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• How do I learn algorithms?

  - by Panthe

  Brief History: Just graduated high school, learned a bit of python and C++, have no friends with any helpful computer knowledge at all. Out of anyone i met in my school years I was probably the biggest nerd, but no one really knew. I consider my self to have a vast amount of knowledge on computers and tech then the average person. built/fixed tons of computers, and ability to troubleshoot pretty much any problem I came across. Now that high school is over, Ive really been thinking about my career. Loving, living computers for the past 15 years of my life I decided to take my ability's and try to learn computer programming, why I didn't start earlier I don't know, seems to be big mistake on my part... Doing some research I concluded that Python was the first programming language I should learn, since it was high level and easier to understand then C++ and Java. I also knew that to become good at what I did I needed to know more then just 2 or 3 languages, which didn't seem like a big problem considering once I learned the way Python worked, mainly syntax changed, and the rest would come naturally. I watched a couple of youtube videos, downloaded some book pdf's and snooped around from some tutorials here and there to get the hang of what to do. A two solid weeks had passed of trying to understand the syntax, create small programs that used the basic functions and understanding how it worked, I think i have got the hang of it. It breaks down into what ive been dealing with all this time (although i kinda knew) is that, input,output, loops, functions and other things derived from 0's and 1's storing data and recalling it, ect. (A VERY BASIC IDEA). Ive been able to create small programs, Hangman, file storing, temperature conversion, Caeser Cipher decode/encoding, Fibonacci Sequence and more, which i can create and understand how each work. Being 2 weeks into this, I have learned alot. Nothing at all compared to what i should be lear ning in the years to come if i get a grip on what I'm doing. While doing these programs I wont stop untill I've done doing a practice problem on a book, which embarresing enough will take me a couple hour depending on the complexity of it. I absolutly will not put aside the challenge until its complete, WHICH CAN BE EXTREMELY DRAINING, ive tried most problems without cheating and reached success, which makes me feel extremely proud of my self after completing something after much trial and error. After all this I have met the demon, alogrithm's which seem to be key to effiecent code. I cant seem to rap my head around some of the computer codes people put out there using numbers, and sometimes even basic functions, I have been able to understand them after a while but i know there are alot more complex things to come, considering my self smart, functions that require complex codes, actually hurt my brain. NOTHING EVER IN LIFE HURT MY BRAIN....... not even math classes in highschool, trying to understand some of the stuff people put out there makes me feel like i have a mental disadvantage lol... i still walk forward though, crossing my fingers that the understanding will come with time. Sorry if is this is long i just wish someone takes all these things into consideration when answering my question. even through all these downsides im still pushing through and continuing to try and get good at this, i know reading these tutorials wont make me any good unless i can become creative and make my own, understand other peoples programs, so this leads me to the simple question i could have asked in the beginning..... WHERE IN THE WORLD DO I START ? Ive been trying to find out how to understand some of the open source projects, how i can work with experianced coders to learn from them and help them, but i dont think thats even possible by the way how far people's knowledge is compared to me, i have no freinds who i can learn from, can someone help me and guide me into the right direction.. i have a huge motivation to get good at coding, anything information would be extremely helpful

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• How do you place an Excel Sheet/Workbook onto a C# .NET Winform?

  - by incognick

  I am trying to create a stand alone application in Visual Studio 2008 C# .Net that will house Excel Workbooks (2007). I am using Office.Interop in order to create the Excel application and I open the workbooks via Workbooks.Open(...). The Interop does not provide any functionality to "move" the workbooks onto a form so I turned to P/Invoke Win32 library. I am able to move the entire excel application onto a WinForm with great success: // pseudo code to give you the idea excel = new Excel.ApplicationClass(); SetParent(excel.Hwnd, form.handle); This allows me to customize the form and control user input. All right click commands and formula editing work properly. Now, the issue I run into is when I want to open two workbooks in two separate forms. I do this by creating two excel application classes and placing each of those in their own form. When I try to reference one workbook to another workbook via =[Book2]Sheet1!A1, for example, it does not update. This is expected as each application is running under its own thread/process. Here are the alternatives I have tried. If you have any suggestions I would be greatly appreciative.(OLE is not an option. VSTO must be available) Create a single application class and move the workbook window into my form. Results: The window moves into my form and displays correctly, however, no right click or left click works on the form and it never gains focus. (I have tried to manually set focus and it does not work either). My guess is, by moving the window outside of the XLDESK application (viewable in Spy++ for Excel Application), the workbook application (EXCEL7) does not receive the correct window messages to gain focus and to behave properly. This leads me to: Move the XLDESK window handle into my form. Results: This allows the workbook to be click-able again but also has an undesired result of moving all child windows into the same form. Create a main excel application that creates workbooks. Create a new excel application for each new window. Move the workbook under the new excel application XLDESK window. Results: This also has the same effect of the 1st option. Unable to click in the workbook. This must mean that the thread that created the workbook is also responsible for the events. Create a windows hook that watches the WndProc procedure. Results: No events watched. The targeted thread must export the hook proc in a DLL export call. Excel does not do this and thus you cannot inject into it's DLL (unless someone can prove me wrong). I am able to watch all threads within my own process but not from an outside process. Excel is created as a separate process. Subclass NativeWindow. Results: Same as #4. After I move the window into my form, all events are captured up until the mouse is directly over the excel sheet making the sheet seem unclickable. One idea I haven't tried yet is just to continually save the excel sheet as the user edits it. This should update all references but I would feel this would cause poor system performance. There will be numerous chart references as well and I'm not sure if this solution would cause problems further down the road. I think in the end, all the workbooks need to be created by the same Excel Application and then moved to get the desired results but I can't seem to find the correct way to move the windows without disabling the user input in the process. Any suggestions?

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• Linked Lists in Java - Help with assignment

  - by doron2010

  I have been trying to solve this assignment all day, please help me. I'm completely lost. Representation of a string in linked lists In every intersection in the list there will be 3 fields : The letter itself. The number of times it appears consecutively. A pointer to the next intersection in the list. The following class CharNode represents a intersection in the list : public class CharNode { private char _data; private int _value; private charNode _next; public CharNode (char c, int val, charNode n) { _data = c; _value = val; _next = n; } public charNode getNext() { return _next; } public void setNext (charNode node) { _next = node; } public int getValue() { return _value; } public void setValue (int v) { value = v; } public char getData() { return _data; } public void setData (char c) { _data = c; } } The class StringList represents the whole list : public class StringList { private charNode _head; public StringList() { _head = null; } public StringList (CharNode node) { _head = node; } } Add methods to the class StringList according to the details : (Pay attention, these are methods from the class String and we want to fulfill them by the representation of a string by a list as explained above) public char charAt (int i) - returns the char in the place i in the string. Assume that the value of i is in the right range. public StringList concat (String str) - returns a string that consists of the string that it is operated on and in its end the string "str" is concatenated. public int indexOf (int ch) - returns the index in the string it is operated on of the first appeareance of the char "ch". If the char "ch" doesn't appear in the string, returns -1. If the value of fromIndex isn't in the range, returns -1. public int indexOf (int ch, int fromIndex) - returns the index in the string it is operated on of the first appeareance of the char "ch", as the search begins in the index "fromIndex". If the char "ch" doesn't appear in the string, returns -1. public boolean equals (String str) - returns true if the string that it is operated on is equal to the string str. Otherwise returns false. This method must be written in recursion, without using loops at all. public int compareTo (String str) - compares between the string that the method is operated on to the string "str" that is in the parameter. The method returns 0 if the strings are equal. If the string in the object is smaller lexicographic from the string "str" in the paramater, a negative number will be returned. And if the string in the object is bigger lexicographic from the string "str", a positive number will be returned. public StringList substring (int i) - returns the list of the substring that starts in the place i in the string on which it operates. Meaning, the sub-string from the place i until the end of the string. Assume the value of i is in the right range. public StringList substring (int i, int j) - returns the list of the substring that begins in the place i and ends in the place j (not included) in the string it operates on. Assume the values of i, j are in the right range. public int length() - will return the length of the string on which it operates. Pay attention to all the possible error cases. Write what is the time complexity and space complexity of every method that you wrote. Make sure the methods you wrote are effective. It is NOT allowed to use ready classes of Java. It is NOT allowed to move to string and use string operations.

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• C#: The input stream is not a valid binary format.

  - by Mcoroklo

  I have a problem with deserializing in C#/ASP.NET, which gives the exact error: The input stream is not a valid binary format. The starting contents (in bytes) are: 41-41-45-41-41-41-44-2F-2F-2F-2F-2F-41-51-41-41-41 ... What I am trying to do I have a structure with 3 classes. I have a class A which is a base class, and then class B and C which are derived from A. I am trying to store random types of B and C in the database using LINQ to SQL, in a column with the type VARCHAR(MAX). I cannot use BINARY as the length is around 15.000. My code... Error is in the LAST codeblock C# Code in Business layer- Storing a record private void AddTraceToDatabase(FightTrace trace) { MemoryStream recieverStream = new MemoryStream(); MemoryStream firedStream = new MemoryStream(); MemoryStream moveStream = new MemoryStream(); BinaryFormatter binaryFormatter = new BinaryFormatter(); binaryFormatter.Serialize(recieverStream,trace.Reciever); binaryFormatter.Serialize(firedStream,trace.FiredBy); binaryFormatter.Serialize(moveStream,trace.Move); string reciever = Convert.ToBase64String(recieverStream.ToArray()); string fired = Convert.ToBase64String(firedStream.ToArray()); string move = Convert.ToBase64String(moveStream.ToArray()); this.dataAccess.AddFightTrace(trace.TraceType.ToString(),reciever,move,fired,trace.DateTime,this.FightId); } C# Code in Data access layer - Storing a record public void AddFightTrace(string type, string reciever, string Move, string firedBy, DateTime firedAt, int fightid) { GameDataContext db = new GameDataContext(); dbFightTrace trace = new dbFightTrace(); trace.TraceType = type; trace.Reciever = reciever; trace.Move = Move; trace.FiredBy = firedBy; trace.FiredAt = firedAt; trace.FightId = fightid; db.dbFightTraces.InsertOnSubmit(trace); db.SubmitChanges(); } C# Code getting the entry in the database public List<dbFightTrace> GetNewTraces(int fightid, DateTime lastUpdate) { GameDataContext db = new GameDataContext(); var data = from d in db.dbFightTraces where d.FightId==fightid && d.FiredAt > lastUpdate select d; return data.ToList(); } C# Factory, converting from LINQ to SQL class to my objects THIS IS HERE THE ERROR COMES public FightTrace CreateTrace(dbFightTrace trace) { TraceType traceType = (TraceType) Enum.Parse(typeof(TraceType), trace.TraceType); BinaryFormatter formatter = new BinaryFormatter(); System.Text.UTF8Encoding enc = new System.Text.UTF8Encoding(); MemoryStream recieverStream = new MemoryStream(enc.GetBytes(trace.Reciever)); recieverStream.Position = 0; MemoryStream firedStream = new MemoryStream(enc.GetBytes(trace.FiredBy)); firedStream.Position = 0; MemoryStream movedStream = new MemoryStream(enc.GetBytes(trace.Move)); movedStream.Position = 0; // THE NEXT LINE HERE CAUSES THE ERROR NPC reciever = formatter.Deserialize(recieverStream) as NPC; Player fired = formatter.Deserialize(firedStream) as Player; BaseAttack attack = formatter.Deserialize(movedStream) as BaseAttack; FightTrace t = new FightTrace(traceType,reciever,attack,fired); t.TraceId = trace.FightTraceId; t.DateTime = trace.FiredAt; return t; } So the error happends when the first Deserialize method is run, with the above error. I have tried several things but I am quite lost on this one.. Thanks! :-)

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• How do I get around this lambda expression outer variable issue?

  - by panamack

  I'm playing with PropertyDescriptor and ICustomTypeDescriptor (still) trying to bind a WPF DataGrid to an object, for which the data is stored in a Dictionary. Since if you pass WPF DataGrid a list of Dictionary objects it will auto generate columns based on the public properties of a dictionary (Comparer, Count, Keys and Values) my Person subclasses Dictionary and implements ICustomTypeDescriptor. ICustomTypeDescriptor defines a GetProperties method which returns a PropertyDescriptorCollection. PropertyDescriptor is abstract so you have to subclass it, I figured I'd have a constructor that took Func and an Action parameters that delegate the getting and setting of the values in the dictionary. I then create a PersonPropertyDescriptor for each Key in the dictionary like this: foreach (string s in this.Keys) { var descriptor = new PersonPropertyDescriptor( s, new Func<object>(() => { return this[s]; }), new Action<object>(o => { this[s] = o; })); propList.Add(descriptor); } The problem is that each property get's its own Func and Action but they all share the outer variable s so although the DataGrid autogenerates columns for "ID","FirstName","LastName", "Age", "Gender" they all get and set against "Gender" which is the final resting value of s in the foreach loop. How can I ensure that each delegate uses the desired dictionary Key, i.e. the value of s at the time the Func/Action is instantiated? Much obliged. Here's the rest of my idea, I'm just experimenting here these are not 'real' classes... // DataGrid binds to a People instance public class People : List<Person> { public People() { this.Add(new Person()); } } public class Person : Dictionary<string, object>, ICustomTypeDescriptor { private static PropertyDescriptorCollection descriptors; public Person() { this["ID"] = "201203"; this["FirstName"] = "Bud"; this["LastName"] = "Tree"; this["Age"] = 99; this["Gender"] = "M"; } //... other ICustomTypeDescriptor members... public PropertyDescriptorCollection GetProperties() { if (descriptors == null) { var propList = new List<PropertyDescriptor>(); foreach (string s in this.Keys) { var descriptor = new PersonPropertyDescriptor( s, new Func<object>(() => { return this[s]; }), new Action<object>(o => { this[s] = o; })); propList.Add(descriptor); } descriptors = new PropertyDescriptorCollection(propList.ToArray()); } return descriptors; } //... other other ICustomTypeDescriptor members... } public class PersonPropertyDescriptor : PropertyDescriptor { private Func<object> getFunc; private Action<object> setAction; public PersonPropertyDescriptor(string name, Func<object> getFunc, Action<object> setAction) : base(name, null) { this.getFunc = getFunc; this.setAction = setAction; } // other ... PropertyDescriptor members... public override object GetValue(object component) { return getFunc(); } public override void SetValue(object component, object value) { setAction(value); } }

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• LinkedList Wrong Display(string builder)

  - by Chris

  Hello, The following program is a basic linked list divided in 3 classes. In the tester class (main) i add several numbers to the list (sorted). But insteed of getting the numbers as a result i get the result: LinkedList.LinkedList Is something wrong with the stringbuilder (the program was first in java where a string buffer was used, but that should be the same i think?) LinkedListTester.cs using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace LinkedList { public class LinkedListTester { static void Main(string[] args) { LinkedList ll = new LinkedList(); ll.addDataSorted(5); ll.addDataSorted(7); ll.addDataSorted(13); ll.addDataSorted(1); ll.addDataSorted(17); ll.addDataSorted(8); Console.WriteLine(ll); } } }/LinkedList/ LinkedList.cs using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace LinkedList { public class LinkedList { //toestand private LinkedListNode first; private LinkedListNode last; //gedrag public LinkedList() { first = null; last = null; } public void addDataInFront(int data) { first = new LinkedListNode(data, first); if (last == null){ last = first; } }/*addDataInFront*/ public void addDataToBack(int data) { if (first == null) { addDataInFront(data); } else { last.setNext(new LinkedListNode(data, null)); last = last.getNext(); } }/*addDataToBack*/ public void addDataSorted(int data) { if (first == null || first.getData() > data) { addDataInFront(data); } else { LinkedListNode currentNode = first; while (currentNode.getNext() != null && currentNode.getNext().getData() < data) { currentNode = currentNode.getNext(); } currentNode.setNext(new LinkedListNode(data, currentNode.getNext())); currentNode = currentNode.getNext(); if (currentNode.getNext() == null) { last = currentNode; } } }/*addDataSorted*/ public String toString() { StringBuilder Buf = new StringBuilder(); LinkedListNode currentNode = first; while (currentNode != null) { Buf.Append(currentNode.getData()); Buf.Append(' '); currentNode = currentNode.getNext(); } return Buf.ToString(); }/*toString*/ }/*LinkedList*/ }/LinkedList/ LinkedListNode: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace LinkedList { public class LinkedListNode { //toestand private int data; private LinkedListNode next; private LinkedListNode previous; //gedrag public LinkedListNode(int data, LinkedListNode next) { this.data = data; this.next = next; this.previous = null; } public LinkedListNode(int data, LinkedListNode next, LinkedListNode previous) { this.data = data; this.next = next; this.previous = previous; } public LinkedListNode getNext() { return next; } public LinkedListNode getPrevious() { return previous; } public void setNext(LinkedListNode next) { this.next = next; } public void setPrevious(LinkedListNode previous) { this.previous = previous; } public int getData() { return data; } }/*LinkedListNode*/ }/LinkedList/

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• ANT: ways to include libraries and license issues

  - by Eric Tobias

  I have been trying to use Ant to compile and ready a project for distribution. I have encountered several problems along the way that I have been finally able to solve but the solution leaves me very unsatisfied. First, let me explain the set-up of the project and its dependencies. I have a project, lets call it Primary which depends on a couple of libraries such as the fantastic Guava. It also depends on another project of mine, lets call it Secondary. The Secondary project also features some dependencies, for example, JDOM2. I have referenced the Jar I build with Ant in Primary. Let me give you the interesting bits of the build.xml so you can get a picture of what I am doing: <project name="Primary" default="all" basedir="."> <property name='build' location='dist' /> <property name='application.version' value='1.0'/> <property name='application.name' value='Primary'/> <property name='distribution' value='${application.name}-${application.version}'/> <path id='compile.classpath'> <fileset dir='libs'> <include name='*.jar'/> </fileset> </path> <target name='compile' description='Compile source files.'> <javac includeantruntime="false" srcdir="src" destdir="bin"> <classpath refid='compile.classpath'/> </javac> <target> <target name='jar' description='Create a jar file for distribution.' depends="compile"> <jar destfile='${build}/${distribution}.jar'> <fileset dir="bin"/> <zipgroupfileset dir="libs" includes="*.jar"/> </jar> </target> The Secodnary project's build.xml is nearly identical except that it features a manifest as it needs to run: <target name='jar' description='Create a jar file for distribution.' depends="compile"> <jar destfile='${dist}/${distribution}.jar' basedir="${build}" > <fileset dir="${build}"/> <zipgroupfileset dir="libs" includes="*.jar"/> <manifest> <attribute name="Main-Class" value="lu.tudor.ssi.kiss.climate.ClimateChange"/> </manifest> </jar> </target> After I got it working, trying for many hours to not include that dependencies as class files but as Jars, I don't have the time or insight to go back and try to figure out what I did wrong. Furthermore, I believe that including these libraries as class files is bad practice as it could give rise to licensing issues while not packaging them and merely including them in a directory along the build Jar would most probably not (And if it would you could choose not to distribute them yourself). I think my inability to correctly assemble the class path, I always received NoClassDefFoundError for classes or libraries in the Primary project when launching Second's Jar, is that I am not very experienced with Ant. Would I require to specify a class path for both projects? Specifying the class path as . should have allowed me to simply add all dependencies to the same folder as Secondary's Jar, should it not?

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• What version-control system is most trivial to set up and use for toy projects?

  - by Norman Ramsey

  I teach the third required intro course in a CS department. One of my homework assignments asks students to speed up code they have written for a previous assignment. Factor-of-ten speedups are routine; factors of 100 or 1000 are not unheard of. (For a factor of 1000 speedup you have to have made rookie mistakes with malloc().) Programs are improved by a sequence is small changes. I ask students to record and describe each change and the resulting improvement. While you're improving a program it is also possible to break it. Wouldn't it be nice to back out? You can see where I'm going with this: my students would benefit enormously from version control. But there are some caveats: Our computing environment is locked down. Anything that depends on a central repository is suspect. Our students are incredibly overloaded. Not just classes but jobs, sports, music, you name it. For them to use a new tool it has to be incredibly easy and have obvious benefits. Our students do most work in pairs. Getting bits back and forth between accounts is problematic. Could this problem also be solved by distributed version control? Complexity is the enemy. I know setting up a CVS repository is too baffling---I myself still have trouble because I only do it once a year. I'm told SVN is even harder. Here are my comments on existing systems: I think central version control (CVS or SVN) is ruled out because our students don't have the administrative privileges needed to make a repository that they can share with one other student. (We are stuck with Unix file permissions.) Also, setup on CVS or SVN is too hard. darcs is way easy to set up, but it's not obvious how you share things. darcs send (to send patches by email) seems promising but it's not clear how to set it up. The introductory documentation for git is not for beginners. Like CVS setup, it's something I myself have trouble with. I'm soliciting suggestions for what source-control to use with beginning students. I suspect we can find resources to put a thin veneer over an existing system and to simplify existing documentation. We probably don't have resources to write new documentation. So, what's really easy to setup, commit, revert, and share changes with a partner but does not have to be easy to merge or to work at scale? A key constraint is that programming pairs have to be able to share work with each other and only each other, and pairs change every week. Our infrastructure is Linux, Solaris, and Windows with a netapp filer. I doubt my IT staff wants to create a Unix group for each pair of students. Is there an easier solution I've overlooked? (Thanks for the accepted answer, which beats the others on account of its excellent reference to Git Magic as well as the helpful comments.)

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• What is the best practice when coding math class/functions ?

  - by Isaac Clarke

  Introductory note : I voluntarily chose a wide subject. You know that quote about learning a cat to fish, that's it. I don't need an answer to my question, I need an explanation and advice. I know you guys are good at this ;) Hi guys, I'm currently implementing some algorithms into an existing program. Long story short, I created a new class, "Adder". An Adder is a member of another class representing the physical object actually doing the calculus , which calls adder.calc() with its parameters (merely a list of objects to do the maths on). To do these maths, I need some parameters, which do not exist outside of the class (but can be set, see below). They're neither config parameters nor members of other classes. These parameters are D1 and D2, distances, and three arrays of fixed size : alpha, beta, delta. I know some of you are more comfortable reading code than reading text so here you go : class Adder { public: Adder(); virtual Adder::~Adder(); void set( float d1, float d2 ); void set( float d1, float d2, int alpha[N_MAX], int beta[N_MAX], int delta[N_MAX] ); // Snipped prototypes float calc( List& ... ); // ... inline float get_d1() { return d1_ ;}; inline float get_d2() { return d2_ ;}; private: float d1_; float d2_; int alpha_[N_MAX]; // A #define N_MAX is done elsewhere int beta_[N_MAX]; int delta_[N_MAX]; }; Since this object is used as a member of another class, it is declared in a *.h : private: Adder adder_; By doing that, I couldn't initialize the arrays (alpha/beta/delta) directly in the constructor ( int T[3] = { 1, 2, 3 }; ), without having to iterate throughout the three arrays. I thought of putting them in static const, but I don't think that's the proper way of solving such problems. My second guess was to use the constructor to initialize the arrays Adder::Adder() { int alpha[N_MAX] = { 0, -60, -120, 180, 120, 60 }; int beta[N_MAX] = { 0, 0, 0, 0, 0, 0 }; int delta[N_MAX] = { 0, 0, 180, 180, 180, 0 }; set( 2.5, 0, alpha, beta, delta ); } void Adder::set( float d1, float d2 ) { if (d1 > 0) d1_ = d1; if (d2 > 0) d2_ = d2; } void Adder::set( float d1, float d2, int alpha[N_MAX], int beta[N_MAX], int delta[N_MAX] ) { set( d1, d2 ); for (int i = 0; i < N_MAX; ++i) { alpha_[i] = alpha[i]; beta_[i] = beta[i]; delta_[i] = delta[i]; } } My question is : Would it be better to use another function - init() - which would initialize arrays ? Or is there a better way of doing that ? My bonus question is : Did you see some mistakes or bad practice along the way ?

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• Can I retrieve objects from a complex query that limits results to fields from a single table?

  - by Sean Redmond

  I have a model whose rows I always want to sort based on the values in another associated model and I was thinking that the way to implement this would be to use set_dataset in the model. This is causing query results to be returned as hashes rather than objects, though, so none of the methods from the class can be used when iterating over the dataset. I basically have two classes class SortFields < Sequel::Model(:sort_fields) set_primary_key :objectid end class Items < Sequel::Model(:items) set_primary_key :objectid one_to_one :sort_fields, :class => SortFields, :key => :objectid end Some backstory: the data is imported from a legacy system into mysql. The values in sort_fields are calculated from multiple other associated tables (some one-to-many, some many-to-many) according to some complicated rules. The likely solution will be to just add the values in sort_fields to items (I want to keep the imported data separate from the calculated data, but I don't have to). First, though, I just want to understand how far you can go with a dataset and still get objects rather than hashes. If I set the dataset to sort on a field in items like so class Items < Sequel::Model(:items) set_primary_key :objectid one_to_one :sort_fields, :class => SortFields, :key => :objectid set_dataset(order(:sortnumber)) end then the expected clause is added to the generated SQL, e.g.: >> Items.limit(1).sql => "SELECT * FROM `items` ORDER BY `sortnumber` LIMIT 1" and queries still return objects: >> Items.limit(1).first.class => Items If I order it by the associated fields though... class Items < Sequel::Model(:items) set_primary_key :objectid one_to_one :sort_fields, :class => SortFields, :key => :objectid set_dataset( eager_graph(:sort_fields). order(:sort1, :sort2, :sort3) ) end ...I get hashes ?> Items.limit(1).first.class => Hash My first thought was that this happens because all fields from sort_fields are included in the results and maybe if selected only the fields from items I would get Items objects again: class Items < Sequel::Model(:items) set_primary_key :objectid one_to_one :sort_fields, :class => SortFields, :key => :objectid set_dataset( eager_graph(:sort_fields). select(:items.*). order(:sort1, :sort2, :sort3) ) end The generated SQL is what I would expect: >> Items.limit(1).sql => "SELECT `items`.* FROM `items` LEFT OUTER JOIN `sort_fields` ON (`sort_fields`.`objectid` = `items`.`objectid`) ORDER BY `sort1`, `sort2`, `sort3` LIMIT 1" It returns the same rows as the set_dataset(order(:sortnumber)) version but it still doesn't work: >> Items.limit(1).first.class => Hash Before I add the sort fields to the items table so that they can all live happily in the same model, is there a way to tell Sequel to return on object when it wants to return a hash?

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• How do I expand my <div> to properly fit more vertical content?

  - by CSS_maniac

  Whenever I try to add margin-top: 30px to my box_1 and box_2 <div>, my bottom <div> gets pushed down and disappears. It seems like my wrapper wont expand to fit the content. How do I get a 30px gap between top and box_1/2 and bottom? <html> <head> <title>Circle Motion</title> <link rel="stylesheet" type="text/css" href="styles.css" /> </head> <body> <div id="outer-wrapper"> <div id="wrapper"> <div id="top"> </div> <div id="box_1"> <img src="chrome_400x400.png" /> </div> <div id="box_2"> <img src="firefox_400x400.png" /> </div> <div id="bottom"> <p>All Rights Reserved - CSS_maniac 2012 ©</p> </div> </div> </div> </body> </html> CSS /* My CSS */ html { height: 100% } body { background-color: grey; } #outer-wrapper { height: 100%; width: 1000px; margin: 0px auto; background-color: #EAFFDB; -moz-border-radius: 15px; border-radius: 15px; } #wrapper { height: 100%; width: 960px; margin: 0px auto; background-color: #EAFFDB; overflow: hidden; } #top { width: 900px; height: 110px; margin-top: 35px; margin-left: 30px; margin-right: 30px; background-color: white; -moz-border-radius: 15px; border-radius: 15px; } #box_1 { width: 430px; height: 430px; background-color: white; -moz-border-radius: 15px; border-radius: 15px; float:left; margin-left: 30px; text-align: center; } #box_2 { width: 430px; height: 430px; background-color: white; -moz-border-radius: 15px; border-radius: 15px; float:right; margin-right: 30px; text-align: center; } #box_1 img { margin: 15px 0px; } #box_2 img { margin: 15px 0px; } #bottom { width: 900px; margin: 0px auto 0px auto; text-align: center; background-color: white; -moz-border-radius: 15px; border-radius: 15px; clear:both; } /* Classes */ .clear { clear: both; }

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• Why is FubuMVC new()ing up my view model in PartialForEach?

  - by Jon M

  I'm getting started with FubuMVC and I have a simple Customer - Order relationship I'm trying to display using nested partials. My domain objects are as follows: public class Customer { private readonly IList<Order> orders = new List<Order>(); public string Name { get; set; } public IEnumerable<Order> Orders { get { return orders; } } public void AddOrder(Order order) { orders.Add(order); } } public class Order { public string Reference { get; set; } } I have the following controller classes: public class CustomersController { public IndexViewModel Index(IndexInputModel inputModel) { var customer1 = new Customer { Name = "John Smith" }; customer1.AddOrder(new Order { Reference = "ABC123" }); return new IndexViewModel { Customers = new[] { customer1 } }; } } public class IndexInputModel { } public class IndexViewModel { public IEnumerable<Customer> Customers { get; set; } } public class IndexView : FubuPage<IndexViewModel> { } public class CustomerPartial : FubuControl<Customer> { } public class OrderPartial : FubuControl<Order> { } IndexView.aspx: (standard html stuff trimmed) <div> <%= this.PartialForEach(x => x.Customers).Using<CustomerPartial>() %> </div> CustomerPartial.ascx: <%@ Control Language="C#" Inherits="FubuDemo.Controllers.Customers.CustomerPartial" %> <div> Customer Name: <%= this.DisplayFor(x => x.Name) %> <br /> Orders: (<%= Model.Orders.Count() %>) <br /> <%= this.PartialForEach(x => x.Orders) %> </div> OrderPartial.ascx: <%@ Control Language="C#" Inherits="FubuDemo.Controllers.Customers.OrderPartial" %> <div> Order <br /> Ref: <%= this.DisplayFor(x => x.Reference) %> </div> When I view Customers/Index, I see the following: Customers Customer Name: John Smith Orders: (1) It seems that in CustomerPartial.ascx, doing Model.Orders.Count() correctly picks up that 1 order exists. However PartialForEach(x = x.Orders) does not, as nothing is rendered for the order. If I set a breakpoint on the Order constructor, I see that it initially gets called by the Index method on CustomersController, but then it gets called by FubuMVC.Core.Models.StandardModelBinder.Bind, so it is getting re-instantiated by FubuMVC and losing the content of the Orders collection. This isn't quite what I'd expect, I would think that PartialForEach would just pass the domain object directly into the partial. Am I missing the point somewhere? What is the 'correct' way to achieve this kind of result in Fubu?

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• How to select chosen columns from two different entities into one DTO using NHibernate?

  - by Pawel Krakowiak

  I have two classes (just recreating the problem): public class User { public virtual int Id { get; set; } public virtual string FirstName { get; set; } public virtual string LastName { get; set; } public virtual IList<OrgUnitMembership> OrgUnitMemberships { get; set; } } public class OrgUnitMembership { public virtual int UserId { get; set; } public virtual int OrgUnitId { get; set; } public virtual DateTime JoinDate { get; set; } public virtual DateTime LeaveDate { get; set; } } There's a Fluent NHibernate map for both, of course: public class UserMapping : ClassMap<User> { public UserMapping() { Table("Users"); Id(e => e.Id).GeneratedBy.Identity(); Map(e => e.FirstName); Map(e => e.LastName); HasMany(x => x.OrgUnitMemberships) .KeyColumn(TypeReflector<OrgUnitMembership> .GetPropertyName(p => p.UserId))).ReadOnly().Inverse(); } } public class OrgUnitMembershipMapping : ClassMap<OrgUnitMembership> { public OrgUnitMembershipMapping() { Table("OrgUnitMembership"); CompositeId() .KeyProperty(x=>x.UserId) .KeyProperty(x=>x.OrgUnitId); Map(x => x.JoinDate); Map(x => x.LeaveDate); References(oum => oum.OrgUnit) .Column(TypeReflector<OrgUnitMembership> .GetPropertyName(oum => oum.OrgUnitId)).ReadOnly(); References(oum => oum.User) .Column(TypeReflector<OrgUnitMembership> .GetPropertyName(oum => oum.UserId)).ReadOnly(); } } What I want to do is to retrieve some users based on criteria, but I would like to combine all columns from the Users table with some columns from the OrgUnitMemberships table, analogous to a SQL query: select u.*, m.JoinDate, m.LeaveDate from Users u inner join OrgUnitMemberships m on u.Id = m.UserId where m.OrgUnitId = :ouid I am totally lost, I tried many different options. Using a plain SQL query almost works, but because there are some nullable enums in the User class AliasToBean fails to transform, otherwise wrapping a SQL query would work like this: return Session .CreateSQLQuery(sql) .SetParameter("ouid", orgUnitId) .SetResultTransformer(Transformers.AliasToBean<UserDTO>()) .List<UserDTO>() I tried the code below as a test (a few different variants), but I'm not sure what I'm doing. It works partially, I get instances of UserDTO back, the properties coming from OrgUnitMembership (dates) are filled, but all properties from User are null: User user = null; OrgUnitMembership membership = null; UserDTO dto = null; var users = Session.QueryOver(() => user) .SelectList(list => list .Select(() => user.Id) .Select(() => user.FirstName) .Select(() => user.LastName)) .JoinAlias(u => u.OrgUnitMemberships, () => membership) //.JoinQueryOver<OrgUnitMembership>(u => u.OrgUnitMemberships) .SelectList(list => list .Select(() => membership.JoinDate).WithAlias(() => dto.JoinDate) .Select(() => membership.LeaveDate).WithAlias(() => dto.LeaveDate)) .TransformUsing(Transformers.AliasToBean<UserDTO>()) .List<UserDTO>();

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• plotting multiple google maps to page

  - by Roland

  I'm trying to append more than one Google Map to a page. But it seems like I'm having some trouble. This would be the template I'm using to ( with Handlebars.js ) to create the same block more than once, about 50 times : <script type="text/x-handlebars-template"> {{#each productListing}} <div class="product-listing-wrapper"> <div class="product-listing"> <div class="left-side-content"> <div class="thumb-wrapper" data-image-link="{{ThumbnailUrl}}"> <i class="thumb"> <img src="{{ThumbnailUrl}}" alt="Thumb"> <span class="zoom-image"></span> </i> </div> <div class="google-maps-wrapper"> <div class="google-coordonates-wrapper"> <div class="google-coordonates"> <p>{{LatLon.Lat}}</p> <p>{{LatLon.Lon}}</p> </div> </div> <div class="google-maps-button"> <a class="google-maps" href="#">Google Maps</a> </div> </div> </div> <div class="right-side-content"> <div class="map-canvas-wrapper"> <div id="map-canvas" class="map-canvas" data-latitude="{{LatLon.Lat}}" data-longitude="{{LatLon.Lon}}"></div> </div> <div class="content-wrapper"></div> </div> </div> </div> {{/each}} And I'm trying to append the map to the #map-canvas id. With the following block of code I'm doing the plotting : Cluster.prototype.initiate_map_assembling = function() { return $(this.map_canvas_wrapper_class).each(function(index, element) { var canvas = $(element).children(); var latitude = $(canvas).attr('data-latitude'); var longitude = $(canvas).attr('data-longitude'); var coordinates = new google.maps.LatLng(latitude, longitude); var options = { zoom: 9, center: coordinates, mapTypeId: google.maps.MapTypeId.ROADMAP }; var map = new google.maps.Map($(canvas), options); var marker = new google.maps.Marker({ position: coordinates, map: map }); }); }; This way I'm "looping" through all the parent classes of the id I'm trying to append the map to, but the map would only append to the first id. I tried to append it to all of the id's in other ways but with the same results. So what would you suggest me to do to make it work as I would expect it, append the map to each of the id's ?

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• jsp getServletContext() error

  - by Reigel

  html <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <title>Murach's Java Servlets and JSP</title> </head> <body> <%-- import packages and classes needed by the scripts --%> <%@ page import="business.*, data.*" %> <% //get parameters from the request String firstName = request.getParameter("firstName"); String lastName = request.getParameter("lastName"); String emailAddress = request.getParameter("emailAddress"); // get the real path for the EmailList.txt file ServletContext sc = this.getServletContext(); String path = sc.getRealPath("/WEB-INF/EmailList.txt"); // use regular Java objects User user = new User(firstName, lastName, emailAddress); UserIO.add(user, path); %> <h1>Thanks for joining our email list</h1> <p>Here is the information that you entered: </p> <table cellspacing="5" cellpadding="5" border="1"> <tr> <td align="right">First name:</td> <td><%= firstName %></td> </tr> <tr> <td align="right">Last name:</td> <td><%= lastName %></td> </tr> <tr> <td align="right">Email Address:</td> <td><%= emailAddress %></td> </tr> </table> <p>To enter another email address, click on the Back <br /> button in your browser or the Return button shown <br /> below.</p> <form action="index.jsp" method="post"> <input type="submit" value="Return" /> </form> </body> </html> and it's giving me this error page... Compilation of 'C:\bea\user_projects\domains\mydomain.\myserver.wlnotdelete\extract\myserver_sample01_WebContent\jsp_servlet__display_email_entry.java' failed: C:\bea\user_projects\domains\mydomain.\myserver.wlnotdelete\extract\myserver_sample01_WebContent\jsp_servlet__display_email_entry.java:140: cannot resolve symbol probably occurred due to an error in /display_email_entry.jsp line 19: ServletContext sc = this.getServletContext(); Full compiler error(s): C:\bea\user_projects\domains\mydomain.\myserver.wlnotdelete\extract\myserver_sample01_WebContent\jsp_servlet__display_email_entry.java:140: cannot resolve symbol symbol : method getServletContext () location: class jsp_servlet.__display_email_entry     ServletContext sc = this.getServletContext(); //[ /display_email_entry.jsp; Line:19]                                    ^ 1 error Thu Jun 03 15:56:09 CST 2010 any hint? I'm really new to JSP, and this is my first learning practice... can't find it by google.com.... thanks!

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• How to implement this .NET client and PHP server synchronization scenario?

  - by pbean

  I have a PHP webserver and a .NET mobile application. The .NET application needs data from a database, which is provided (for now) by the php webserver. I'm fairly new to this kind of scenario so I'm not sure what the best practices are. I ran into a couple of problems and I am not certain how to overcome them. For now, I have the following setup. I run a PHP SOAP server which has a couple of operations which simply retrieve data from the database. For this web service I have created a WSDL file. In Visual Studio I added a web reference to my project using the WSDL file and it generated some classes for it. I simply call something like "MyWebService.GetItems();" and I get an array of items in my .NET application, which come straight from the database. Next I also serialize all these retrieved objects to local (permanent) storage. I face a couple of challenges which I don't know how to resolve properly. The idea is for the mobile client to synchronize the data once (at the start of the day), before working, and then use the local storage throughout the day, and synchronize it back at the end of the day. At the moment all data is downloaded through SOAP, and not a subset (only what is needed). How would I know which new information should be sent to the client? Only the server knows what is new, but only the client knows for sure which data it already has. I seem to be doing double work now. The data which is transferred with SOAP basically already are serialized objects. But at the moment I first retrieve all objects through SOAP and the .NET framework automatically deserializes it. Then I serialize all data again myself. It would be more efficient to simply download it to storage, and then deserialize it. The mobile device does not have a lot of memory. In my test data this is not really a problem, but with potentially tenths of thousands of records I can imagine this will become a problem. Currently when I call the SOAP method, it loads all data into memory (as an array) but as described above perhaps it would be better to have it stored into storage directly, and only retrieve from storage the objects that are needed. But how would I store this? An array would serialize to one big XML (or binary) file from which I cannot choose which objects to load. Would I make (possible tenths of thousands) separate files? Also at the end of the day when I want to send the changes back to the server, how would I know which objects to send... since they're not in memory? I hope my troubles are clear and I hope you are able to help me figure out how to implement this the best way. :) Some things are already fixed (like using .NET on the mobile device, using PHP and having a MySQL database server) but other things can most certainly be changed (like using SOAP).

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• Can i create different observables and different corresponding observers in java?

  - by mithun1538

  Hello everyone, Currently, I have one observable and many observers. What i need is different observables, and depending on the observable, different observers. How do I achieve this? ( For understanding, assume I have different apples - say apple1 apple2... I have observer_1 observing apple1, observer_2 observing apple2, observer_3 observing apple 2 and so on..). I tried creating different objects of the Observable class, but since observers are observing the same class of observable, I don't know how to access a particular instance of the Observable. I have included the following servlet code that contains Observer and Observable classes: public class CustomerServlet extends HttpServlet { public String getNextMessage() { // Create a message sink to wait for a new message from the // message source. return new MessageSink().getNextMessage(source); } @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ObjectOutputStream dout = new ObjectOutputStream(response.getOutputStream()); String recMSG = getNextMessage(); dout.writeObject(recMSG); dout.flush(); } public void broadcastMessage(String message) { // Send the message to all the HTTP-connected clients by giving the // message to the message source source.sendMessage(message); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { try { ObjectInputStream din= new ObjectInputStream(request.getInputStream()); String message = (String)din.readObject(); ObjectOutputStream dout = new ObjectOutputStream(response.getOutputStream()); dout.writeObject("1"); dout.flush(); if (message != null) { broadcastMessage(message); } // Set the status code to indicate there will be no response response.setStatus(response.SC_NO_CONTENT); } catch (Exception e) { e.printStackTrace(); } } @Override public String getServletInfo() { return "Short description"; }// </editor-fold> MessageSource source = new MessageSource(); } class MessageSource extends Observable { public void sendMessage(String message) { setChanged(); notifyObservers(message); } } class MessageSource extends Observable { public void sendMessage(String message) { setChanged(); notifyObservers(message); } } class MessageSink implements Observer { String message = null; // set by update() and read by getNextMessage() // Called by the message source when it gets a new message synchronized public void update(Observable o, Object arg) { // Get the new message message = (String)arg; // Wake up our waiting thread notify(); } // Gets the next message sent out from the message source synchronized public String getNextMessage(MessageSource source) { // Tell source we want to be told about new messages source.addObserver(this); // Wait until our update() method receives a message while (message == null) { try { wait(); } catch (Exception e) { System.out.println("Exception has occured! ERR ERR ERR"); } } // Tell source to stop telling us about new messages source.deleteObserver(this); // Now return the message we received // But first set the message instance variable to null // so update() and getNextMessage() can be called again. String messageCopy = message; message = null; return messageCopy; } }

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• How to Correct & Improve the Design of this Code?

  - by DaveDev

  HI Guys, I've been working on a little experiement to see if I could create a helper method to serialize any of my types to any type of HTML tag I specify. I'm getting a NullReferenceException when _writer = _viewContext.Writer; is called in protected virtual void Dispose(bool disposing) {/*...*/} I think I'm at a point where it almost works (I've gotten other implementations to work) and I was wondering if somebody could point out what I'm doing wrong? Also, I'd be interested in hearing suggestions on how I could improve the design? So basically, I have this code that will generate a Select box with a number of options: // the idea is I can use one method to create any complete tag of any type // and put whatever I want in the content area <% using (Html.GenerateTag<SelectTag>(Model, new { href = Url.Action("ActionName") })) { %> <%foreach (var fund in Model.Funds) {%> <% using (Html.GenerateTag<OptionTag>(fund)) { %> <%= fund.Name %> <% } %> <% } %> <% } %> This Html.GenerateTag helper is defined as: public static MMTag GenerateTag<T>(this HtmlHelper htmlHelper, object elementData, object attributes) where T : MMTag { return (T)Activator.CreateInstance(typeof(T), htmlHelper.ViewContext, elementData, attributes); } Depending on the type of T it'll create one of the types defined below, public class HtmlTypeBase : MMTag { public HtmlTypeBase() { } public HtmlTypeBase(ViewContext viewContext, params object[] elementData) { base._viewContext = viewContext; base.MergeDataToTag(viewContext, elementData); } } public class SelectTag : HtmlTypeBase { public SelectTag(ViewContext viewContext, params object[] elementData) { base._tag = new TagBuilder("select"); //base.MergeDataToTag(viewContext, elementData); } } public class OptionTag : HtmlTypeBase { public OptionTag(ViewContext viewContext, params object[] elementData) { base._tag = new TagBuilder("option"); //base.MergeDataToTag(viewContext, _elementData); } } public class AnchorTag : HtmlTypeBase { public AnchorTag(ViewContext viewContext, params object[] elementData) { base._tag = new TagBuilder("a"); //base.MergeDataToTag(viewContext, elementData); } } all of these types (anchor, select, option) inherit from HtmlTypeBase, which is intended to perform base.MergeDataToTag(viewContext, elementData);. This doesn't happen though. It works if I uncomment the MergeDataToTag methods in the derived classes, but I don't want to repeat that same code for every derived class I create. This is the definition for MMTag: public class MMTag : IDisposable { internal bool _disposed; internal ViewContext _viewContext; internal TextWriter _writer; internal TagBuilder _tag; internal object[] _elementData; public MMTag() {} public MMTag(ViewContext viewContext, params object[] elementData) { } public void Dispose() { Dispose(true /* disposing */); GC.SuppressFinalize(this); } protected virtual void Dispose(bool disposing) { if (!_disposed) { _disposed = true; _writer = _viewContext.Writer; _writer.Write(_tag.ToString(TagRenderMode.EndTag)); } } protected void MergeDataToTag(ViewContext viewContext, object[] elementData) { Type elementDataType = elementData[0].GetType(); foreach (PropertyInfo prop in elementDataType.GetProperties()) { if (prop.PropertyType.IsPrimitive || prop.PropertyType == typeof(Decimal) || prop.PropertyType == typeof(String)) { object propValue = prop.GetValue(elementData[0], null); string stringValue = propValue != null ? propValue.ToString() : String.Empty; _tag.Attributes.Add(prop.Name, stringValue); } } var dic = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase); var attributes = elementData[1]; if (attributes != null) { foreach (PropertyDescriptor descriptor in TypeDescriptor.GetProperties(attributes)) { object value = descriptor.GetValue(attributes); dic.Add(descriptor.Name, value); } } _tag.MergeAttributes<string, object>(dic); _viewContext = viewContext; _viewContext.Writer.Write(_tag.ToString(TagRenderMode.StartTag)); } } Thanks Dave

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• CoreData, transient atribute and EXC_BAD_ACCESS.

  - by Lukasz

  I'm trying to build simple file browser and i'm stuck. I defined classes, build window, add controllers, views.. Everything works but only ONE time. Selecting again Folder in NSTableView or trying to get data from Folder.files causing silent EXC_BAD_ACCESS (code=13, address0x0) from main. Info about files i keep outside of CoreData, in simple class, I don't want to save them: #import <Foundation/Foundation.h> @interface TPDrawersFileInfo : NSObject @property (nonatomic, retain) NSString * filename; @property (nonatomic, retain) NSString * extension; @property (nonatomic, retain) NSDate * creation; @property (nonatomic, retain) NSDate * modified; @property (nonatomic, retain) NSNumber * isFile; @property (nonatomic, retain) NSNumber * size; @property (nonatomic, retain) NSNumber * label; +(TPDrawersFileInfo *) initWithURL: (NSURL *) url; @end @implementation TPDrawersFileInfo +(TPDrawersFileInfo *) initWithURL: (NSURL *) url { TPDrawersFileInfo * new = [[TPDrawersFileInfo alloc] init]; if (new!=nil) { NSFileManager * fileManager = [NSFileManager defaultManager]; NSError * error; NSDictionary * infoDict = [fileManager attributesOfItemAtPath: [url path] error:&error]; id labelValue = nil; [url getResourceValue:&labelValue forKey:NSURLLabelNumberKey error:&error]; new.label = labelValue; new.size = [infoDict objectForKey: @"NSFileSize"]; new.modified = [infoDict objectForKey: @"NSFileModificationDate"]; new.creation = [infoDict objectForKey: @"NSFileCreationDate"]; new.isFile = [NSNumber numberWithBool:[[infoDict objectForKey:@"NSFileType"] isEqualToString:@"NSFileTypeRegular"]]; new.extension = [url pathExtension]; new.filename = [[url lastPathComponent] stringByDeletingPathExtension]; } return new; } Next I have class Folder, which is NSManagesObject subclass // Managed Object class to keep info about folder content @interface Folder : NSManagedObject { NSArray * _files; } @property (nonatomic, retain) NSArray * files; // Array with TPDrawersFileInfo objects @property (nonatomic, retain) NSString * url; // url of folder -(void) reload; //if url changed, load file info again. @end @implementation Folder @synthesize files = _files; @dynamic url; -(void)awakeFromInsert { [self addObserver:self forKeyPath:@"url" options:NSKeyValueObservingOptionNew context:@"url"]; } -(void)awakeFromFetch { [self addObserver:self forKeyPath:@"url" options:NSKeyValueObservingOptionNew context:@"url"]; } -(void)prepareForDeletion { [self removeObserver:self forKeyPath:@"url"]; } -(void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if (context == @"url") { [self reload]; } } -(void) reload { NSMutableArray * result = [NSMutableArray array]; NSError * error = nil; NSFileManager * fileManager = [NSFileManager defaultManager]; NSString * percented = [self.url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]; NSArray * listDir = [fileManager contentsOfDirectoryAtURL: [NSURL URLWithString: percented] includingPropertiesForKeys: [NSArray arrayWithObject: NSURLCreationDateKey ] options:NSDirectoryEnumerationSkipsHiddenFiles error:&error]; if (error!=nil) {NSLog(@"Error <%@> reading <%@> content", error, self.url);} for (id fileURL in listDir) { TPDrawersFileInfo * fi = [TPDrawersFileInfo initWithURL:fileURL]; [result addObject: fi]; } _files = [NSArray arrayWithArray:result]; } @end In app delegate i defined @interface TPAppDelegate : NSObject <NSApplicationDelegate> { IBOutlet NSArrayController * foldersController; Folder * currentFolder; } - (IBAction)chooseDirectory:(id)sender; // choose folder and - (Folder * ) getFolderObjectForPath: path { //gives Folder object if already exist or nil if not ..... } - (IBAction)chooseDirectory:(id)sender { //Opens panel, asking for url NSOpenPanel * panel = [NSOpenPanel openPanel]; [panel setCanChooseDirectories:YES]; [panel setCanChooseFiles:NO]; [panel setMessage:@"Choose folder to show:"]; NSURL * currentDirectory; if ([panel runModal] == NSOKButton) { currentDirectory = [[panel URLs] objectAtIndex:0]; } Folder * folderObject = [self getFolderObjectForPath:[currentDirectory path]]; if (folderObject) { //if exist: currentFolder = folderObject; } else { // create new one Folder * newFolder = [NSEntityDescription insertNewObjectForEntityForName:@"Folder" inManagedObjectContext:self.managedObjectContext]; [newFolder setValue:[currentDirectory path] forKey:@"url"]; [foldersController addObject:newFolder]; currentFolder = newFolder; } [foldersController setSelectedObjects:[NSArray arrayWithObject:currentFolder]]; } Please help ;)

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• C++ pimpl idiom wastes an instruction vs. C style?

  - by Rob

  (Yes, I know that one machine instruction usually doesn't matter. I'm asking this question because I want to understand the pimpl idiom, and use it in the best possible way; and because sometimes I do care about one machine instruction.) In the sample code below, there are two classes, Thing and OtherThing. Users would include "thing.hh". Thing uses the pimpl idiom to hide it's implementation. OtherThing uses a C style – non-member functions that return and take pointers. This style produces slightly better machine code. I'm wondering: is there a way to use C++ style – ie, make the functions into member functions – and yet still save the machine instruction. I like this style because it doesn't pollute the namespace outside the class. Note: I'm only looking at calling member functions (in this case, calc). I'm not looking at object allocation. Below are the files, commands, and the machine code, on my Mac. thing.hh: class ThingImpl; class Thing { ThingImpl *impl; public: Thing(); int calc(); }; class OtherThing; OtherThing *make_other(); int calc(OtherThing *); thing.cc: #include "thing.hh" struct ThingImpl { int x; }; Thing::Thing() { impl = new ThingImpl; impl->x = 5; } int Thing::calc() { return impl->x + 1; } struct OtherThing { int x; }; OtherThing *make_other() { OtherThing *t = new OtherThing; t->x = 5; } int calc(OtherThing *t) { return t->x + 1; } main.cc (just to test the code actually works...) #include "thing.hh" #include <cstdio> int main() { Thing *t = new Thing; printf("calc: %d\n", t->calc()); OtherThing *t2 = make_other(); printf("calc: %d\n", calc(t2)); } Makefile: all: main thing.o : thing.cc thing.hh g++ -fomit-frame-pointer -O2 -c thing.cc main.o : main.cc thing.hh g++ -fomit-frame-pointer -O2 -c main.cc main: main.o thing.o g++ -O2 -o $@ $^ clean: rm *.o rm main Run make and then look at the machine code. On the mac I use otool -tv thing.o | c++filt. On linux I think it's objdump -d thing.o. Here is the relevant output: Thing::calc(): 0000000000000000 movq (%rdi),%rax 0000000000000003 movl (%rax),%eax 0000000000000005 incl %eax 0000000000000007 ret calc(OtherThing*): 0000000000000010 movl (%rdi),%eax 0000000000000012 incl %eax 0000000000000014 ret Notice the extra instruction because of the pointer indirection. The first function looks up two fields (impl, then x), while the second only needs to get x. What can be done?

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• Many to many self join through junction table

  - by Peter

  I have an EF model that can self-reference through an intermediary class to define a parent/child relationship. I know how to do a pure many-to-many relationship using the Map command, but for some reason going through this intermediary class is causing problems with my mappings. The intermediary class provides additional properties for the relationship. See the classes, modelBinder logic and error below: public class Equipment { [Key] public int EquipmentId { get; set; } public virtual List<ChildRecord> Parents { get; set; } public virtual List<ChildRecord> Children { get; set; } } public class ChildRecord { [Key] public int ChildId { get; set; } [Required] public int Quantity { get; set; } [Required] public Equipment Parent { get; set; } [Required] public Equipment Child { get; set; } } I've tried building the mappings in both directions, though I only keep one set in at a time: modelBuilder.Entity<ChildRecord>() .HasRequired(x => x.Parent) .WithMany(x => x.Children ) .WillCascadeOnDelete(false); modelBuilder.Entity<ChildRecord>() .HasRequired(x => x.Child) .WithMany(x => x.Parents) .WillCascadeOnDelete(false); OR modelBuilder.Entity<Equipment>() .HasMany(x => x.Parents) .WithRequired(x => x.Child) .WillCascadeOnDelete(false); modelBuilder.Entity<Equipment>() .HasMany(x => x.Children) .WithRequired(x => x.Parent) .WillCascadeOnDelete(false); Regardless of which set I use, I get the error: The foreign key component 'Child' is not a declared property on type 'ChildRecord'. Verify that it has not been explicitly excluded from the model and that it is a valid primitive property. when I try do deploy my ef model to the database. If I build it without the modelBinder logic in place then I get two ID columns for Child and two ID columns for Parent in my ChildRecord table. This makes sense since it tries to auto create the navigation properties from Equipment and doesn't know that there are already properties in ChildRecord to fulfill this need. I tried using Data Annotations on the class, and no modelBuilder code, this failed with the same error as above: [Required] [ForeignKey("EquipmentId")] public Equipment Parent { get; set; } [Required] [ForeignKey("EquipmentId")] public Equipment Child { get; set; } AND [InverseProperty("Child")] public virtual List<ChildRecord> Parents { get; set; } [InverseProperty("Parent")] public virtual List<ChildRecord> Children { get; set; } I've looked at various other answers around the internet/SO, and the common difference seems to be that I am self joining where as all the answers I can find are for two different types. Entity Framework Code First Many to Many Setup For Existing Tables Many to many relationship with junction table in Entity Framework? Creating many to many junction table in Entity Framework

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• Update transaction in SQL Server 2008 R2 from ASP.Net not working

  - by Amarus

  Hello! Even though I've been a stalker here for ages, this is the first post I'm making. Hopefully, it won't end here and more optimistically future posts might actually be me trying to give a hand to someone else, I do owe this community that much and more. Now, what I'm trying to do is simple and most probably the reason behind it not working is my own stupidity. However, I'm stumped here. I'm working on an ASP.Net website that interacts with an SQL Server 2008 R2 database. So far everything has been going okay but updating a row (or more) just won't work. I even tried copying and pasting code from this site and others but it's always the same thing. In short: No exception or errors are shown when the update command executes (it even gives the correct count of affected rows) but no changes are actually made on the database. Here's a simplified version of my code (the original had more commands and tons of parameters each, but even when it's like this it doesn't work): protected void btSubmit_Click(object sender, EventArgs e) { using (SqlConnection connection = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["ApplicationServices"].ConnectionString)) { string commandString = "UPDATE [impoundLotAlpha].[dbo].[Vehicle]" + "SET [VehicleMake] = @VehicleMake" + " WHERE [ComplaintID] = @ComplaintID"; using (SqlCommand command = new SqlCommand(commandString, connection)) { SqlTransaction transaction = null; try { command.Connection.Open(); transaction = connection.BeginTransaction(IsolationLevel.Serializable); command.Transaction = transaction; SqlParameter complaintID = new SqlParameter("@complaintID", SqlDbType.Int); complaintID.Value = HttpContext.Current.Request.QueryString["complaintID"]; command.Parameters.Add(complaintID); SqlParameter VehicleMake = new SqlParameter("@VehicleMake", SqlDbType.VarChar, 20); VehicleMake.Value = tbVehicleMake.Text; command.Parameters.Add(VehicleMake); command.ExecuteNonQuery(); transaction.Commit(); } catch { transaction.Rollback(); throw; } finally { connection.Close(); } } } } I've tried this with the "SqlTransaction" stuff and without it and nothing changes. Also, since I'm doing multiple updates at once, I want to have them act as a single transaction. I've found that it can be either done like this or by use of the classes included in the System.Transactions namespace (CommittableTransaction, TransactionScope...). I tried all I could find but didn't get any different results. The connection string in web.config is as follows: <connectionStrings> <add name="ApplicationServices" connectionString="Data Source=localhost;Initial Catalog=ImpoundLotAlpha;Integrated Security=True" providerName="System.Data.SqlClient"/> </connectionStrings> So, tldr; version: What is the mistake that I did with that record update attempt? (Figured it out, check below if you're having a similar issue.) What is the best method to gather multiple update commands as a single transaction? Thanks in advance for any kind of help and/or suggestions! Edit: It seems that I was lacking some sleep yesterday cause this time it only took me 5 minutes to figure out my mistake. Apparently the update was working properly but I failed to notice that the textbox values were being overwritten in Page_Load. For some reason I had this part commented: if (IsPostBack) return; The second part of the question still stands. But should I post this as an answer to my own question or keep it like this?

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• C++ class functions calling fortran subroutine

  - by user2863626

  Okay so I am trying to make my code work. It is a simple C++ program with a class "CArray". This class has 2 properties, the array size, and the value. I want the main C++ program to create two instances of the class CArray. In the class CArray, I have a function called "AddArray( CArray )" where it adds another array to the current array. The problem I am stuck with, is that I want the function "AddArray" to add the two arrays in fortran. I know, much more complicated, but that is what I need. I am having issues with linking the two inside the class code. #include <iostream> using namespace std; class CArray { public: CArray(); ~CArray(); int Size; int* Val; void SetSize( int ); void SetValues(); void GetArray(); extern "C" { void Add( int*, int*, int*, int*); void Subtract( int*, int*, int*, int*); void Muliply( int*, int*, int *, int* ); } void AddArray( CArray ); void SubtractArray( CArray ); void MultiplyArray( CArray ); }; Also here is the CArray function file. #include "Array.h" #include <iostream> using namespace std; CArray::CArray() { } CArray::~CArray() { } void CArray::SetSize( int s ) { Size = s; for ( int i=0; i<s; i++ ) { Val = new int[Size]; } } void CArray::SetValues() { for ( int i=0; i<Size; i++ ) { cout << "Element " << i+1 << ": "; cin >> Val[i]; } } void CArray::GetArray() { for ( int i=0; i<Size; i++ ) { cout << Val[i] << " "; } } void CArray::AddArray( CArray a ) { if ( Size == a.Size ) { Add(&Val, &a.Val); } else { cout << "Array dimensions do not agree!" << endl; } } void CArray::SubtractArray( CArray a ) { Subtract( &Val, &a, &Size, &a.Size); GetArray(); } Here is my Fortran code. module SubtractArrays use ico_c_binding implicit none contains subroutine Subtract(a,b,s1,s2) bind(c,name='Subtract') integer s1,s2 integer a(s1),b(s2) if ( s1.eq.s2 ) do i=1,s1 a(i) = a(i) - b(i) end return end end If someone could just help me with setting me up to send arrays of integers from C++ classes to fortran I would greatly appreciate it! Thank you, Josh Derrick

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• count specific things within a code in c++

  - by shap

  can anyone help me make this more generalised and more pro? #include <fstream> #include <iostream> #include <string> #include <vector> using namespace std; int main() { // open text file for input: string file_name; cout << "please enter file name: "; cin >> file_name; // associate the input file stream with a text file ifstream infile(file_name.c_str()); // error checking for a valid filename if ( !infile ) { cerr << "Unable to open file " << file_name << " -- quitting!\n"; return( -1 ); } else cout << "\n"; // some data structures to perform the function vector<string> lines_of_text; string textline; // read in text file, line by while (getline( infile, textline, '\n' )) { // add the new element to the vector lines_of_text.push_back( textline ); // print the 'back' vector element - see the STL documentation cout << lines_of_text.back() << "\n"; } cout<<"OUTPUT BEGINS HERE: "<<endl<<endl; cout<<"the total capacity of vector: lines_of_text is: "<<lines_of_text.capacity()<<endl; int PLOC = (lines_of_text.size()+1); int numbComments =0; int numbClasses =0; cout<<"\nThe total number of physical lines of code is: "<<PLOC<<endl; for (int i=0; i<(PLOC-1); i++) //reads through each part of the vector string line-by-line and triggers if the //it registers the "//" which will output a number lower than 100 (since no line is 100 char long and if the function does not //register that character within the string, it outputs a public status constant that is found in the class string and has a huge value //alot more than 100. { string temp(lines_of_text [i]); if (temp.find("//")<100) numbComments +=1; } cout<<"The total number of comment lines is: "<<numbComments<<endl; for (int j=0; j<(PLOC-1); j++) { string temp(lines_of_text [j]); if (temp.find("};")<100) numbClasses +=1; } cout<<"The total number of classes is: "<<numbClasses<<endl;

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• Problem in arranging contents of Class in JAVA

  - by LuckySlevin

  Hi, I have some classes and I'm trying to fill the objects of this class. Here is what i've tried. (Question is at the below) public class Team { private String clubName; private String preName; private ArrayList<String> branches; public Team(String clubName, String preName) { this.clubName = clubName; this.preName = preName; branches = new ArrayList<String>(); } public Team() { // TODO Auto-generated constructor stub } public String getClubName() { return clubName; } public String getPreName() { return preName; } public ArrayList<String> getBranches() { return branches; } public void setClubName(String clubName) { this.clubName = clubName; } public void setPreName(String preName) { this.preName = preName; } public void setBranches(ArrayList<String> branches) { this.branches = branches; } } public class Branch { private ArrayList<Player> players = new ArrayList<Player>(); String brName; public Branch() {} public void setBr(String brName){this.brName = brName;} public String getBr(){return brName;} public ArrayList<Player> getPlayers() { return players; } public void setPlayers(ArrayList<Player> players) { this.players = players; } } //TEST CLASS public class test { /** * @param args * @throws IOException */ public static void main(String[] args) throws IOException { String a,b,c; String q = "q"; int brCount = 0, tCount = 0; BufferedReader input = new BufferedReader(new InputStreamReader(System.in)); Team[] teams = new Team[30]; Branch[] myBranch = new Branch[30]; for(int z = 0 ; z <30 ;z++) { teams[z] = new Team(); myBranch[z] = new Branch(); } ArrayList<String> tmp = new ArrayList<String>(); int k = 0; int secim = Integer.parseInt(input.readLine()); while(secim != 0) { if(k!=0) secim = Integer.parseInt(input.readLine()); k++; switch(secim) { case 1 : brCount = 0; a = input.readLine(); teams[tCount].setClubName(a); b= input.readLine(); teams[tCount].setPreName(b); c = input.readLine(); while(c.equals(q) == false) { if(brCount != 0) {c = input.readLine();} if(c.equals(q)== false){ myBranch[brCount].brName = c; tmp.add(myBranch[brCount].brName); brCount++; } System.out.println(brCount); } teams[tCount].setBranches(tmp); for(int i=0;i<=tCount;i++ ){ System.out.print("a :" + teams[i].getClubName()+ " " + teams[i].getPreName()+ " "); System.out.println(teams[i].getBranches());} tCount++; break; case 2: String src = input.readLine();//LATERRRRRRRr } } } } The problem is one of my class elements. I have an arraylist as an element of a class. When i enter: AAA as preName BBB as clubName c d e as Branches Then as a second element www as preName GGG as clubName a b as branches The result is coming like: AAA BBB c,d,e,a,b GGG www c,d,e,a,b Which means ArrayList part of the class is putting it on and on. I tried to use clear() method but caused problems. Any ideas.

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