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• Can't understand sessions in Rails

  - by ciss

  Hello everyone. Please don't bit my for my misunderstanding. The sessions are very new for me, and i have some problems. Okay i read many information about sessions and especially rails session. But this don't give me right imagine about sessions. Did i understand right, when users send request to server (get) - Server create a new session (and store this some file in hard drive with session id), session id - is a random generated num? so, server create a new session (and store session on drive) after this server send back answer to client and set session_id in cookies? Ok, i debug some params and see some results: debug(session): {:_csrf_token=>"jeONIfNxFmnpDn/xt6I0icNK1m3EB3CzT9KMntNk7KU=", :session_id=>"06c5628155efaa6446582c491499af6d", "flash"=>{}} debug(cookies): {"remember_user_token"=>"1::3GFRFyXb83lffzwPDPQd", "_blog_session"=>"BAh7CDoQX2NzcmZfdG9rZW4iMWplT05JZk54Rm1ucERuL3h0NkkwaWNOSzFtM0VCM0N6VDlLTW50Tms3S1U9Og9zZXNzaW9uX2lkIiUwNmM1NjI4MTU1ZWZhYTY0NDY1ODJjNDkxNDk5YWY2ZCIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6Rmxhc2g6OkZsYXNoSGFzaHsABjoKQHVzZWR7AA==--348c88b594e98f4bf6389d94383134fbe9b03095"} Okay, i know, what _csrf_token helps to prevent csrf. session_id - is id of the session which stored on hard drive (by default) but what is _blog_session in cookies? also, remeber_user_token containes my id (1::*) and what about second part, what is it? Sorry for this stupid questions, i know what i can easy use any nice auth-plugins (authlogic/clearance/devise), but i want to fully understand sessions. Thank you. (also sorry for my english, this is not my native language)

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• How to put a pre-existing sqlite file into <Application_Home>/Library/?

  - by Byron Cox

  My app uses Core Data. I have run the app in the simulator which has successfully created and populated the corresponding sqlite file. I now want to get this pre-existing sqlite file on to an actual device and be part of my app. I have located the simulator generated sqlite file at /Library/Application Support/iPhone Simulator/6.0/Applications/identifier/Documents/myapp.sqlite and dragged it into Xcode. This has added it to my application bundle but not in an appropriate directory (with the consequence that the sqlite file can be read but not written to). From reading about the file system I believe that the best place to put the sqlite file would be in a custom directory 'Database' under Application_Home/Library/. I don't seem to be able to do this within Xcode and despite searching I am unable to figure out how to do the following: (1) Create a sub-directory called 'Database' in Application_Home/Library/ ? (2) Transfer the sqlite file to my newly created 'Database' directory ? Many thanks to @Daij-Djan of his answer below. One other question: the path to the sqlite file will be used by the persistent store coordinator. Now depending on the size of the sqlite file it may take a while to copy or move. How can you ensure that the example code provided by @Daij-Djan has executed and finished before the persistent store coordinator tries to reference the sqlite file? Thanks for any help in advance.

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• MySql "comments" parameter as descriptor?

  - by Nick

  So, I'm trying to learn a lot at once, and this place is really helpful! I'm making a little running log website for myself and maybe a few other people, and I have it so that the user can add workouts for each day. With each workout, I have a variety of information the user can fill out for the workout, such as running distance, time, quality of run, course, etc... I store this in a MySql database as a table with fields titled "distance", "time", "runquality", etc... Now, these field titles don't match up with what I want displayed on the running log, so I was thinking of using the "Comments" attribute for a field to store its human-readable title--thus the field "runquality" would have "Quality of run" as its comment, and then I would pull the comment with a SQL query and display it instead of the field name. Is this a good theoretical/practical way of going about it? And what sort of SQL would I use to pull the comment for the field anyway? Secondly, suppose I want to add the ability for the user to create their own workout descriptors. So say a user wants to add a "temperature" descriptor for their workout. Should I create a script that adds fields to my workout table, or should I create a separate table listing only workout descriptors and somehow link the descriptor table with the "contents" table? I haven't learned any theory about database design or anything so any help is appreciated!

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• Utilizing a Queue

  - by Nathan

  I'm trying to store records of transactions all together and by category for the last 1, 7, 30 or 360 days. I've tried a couple things, but they've brutally failed. I had an idea of using a queue with 360 values, one for each day, but I don't know enough about queue's to figure out how that would work. Input will be an instance of this class: class Transaction { public string TotalEarned { get; set; } public string TotalHST { get; set; } public string TotalCost { get; set; } public string Category { get; set; } } New transactions can occur at any time during the day, and there could be as many as 15 transactions in a day. My program is using a plain text file as external storage, but how I load it depends on how I decide to store this data. What would be the best way to do this?

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• Getting hover text with selenium in java

  - by BinaryEmpire

  I am trying to figure out how to get the product availability text from a page like http://www.walmart.com/browse/TV-Video/TVs/_/N-96v3? (once a store has been selected) I selected 76574 as my zipcode and went to the "In My Store" tab The code I have now is WebElement hoverElement = driver.findElement(By.xpath(".//*[@id='Body_15992428']/span")); WebElement hidden = driver.findElement(By.xpath(".//*[@id='slapInfo_NoVariant_15992428']/div")); Actions builder = new Actions(driver); builder.clickAndHold(hoverElement).build().perform(); System.out.println(hidden.getText()); **Edit: I tried profile.setEnableNativeEvents(false); and the text is now displayed in the automated browser window. I still cannot get to the text I want though. It does not throw an exception, only displays nothing because the driver thinks its still hidden. Any one know how to fix this? I keep getting Exception in thread "main" org.openqa.selenium.InvalidElementStateException: Cannot perform native interaction: Could not load native events component. Even after I do profile.setEnableNativeEvents(true); Are there any other ways I can get the hidden text, or what am I doing wrong here? Additionally while I was inspecting the code with firebug, I saw that there is this code <script type="text/javascript"> WALMART.$(document).ready(function(){ WALMART.$('#Body_15992428').hover(function(){ WALMART.$('#SeeStoreAvailBubble').wmBubble('update',WALMART.$('#bubbleMsgUpdate_15992428').html()); }); }); </script> I dont really know how to do things directly with javascript but is there is any way of getting the message text directly from that with a javascript executor?

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• Why don't I need to bind my vertex buffer object before calling glDrawArrays?

  - by valmo

  I'm a bit confused why this still renders. I thought you need to bind a vertex buffer object so that glDrawArrays knows which vertex buffer to use. Here is my initialisation code.. // Create and bind vertex array to store vertex attribute states. glGenVertexArraysOES(NUM_VERTEX_ARRAYS, &m_vertexArray); glBindVertexArrayOES(m_vertexArray); // Create and bind vertex buffer to store vertex data. glGenBuffers(NUM_VERTEX_BUFFERS, &m_vertexBuffer); glBindBuffer(GL_ARRAY_BUFFER, m_vertexBuffer); glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * 36, &m_vertices[0], GL_STATIC_DRAW); glEnableVertexAttribArray(VertexAttribPosition); glVertexAttribPointer(VertexAttribPosition, 3, GL_FLOAT, GL_FALSE, 24, BUFFER_OFFSET(0)); glEnableVertexAttribArray(VertexAttribNormal); glVertexAttribPointer(VertexAttribNormal, 3, GL_FLOAT, GL_FALSE, 24, BUFFER_OFFSET(12)); glBindBuffer(GL_ARRAY_BUFFER, 0); glBindVertexArrayOES(0); Here is my render code. I'm confused why glDrawArrays still works when I bind 0 to GL_ARRAY_BUFFER. glBindVertexArrayOES(m_vertexArray); glBindBuffer(GL_ARRAY_BUFFER, 0); glDrawArrays(GL_TRIANGLES, 0, 36); glBindVertexArrayOES(0);

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• Best practices for (over)using Azure queues

  - by John

  Hi, I'm in the early phases of designing an Azure-based application. One of the things that attracts me to Azure is the scalability, given the variability of the demand I'm likely to expect. As such I'm trying to keep things loosely coupled so I can add instances when I need to. The recommendations I've seen for architecting an application for Azure include keeping web role logic to a minimum, and having processing done in worker roles, using queues to communicate and some sort of back-end store like SQL Azure or Azure Tables. This seems like a good idea to me as I can scale up either or both parts of the application without any issue. However I'm curious if there are any best practices (or if anyone has any experiences) for when it's best to just have the web role talk directly to the data store vs. sending data by the queue? I'm thinking of the case where I have a simple insert to do from the web role - while I could set this up as a message, send it on the queue, and have a worker role pick it up and do the insert, it seems like a lot of double-handling. However I also appreciate that it may be the case that this is better in the long run, in case the web role gets overwhelmed or more complex logic ends up being required for the insert. I realise this might be a case where the answer is "it depends entirely on the situation, check your perf metrics" - but if anyone has any thoughts I'd be very appreciative! Thanks John

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• Serialization of Entity Framework Models with .NET WCF Rest Service

  - by Chris Phillips

  I'm trying to put together a very simple REST-style interface for communicating with our partners. An example object in the API is a partner, which we'd like to have serialized like this: <partner> <id>ID</id> <name>NAME</name> </partner> This is fairly simply to achieve using the .NET 4.0 WCF REST template if we simply declare a partner class as: public class Partner { public int Id {get; set;} public string Name {get; set;} } But when I use the Entity Framework to define and store Partner objects, the resulting serialization looks something like this: <Partner p1:Id="NCNameString" p1:Ref="NCNameString" xmlns:p1="http://schemas.microsoft.com/2003/10/Serialization/" xmlns="http://schemas.datacontract.org/2004/07/TheTradeDesk.AdPlatform.Provisioning"> <EntityKey p1:Id="NCNameString" p1:Ref="NCNameString" xmlns="http://schemas.datacontract.org/2004/07/System.Data.Objects.DataClasses"> <EntityContainerName xmlns="http://schemas.datacontract.org/2004/07/System.Data">String content</EntityContainerName> <EntityKeyValues xmlns="http://schemas.datacontract.org/2004/07/System.Data"> ... This XML is obviously unacceptable for use as an external API. What are suggested mechanisms for using EF for the data store but maintaining a simple XML serialization interface?

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• How to map a 0..1 to 1 relationship in Entity Framework 3

  - by sako73

  I have two tables, Users, and Address. A the user table has a field that maps to the primary key of the address table. This field can be null. In plain english, Address exist independent of other objects. A user may be associated with one address. In the database, I have this set up as a foreign key relationship. I am attempting to map this relationship in the Entity Framework. I am getting errors on the following code: <Association Name="fk_UserAddress"> <End Role="User" Type="GenesisEntityModel.Store.User" Multiplicity="1"/> <End Role="Address" Type="GenesisEntityModel.Store.Address" Multiplicity="0..1" /> <ReferentialConstraint> <Principal Role="Address"> <PropertyRef Name="addressId"/> </Principal> <Dependent Role="User"> <PropertyRef Name="addressId"/> </Dependent> </ReferentialConstraint> </Association> It is giving a "The Lower Bound of the multiplicity must be 0" error. I would appreciate it if anyone could explain the error, and the best way to solve it. Thanks for any help.

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• What is the correct high level schema.org microdata itemtype for a retail brand/company homepage?

  - by kpowz

  I'd like to hear which schema.org itemtype others would recommend using or have used in the case of completing a retail brand's company homepage microdata. Take for example TOMS's shoes: Example #1 - Using /Corporation as the high-level itemtype one can include a lot of great /Organization microdata, but nothing about the retail store. <html itemscope='itemscope' itemtype="http://schema.org/Website> <head></head> <body itemscope='itemscope' itemtype="http://schema.org/Corporation> various microdata here probably including Product microdata </body> </html> NOTE: the only schema.org property specific to /Corporation is tickerSymbol & TOMS doesn't have one. Example #2 - This code would work if TOMS started their own channel of physical retail stores & each location had it's own homepage. However, for TOMS's.com, although accurate schematically & more descriptive at the face, this is incorrect microdata markup for TOMS.com, because /ShoeStore derives from /LocalBusiness - which must represent a physical place. <html itemscope='itemscope' itemtype='http://schema.org/Website'> <head></head> <body itemscope='itemscope' itemtype='http://schema.org/ShoeStore'> a whole bunch of jabber here </body> </html> NOTE: Since TOMS is virtual & thus can't be a /Store this means you lose really cool properties like 'currenciesAccepted', 'paymentAccepted' & 'priceRange'. Is this just a 'sit and wait' situation until more schemas are approved for 'virtual places' or is there a validation-passing way to get the best of both worlds?

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• Cassandra instead of MySQL for social networking app

  - by Christopher McCann

  I am in the middle of building a new app which will have very similar features to Facebook and although obviously it wont ever have to deal with the likes of 400,000,000 million users it will still be used by a substantial user base and most of them will demand it run very very quickly. I have extensive experience with MySQL but a social app offers complexities which MySQL is not well suited too. I know Facebook, Twitter etc have moved towards Cassandra for a lot of their data but I am not sure how far to go with it. For example would you store such things as user data - username, passwords, addresses etc in Cassandra? Would you store e-mails, comments, status updates etc in Cassandra? I have also read alot that something like neo4j is much better for representing the friend relationships used by social apps as it is a graph database. I am only just starting down the NoSQL route so any guidance is greatly appreciated. Would anyone be able to advise me on this? I hope I am not being too general!

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• [Ruby] Modifying object inside a loop doesn't change object outside of the loop?

  - by Jergason

  I am having problems with modifying objects inside blocks and not getting the expected values outside the blocks. This chunk of code is supposed to transform a bunch of points in 3d space, calculate a score (the rmsd or root mean squared deviation), and store both the score and the set of points that produced that score if it is lower than the current lowest score. At the end, I want to print out the best bunch of points. first = get_transformed_points(ARGV[0]) second = get_transformed_points(ARGV[1]) best_rmsd = first.rmsd(second) best_points = second #transform the points around x, y, and z and get the rmsd. If the new points # have a smaller rmsd, store them. ROTATION = 30 #rotate by ROTATION degrees num_rotations = 360/ROTATION radians = ROTATION * (Math::PI/180) num_rotations.times do |i| second = second * x_rotate num_rotations.times do |j| second = second * y_rotate num_rotations.times do |k| second = second * z_rotate rmsd = first.rmsd(second) if rmsd < best_rmsd then best_points = second best_rmsd = rmsd end end end end File.open("#{ARGV[1]}.out", "w") {|f| f.write(best_points.to_s)} I can print out the points that are getting stored inside the block, and they are getting transformed and stored correctly. However, when I write out the points to a file at the end, they are the same as the initial set of points. Somehow the best_points = second chunk doesn't seem to be doing anything outside of the block. It seems like there are some scoping rules that I don't understand here. I had thought that since I declared and defined best_points above, outside of the blocks, that it would be updated inside the blocks. However, it seems that when the blocks end, it somehow reverts back to the original value. Any ideas how to fix this? Is this a problem with blocks specifically?

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• Modifying bundled properties from visitor

  - by ravenspoint

  How should I modify the bundled properties of a vertex from inside a visitor? I would like to use the simple method of sub-scripting the graph, but the graph parameter passed into the visitor is const, so compiler disallows changes. I can store a reference to the graph in the visitor, but this seems weird. /** A visitor which identifies vertices as leafs or trees */ class bfs_vis_leaf_finder:public default_bfs_visitor { public: /** Constructor @param[in] total reference to int variable to store total number of leaves @param[in] g reference to graph ( used to modify bundled properties ) */ bfs_vis_leaf_finder( int& total, graph_t& g ) : myTotal( total ), myGraph( g ) { myTotal = 0; } /** Called when the search finds a new vertex If the vertex has no children, it is a leaf and the total leaf count is incremented */ template <typename Vertex, typename Graph> void discover_vertex( Vertex u, Graph& g) { if( out_edges( u, g ).first == out_edges( u, g ).second ) { myTotal++; //g[u].myLevel = s3d::cV::leaf; myGraph[u].myLevel = s3d::cV::leaf; } else { //g[u].myLevel = s3d::cV::tree; myGraph[u].myLevel = s3d::cV::tree; } } int& myTotal; graph_t& myGraph; };

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• The most efficient way to calculate an integral in a dataset range

  - by Annalisa

  I have an array of 10 rows by 20 columns. Each columns corresponds to a data set that cannot be fitted with any sort of continuous mathematical function (it's a series of numbers derived experimentally). I would like to calculate the integral of each column between row 4 and row 8, then store the obtained result in a new array (20 rows x 1 column). I have tried using different scipy.integrate modules (e.g. quad, trpz,...). The problem is that, from what I understand, scipy.integrate must be applied to functions, and I am not sure how to convert each column of my initial array into a function. As an alternative, I thought of calculating the average of each column between row 4 and row 8, then multiply this number by 4 (i.e. 8-4=4, the x-interval) and then store this into my final 20x1 array. The problem is...ehm...that I don't know how to calculate the average over a given range. The question I am asking are: Which method is more efficient/straightforward? Can integrals be calculated over a data set like the one that I have described? How do I calculate the average over a range of rows?

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• Rationale in selecting Hash Key type

  - by Amrish

  Guys, I have a data structure which has 25 distinct keys (integer) and a value. I have a list of these objects (say 50000) and I intend to use a hash table to store/retrieve them. I am planning to take one of these approaches. Create a integer hash from these 25 integer keys and store it on a hash table. (Yeah! I have some means to handle collisions) Make a string concatenation on the individual keys and use it as a hash key for the hash table. For example, if the key values are 1,2,4,6,7 then the hash key would be "12467". Assuming that I have a total of 50000 records each with 25 distinct keys and a value, then will my second approach be a overkill when it comes to the cost of string comparisons it needs to do to retrieve and insert a record? Some more information! Each bucket in the hash table is a balanced binary tree. I am using the boost library's hash_combine method to create the hash from the 25 keys.

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• Trying to get codeblocks working on Mac, running Lion. Can't get the compiler set up properly

  - by tjtoml

  First off, sorry if this is a stupid question. I installed code::blocks to try and get to know the program and start working on teaching myself c++. I have a MacBook Pro with OS 10.7.3. I ave code::blocks 10.05. When I try to build a "Hello world" nothing happens. Based on some googling I've figured out that it's because code::blocks doesn't know where to find the debugger/compiler. Further googling yielded me this page which tells me to install Xcode and to fix some things in the code::blocks settings. However, this wiki obviously has not been updated since Apple went to the App store, because the file paths it gives for the compiler do not exist (there is no /Developer/* even after installing Xcode). Xcode 4.3.2 was already installed when I installed code::blocks and code::blocks "auto-detected" several compilers. They did not work. If anyone knows where Xcode hides its compilers now that Apple has moved to the app store, I would be much obliged.

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• Storing data in a MySQL database using MySQL & PHP

  - by comma

  I'm new to PHP and MySQL and I'm trying to store a users entered data from the following fields $skill, $experience, $years which a user can also add additional fields of $skill, $experience, $years if needed so in instead of 1 of each field there might be multiples of each field. I was wondering how can I store the fields in my MySQL database using PHP and MySQL? I have the following script but I know its wrong. can some one help me fix the script listed below? Here is the PHP and MySQL code. $skill = serialize($_POST['skill']); $experience = serialize($_POST['experience']); $years = serialize($_POST['years']); for (($s = 0; $s < count($skill); $s++) && ($x = 0; $x < count($experience); $x++) && ($g = 0; $g < count($years); $g++)){ $mysqli = mysqli_connect("localhost", "root", "", "sitename"); $query1 = "INSERT INTO learned_skills (skill, experience, years) VALUES ('" . $skill[$s] . "', '" . $experience[$x] . "', '" . $years[$g] . "')"; if (!mysqli_query($mysqli, $query1)) { print mysqli_error($mysqli); return; } } Here is my MySQL table. CREATE TABLE learned_skills ( id INT UNSIGNED NOT NULL AUTO_INCREMENT, skill TEXT NOT NULL, experience TEXT NOT NULL, years INT NOT NULL, PRIMARY KEY (id) ); CREATE TABLE u_skills ( id INT UNSIGNED NOT NULL AUTO_INCREMENT, skill_id INT UNSIGNED NOT NULL, users_id INT UNSIGNED NOT NULL, PRIMARY KEY (id) );

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• Random number generation in MVC applications

  - by SlimShaggy

  What is the correct way of generating random numbers in an ASP.NET MVC application if I need exactly one number per request? According to MSDN, in order to get randomness of sufficient quality, it is necessary to generate multiple numbers using a single System.Random object, created once. Since a new instance of a controller class is created for each request in MVC, I cannot use a private field initialized in the controller's constructor for the Random object. So in what part of the MVC app should I create and store the Random object? Currently I store it in a static field of the controller class and lazily initialize it in the action method that uses it: public class HomeController : Controller { ... private static Random random; ... public ActionResult Download() { ... if (random == null) random = new Random(); ... } } Since the "random" field can be accessed by multiple instances of the controller class, is it possible for its value to become corrupted if two instances attempt to initialize it simultaneously? And one more question: I know that the lifetime of statics is the lifetime of the application, but in case of an MVC app what is it? Is it from IIS startup till IIS shutdown?

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• Domain Authentication from .NET Client over VPN

  - by Holy Christ

  I am writing a ClickOnce WPF app that will sometimes be used over VPN. The app uses resources available only to domain authenticated users. Some of the things include accessing SSRS Reports, accessing LDAP to lookup user information, hitting web services, etc. When a user logs in from a machine that is not authenticated on the domain, I need to somehow get his credentials, authenticate him on the domain, and store his credentials. What is the recommended approach for authenticating domain users over VPN? How can I securely store the credentials? I've found several articles but, not much posted recently and a lot of the solutions seem kinda hacky, or aren't very secure (ie - storing strings clear text in memory). It would be cool if I could use the ActiveDicrtoryMembershipProvider, but that seems to be geared for use in web apps. EDIT: The above is kind of a workaround. The user must enter their domain credentials to authenticate on the VPN. It would be ideal to access the credentials the user has already entered to login to the VPN instead of the WindowsIdentity.GetCurrent() (which returns the user logged into the computer). Any ideas on how that could work? We use Juniper Networks to connect to the VPN. Thanks!

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• Regularly update database without browser/user

  - by Chris M

  I currently have a MySQL database which I was hoping to use to store regularly updated data from a temperature sensor connected to the internet. I currently have a page that, when opened, will grab the current temperature and the current timestamp and add it as an entry to the database, but I was looking for a way to do that without me refreshing the page every 5 seconds. Detail: The data comes from an Arduino Ethernet, posted to an IP address. Currently, I'm using cURL to grab the data from the IP, add a timestamp and save it to the DB. Obviously only updates when the page is refreshed (it uses PHP). Here is a live feed of the data - http://wetdreams.org.uk/ChrisProject/UI/live_graph_two.html TL;DR - Basically I need a middle man to grab the data from the IP and post it to a MySQL Edit: Thanks for all the advice. There might be a little bit of confusion, I'm looking for a solution that (ideally) doesn't require a computer to be on at all (other than the Server containing Database). Since I'm looking to store data over long periods of time (weeks), I'd like to set it up and leave a script running on the server (or Arduino) that gets the temp and posts it to the Database. In my head I would like to have a page on the server that automatically (without any browser open, or any other prompting other than a timer) calls a PHP script. Hope that clears things up!

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• Schema for storing "binary" values, such as Male/Female, in a database

  - by latentflip

  Intro I am trying to decide how best to set up my database schema for a (Rails) model. I have a model related to money which indicates whether the value is an income (positive cash value) or an expense (negative cash value). I would like separate column(s) to indicate whether it is an income or an expense, rather than relying on whether the value stored is positive or negative. Question: How would you store these values, and why? Have a single column, say Income, and store 1 if it's an income, 0 if it's an expense, null if not known. Have two columns, Income and Expense, setting their values to 1 or 0 as appropriate. Something else? I figure the question is similar to storing a person's gender in a database (ignoring aliens/transgender/etc) hence my title. My thoughts so far Lookup might be easier with a single column, but there is a risk of mistaking 0 (false, expense) for null (unknown). Having seperate columns might be more difficult to maintain (what happens if we end up with a 1 in both columns? Maybe it's not that big a deal which way I go, but it would be great to have any concerns/thoughts raised before I get too far down the line and have to change my code-base because I missed something that should have been obvious! Thanks, Philip

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• best practices question: How to save a collection of images and a java object in a single file? File

  - by Richard

  Hi all, I am making a java program that has a collection of flash-card like objects. I store the objects in a jtree composed of defaultmutabletreenodes. Each node has a user object attached to it with has a few string/native data type parameters. However, i also want each of these objects to have an image (typical formats, jpg, png etc). I would like to be able to store all of this information, including the images and the tree data to the disk in a single file so the file can be transferred between users and the entire tree, including the images and parameters for each object, can be reconstructed. I had not approached a problem like this before so I was not sure what the best practices were. I found XLMEncoder (http://java.sun.com/j2se/1.4.2/docs/api/java/beans/XMLEncoder.html) to be a very effective way of storing my tree and the native data type information. However I couldn't figure out how to save the image data itself inside of the XML file, and I'm not sure it is possible since the data is binary (so restricted characters would be invalid). My next thought was to associate a hash string instead of an image within each user object, and then gzip together all of the images, with the hash strings as the names and the XMLencoded tree in the same compmressed file. That seemed really contrived though. Does anyone know a good approach for this type of issue? THanks! Thanks!

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• Calling NSFetchedResultsController & CoreData experts

  - by JK

  I am having a few nagging issues with NSFetchedResultsController and CoreData, any of which I would be very grateful to get help on. Issue 1 - Updates: I update my store on a background thread which results in certain rows being delete, inserted or updated. The changes are merged into the context on the main thread using the "mergeChangesFromContextDidSaveNotification:" method. Inserts and deletes are updated properly, but updates are not (e.g. the cell label is not updated with the change) although I have confirmed the updates to come through the contextDidSaveNotifcation, exactly like the inserts and deleted. My current workaround is to temporarily change the staleness interval of the context to 0, but this does not seem like the ideal solution. Issue 2 - Deleting objects: My fetch batch size is 20. If an object is deleted by the background thread which is in the first 20 rows, everything works fine. But if the object is after the first 20 rows and the table is scrolled down, a "CoreData could not fulfill a fault" error is raised. I have tried resaving the context and reperforming the frc fetch - all to no avail. Note: In this scenario, the frc delegate method "didChangeObject...." is not called for the delete - I assume this is because the object in question had not been faulted at that time (as it is was outside the initial fetch range). But for some reason, the context still thinks the object is around, although is has been deleted from the store. Issue 3 - Deleting sections : When the deletion of a row leads to the deletion of a section, I have gotten the "invalid number of rows in section???" error. I have worked around this by removing the "reloadSection" line from the NSFetchedResultsChangeMove: section and replacing it with "[tableView insertRowsAtIndexPaths...." This seems to work, but once again, I am not sure if this is the best solution. Any help would be greatly appreciated. Thank you!

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• Caching queries in Django

  - by dolma33

  In a django project I only need to cache a few queries, using, because of server limitations, a cache table instead of memcached. One of those queries looks like this: Let's say I have a Parent object, which has a lot of Child objects. I need to store the result of the simple query parent.childs.all(). I have no problem with that, and everything works as expected with some code like key = "%s_children" %(parent.name) value = cache.get(key) if value is None: cache.set(key, parent.children.all(), CACHE_TIMEOUT) value = cache.get(key) But sometimes, just sometimes, the cache.set does nothing, and, after executing cache.set, cache.get(key) keeps returning None. After some test, I've noticed that cache.set is not working when parent.children.all().count() has higher values. That means that if I'm storing inside of key (for example) 600 children objects, it works fine, but it wont work with 1200 children. So my question is: is there a limit to the data that a key could store? How can I override it? Second question: which way is "better", the above code, or the following one? key = "%s_children" %(parent.name) value = cache.get(key) if value is None: value = parent.children.all() cache.set(key, value, CACHE_TIMEOUT) The second version won't cause errors if cache.set doesn't work, so it could be a workaround to my issue, but obviously not a solution. In general, let's forget about my issue, which version would you consider "better"?

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• Creating an adjacency List for DFS

  - by user200081

  I'm having trouble creating a Depth First Search for my program. So far I have a class of edges and a class of regions. I want to store all the connected edges inside one node of my region. I can tell if something is connected by the getKey() function I have already implemented. If two edges have the same key, then they are connected. For the next region, I want to store another set of connected edges inside that region, etc etc. However, I am not fully understanding DFS and I'm having some trouble implementing it. I'm not sure when/where to call DFS again. Any help would be appreciated! class edge { private: int source, destination, length; int key; edge *next; public: getKey(){ return key; } } class region { edge *data; edge *next; region() { data = new edge(); next = NULL; } }; void runDFS(int i, edge **edge, int a) { region *head = new region(); aa[i]->visited == true;//mark the first vertex as true for(int v = 0; v < a; v++) { if(tem->edge[i].getKey() == tem->edge[v].getKey()) //if the edges of the vertex have the same root { if(head->data == NULL) { head->data = aa[i]; head->data->next == NULL; } //create an edge if(head->data) { head->data->next = aa[i]; head->data->next->next == NULL; }//if there is already a node connected to ti } if(aa[v]->visited == false) runDFS(v, edge, a); //call the DFS again } //for loop }

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