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  • What does it mean to pass a &variable to a function? E.g., string& insert ( size_t pos1, const strin

    - by Bob Montgomery
    I understand passing a pointer, and returning a pointer: char * strcat ( char * destination, const char * source ); You're passing a variable that contains the address to a char; returning the same. But what does it mean to pass something using the reference operator? Or to return it? string& insert ( size_t pos1, const string& str ); I mean, I understand what actually happens, I just don't understand the notation. Why isn't the notation this instead: string * insert ( size_t pos1, const string * str ); //made up I presume it has something to do with passing/returning the instance of a class, but what? Is this syntax valid; if not why not and if so what does it mean? char & strcat ( char & destination, const char & source ); //made up (all of the function declarations, except the last made-up two, are from http://www.cplusplus.com )

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  • Help with Java Generics: Cannot use "Object" as argument for "? extends Object"

    - by AniDev
    Hello, I have the following code: import java.util.*; public class SellTransaction extends Transaction { private Map<String,? extends Object> origValueMap; public SellTransaction(Map<String,? extends Object> valueMap) { super(Transaction.Type.Sell); assignValues(valueMap); this.origValueMap=valueMap; } public SellTransaction[] splitTransaction(double splitAtQuantity) { Map<String,? extends Object> valueMapPart1=origValueMap; valueMapPart1.put(nameMappings[3],(Object)new Double(splitAtQuantity)); Map<String,? extends Object> valueMapPart2=origValueMap; valueMapPart2.put(nameMappings[3],((Double)origValueMap.get(nameMappings[3]))-splitAtQuantity); return new SellTransaction[] {new SellTransaction(valueMapPart1),new SellTransaction(valueMapPart2)}; } } The code fails to compile when I call valueMapPart1.put and valueMapPart2.put, with the error: The method put(String, capture#5-of ? extends Object) in the type Map is not applicable for the arguments (String, Object) I have read on the Internet about generics and wildcards and captures, but I still don't understand what is going wrong. My understanding is that the value of the Map's can be any class that extends Object, which I think might be redundant, because all classes extend Object. And I cannot change the generics to something like ? super Object, because the Map is supplied by some library. So why is this not compiling? Also, if I try to cast valueMap to Map<String,Object>, the compiler gives me that 'Unchecked conversion' warning. Thanks!

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  • How to define and use a friend function to a temlate class with the same template?

    - by Narek
    I have written the following code: #include <iostream> using namespace std; template <class T> class AA { T a; public: AA() { a = 7; } friend void print(const AA<T> & z); }; template <class T> void print(const AA<T> & z) { cout<<"Print: "<<z.a<<endl; } void main() { AA<int> a; print<int>(a); } And getting the following error: error C2248: 'AA<T>::a' : cannot access private member declared in class 'AA<T>' 1> with 1> [ 1> T=int 1> ] 1> c:\users\narek\documents\visual studio 2008\projects\aaa\aaa\a.cpp(7) : see declaration of 'AA<T>::a' 1> with 1> [ 1> T=int 1> ] 1> c:\users\narek\documents\visual studio 2008\projects\aaa\aaa\a.cpp(30) : see reference to function template instantiation 'void print<int>(const AA<T> &)' being compiled 1> with 1> [ 1> T=int 1> ] What's wrong?

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  • Oracle User definied aggregate function for varray of varchar

    - by baju
    I am trying to write some aggregate function for the varray and I get this error code when I'm trying to use it with data from the DB: ORA-00600 internal error code, arguments: [kodpunp1], [], [], [], [], [], [], [], [], [], [], [] [koxsihread1], [0], [3989], [45778], [], [], [], [], [], [], [], [] Code of the function is really simple(in fact it does nothing ): create or replace TYPE "TEST_VECTOR" as varray(10) of varchar(20) ALTER TYPE "TEST_VECTOR" MODIFY LIMIT 4000 CASCADE create or replace type Test as object( lastVector TEST_VECTOR, STATIC FUNCTION ODCIAggregateInitialize(sctx in out Test) return number, MEMBER FUNCTION ODCIAggregateIterate(self in out Test, value in TEST_VECTOR) return number, MEMBER FUNCTION ODCIAggregateMerge(self IN OUT Test, ctx2 IN Test) return number, MEMBER FUNCTION ODCIAggregateTerminate(self IN Test, returnValue OUT TEST_VECTOR, flags IN number) return number ); create or replace type body Test is STATIC FUNCTION ODCIAggregateInitialize(sctx in out Test) return number is begin sctx := Test(TEST_VECTOR()); return ODCIConst.Success; end; MEMBER FUNCTION ODCIAggregateIterate(self in out Test, value in TEST_VECTOR) return number is begin self.lastVector := value; return ODCIConst.Success; end; MEMBER FUNCTION ODCIAggregateMerge(self IN OUT Test, ctx2 IN Test) return number is begin return ODCIConst.Success; end; MEMBER FUNCTION ODCIAggregateTerminate(self IN Test, returnValue OUT TEST_VECTOR, flags IN number) return number is begin returnValue := self.lastVector; return ODCIConst.Success; end; end; create or replace FUNCTION test_fn (input TEST_VECTOR) RETURN TEST_VECTOR PARALLEL_ENABLE AGGREGATE USING Test; Next I create some test data: create table t1_test_table( t1_id number not null, t1_value TEST_VECTOR not null, Constraint PRIMARY_KEY_1 PRIMARY KEY (t1_id) ) Next step is to put some data to the table insert into t1_test_table (t1_id,t1_value) values (1,TEST_VECTOR('x','y','z')) Now everything is prepared to perform queries: Select test_fn(TEST_VECTOR('y','x')) from dual Query above work well Select test_fn(t1_value) from t1_test_table where t1_id = 1 Version of Oracle DBMS I use: 11.2.0.3.0 Does anyone tried do such a thing? What can be the reason that it does not work? How to solve it? Thanks in advance for help.

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  • Convert enumerated records to php object

    - by Matt H
    I have a table containing a bunch of records like this: +-----------+--------+----------+ | extension | fwd_to | type | +-----------+--------+----------+ | 800 | 11111 | noanswer | | 800 | 12345 | uncond | | 800 | 22222 | unavail | | 800 | 54321 | busy | | 801 | 123 | uncond | +-----------+--------+----------+ etc The query looks like this: select fwd_to, type from forwards where extension='800'; Now I get back an array containing objects which look like the following when printed with Kohana::debug: (object) stdClass Object ( [fwd_to] => 11111 [type] => noanswer ) (object) stdClass Object ( [fwd_to] => 12345 [type] => uncond ) (object) stdClass Object ( [fwd_to] => 22222 [type] => unavail ) (object) stdClass Object ( [fwd_to] => 54321 [type] => busy ) What I'd like to do is convert this to an object of this form: (object) stdClass Object ( [busy] => 54321 [uncond] => 12345 [unavail] => 22222 [noanswer] => 11111 ) The reason being I want to then call json_encode on it. This will allow me to use jquery populate to populate a form. Is there a suggested way I can do this nicely? I'm fairly new to PHP and I'm sure this is easy but it's eluding me at the moment.

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  • Serialize JavaScript's navigator object

    - by kappa
    Hi, I'm creating a page to help diagnose the problem our users are experiencing with our web pages (you know, asking a user "What browser are you using?" usually leads to "Internet"). This page already submits to me all the HTTP headers and now I'm trying to have JavaScript give some more informations, so I thought it would be great to have the user's navigator JavaScript object and I started looking how to serialize it so I can submit it through a form. The problem is I'm not able to serialize the navigator object using any JSON library I know of, everyone returns an empty object (?!), so I decided to write an ad-hoc serializer. You can find the code here: <!DOCTYPE html> <html> <head> <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.min.js" type="text/javascript"></script> <script type="text/javascript"> function serialize (object) { var type = typeof object; if (object === null) { return '"nullValue"'; } if (type == 'string' || type === 'number' || type === 'boolean') { return '"' + object + '"'; } else if (type === 'function') { return '"functionValue"'; } else if (type === 'object') { var output = '{'; for (var item in object) { if (item !== 'enabledPlugin') { output += '"' + item + '":' + serialize(object[item]) + ','; } } return output.replace(/\,$/, '') + '}'; } else if (type === 'undefined') { return '"undefinedError"'; } else { return '"unknownTypeError"'; } }; $(document).ready(function () { $('#navigator').text(serialize(navigator)); }); </script> <style type="text/css"> #navigator { font-family: monospaced; } </style> <title>Serialize</title> </head> <body> <h1>Serialize</h1> <p id="navigator"></p> </body> </html> This code seems to work perfectly in Firefox, Opera, Chrome and Safari but (obviously) doesn't work in Internet Explorer (at least version 8.0), it complains that "Property or method not supported by the object" at line for (var item in object) {. Do you have any hint on how to fix the code or how to reach the goal (serialize the navigator object) by other means?

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  • C#: Object having two constructors: how to limit which properties are set together?

    - by Dr. Zim
    Say you have a Price object that accepts either an (int quantity, decimal price) or a string containing "4/$3.99". Is there a way to limit which properties can be set together? Feel free to correct me in my logic below. The Test: A and B are equal to each other, but the C example should not be allowed. Thus the question How to enforce that all three parameters are not invoked as in the C example? AdPrice A = new AdPrice { priceText = "4/$3.99"}; // Valid AdPrice B = new AdPrice { qty = 4, price = 3.99m}; // Valid AdPrice C = new AdPrice { qty = 4, priceText = "2/$1.99", price = 3.99m};// Not The class: public class AdPrice { private int _qty; private decimal _price; private string _priceText; The constructors: public AdPrice () : this( qty: 0, price: 0.0m) {} // Default Constructor public AdPrice (int qty = 0, decimal price = 0.0m) { // Numbers only this.qty = qty; this.price = price; } public AdPrice (string priceText = "0/$0.00") { // String only this.priceText = priceText; } The Methods: private void SetPriceValues() { var matches = Regex.Match(_priceText, @"^\s?((?<qty>\d+)\s?/)?\s?[$]?\s?(?<price>[0-9]?\.?[0-9]?[0-9]?)"); if( matches.Success) { if (!Decimal.TryParse(matches.Groups["price"].Value, out this._price)) this._price = 0.0m; if (!Int32.TryParse(matches.Groups["qty"].Value, out this._qty)) this._qty = (this._price > 0 ? 1 : 0); else if (this._price > 0 && this._qty == 0) this._qty = 1; } } private void SetPriceString() { this._priceText = (this._qty > 1 ? this._qty.ToString() + '/' : "") + String.Format("{0:C}",this.price); } The Accessors: public int qty { get { return this._qty; } set { this._qty = value; this.SetPriceString(); } } public decimal price { get { return this._price; } set { this._price = value; this.SetPriceString(); } } public string priceText { get { return this._priceText; } set { this._priceText = value; this.SetPriceValues(); } } }

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  • Function signature-like expressions as C++ template arguments

    - by Jeff Lee
    I was looking at Don Clugston's FastDelegate mini-library and noticed a weird syntactical trick with the following structure: TemplateClass< void( int, int ) > Object; It almost appears as if a function signature is being used as an argument to a template instance declaration. This technique (whose presence in FastDelegate is apparently due to one Jody Hagins) was used to simplify the declaration of template instances with a semi-arbitrary number of template parameters. To wit, it allowed this something like the following: // A template with one parameter template<typename _T1> struct Object1 { _T1 m_member1; }; // A template with two parameters template<typename _T1, typename _T2> struct Object2 { _T1 m_member1; _T2 m_member2; }; // A forward declaration template<typename _Signature> struct Object; // Some derived types using "function signature"-style template parameters template<typename _Dummy, typename _T1> struct Object<_Dummy(_T1)> : public Object1<_T1> {}; template<typename _Dummy, typename _T1, typename _T2> struct Object<_Dummy(_T1, _T2)> : public Object2<_T1, _T2> {}; // A. "Vanilla" object declarations Object1<int> IntObjectA; Object2<int, char> IntCharObjectA; // B. Nifty, but equivalent, object declarations typedef void UnusedType; Object< UnusedType(int) > IntObjectB; Object< UnusedType(int, char) > IntCharObjectB; // C. Even niftier, and still equivalent, object declarations #define DeclareObject( ... ) Object< UnusedType( __VA_ARGS__ ) > DeclareObject( int ) IntObjectC; DeclareObject( int, char ) IntCharObjectC; Despite the real whiff of hackiness, I find this kind of spoofy emulation of variadic template arguments to be pretty mind-blowing. The real meat of this trick seems to be the fact that I can pass textual constructs like "Type1(Type2, Type3)" as arguments to templates. So here are my questions: How exactly does the compiler interpret this construct? Is it a function signature? Or, is it just a text pattern with parentheses in it? If the former, then does this imply that any arbitrary function signature is a valid type as far as the template processor is concerned? A follow-up question would be that since the above code sample is valid code, why doesn't the C++ standard just allow you to do something like the following, which is does not compile? template<typename _T1> struct Object { _T1 m_member1; }; // Note the class identifier is also "Object" template<typename _T1, typename _T2> struct Object { _T1 m_member1; _T2 m_member2; }; Object<int> IntObject; Object<int, char> IntCharObject;

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  • facebook open graph meta property og:type of 'website'. The property 'object-name' requires an object of og:type 'object-name'

    - by chinmayahd
    in cake php 1.3 in view ctp i have follow code: $url = 'http://example.com/exmp/explus/books/view/'.$book['Book']['id']; echo $this->Html->meta(array('property' => 'fb:app_id', 'content' => '*******'),'',array('inline'=>false)); echo $this->Html->meta(array('property' => 'og:type', 'content' => 'book'),'',array('inline'=>false)); echo $this->Html->meta(array('property' => 'og:url', 'content' => $url ),'',array('inline'=>false)); echo $this->Html->meta(array('property' => 'og:title', 'content' => $book['Book']['title']),'',array('inline'=>false)); echo $this->Html->meta(array('property' => 'og:description', 'content' => $book['Book']['title']),'',array('inline'=>false)); $imgurl = '../image/'.$book['Book']['id']; echo $this->Html->meta(array('property' => 'og:image', 'content' => $imgurl ),'',array('inline'=>false)); ?> and it gives the following error when i am posting it' { "error": { "message": "(#3502) Object at URL http://example.com/exmp/explus/books/view/234' has og:type of 'website'. The property 'book' requires an object of og:type 'book'. ", "type": "OAuthException", "code": 3502 } } is any one know how to solve it?

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  • Where are the function address literals in c++?

    - by academicRobot
    First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens). <UPDATE> After some reading with help from answer by Chris Dodd, what I'm looking for is literal function addresses as template parameters. Chris' answer indicates how to do this for standard functions, but how can the addresses of member functions be used as template parameters? Since the standard prohibits non-static member function addresses as template parameters (c++03 14.3.2.3), I suspect the work around is quite complicated. Any ideas for a workaround? Below the original form of the question is left as is for context. </UPDATE> The idea is that when you make a conventional function call, it compiles to something like this: callq <immediate address> But if you make a function call using a function pointer, it compiles to something like this: mov <memory location>,%rax callq *%rax Which is all well and good. However, what if I'm writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to template <int int_literal> struct my_template {...};` I'd like to write template <func_literal_t func_literal> struct my_template {...}; and have calls to func_literal within my_template compile to callq <immediate address>. Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language? Solutions that are not portable are fine. Solutions that include the use of member function pointers would be ideal. I'm not particularly interested in being told "You are a <socially unacceptable term for a person of low IQ>, just use function pointers/functors." This is a curiosity based question, and it seems that it might be useful in some (albeit limited) applications. It seems like this should be possible since function names are just placeholders for a (relative) memory address, so why not allow more liberal use (e.g. aliasing) of this placeholder. p.s. I use function pointers and functions objects all the the time and they are great. But this post got me thinking about the don't pay for what you don't use principle in relation to function calls, and it seems like forcing the use of function pointers or similar facility when the function is known at compile time is a violation of this principle, though a small one. Edit The intent of this question is not to implement delegates, rather to identify a pattern that will embed a conventional function call, (in immediate mode) directly into third party code, possibly a template.

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  • SQL SERVER – Puzzle to Win Print Book – Write T-SQL Self Join Without Using FIRST _VALUE and LAST_VALUE

    - by pinaldave
    Last week we asked a puzzle SQL SERVER – Puzzle to Win Print Book – Functions FIRST_VALUE and LAST_VALUE with OVER clause and ORDER BY . This puzzle got very interesting participation. The details of the winner is listed here. In this puzzle we received two very important feedback. This puzzle cleared the concepts of First_Value and Last_Value to the participants. As this was based on SQL Server 2012 many could not participate it as they have yet not installed SQL Server 2012. I really appreciate the feedback of user and decided to come up something as fun and helps learn new feature of SQL Server 2012. Please read yesterday’s blog post SQL SERVER – Introduction to LEAD and LAG – Analytic Functions Introduced in SQL Server 2012 before continuing this puzzle as it is based on yesterday’s post. Yesterday I ran following query which uses functions LEAD and LAG. USE AdventureWorks GO SELECT s.SalesOrderID,s.SalesOrderDetailID,s.OrderQty, FIRST_VALUE(SalesOrderDetailID) OVER (ORDER BY SalesOrderDetailID) FstValue, LAST_VALUE(SalesOrderDetailID) OVER (ORDER BY SalesOrderDetailID) LstValue FROM Sales.SalesOrderDetail s WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY s.SalesOrderID,s.SalesOrderDetailID,s.OrderQty GO The above query will give us the following result: Puzzle: Now use T-SQL Self Join where same table is joined to itself and get the same result without using LEAD or LAG functions. Hint: Introduction to JOINs – Basic of JOINs Self Join A new analytic functions in SQL Server Denali CTP3 – LEAD() and LAG() Rules Leave a comment with your detailed answer by Nov 21's blog post. Open world-wide (where Amazon ships books) If you blog about puzzle’s solution and if you win, you win additional surprise gift as well. Prizes Print copy of my new book SQL Server Interview Questions Amazon|Flipkart If you already have this book, you can opt for any of my other books SQL Wait Stats [Amazon|Flipkart|Kindle] and SQL Programming [Amazon|Flipkart|Kindle]. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Removing Leading Zeros From Column in Table

    - by pinaldave
    Some questions surprises me and make me write code which I have never explored before. Today was similar experience as well. I have always received the question regarding how to reserve leading zeroes in SQL Server while displaying them on the SSMS or another application. I have written articles on this subject over here. SQL SERVER – Pad Ride Side of Number with 0 – Fixed Width Number Display SQL SERVER – UDF – Pad Ride Side of Number with 0 – Fixed Width Number Display SQL SERVER – Preserve Leading Zero While Coping to Excel from SSMS Today I received a very different question where the user wanted to remove leading zero and white space. I am using the same sample sent by user in this example. USE tempdb GO -- Create sample table CREATE TABLE Table1 (Col1 VARCHAR(100)) INSERT INTO Table1 (Col1) SELECT '0001' UNION ALL SELECT '000100' UNION ALL SELECT '100100' UNION ALL SELECT '000 0001' UNION ALL SELECT '00.001' UNION ALL SELECT '01.001' GO -- Original data SELECT * FROM Table1 GO -- Remove leading zeros SELECT SUBSTRING(Col1, PATINDEX('%[^0 ]%', Col1 + ' '), LEN(Col1)) FROM Table1 GO -- Clean up DROP TABLE Table1 GO Here is the resultset of above script. It will remove any leading zero or space and will display the number accordingly. This problem is a very generic problem and I am confident there are alternate solutions to this problem as well. If you have an alternate solution or can suggest a sample data which does not satisfy the SUBSTRING solution proposed, I will be glad to include them in follow up blog post with due credit. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Removing Leading Zeros From Column in Table – Part 2

    - by pinaldave
    Earlier I wrote a blog post about Remvoing Leading Zeros from Column In Table. It was a great co-incident that my friend Madhivanan (no need of introduction for him) also post a similar article over on BeyondRelational.com. I strongly suggest to read his blog as well as he has suggested some cool solutions to the same problem. On original blog post asked two questions 1) if my sample for testing is correct and 2) If there is any better method to achieve the same. The response was amazing. I am proud on our SQL Community that we all keep on improving on each other’s contribution. There are some really good suggestions as a comment. Let us go over them right now. Improving the ResultSet I had missed including all zeros in my sample set which was an overlook. Here is the new sample which includes all zero values as well. USE tempdb GO -- Create sample table CREATE TABLE Table1 (Col1 VARCHAR(100)) INSERT INTO Table1 (Col1) SELECT '0001' UNION ALL SELECT '000100' UNION ALL SELECT '100100' UNION ALL SELECT '000 0001' UNION ALL SELECT '00.001' UNION ALL SELECT '01.001' UNION ALL SELECT '0000' GO Now let us go over some of the fantastic solutions which we have received. Response from Rainmaker SELECT CASE PATINDEX('%[^0 ]%', Col1 + ' ‘') WHEN 0 THEN '' ELSE SUBSTRING(Col1, PATINDEX('%[^0 ]%', Col1 + ' '), LEN(Col1)) END FROM Table1 Response from Harsh Solution 1 SELECT SUBSTRING(Col1, PATINDEX('%[^0 ]%', Col1 + 'a'), LEN(Col1)) FROM Table1 Response from Harsh Solution 2 SELECT RIGHT(Col1, LEN(Col1)+1 -PATINDEX('%[^0 ]%', Col1 + 'a' )) FROM Table1 Response from lucazav SELECT T.Col1 , label = CAST( CAST(REPLACE(T.Col1, ' ', '') AS FLOAT) AS VARCHAR(10)) FROM Table1 AS T Response from iamAkashSingh SELECT REPLACE(LTRIM(REPLACE(col1,'0',' ')),' ','0') FROM table1 Here is the resultset of above scripts. It will remove any leading zero or space and will display the number accordingly. If you believe there is a better solution, please leave a comment. I am just glad to see so many various responses and all of them teach us something new. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Web workflow solution - how should I approach the design?

    - by Tom Pickles
    We've been tasked with creating a web based workflow tool to track change management. It has a single workflow with multiple synchronous tasks for the most part, but branch out at a point to tasks running in parallel which meet up later on. There will be all sorts of people using the application, and all of them will need to see their outstanding tasks for each change, but only theirs, not others. There will also be a high level group of people who oversee all changes, so need to see everything. They will need to see tasks which have not been done in the specified time, who's responsible etc. The data will be persisted to a SQL database. It'll all be put together using .Net. I've been trying to learn and implement OOP into my designs of late, but I'm wondering if this is moot in this instance as it may be better to have the business logic for this in stored procedures in the DB. I could use POCO's, a front end layer and a data access layer for the web application and just use it as a mechanism for CRUD actions on the DB, then use SP's fired in the DB to apply the business rules. On the other hand, I could use an object oriented design within the web app, but as the data in the app is state-less, is this a bad idea? I could try and model out the whole application into a class structure, implementing interfaces, base classes and all that good stuff. So I would create a change class, which contained a list of task classes/types, which defined each task, and implement an ITask interface etc. Put end-user types into the tasks to identify who should be doing what task. Then apply all the business logic in the respective class methods etc. What approach do you guys think I should be using for this solution?

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  • When too much encapsulation was reached

    - by Samuel
    Recently, I read a lot of gook articles about how to do a good encapsulation. And when I say "good encapsulation", I don't talk about hiding private fields with public properties; I talk about preventing users of your Api to do wrong things. Here is two good articles about this subject: http://blog.ploeh.dk/2011/05/24/PokayokeDesignFromSmellToFragrance.aspx http://lostechies.com/derickbailey/2011/03/28/encapsulation-youre-doing-it-wrong/ At my job, the majority a our applications are not destined to other programmers but rather to the customers. About 80% of the application code is at the top of the structure (Not used by other code). For this reason, there is probably no chance ever that this code will be used by other application. An example of encapsulation that prevent user to do wrong thing with your Api is to return an IEnumerable instead of IList when you don't want to give the ability to the user to add or remove items in the list. My question is: When encapsulation could be considered like too much of purism object oriented programming while keeping in mind that each hour of programming is charged to the customer? I want to do good code that is maintainable, easy to read and to use but when this is not a public Api (Used by other programmer), where could we put the line between perfect code and not so perfect code? Thank you.

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  • Manager/Container class vs static class methods

    - by Ben
    Suppose I a have a Widget class that is part of a framework used independently by many applications. I create Widget instances in many situations and their lifetimes vary. In addition to Widget's instance specified methods, I would like to be able to perform the follow class wide operations: Find a single Widget instance based on a unique id Iterate over the list of all Widgets Remove a widget from the set of all widgets In order support these operations, I have been considering two approaches: Container class - Create some container or manager class, WidgetContainer, which holds a list of all Widget instances, support iteration and provides methods for Widget addition, removal and lookup. For example in C#: public class WidgetContainer : IEnumerable<Widget { public void AddWidget(Widget); public Widget GetWidget(WidgetId id); public void RemoveWidget(WidgetId id); } Static class methods - Add static class methods to Widget. For example: public class Widget { public Widget(WidgetId id); public static Widget GetWidget(WidgetId id); public static void RemoveWidget(WidgetId id); public static IEnumerable<Widget AllWidgets(); } Using a container class has the added problem of how to access the container class. Make it a singleton?..yuck! Create some World object that provides access to all such container classes? I have seen many frameworks that use the container class approach, so what is the general consensus?

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  • SQL Server script commands to check if object exists and drop it

    - by deadlydog
    Over the past couple years I’ve been keeping track of common SQL Server script commands that I use so I don’t have to constantly Google them.  Most of them are how to check if a SQL object exists before dropping it.  I thought others might find these useful to have them all in one place, so here you go: 1: --=============================== 2: -- Create a new table and add keys and constraints 3: --=============================== 4: IF NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'TableName' AND TABLE_SCHEMA='dbo') 5: BEGIN 6: CREATE TABLE [dbo].[TableName] 7: ( 8: [ColumnName1] INT NOT NULL, -- To have a field auto-increment add IDENTITY(1,1) 9: [ColumnName2] INT NULL, 10: [ColumnName3] VARCHAR(30) NOT NULL DEFAULT('') 11: ) 12: 13: -- Add the table's primary key 14: ALTER TABLE [dbo].[TableName] ADD CONSTRAINT [PK_TableName] PRIMARY KEY NONCLUSTERED 15: ( 16: [ColumnName1], 17: [ColumnName2] 18: ) 19: 20: -- Add a foreign key constraint 21: ALTER TABLE [dbo].[TableName] WITH CHECK ADD CONSTRAINT [FK_Name] FOREIGN KEY 22: ( 23: [ColumnName1], 24: [ColumnName2] 25: ) 26: REFERENCES [dbo].[Table2Name] 27: ( 28: [OtherColumnName1], 29: [OtherColumnName2] 30: ) 31: 32: -- Add indexes on columns that are often used for retrieval 33: CREATE INDEX IN_ColumnNames ON [dbo].[TableName] 34: ( 35: [ColumnName2], 36: [ColumnName3] 37: ) 38: 39: -- Add a check constraint 40: ALTER TABLE [dbo].[TableName] WITH CHECK ADD CONSTRAINT [CH_Name] CHECK (([ColumnName] >= 0.0000)) 41: END 42: 43: --=============================== 44: -- Add a new column to an existing table 45: --=============================== 46: IF NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.COLUMNS where TABLE_SCHEMA='dbo' 47: AND TABLE_NAME = 'TableName' AND COLUMN_NAME = 'ColumnName') 48: BEGIN 49: ALTER TABLE [dbo].[TableName] ADD [ColumnName] INT NOT NULL DEFAULT(0) 50: 51: -- Add a description extended property to the column to specify what its purpose is. 52: EXEC sys.sp_addextendedproperty @name=N'MS_Description', 53: @value = N'Add column comments here, describing what this column is for.' , 54: @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE', 55: @level1name = N'TableName', @level2type=N'COLUMN', 56: @level2name = N'ColumnName' 57: END 58: 59: --=============================== 60: -- Drop a table 61: --=============================== 62: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'TableName' AND TABLE_SCHEMA='dbo') 63: BEGIN 64: DROP TABLE [dbo].[TableName] 65: END 66: 67: --=============================== 68: -- Drop a view 69: --=============================== 70: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.VIEWS WHERE TABLE_NAME = 'ViewName' AND TABLE_SCHEMA='dbo') 71: BEGIN 72: DROP VIEW [dbo].[ViewName] 73: END 74: 75: --=============================== 76: -- Drop a column 77: --=============================== 78: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.COLUMNS where TABLE_SCHEMA='dbo' 79: AND TABLE_NAME = 'TableName' AND COLUMN_NAME = 'ColumnName') 80: BEGIN 81: 82: -- If the column has an extended property, drop it first. 83: IF EXISTS (SELECT * FROM sys.fn_listExtendedProperty(N'MS_Description', N'SCHEMA', N'dbo', N'Table', 84: N'TableName', N'COLUMN', N'ColumnName') 85: BEGIN 86: EXEC sys.sp_dropextendedproperty @name=N'MS_Description', 87: @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE', 88: @level1name = N'TableName', @level2type=N'COLUMN', 89: @level2name = N'ColumnName' 90: END 91: 92: ALTER TABLE [dbo].[TableName] DROP COLUMN [ColumnName] 93: END 94: 95: --=============================== 96: -- Drop Primary key constraint 97: --=============================== 98: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='PRIMARY KEY' AND TABLE_SCHEMA='dbo' 99: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'PK_Name') 100: BEGIN 101: ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [PK_Name] 102: END 103: 104: --=============================== 105: -- Drop Foreign key constraint 106: --=============================== 107: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='FOREIGN KEY' AND TABLE_SCHEMA='dbo' 108: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'FK_Name') 109: BEGIN 110: ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [FK_Name] 111: END 112: 113: --=============================== 114: -- Drop Unique key constraint 115: --=============================== 116: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' 117: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'UNI_Name') 118: BEGIN 119: ALTER TABLE [dbo].[TableNames] DROP CONSTRAINT [UNI_Name] 120: END 121: 122: --=============================== 123: -- Drop Check constraint 124: --=============================== 125: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='CHECK' AND TABLE_SCHEMA='dbo' 126: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'CH_Name') 127: BEGIN 128: ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [CH_Name] 129: END 130: 131: --=============================== 132: -- Drop a column's Default value constraint 133: --=============================== 134: DECLARE @ConstraintName VARCHAR(100) 135: SET @ConstraintName = (SELECT TOP 1 s.name FROM sys.sysobjects s JOIN sys.syscolumns c ON s.parent_obj=c.id 136: WHERE s.xtype='d' AND c.cdefault=s.id 137: AND parent_obj = OBJECT_ID('TableName') AND c.name ='ColumnName') 138: 139: IF @ConstraintName IS NOT NULL 140: BEGIN 141: EXEC ('ALTER TABLE [dbo].[TableName] DROP CONSTRAINT ' + @ConstraintName) 142: END 143: 144: --=============================== 145: -- Example of how to drop dynamically named Unique constraint 146: --=============================== 147: DECLARE @ConstraintName VARCHAR(100) 148: SET @ConstraintName = (SELECT TOP 1 CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS 149: WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' 150: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME LIKE 'FirstPartOfConstraintName%') 151: 152: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' 153: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = @ConstraintName) 154: BEGIN 155: EXEC ('ALTER TABLE [dbo].[TableName] DROP CONSTRAINT ' + @ConstraintName) 156: END 157: 158: --=============================== 159: -- Check for and drop a temp table 160: --=============================== 161: IF OBJECT_ID('tempdb..#TableName') IS NOT NULL DROP TABLE #TableName 162: 163: --=============================== 164: -- Drop a stored procedure 165: --=============================== 166: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_TYPE='PROCEDURE' AND ROUTINE_SCHEMA='dbo' AND 167: ROUTINE_NAME = 'StoredProcedureName') 168: BEGIN 169: DROP PROCEDURE [dbo].[StoredProcedureName] 170: END 171: 172: --=============================== 173: -- Drop a UDF 174: --=============================== 175: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_TYPE='FUNCTION' AND ROUTINE_SCHEMA='dbo' AND 176: ROUTINE_NAME = 'UDFName') 177: BEGIN 178: DROP FUNCTION [dbo].[UDFName] 179: END 180: 181: --=============================== 182: -- Drop an Index 183: --=============================== 184: IF EXISTS (SELECT * FROM SYS.INDEXES WHERE name = 'IndexName') 185: BEGIN 186: DROP INDEX TableName.IndexName 187: END 188: 189: --=============================== 190: -- Drop a Schema 191: --=============================== 192: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = 'SchemaName') 193: BEGIN 194: EXEC('DROP SCHEMA SchemaName') 195: END And here’s the same code, just not in the little code view window so that you don’t have to scroll it.--=============================== -- Create a new table and add keys and constraints --=============================== IF NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'TableName' AND TABLE_SCHEMA='dbo') BEGIN CREATE TABLE [dbo].[TableName]  ( [ColumnName1] INT NOT NULL, -- To have a field auto-increment add IDENTITY(1,1) [ColumnName2] INT NULL, [ColumnName3] VARCHAR(30) NOT NULL DEFAULT('') ) -- Add the table's primary key ALTER TABLE [dbo].[TableName] ADD CONSTRAINT [PK_TableName] PRIMARY KEY NONCLUSTERED ( [ColumnName1],  [ColumnName2] ) -- Add a foreign key constraint ALTER TABLE [dbo].[TableName] WITH CHECK ADD CONSTRAINT [FK_Name] FOREIGN KEY ( [ColumnName1],  [ColumnName2] ) REFERENCES [dbo].[Table2Name]  ( [OtherColumnName1],  [OtherColumnName2] ) -- Add indexes on columns that are often used for retrieval CREATE INDEX IN_ColumnNames ON [dbo].[TableName] ( [ColumnName2], [ColumnName3] ) -- Add a check constraint ALTER TABLE [dbo].[TableName] WITH CHECK ADD CONSTRAINT [CH_Name] CHECK (([ColumnName] >= 0.0000)) END --=============================== -- Add a new column to an existing table --=============================== IF NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.COLUMNS where TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND COLUMN_NAME = 'ColumnName') BEGIN ALTER TABLE [dbo].[TableName] ADD [ColumnName] INT NOT NULL DEFAULT(0) -- Add a description extended property to the column to specify what its purpose is. EXEC sys.sp_addextendedproperty @name=N'MS_Description',  @value = N'Add column comments here, describing what this column is for.' ,  @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE', @level1name = N'TableName', @level2type=N'COLUMN', @level2name = N'ColumnName' END --=============================== -- Drop a table --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'TableName' AND TABLE_SCHEMA='dbo') BEGIN DROP TABLE [dbo].[TableName] END --=============================== -- Drop a view --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.VIEWS WHERE TABLE_NAME = 'ViewName' AND TABLE_SCHEMA='dbo') BEGIN DROP VIEW [dbo].[ViewName] END --=============================== -- Drop a column --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.COLUMNS where TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND COLUMN_NAME = 'ColumnName') BEGIN -- If the column has an extended property, drop it first. IF EXISTS (SELECT * FROM sys.fn_listExtendedProperty(N'MS_Description', N'SCHEMA', N'dbo', N'Table', N'TableName', N'COLUMN', N'ColumnName') BEGIN EXEC sys.sp_dropextendedproperty @name=N'MS_Description',  @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE', @level1name = N'TableName', @level2type=N'COLUMN', @level2name = N'ColumnName' END ALTER TABLE [dbo].[TableName] DROP COLUMN [ColumnName] END --=============================== -- Drop Primary key constraint --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='PRIMARY KEY' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'PK_Name') BEGIN ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [PK_Name] END --=============================== -- Drop Foreign key constraint --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='FOREIGN KEY' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'FK_Name') BEGIN ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [FK_Name] END --=============================== -- Drop Unique key constraint --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'UNI_Name') BEGIN ALTER TABLE [dbo].[TableNames] DROP CONSTRAINT [UNI_Name] END --=============================== -- Drop Check constraint --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='CHECK' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'CH_Name') BEGIN ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [CH_Name] END --=============================== -- Drop a column's Default value constraint --=============================== DECLARE @ConstraintName VARCHAR(100) SET @ConstraintName = (SELECT TOP 1 s.name FROM sys.sysobjects s JOIN sys.syscolumns c ON s.parent_obj=c.id WHERE s.xtype='d' AND c.cdefault=s.id  AND parent_obj = OBJECT_ID('TableName') AND c.name ='ColumnName') IF @ConstraintName IS NOT NULL BEGIN EXEC ('ALTER TABLE [dbo].[TableName] DROP CONSTRAINT ' + @ConstraintName) END --=============================== -- Example of how to drop dynamically named Unique constraint --=============================== DECLARE @ConstraintName VARCHAR(100) SET @ConstraintName = (SELECT TOP 1 CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS  WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME LIKE 'FirstPartOfConstraintName%') IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = @ConstraintName) BEGIN EXEC ('ALTER TABLE [dbo].[TableName] DROP CONSTRAINT ' + @ConstraintName) END --=============================== -- Check for and drop a temp table --=============================== IF OBJECT_ID('tempdb..#TableName') IS NOT NULL DROP TABLE #TableName --=============================== -- Drop a stored procedure --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_TYPE='PROCEDURE' AND ROUTINE_SCHEMA='dbo' AND ROUTINE_NAME = 'StoredProcedureName') BEGIN DROP PROCEDURE [dbo].[StoredProcedureName] END --=============================== -- Drop a UDF --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_TYPE='FUNCTION' AND ROUTINE_SCHEMA='dbo' AND  ROUTINE_NAME = 'UDFName') BEGIN DROP FUNCTION [dbo].[UDFName] END --=============================== -- Drop an Index --=============================== IF EXISTS (SELECT * FROM SYS.INDEXES WHERE name = 'IndexName') BEGIN DROP INDEX TableName.IndexName END --=============================== -- Drop a Schema --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = 'SchemaName') BEGIN EXEC('DROP SCHEMA SchemaName') END

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  • Is comparing an OO compiler to a SQL compiler/optimizer valid?

    - by Brad
    I'm now doing a lot of SQL development at my new job where as before I was doing Object Oriented desktop app stuff. I keep running across very large scripts (thousands of lines) and wanting to refactor in some way. I am seeing that SQL is a different sort of beast and it's probably fine to have these big scripts for the most part but while explaining this to me people are also insisting that the whole idea of refactoring is bad. That stuff like the .NET compiler are actually burdened by refactored code and that a big wall of code is more efficient and better design than code designed for reuse, readability and scalability. The other argument is that OO compilers are almost dangerously inefficient and don't have efficient memory management or runs too many CPU instructions compared to older "simpler" compilers and compared to SQL. Are these valid complaints? Even if some compiler like a C compiler is modestly more "efficient" (whatever that means on this high of a level without seeing code) would you want to write applications in C over C# or Java? Is comparing an OO compiler to a SQL compiler/optimizer even valid?

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  • Getting rid of Massive View Controller in iOS?

    - by Earl Grey
    I had a discussion with my colleague about the following problem. We have an application where we need filtering functionality. On any main screen within the upper navigation bar, there is a button in the upper right corner. Once you touch that button, an custom written Alert View like view will pop up modally, behind it a semitransparent black overlay view. In that modal view, there is a table view of options, and you can choose one exclusively. Based on your selection, once this modal view is closed, the list of items in the main view is filtered. It is simply a modally presented filter to filter the main table view.This UI design is dictated by the design department, I cannot do anything about it so let accept this as a premise. Also the main filter button in the navbar will change colours to indicate that the filter is active. The question I have is about implementation. I suggested to my colleague that we create a separate XYZFilter class that will be an instance created by the main view controller acquire the filtering options handle saving and restoration of its state - i.e. last filter selected provide its two views - the overlay view and the modal view be the datasource for the table in its modal view. For some unknown reason, my colleague was not impressed by that approach at all. He simply wants to do these functionalities in the main view controller, maybe out of being used to do this in the past like that :-/ Is there any fundamental problem with my approach? I want to keep the view controller small, not to have spaghetti code create a reusable component (for use outside the project) have more object oriented, decoupled approach. prevent duplication of code as we need the filtering in two different places but it looks the same in both.. Any advice?

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  • Architectural Composition Languages

    - by C. Lawrence Wenham
    Recently stumbled upon this paper (PDF) talking about ACLs, or Architectural Composition Languages. They're a fusion of two earlier lines of research: Architectural Definition Languages (such as UML) and Object Composition Languages (such as XAML, WWF, or scripting languages). The goal of an ACL is to have a high-level description of a program's architecture which can also be compiled into a runnable program. The high-level description assists automated analysis, while the 'executability' means changes can be tested immediately. You would still author the components of the program in a conventional programming language (C, Java, Python, etc), but they would be composed into a complete program by the ACL. One of the expected benefits is that a program can be ported to a different platform by swapping in "similar but different" components. I've been hankering for something like this for a long time (see this answer I gave on a StackOverflow question a few years ago). The paper mentions that the researchers were working on a language called ACL/1 that initially targeted Java, but would be ported to support .Net as well. However, I can't find any more mention of ACL/1 anywhere. Has there been any more work done on this? Are there any other implementations of the ACL concept that are available for use or experimentation?

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  • What is the ideal length of a method?

    - by iPhoneDeveloper
    In object-oriented programming, there is no exact rule on the maximum length of a method , but I still found these two qutes somewhat contradicting each other, so I would like to hear what you think. In Clean Code: A Handbook of Agile Software Craftsmanship, Robert Martin says: The first rule of functions is that they should be small. The second rule of functions is that they should be smaller than that. Functions should not be 100 lines long. Functions should hardly ever be 20 lines long. and he gives an example from Java code he sees from Kent Beck: Every function in his program was just two, or three, or four lines long. Each was transparently obvious. Each told a story. And each led you to the next in a compelling order. That’s how short your functions should be! This sounds great, but on the other hand, in Code Complete, Steve McConnell says something very different: The routine should be allowed to grow organically up to 100-200 lines, decades of evidence say that routines of such length no more error prone then shorter routines. And he gives a reference to a study that says routines 65 lines or long are cheaper to develop. So while there are diverging opinions about the matter, is there a functional best-practice towards determining the ideal length of a method for you?

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  • How to drastically improve code coverage?

    - by Peter Kofler
    I'm tasked with getting a legacy application under unit test. First some background about the application: It's a 600k LOC Java RCP code base with these major problems massive code duplication no encapsulation, most private data is accessible from outside, some of the business data also made singletons so it's not just changeable from outside but also from everywhere. no business model, business data is stored in Object[] and double[][], so no OO. There is a good regression test suite and an efficient QA team is testing and finding bugs. I know the techniques how to get it under test from classic books, e.g. Michael Feathers, but that's too slow. As there is a working regression test system I'm not afraid to aggressively refactor the system to allow unit tests to be written. How should I start to attack the problem to get some coverage quickly, so I'm able to show progress to management (and in fact to start earning from safety net of JUnit tests)? I do not want to employ tools to generate regression test suites, e.g. AgitarOne, because these tests do not test if something is correct.

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  • Teaching OO to VBA developers [closed]

    - by Eugene
    I work with several developers that come from less object oriented background like (VB6, VBA) and are mostly self-taught. As part of moving away from those technologies we recently we started having weekly workshops to go over the features of C#.NET and OO practices and design principles. After a couple of weeks of basic introduction I noticed that they had a lot of problems implementing even basic code. For instance it took probably 15 minutes to implement a Stack.push() and a full hour to implement a simple Stack fully. These developers were trying to do things like passing top index as a parameter to the method, not creating an private array, using variables out of scope. But most of all not going through the "design (dia/mono)log" (I need something to do X, so maybe I'll make an array, or put it here). I am a little confused because they are smart people and are able to produce functional code in their traditional environments. I'm curious if anybody else has encountered a similar thing and if there are any particular resources, exercises, books, ideas that would be helpful in this circumstance.

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  • Inheritance vs composition in this example

    - by Gerenuk
    I'm wondering about the differences between inheritance and composition examined with concrete code relevant arguments. In particular my example was Inheritance: class Do: def do(self): self.doA() self.doB() def doA(self): pass def doB(self): pass class MyDo(Do): def doA(self): print("A") def doB(self): print("B") x=MyDo() vs Composition: class Do: def __init__(self, a, b): self.a=a self.b=b def do(self): self.a.do() self.b.do() x=Do(DoA(), DoB()) (Note for composition I'm missing code so it's not actually shorter) Can you name particular advantages of one or the other? I'm think of: composition is useful if you plan to reuse DoA() in another context inheritance seems easier; no additional references/variables/initialization method doA can access internal variable (be it a good or bad thing :) ) inheritance groups logic A and B together; even though you could equally introduce a grouped delegate object inheritance provides a preset class for the users; with composition you'd have to encapsule the initialization in a factory so that the user does have to assemble the logic and the skeleton ... Basically I'd like to examine the implications of inheritance vs composition. I heard often composition is prefered, but I'd like to understand that by example. Of course I can always start with one and refactor later to the other.

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  • Parallel Class/Interface Hierarchy with the Facade Design Pattern?

    - by Mike G
    About a third of my code is wrapped inside a Facade class. Note that this isn't a "God" class, but actually represents a single thing (called a Line). Naturally, it delegates responsibilities to the subsystem behind it. What ends up happening is that two of the subsystem classes (Output and Timeline) have all of their methods duplicated in the Line class, which effectively makes Line both an Output and a Timeline. It seems to make sense to make Output and Timeline interfaces, so that the Line class can implement them both. At the same time, I'm worried about creating parallel class and interface structures. You see, there are different types of lines AudioLine, VideoLine, which all use the same type of Timeline, but different types of Output (AudioOutput and VideoOutput, respectively). So that would mean that I'd have to create an AudioOutputInterface and VideoOutputInterface as well. So not only would I have to have parallel class hierarchy, but there would be a parallel interface hierarchy as well. Is there any solution to this design flaw? Here's an image of the basic structure (minus the Timeline class, though know that each Line has-a Timeline): NOTE: I just realized that the word 'line' in Timeline might make is sound like is does a similar function as the Line class. They don't, just to clarify.

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