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  • Parent-child table layout

    - by cyberzed
    I'm currently planning a piece of software for dogbreeders and I'm in doubt about my datadesign...whether I'm doing something smart or stupid :) The plan at the moment is one holistic "dog" table sorta like this... Id | Name | FatherId | MotherId ------------------------------- 1 | A | 0 | 0 2 | B | 1 | 0 3 | C | 0 | 0 4 | D | 0 | 3 5 | E | 1 | 3 6 | F | 5 | 2 7 | G | 4 | 3 My questions is, is it common to make it like this or is it really sloppy. I can see a quick lookup reason to have it but I'm really in doubt whether it's good or bad in the end. I thinking it would be better designed if I had a rel-table on the side with Id coupling, but I'm really in doubt how well any of the cases are. A side note is that it'll only be me personally looking at the data this way (or someone adopting the project from me)

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  • Should Service Depend on Many Repositories, or Break Them Up?

    - by Josh Pollard
    I'm using a repository pattern for my data access. So I basically have a repository per table/class. My UI currently uses service classes to actually get things done, and these service classes wrap, and therefore depend on repositories. In many cases my services are only dependent upon one or two repositories, so things aren't too crazy. Unfortunately, one of my forms in the UI expects the user to enter data that will span five different tables. For this form I made a single service class that depends upon five repositories. Then the methods within the service for saving and loading the data call the appropriate methods on all of the corresponding repositories. As you can imagine, the save and load methods in this service are really big. Also, unit testing this service is getting really difficult because I have to setup so many fake repositories. Would it have been a better choice to break this single service apart into a few smaller services? It would put more code at the UI layer, but would make the services smaller and more testable.

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  • How to map one class against multiple tables with SQLAlchemy?

    - by tote
    Lets say that I have a database structure with three tables that look like this: items - item_id - item_handle attributes - attribute_id - attribute_name item_attributes - item_attribute_id - item_id - attribute_id - attribute_value I would like to be able to do this in SQLAlchemy: item = Item('item1') item.foo = 'bar' session.add(item) session.commit() item1 = session.query(Item).filter_by(handle='item1').one() print item1.foo # => 'bar' I'm new to SQLAlchemy and I found this in the documentation (http://www.sqlalchemy.org/docs/05/mappers.html#mapping-a-class-against-multiple-tables): j = join(items, item_attributes, items.c.item_id == item_attributes.c.item_id). \ join(attributes, item_attributes.c.attribute_id == attributes.c.attribute_id) mapper(Item, j, properties={ 'item_id': [items.c.item_id, item_attributes.c.item_id], 'attribute_id': [item_attributes.c.attribute_id, attributes.c.attribute_id], }) It only adds item_id and attribute_id to Item and its not possible to add attributes to Item object. Is what I'm trying to achieve possible with SQLAlchemy? Is there a better way to structure the database to get the same behaviour of "dynamic columns"?

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  • What is the point declaring variables at the end of class?

    - by serhio
    I saw multiple examples in MSDN that uses to declare the internal fields at the end of the class. What is the point? I find this a little embarrassing, because each time Visual Studio adds a method it adds it to the end of the class, so there is need every time to move it... class A { public A(){} // Methods, Properties, etc ... private string name; } class A { private string name; public A(){} // Methods, Properties, etc ... }

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  • In java web application, where should i store users photos?

    - by stunaz
    Hello, this questions may be stupid, but i dont really see how to resolve it : lest say that in my application, i have a user. This user edit his profile, and need to edit his avatar. Where should i store the avatar file? first of all i was saving all the files in src\main\webapp\resources , but each time i redeploy that folder empties. so i dedide to place in an other location : c:\wwwdir\resources, but i can't link local resources from remote pages, so i was not able to display any avatar . any idea? advise? link?

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  • How to store opening weekdays in a database

    - by JoaoPedro
    I have a group of checkboxes where the user selects some of the weekdays (the opening days of a store). How can I save the selected days? Should I save something like 0111111 (zero means closed on sunday) on the same field and split the result when reading the data? Or create a field for each day and store 0 or 1 on each (weird)?

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  • C++ setting up "flags"

    - by sub
    Example: enum Flags { A, B, C, D }; class MyClass { std::string data; int foo; // Flags theFlags; (???) } How can I achieve that it is possible to set any number of the "flags" A,B,C and D in the enum above in an instance of MyClass? My goal would be something like this: if ( MyClassInst.IsFlagSet( A ) ) // ... MyClassInst.SetFlag( A ); //... Do I have to use some array or vector? If yes, how? Are enums a good idea in this case?

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  • fast load big object graph from DB

    - by Famos
    Hi I have my own data structure written in C# like: public class ElectricScheme { public List<Element> Elements { get; set; } public List<Net> Nets { get; set; } } public class Element { public string IdName { get; set; } public string Func { get; set; } public string Name { get; set; } public BaseElementType Type { get; set; } public List<Pin> Pins { get; set; } } public class Pin { public string IdName { get; set; } public string Name { get; set; } public BasePinType PinType { get; set; } public BasePinDirection PinDirection { get; set; } } public class Net { public string IdName { get; set; } public string Name { get; set; } public List<Tuple<Element,Pin>> ConnectionPoints { get; set; } } Where Elements count ~19000, each element contain =3 Pin, Nets count ~20000, each net contain =3 pair (Element, Pin) Parse txt (file size ~17mb) file takes 5 minutes. Serilization / Deserialization by default serializer ~3 minutes. Load from DB 20 minutes and not loaded... I use Entity Framework like public ElectricScheme LoadScheme(int schemeId) { var eScheme = (from s in container.ElectricSchemesSet where s.IdElectricScheme.Equals(schemeId) select s).FirstOrDefault(); if (eScheme == null) return null; container.LoadProperty(eScheme, "Elements"); container.LoadProperty(eScheme, "Nets"); container.LoadProperty(eScheme, "Elements.Pins"); return eScheme; } The problem is dependencies between Element and Pin... (for ~19000 elements ~95000 pins) Any ideas?

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  • Why there are no semicolons and {} blocks in some languages

    - by Incognito
    I know the question has no practical value, but it is interesting why in some languages semicolons and {} blocks are removed although their predecessor have them. Actually it makes me nervous to write a code in Python as there are no ";" and {}. Also in new language Google-GO semicolons are also missing although it says that lexer uses a rule to insert semicolons automatically as it scans. So is there any secret :) reason for this.

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  • Business object and linq2SQL

    - by Overdose
    What is the optimal way to write the code which interacts with DB using linq2SQL? I need to add some business logic to the entities. So I guess there are two ways: Write some wrapper class. The main minus is that many fields are the same, so i don't feel it as DRY style. Add business logic methods to linq2sql entities(these classes are partial) directly ???

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  • Patterns to deal with with functions that can have different kinds of results.

    - by KaptajnKold
    Suppose you have an method on an object that given the some input alters the objects state if the input validates according to some complex logic. Now suppose that when the input doesn't validate, it can be due to several different things, each of which we would like to be able to deal with in different ways. I'm sure many of you are thinking: That's what exceptions are for! I've thought of this also. But my reservation against using exceptions is that in some cases there is nothing exceptional about the input not validating and I really would like to avoid using exceptions to control what is really just in the expected flow of the program. If there were only one interpretation possible, I could simply choose to return a boolean value indicating whether or not the operation resulted in a state change or not and the respond appropriately when it did not. There is of course also the option to return a status code which the client can then choose to interpret or not. I don't like this much either because there is nothing semantic about status codes. The solution I have so far is to always check for each possible situation which I am able to handle before I call the method which then returns a boolean to inform the client if the object changed state. This leaves me the flexibility to handle as few or as many as the possible situations as I wish depending on the context I am in. It also has the benefit of making the method I am calling simpler to write. The drawback is that there is quite a lot of duplication in the client code wherever I call the method. Which of these solutions do you prefer and why? What other patterns do people use for providing meaningful feedback from functions? I know that some languages support multiple return values, and I if I had that option I would surely prefer it.

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  • incapsulation of a code inmatlab

    - by user531225
    my code is pathname=uigetdir; filename=uigetfile('*.txt','choose a file name.'); data=importdata(filename); element= (data.data(:,10)); in_array=element; pattern= [1 3]; locations = cell(1, numel(pattern)); for p = 1:(numel(pattern)) locations{p} = find(in_array == pattern(p)); end idx2 = []; for p = 1:numel(locations{1}) start_value = locations{1}(p); for q = 2:numel(locations) found = true; if (~any((start_value + q - 1) == locations{q})) found = false; break; end end if (found) idx2(end + 1) = locations{1}(p); end end [m2,n2]=size(idx2) res_name= {'one' 'two'}; res=[n n2]; In this code I finding a pattern in one of the column of my data file and counting how many times it's repeated. I have like 200 files that I want to do the same with them but unfotunatlly I'm stuck. this is what I have added so far pathname=uigetdir; files=dir('*.txt'); for k=1:length(files) filename=files(k).name; data(k)=importdata(files(k).name); element{k}=data(1,k).data(:,20); in_array=element;pattern= [1 3]; locations = cell(1, numel(pattern)); for p = 1:(numel(pattern)) locations{p} = find(in_array{k}== pattern(p)); end idx2{k} = []; how can I continue this code..??

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  • A self-creator: What pattern is this? php

    - by user151841
    I have several classes that are basically interfaces to database rows. Since the class assumes that a row already exists ( __construct expects a field value ), there is a public static function that allows creation of the row and returns an instance of the class. Here's a pseudo-code example : class fruit { public $id; public function __construct( $id ) { $this->id = $id; $sql = "SELECT * FROM Fruits WHERE id = $id"; ... $this->arrFieldValues[$field] = $row[$value]; } public function __get( $var ) { return $this->arrFieldValues[$var]; } public function __set( $var, $val ) { $sql = "UPDATE fruits SET $var = $val WHERE id = $this->id"; } public static function create( $id ) { $sql = "INSERT INTO Fruits ( fruit_name ) VALUE ( '$fruit' )"; $id = mysql_insert_id(); $fruit = & new fruit($id); return $fruit; } } $obj1 = fruit::create( "apple" ); $obj2 = & new fruit( 12 ); What is this pattern called? Edit: I changed the example to one that has more database-interface functionality. For most of the time, this kind of class would be instantiated normally, through __construct(). But sometimes when you need to create a new row first, you would call create().

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  • Adding interfaces that won't be actually used

    - by devoured elysium
    I currently have two interfaces(that I'll name here IA and IB): interface IA { int Width; int Height; ... } interface IB { int Width; int Height; ... } that share the same two properties: they both have a Width and a Height property. I was thinking if there is any point in defining an IMatrix interface containing a Width and Height properties: interface IMatrix { int Width; int Height; } The thing is that although they share both the same properties, I won't make use of polymorphism with IMatrix in any of my coding: i.e., there won't by any situation where I'll want to use an IMatrix, I'll just want to use IA and IB. Adding an IMatrix seems more like over-engineering than other thing, but I'd like to ask you guys what your opinion is on the matter. Thanks

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  • DDD and avoiding CRUD

    - by g_b
    It seems that on most articles I read, CRUD is to be avoided in DDD as we are dealing with modeling business process and not data. However, I find it hard to see not to have CRUD operations on certain entities. For example, in a school grading system, before teachers can grade students, a SchoolYear has to be present or perhaps a GradingPeriod. I can't see how we can manage GradingPeriods without CRUD. Could someone enlighten me on this?

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  • When to Use Properties & When to Use Methods?

    - by DaveDev
    Hi Guys I was looking at the following line of code foreach (PropertyInfo prop in t.GetProperties()) and I noticed that tprovides a method to return the type's properties instead of a property like t.Properties This makes me wonder why sometimes people use properties to make a type's data avilable and other times there's a method provided? Is there some logic behind the decision? Thanks Dave

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  • What exactly is GRASP's Controller about?

    - by devoured elysium
    What is the idea behind Grasp's Controller pattern? My current interpretation is that sometimes you want to achieve something that needs to use a couple of classes but none of those classes could or has access to the information needed to do it, so you create a new class that does the job, having references to all the needed classes(this is, could be the information expert). Is this a correct view of what Grasp's Controller is about? Generally when googling or SO'ing controller, I just get results about MVC's (and whatnot) which are topics that I don't understand about, so I'd like answers that don't assume I know ASP.NET's MVC or something :( Thanks

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  • database deign advice wanted: double data entry

    - by john
    hi, I'm designing a database for capturing clinical trial data. The data are entered twice by two persons, independently and the results must be matched. What are the best database tools to use to achieve the best results. Any one has similar experiences? Your helps are highly appreciated. thanks.

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  • how to guarantee atomicity across two databases (the filesystem and your RDBMS)?

    - by Lock up
    i am working on a online file management project.In which we are storing references on the database(sql server) and files data on the on file system;.In which we are facing a problem of coordination between file system and database while we are uploading a file and also in case of deleting a file that first we create a reference in the data base or store files on file system;;the problem is that if create a reference in the database first and then storing a file on file system.bur while storing files on the file system any type of error occur.then reference for that file is created in the database but no file data on the file system;; please give me some solution how to deal with such situation;;i am badly in need of it;; and reason for that?

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  • Having access to a private variable from other classes in Java

    - by Crystal
    If I want to create a form that adds people to a List, how do I have access to that List from another class? Where would I define that List so other classes can access the members, the size, etc? For example, if I have Class Foo that has the GUI for my form, along with buttons to add and remove people to the List, it would make sense to me to declare the List as a private instance variable of Class Foo. But then if I have another class, Class Bar, how does it get the values that are currently in that List to update some other graphical components? Or is that the wrong place to declare the List in general? Thanks.

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