObject>>& child : other.constructions){ constructions.push_back(std::move(child)); } } return *this; } template<typename GOType> void push_back(seed_type seed, function<void(GOType*)> func = [](GOType* null){}){ constructions.push_back(make_unique<Construction<GOType>>(seed, func)); } vector<unique_ptr<Construction<GameObject>>> constructions; } CResult; //finally, the GameObject class GameObject { public: GameObject(seed_type seed); GameObject(const GameObject&); virtual void tick(unsigned int delta); inline Matrix4f trafoMatrix(){ return physicsObject_->transformationMatrix(); } //getter inline seed_type seed() const{ return seed_; } inline CResult& properties(){ return properties_; } inline const RenderObject& renderObject() const{ return *renderObject_; } inline weak_ptr<PhysicsObject> physicsObject() { return physicsObject_; } protected: virtual CResult construct_(seed_type seed) = 0; CResult properties_; shared_ptr<RenderObject> renderObject_; shared_ptr<PhysicsObject> physicsObject_; seed_type seed_; }; 3. PhysicsObject That's a bit easier. It is responsible for position, velocity and acceleration. It will also handle collisions in the future. It contains three Transformation objects, two of which are optional. I'm not going to include the accessors on the PhysicsObject class because I tried my first approach on it and it's just pure madness (way over 30 functions). Also missing: the named constructors that construct PhysicsObjects with different behaviour. class Transformation{ Vector3f translation_; Vector3f rotation_; Vector3f scaling_; public: Transformation() : translation_{ 0, 0, 0 }, rotation_{ 0, 0, 0 }, scaling_{ 1, 1, 1 } {}; Transformation(Vector3f translation, Vector3f rotation, Vector3f scaling); inline Vector3f translation(){ return translation_; } inline void translation(float x, float y, float z){ translation(Vector3f(x, y, z)); } inline void translation(Vector3f newTranslation){ translation_ = newTranslation; } inline void translate(float x, float y, float z){ translate(Vector3f(x, y, z)); } inline void translate(Vector3f summand){ translation_ += summand; } inline Vector3f rotation(){ return rotation_; } inline void rotation(float pitch, float yaw, float roll){ rotation(Vector3f(pitch, yaw, roll)); } inline void rotation(Vector3f newRotation){ rotation_ = newRotation; } inline void rotate(float pitch, float yaw, float roll){ rotate(Vector3f(pitch, yaw, roll)); } inline void rotate(Vector3f summand){ rotation_ += summand; } inline Vector3f scaling(){ return scaling_; } inline void scaling(float x, float y, float z){ scaling(Vector3f(x, y, z)); } inline void scaling(Vector3f newScaling){ scaling_ = newScaling; } inline void scale(float x, float y, float z){ scale(Vector3f(x, y, z)); } void scale(Vector3f factor){ scaling_(0) *= factor(0); scaling_(1) *= factor(1); scaling_(2) *= factor(2); } Matrix4f matrix(){ return WMatrix::Translation(translation_) * WMatrix::Rotation(rotation_) * WMatrix::Scale(scaling_); } }; class PhysicsObject; typedef void tickFunction(PhysicsObject& self, unsigned int delta); class PhysicsObject{ PhysicsObject(const Transformation& trafo) : transformation_(trafo), transformationVelocity_(nullptr), transformationAcceleration_(nullptr), tick_(nullptr) {} PhysicsObject(PhysicsObject&& other) : transformation_(other.transformation_), transformationVelocity_(std::move(other.transformationVelocity_)), transformationAcceleration_(std::move(other.transformationAcceleration_)), tick_(other.tick_) {} Transformation transformation_; unique_ptr<Transformation> transformationVelocity_; unique_ptr<Transformation> transformationAcceleration_; tickFunction* tick_; public: void tick(unsigned int delta){ tick_ ? tick_(*this, delta) : 0; } inline Matrix4f transformationMatrix(){ return transformation_.matrix(); } } 4. RenderObject RenderObject is a base class for different types of things that could be rendered, i.e. Meshes, Light Sources or Sprites. DISCLAIMER: I did not write this code, I'm working on this project with someone else. class RenderObject { public: RenderObject(float renderDistance); virtual ~RenderObject(); float renderDistance() const { return renderDistance_; } void setRenderDistance(float rD) { renderDistance_ = rD; } protected: float renderDistance_; }; struct NullRenderObject : public RenderObject{ NullRenderObject() : RenderObject(0.f){}; }; class Light : public RenderObject{ public: Light() : RenderObject(30.f){}; }; class Mesh : public RenderObject{ public: Mesh(unsigned int seed) : RenderObject(20.f) { meshID_ = 0; textureID_ = 0; if (seed == 1) meshID_ = Model::getMeshID("EM-208_heavy"); else meshID_ = Model::getMeshID("cube"); }; unsigned int getMeshID() const { return meshID_; } unsigned int getTextureID() const { return textureID_; } private: unsigned int meshID_; unsigned int textureID_; }; I guess this shows my issue quite nicely: You see a few accessors in GameObject which return weak_ptrs to access members of members, but that is not really what I want. Also please keep in mind that this is NOT, by any means, finished or production code! It is merely a prototype and there may be inconsistencies, unnecessary public parts of classes and such.

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  • Architecture Best Practice (MVC): Repository Returns Object & Object Member Accessed Directly or Repository Returns Object Member

    - by coderabbi
    Architecturally speaking, which is the preferable approach (and why)? $validation_date = $users_repository->getUser($user_id)->validation_date; Seems to violate Law of Demeter by accessing member of object returned by method call Seems to violate Encapsulation by accessing object member directly $validation_date = $users_repository->getUserValidationDate($user_id); Seems to violate Single Responsibility Principle as $users_repository no longer just returns User objects

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  • iTextSharp - Bug in the table functions?

    - by Matthias
    Hello all together, I try to make a table like this: PdfPTable Table = new PdfPTable(6); PdfPCell Cell = new PdfPCell(new Phrase("a", Font1)); Cell.Rowspan = 2; Cell.Colspan = 2; Table.AddCell(Cell); Cell = new PdfPCell(new Phrase("b", Font1)); Cell.Rowspan = 2; Cell.Colspan = 2; Table.AddCell(Cell); Cell = new PdfPCell(new Phrase("c", Font1)); Cell.Colspan = 2; Table.AddCell(Cell); Cell = new PdfPCell(new Phrase("d", Font1)); Cell.Colspan = 2; Table.AddCell(Cell); That works fine. But changing the number of columns will destory the table. Is it a bug or do I make something wrong? This code destroys the table: PdfPTable Table = new PdfPTable(17); PdfPCell Cell = new PdfPCell(new Phrase("a", Font1)); Cell.Rowspan = 2; Cell.Colspan = 2; Table.AddCell(Cell); Cell = new PdfPCell(new Phrase("b", Font1)); Cell.Rowspan = 2; Cell.Colspan = 10; Table.AddCell(Cell); Cell = new PdfPCell(new Phrase("c", Font1)); Cell.Colspan = 5; Table.AddCell(Cell); Cell = new PdfPCell(new Phrase("d", Font1)); Cell.Colspan = 5; Table.AddCell(Cell); Edit: The table should have this layout: |-------------------------------------------------------| | Cell "a" with | Cell "b" with | Cell "c", colspan = 5 | | colspan = 2 | colspan = 10 |-----------------------| | rowspan = 2 | rowspan = 2 | Cell "d", colspan = 5 | |-------------------------------------------------------| Best regards, Matthias

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  • Two n x m relationships with the same table in mysql

    - by Christian
    I want to create a database in which there's an n x m relationship between the table drug and the table article and an n x m relationship between the table target and the table article. I get the error: Cannot delete or update a parent row: a foreign key constraint fails What do I have to change in my code? DROP TABLE IF EXISTS `textmine`.`article`; CREATE TABLE `textmine`.`article` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT 'Pubmed ID', `abstract` blob NOT NULL, `authors` blob NOT NULL, `journal` varchar(256) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; DROP TABLE IF EXISTS `textmine`.`drugs`; CREATE TABLE `textmine`.`drugs` ( `id` int(10) unsigned NOT NULL COMMENT 'This ID is taken from the biosemantics dictionary', `primaryName` varchar(256) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; DROP TABLE IF EXISTS `textmine`.`targets`; CREATE TABLE `textmine`.`targets` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `primaryName` varchar(256) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; DROP TABLE IF EXISTS `textmine`.`containstarget`; CREATE TABLE `textmine`.`containstarget` ( `targetid` int(10) unsigned NOT NULL, `articleid` int(10) unsigned NOT NULL, KEY `target` (`targetid`), KEY `article` (`articleid`), CONSTRAINT `article` FOREIGN KEY (`articleid`) REFERENCES `article` (`id`), CONSTRAINT `target` FOREIGN KEY (`targetid`) REFERENCES `targets` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; DROP TABLE IF EXISTS `textmine`.`contiansdrug`; CREATE TABLE `textmine`.`contiansdrug` ( `drugid` int(10) unsigned NOT NULL, `articleid` int(10) unsigned NOT NULL, KEY `drug` (`drugid`), KEY `article` (`articleid`), CONSTRAINT `article` FOREIGN KEY (`articleid`) REFERENCES `article` (`id`), CONSTRAINT `drug` FOREIGN KEY (`drugid`) REFERENCES `drugs` (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;

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  • Singleton with inheritance, Derived class is not able to get instantiated in parent?

    - by yesraaj
    Below code instantiates a derived singleton object based on environment variable. The compiler errors saying error C2512: 'Dotted' : no appropriate default constructor. I don't understand what the compiler is complaining about. #include <stdlib.h> #include <iostream> #include <string> using namespace std; class Dotted; class Singleton{ public: static Singleton instant(){ if (!instance_) { char * style = getenv("STYLE"); if (!style){ if (strcmp(style,"dotted")==0) { instance_ = new Dotted(); return *instance_; } } else{ instance_ = new Singleton(); return *instance_; } } return *instance_; } void print(){cout<<"Singleton";} ~Singleton(){}; protected: Singleton(){}; private: static Singleton * instance_; Singleton(const Singleton & ); void operator=(const Singleton & ); }; class Dotted:public Singleton{ public: void print(){cout<<"Dotted";} protected: Dotted(); }; Dotted::Dotted():Singleton(){} int main(){ Singleton::instant().print(); cin.get(); }

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  • Why doesn't interface inheritance work when writing shell extensions in c#?

    - by Factor Mystic
    According to this article about writing shell extensions in .Net, inheriting the shell interfaces as you might naturally do when writing code doesn't work. I've observed this in my own code as well. Doesn't work: public interface IPersist { // stuff specific only to IPersist } public interface IPersistFolder : IPersist { // stuff specific only to IPersistFolder } Does work: public interface IPersistFolder { // stuff specific to IPersist only // stuff specific to IPersistFolder only } The article notes this fact: Lo and behold, it worked! Notice that I've abandoned any idea that IPersistFolder is inherited from anything at all and just included the stubs from IPersist right in its definition. In all candor, I can't tell you why this is but it definitely works just fine and shouldn't give you any problems. So my I'll ask the question this guy didn't know; why didn't the original code work?

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  • Help with these warnings. [inheritance].

    - by sil3nt
    Hello there. I have a set of code, which mimics a basic library cataloging system. There is a base class named items, in which the the general id,title and year variables are defined and 3 other derived classes (DVD,Book and CD). Base [Items] Derived [DVD,Book,CD]. The programs runs, however I get the following warnings, I'm not sure how to fix these. "C:\Program Files\gcc\bin/g++" -Os -mconsole -g -Wall -Wshadow -fno-common mainA4.cpp -o mainA4.exe In file included from mainA4.cpp:5: a4.h: In constructor `DVD::DVD(int, std::string, int, std::string)': a4.h:28: warning: `DVD::director' will be initialized after a4.h:32: warning: base `Items' a4.h:32: warning: when initialized here a4.h: In constructor `Book::Book(int, std::string, int, std::string, int)': a4.h:48: warning: `Book::numPages' will be initialized after a4.h:52: warning: base `Items' a4.h:52: warning: when initialized here a4.h: In constructor `CD::CD(int, std::string, int, std::string, int)': a4.h:66: warning: `CD::numSongs' will be initialized after a4.h:70: warning: base `Items' a4.h:70: warning: when initialized here Exit code: 0

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  • Netlogo: error when putting variable in table, only constants allowe??

    - by Chantal
    Hello, Currently I am working on a Netlogo program where I need to use nodes and links for vehicle routing problem. (links are called streets in the program) Here I have some practical problems of how to input variable linkspeed in a table with another node. Constants like 200 etc are fine. Online I found some examples where variables are used, but I do not know why I keep getting the following error: Expected a constant. (or why netlogo expects a constant) Here is the relevant piece of code: extensions [table] streets-own [linkspeed linktoll] nodes-own [netw] ;; In another piece of code linkspeed is assigned successfully to the links to cheapcalc ;; start conditions set costs very high 300000 ;; state 3 unsearched state 2 searching state 1 searched (for later purposes) ask nodes [ set i 0 set j count nodes set netw table:make while [i < j][ table:put netw (i) [3000000 3] set i (i + 1)]] set i 0 let k 0 ask node 35 ;; here i use node 35 as an example. ;; node 35 is connected to node 34, 36, 20 and 50 [table:put netw (35) [0 1] ;; node need to search costs to travel to itself ;; putting constants is ok. while [i < j] [ask my-links [ask both-ends [if (who != 35) [set color blue ;; set temp ([linkspeed] of street 35 who) ;; here my real goal is to put this in stat of i. but i is easier than linkspeed. table:put netw (who) [ i 2 ] ] ] ] set i (i + 1)] ] ;; next node for later, no it is just repetition of the same. end I hope somebody knows what is going on... Kind regards, Chantal

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