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• Setting up a "to-many" relationship value dependency for a transient Core Data attribute

  - by Greg Combs

  I've got a relatively complicated Core Data relationship structure and I'm trying to figure out how to set up value dependencies (or observations) across various to-many relationships. Let me start out with some basic info. I've got a classroom with students, assignments, and grades (students X assignments). For simplicity's sake, we don't really have to focus much on the assignments yet. StudentObj <--->> ScoreObj <<---> AssignmentObj Each ScoreObj has a to-one relation with the StudentObj and the AssignmentObj. ScoreObj has real attributes for the numerical grade, the turnInDate, and notes. AssignmentObj.scores is the set of Score objects for that assignment (N = all students). AssignmentObj has real attributes for name, dueDate, curveFunction, gradeWeight, and maxPoints. StudentObj.scores is the set of Score objects for that student (N = all assignments). StudentObj also has real attributes like name, studentID, email, etc. StudentObj has a transient (calculated, not stored) attribute called gradeTotal. This last item, gradeTotal, is the real pickle. it calculates the student's overall semester grade using the scores (ScoreObj) from all their assignments, their associated assignment gradeWeights, curves, and maxPoints, and various other things. This gradeTotal value is displayed in a table column, along with all the students and their individual assignment grades. Determining the value of gradeTotal is a relatively expensive operation, particularly with a large class, therefore I want to run it only when necessary. For simplicity's sake, I'm not storing that gradeTotal value in the core data model. I don't mind caching it somewhere, but I'm having a bitch of a time determining where and how to best update that cache. I need to run that calculation for each student whenever any value changes that affects their gradeTotal. If this were a simple to-one relationship, I know I could use something like keyPathsForValuesAffectingGradeTotal ... but it's more like a many-to-one-to-many relationship. Does anyone know of an elegant (and KVC correct) solution? I guess I could tear through all those score and assignment objects and tell them to register their students as observers. But this seems like a blunt force approach.

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• Javascript wont change value in TextBox

  - by mattgcon

  Here is my javascript function AppendValues(e) { var lghtcnt = 0; var vars = e.id.split(';'); var highcnt = false; var lghtid = ""; var maxltcnt = 100; for (var x = 0; x < vars.length; x++) { var tokens = vars[x].split('|'); var pram = tokens if (tokens[0] == "ID"){ lghtid = tokens[1]; } if (tokens[0] == "LTC"){ var itemcnt = 0; var currentcnt = 0; currentcnt = parseInt(tokens[1].toString()); var txtid = document.getElementById(vars[0] + ';' + vars[1] + ';' + vars[2] + ';' + vars[3] + ';' + vars[4]); if (e.checked) { totallightcnt += currentcnt; if (totallightcnt > maxltcnt) { document.getElementById(vars[0] + ';' + vars[1] + ';' + vars[2] + ';' + vars[3] + ';' + vars[4]).value = 0; alert('This puts you over the limit of 100 total lights, please make adjustments.'); break; } document.getElementById(vars[0] + ';' + vars[1] + ';' + vars[2] + ';' + vars[3] + ';' + vars[4]).value = currentcnt.toString(); } else { totallightcnt -= currentcnt; document.getElementById(vars[0] + ';' + vars[1] + ';' + vars[2] + ';' + vars[3] + ';' + vars[4]).value = 0; break; } } if (highcnt) { break; } } } Here is the issue, when I check the value it DOES say theupdated value but it does not display to the user on the webpage. What could be the issue?

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• NHibernate and objects with value-semantics

  - by Groo

  Problem: If I pass a class with value semantics (Equals method overridden) to NHibernate, NHibernate tries to save it to db even though it just saved an entity equal by value (but not by reference) to the database. What am I doing wrong? Here is a simplified example model for my problem: Let's say I have a Person entity and a City entity. One thread (producer) is creating new Person objects which belong to a specific existing City, and another thread (consumer) is saving them to a repository (using NHibernate as DAL). Since there is lot of objects being flushed at a time, I am using Guid.Comb id's to ensure that each insert is made using a single SQL command. City is an object with value-type semantics (equal by name only -- for this example purposes only): public class City : IEquatable<City> { public virtual Guid Id { get; private set; } public virtual string Name { get; set; } public virtual bool Equals(City other) { if (other == null) return false; return this.Name == other.Name; } public override bool Equals(object obj) { return Equals(obj as City); } public override int GetHashCode() { return this.Name.GetHashCode(); } } Fluent NH mapping is something like: public class PersonMap : ClassMap<Person> { public PersonMap() { Id(x => x.Id) .GeneratedBy.GuidComb(); References(x => x.City) .Cascade.SaveUpdate(); } } public class CityMap : ClassMap<City> { public CityMap() { Id(x => x.Id) .GeneratedBy.GuidComb(); Map(x => x.Name); } } Right now (with my current NHibernate mapping config), my consumer thread maintains a dictionary of cities and replaces their references in incoming person objects (otherwise NHibernate will see a new, non-cached City object and try to save it as well), and I need to do it for every produced Person object. Since I have implemented City class to behave like a value type, I hoped that NHibernate would compare Cities by value and not try to save them each time -- i.e. I would only need to do a lookup once per session and not care about them anymore. Is this possible, and if yes, what am I doing wrong here?

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• .Net friendly, local, key-value pair, replicatable datastore

  - by Brad Mathews

  I am looking for a key/value type datastore with very specific requirements. Anyone know anything that will work? Needs to be a component of some sort. No additional installation needed. The datastore needs to be on the local hard drive. I am using VB.Net for a desktop app running Windows XP through 7 so it needs to callable by that environment. It needs to replicatable. If I have four copies of my app running on the network, each local copy of the datastore needs to replicate with the others. As close to real time as possible. The first three are easy, I can do that with ADO.Net out of the box. The last one, replication, is the one I do not have answer to. Does such an animal exist? Thanks, Brad

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• non-copyable objects and value initialization: g++ vs msvc

  - by R Samuel Klatchko

  I'm seeing some different behavior between g++ and msvc around value initializing non-copyable objects. Consider a class that is non-copyable: class noncopyable_base { public: noncopyable_base() {} private: noncopyable_base(const noncopyable_base &); noncopyable_base &operator=(const noncopyable_base &); }; class noncopyable : private noncopyable_base { public: noncopyable() : x_(0) {} noncopyable(int x) : x_(x) {} private: int x_; }; and a template that uses value initialization so that the value will get a known value even when the type is POD: template <class T> void doit() { T t = T(); ... } and trying to use those together: doit<noncopyable>(); This works fine on msvc as of VC++ 9.0 but fails on every version of g++ I tested this with (including version 4.5.0) because the copy constructor is private. Two questions: Which behavior is standards compliant? Any suggestion of how to work around this in gcc (and to be clear, changing that to T t; is not an acceptable solution as this breaks POD types). P.S. I see the same problem with boost::noncopyable.

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• openssl api verify the public key matches private key

  - by AC

  How do I write an openssl server that on a single port has two different active RSA private keys? The openssl documentation seems to implies there can only be one rsa private key active at time with in a context. So I was thinking I have two active context, but what is the code to handle figuring out which connection matches which context. Or am I going about this the wrong way.

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• LINQ transform Dictionary<key,value> to Dictionary<value,key>

  - by code4life

  I'm having a low-brainwave day... Does anyone know of a quick & elegant way to transform a Dictionary so that the key becomes the value and vice-versa? Example: var originalDictionary = new Dictionary<int, string>() { {1, "One"}, {2, "Two"}, {3, "Three"} }; becomes var newDictionary = new Dictionary<string, int>(); // contents: // { // {"One". 1}, {"Two". 2}, {"Three", 3} // };

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• Is it possible to learn maths via programming, or you should learn maths for programming?

  - by SAFAD

  I am not the best in maths, not very horrid either, but lower than the average, I've always been thinking to improve my maths, but schools and books didn't do the job because I get bored too fast. The only thing I don't get bored with is coding and gaming, so I thought what if coding a program that solves mathematical problems will help me understand maths better, most of these problems are limits (calculus), functions, Differential calculus, and some other subjects (I already said am not that good) similar to the previous noted. My question is: Am I able to achieve a better knowledge in maths if I do some specific program coding, and if possible, is physics possible that way too? Or am I wrong and Maths should be learned before programming to help improve my coding? P.S : C++ is the preferred language.

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• KeyTouch remaps the delete key

  - by Robert Gowland

  I installed KeyTouch, but it decided that the delete key should be the KeyTouch hot key. So, when I pressed deleted, KeyTouch came up. Next I uninstalled KeyTouch and now the delete key doesn't do anything. Is there any way to remap the delete key to actually delete? Notes: I tried reinstalling KeyTouch, and the same thing happens. KeyTouch does not allow the user to map the delete key. EDIT xev shows keycode 119 when I press the delete key xmodmap shows keycode 119 mapped to Delete NoSymbol Delete running xmodmap -e "keycode 119 = Delete" from the command line does not resolve the issue

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• PHP: Next Available Value in an Array, starting with a non-indexed value

  - by Erik Smith

  I've been stumped on this PHP issue for about a day now. Basically, we have an array of hours formatted in 24-hour format, and an arbitrary value ($hour) (also a 24-hour). The problem is, we need to take $hour, and get the next available value in the array, starting with the value that immediately proceeds $hour. The array might look something like: $goodHours = array('8,9,10,11,12,19,20,21). Then the hour value might be: $hour = 14; So, we need some way to know that 19 is the next best time. Additionally, we might also need to get the second, third, or fourth (etc) available value. The issue seems to be that because 14 isn't a value in the array, there is not index to reference that would let us increment to the next value. To make things simpler, I've taken $goodHours and repeated the values several times just so I don't have to deal with going back to the start (maybe not the best way to do it, but a quick fix). I have a feeling this is something simple I'm missing, but I would be so appreciative if anyone could shed some light. Erik

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• Python: Access dictionary value inside of tuple and sort quickly by dict value

  - by Aquat33nfan

  I know that wasn't clear. Here's what I'm doing specifically. I have my list of dictionaries here: dict = [{int=0, value=A}, {int=1, value=B}, ... n] and I want to take them in combinations, so I used itertools and it gave me a tuple (Well, okay it gave me a memory object that I then used enumerate on so I could loop over it and enumerate gave ma tuple): for (index, tuple) in enumerate(combinations(dict, 2)): and this is where I have my problem. I want to identify which of the two items in the combination has the bigger 'int' value and which has the smaller value and assign them to variables (I'm actually using more than 2 in the combination so I can't just say if tuple[0]['int'] tuple[1]['int'] and do the assignment because I'd have to list this out a bunch of times and that's hard to manage). I was going to assign each 'int' value to a variable, sort it in a list, index the 'int' value in the list by 1, 2, 3, 4, 5 ... etc., then go back and access the dictionary I wanted by the int value and then assign the dictionary to a variable so I knew which was bigger. But I have a big list and lists and variable assignments are resource intensive and this is taking a long time (I had only a little bit of that written and it was taking forever to run). So I was hoping someone knew a fast way to do this. I actually could list out every possible combination of assignmnets using the if/thens but it's just like 5 pages of if/thens and assignments and is hard to read and manage when I want to change it. You've probably gathered this, but I"m new at programming. thx

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• Setting winforms ToolStripMenuItem ShortcutKeys to numpad key does not work

  - by Axarydax

  We have the ability to define ShortcutKeys for WinForms application menu items. That way I can tell a menu item File-Save to have a shortcut key Ctrl+S and the menu item's handler is "magically" executed after pressing Ctrl+S. The trouble is with the numeric keypad keys, the ShortcutKey property does not accept them (I don't understand how are they different from the other acceptable keys. MSDN states that the property accepts type System.Windows.Forms.Keys (One of the Keys values. The default is None.); and an InvalidEnumArgumentException would be thrown when the parameter is not one of Keys values. But for example Keys.Divide IS one of Keys values, and yet it can't be used. So how can I set a menu item to have a shortcut for Numpad * or Numpad +? Do I need to handle the key in Form's ProcessCmdKey event? Thanks

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• search array and get array key

  - by SoulieBaby

  Hi all, I have an array, which I'd like to search for a value in and retreive the array key if it exists, but not sure how to even go about doing that. Here's my array: Array ( [hours] => Array ( [0] => 5 [1] => 5 [2] => 6 [3] => 6 [4] => 8 [5] => 10 ) ) So I'd like to search the hours array for 10, if 10 exists in the array, I want the key (5) to be returned. If that makes sense? Am trying to do it dynamically so the search string (10) will change, but I figure if I can get it working for number 10, I can get it working with a variable number :)

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• Manage Foreign key and Drop downlist for optional field in .NET

  - by Brij

  What is the best way to handle following situation? A dropdown(for master table) is optional in a particular form. But, In database table the field is constrained with foreign key. If user don't select from dropdown then It creates problem because of foreign key. One solution is to create default option in master table and use it in case of blank selection. but in dropdown, we need to handle this to show on top. Is it perfect solution? Is there any other optimized solution for this? Thanks

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• Check For Duplicate Records VS try/catch Unique Key Constraint

  - by Jed

  I have a database table that has a Unique Key constraint defined to avoid duplicate records from occurring. I'm curious if it is bad practice to NOT manually check for duplicate records prior to running an INSERT statement on the table. In other words, should I run a SELECT statement using a WHERE clause that checks for duplicate values of the record that I am about to INSERT. If a record is found, then do not run the INSERT statement, otherwise go ahead and run the INSERT.... OR Just run the INSERT statement and try/catch the exception that may be thrown due to a Unique Key violation. I'm weighing the two perspectives and can't decide which is best- 1. Don't waste a SELECT call to check for duplicates when I can just trap for an exception VS 2. Don't be lazy by implementing ugly try/catch logic VS 3. ???Your thoughts here??? :)

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• 64 bit public key encryption

  - by sourabh0612

  Need to generate 64 bit public-private key pair can't find out any standard algorithm....... Someone please reply asap

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• add ANOTHER primary key to a table which is UNIQUE

  - by gdubs

  so im having problems with adding another primary key to my table. i have 3 columns: 1. Account ID (Identity) 2. EmailID 3. Data field when i made the table i had this to make the Account ID and the Email ID unique PRIMARY KEY (AccountID, EmailID) i thought that would make my emailid unique, but then after i tried inserting another row with the same emailid it went through. so i thought i missed something out. now for my question: IF, i had to use alter, How do i alter the table/PK Constraint to modify the EmailID field and make it Unique IF i decided to drop the table and made a new one, how do i make those two primary keys uniqe? Thanks a bunch!!

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• jQuery Event Keypress: Which key was pressed?

  - by BlaM

  With jQuery, how do I find out which key was pressed when I bind to the keypress event? $('#searchbox input').bind('keypress', function(e) {}); I want to trigger an submit when ENTER is pressed. [Update] Even though I found the (or better: one) answer myself, there seems to be some room for variation ;) Is there a difference between keyCode and which - especially if I'm just looking for ENTER, which will never be a unicode key? Do some browsers provide one property and others provide the other one?

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• C# Processing Enter Key on Custom Container

  - by tycobb

  I am currently building a custom container control. Everything was going along smoothly until I hit a snag during testing. I noticed that the Enter key is not getting processed to the control that has focus inside the container. Everything else works as expected though. I am able to click the button with either the mouse or space bar, but enter does not want to get processed. After doing endless searches on container controls and processing the enter key I have come up with no solution. I tried returning Enter as true in IsInputKey(Keys keyData) and that didn't work. Neither did setting KeyPreview on the form. I have tried it with my custom button and .NET's standard button. Like I mentioned earlier, spacebar will trigger the desired effect. Please tell me what I am missing. There has to be an easy / stupid simple way to get Enter to process over to the active child control.

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• Hibernate/JPA and PostgreSQL - Primary Key?

  - by Shadowman

  I'm trying to implement some basic entities using Hibernate/JPA. Initially the code was deployed on MySQL and was working fine. Now, I'm porting it over to use PostgreSQL. In MySQL, my entity class defines its primary key as an auto-incrementing long value with the following syntax: @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; However, I've found that I get errors with PostgreSQL when I try and insert numerous records at a time. What do I need to annotate my primary key with to get the same auto-incrementing behavior in PostgreSQL as I have with MySQL? Thanks for any help you can provide!

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• Bash script function return value problem

  - by Eedoh

  Hi to all. Can anyone help me return the correct value from a bash script function? Here's my function that should return first (and only) line of the file passed as an argument: LOG_FILE_CREATION_TIME() { return_value=`awk 'NR==1' $1` return return_value } And here's my call of that function in the other script: LOG_FILE_CREATION_TIME "logfile" timestamp=$? echo "Timestamp = $timestamp" I always get some random values with this code. If, for example, there's a value of 62772031 in the "logfile", I get Timestamp = 255 as an output. For some other values in the file, I get other random values as a return value, never the correct one. Any ideas?

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• Multiple foreign keys from one table linking to single primary key in second table

  - by croker10

  Hi all, I have a database with three tables, a household table, an adults table and a users table. The Household table contains two foreign keys, iAdult1ID and iAdult2ID. The Users table has a iUserID primary key and the Adult table has a corresponding iUserID foreign key. One of the columns in the Users table is strUsername, an e-mail address. I am trying to write a query that will allow me to search for an e-mail address for either adult that has a relation to the household. So I have two questions, assuming that all the values are not null, how can I do this? And two, in reality, iAdult2ID can be null, is it still possible to write a query to do this? Thanks for your help. Let me know if you need any more information.

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• How to handle Foreign key for optional field in .NET

  - by brz dot net

  What is the best way to handle following situation? A dropdown(for master table) is optional in a particular form. But, In database table the field is constrained with foreign key. If user don't select from dropdown then It creates problem because of foreign key. One solution is to create default option in master table and use it in case of blank selection. but in dropdown, we need to handle this to show on top. Is it perfect solution? Is there any other optimized solution for this? Thanks

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• MySQL query against pseudo-key-value pair data in WordPress custom query

  - by andrevr

  I'm writing a custom WordPress query to use some of the data which the Woothemes Diarise theme creates. Diarise is an event planner theme with calendar blah, blah... and uses custom fields to store the event start and end dates in WP custom fields in the *wp_postmeta* table, which implements a key-value store. So for each post in the "event" category, there are 2 records in *wp_postmeta*, named *event_start_date* and *event_end_date* that I'm interested in. The task is to compare a tourist's arrival and departure dates with the start and end dates of events, yielding a what's on list of events available. We thought we'd killed it with a grand flash of logic, that goes like this: Disregard any event that ends before the tourist arrives, and any that begin after the departure date. I wrote this query: SELECT wposts.* FROM wp_posts wposts LEFT JOIN wp_postmeta wpostmeta ON wposts.ID = wpostmeta.post_id LEFT JOIN wp_term_relationships ON (wposts.ID = wp_term_relationships.object_id) LEFT JOIN wp_term_taxonomy ON (wp_term_relationships.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id) WHERE wp_term_taxonomy.taxonomy = 'category' AND wp_term_taxonomy.term_id IN(3,4) AND ( wpostmeta.meta_key = 'event_start_date' AND NOT ( concat(subst(wpostmeta.meta_value,7,4),'-',subst(wpostmeta.meta_value,4,2),'-',subst(wpostmeta.meta_value,1,2) > '2010-07-31' ) ) AND ( wpostmeta.meta_key = 'event_end_date' AND NOT ( concat(subst(wpostmeta.meta_value,7,4),'-',subst(wpostmeta.meta_value,4,2),'-',subst(wpostmeta.meta_value,1,2) < '2010-05-01' ) ) ) ORDER BY wpostmeta.meta_value ASC And, of course it returns no records. The problem I believe is in the dual reference to wpostmeta.meta_key, but how to get around that?

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• Multiple Foriegn Keys from One Table linking to single Primary Key in second Table

  - by croker10

  Hi all, I have a database with three tables, a household table, an adults table and a users table. The Household table contains two foreign keys, iAdult1ID and iAdult2ID. The Users table has a iUserID primary key and the Adult table has a corresponding iUserID foreign key. One of the columns in the Users table is strUsername, an e-mail address. I am trying to write a query that will allow me to search for an e-mail address for either adult that has a relation to the household. So I have two questions, assuming that all the values are not null, how can I do this? And two, in reality, iAdult2ID can be null, is it still possible to write a query to do this? Thanks for your help. Let me know if you need any more information.

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