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  • Web Applications Development: Security practices for Application design

    - by Shyam
    Hi, As I am creating more web applications that are targeted for multiple users, I figured out that I have to start thinking about user management and security. At a glance and in my ideal world, all users belong to a group. Permissions and access is thus defined per group (and inherited by the users of that group). Logically, I have my group of administrators, which are identified with a level "7" (integer) clearance. A group of webusers have for example level "1". This in generally all works great for me, but I need some kind of list that I have to keep in mind how I secure my system, and some general practices. I am not looking for a specific environment; I want to learn the why's and how's. An example is privilege escalation. If someone would be able to "push" themselves inside a group with higher privileges, for example the Administration, how can I prevent this, or what measures should I take to have some sort of precaution? I don't like in that case to walk into a caveat. My question is basically: where can I find a good resource, list, policy, book that explains the security of web applications, the why's, the how's and readable if you don't have any experience in the realm of advanced security? I prefer a free resource, as I believe I couldn't be the first one who thought about this. Thank you for your answers, comments and feedback.

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  • How to find whole graph coverage path in dynamic state-flow diagram?

    - by joseph
    Hello, As I've been researching algorithms for path finding in graph, I found interesting problem. Definition of situation: 1)State diagram can have p states, and s Boolean Fields, and z Int Fields 2)Every state can have q ingoing and r outgoing transitions, and h Int fields (h belongs to z - see above) 3)Every transition can have only 1 event, and only 1 action 4)every action can change n Boolean Fields, and x Int Fields 5)every event can have one trigger from combination of any count of Boolean Fields in diagram 6)Transition can be in OPEN/CLOSED form. If the transition is open/closed depends on trigger2 compounded from 0..c Boolean fields. 7) I KNOW algorithm for finding shortest paths from state A to state B. 8) I KNOW algorithm for finding path that covers all states and transitions of whole state diagram, if all transitions are OPEN. Now, what is the goal: I need to find shortest path that covers all states and transitions in dynamically changing state diagram described above. When an action changes some int field, the algorithm should go through all states that have changed int field. The algorithm should also be able to open and close transition (by going through transitions that open and close another transitions by action) in the way that the founded path will be shortest and covers all transitions and states. Any idea how to solve it? I will be really pleased for ANY idea. Thanks for answers.

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  • Linq to SQL duplicating entry when referencing FK

    - by Oscar
    Hi! I am still facing some problems when using LINQ-to-SQL. I am also looking for answers by myself, but this problem is so akward that I am having problems to find the right keywords to look for it. I have this code here: public CustomTask SaveTask(string token, CustomTask task) { TrackingDataContext dataConext = new TrackingDataContext(); //Check the token for security if (SessionTokenBase.Instance.ExistsToken(Convert.ToInt32(token)) == null) return null; //Populates the Task - the "real" Linq to SQL object Task t = new Task(); t.Title = task.Title; t.Description = task.Description; //****The next 4 lines are important**** if (task.Severity != null) t.Severity = task.Severity; else t.SeverityID = task.SeverityID; t.StateID = task.StateID; if (task.TeamMember != null) t.TeamMember = task.TeamMember; else t.ReporterID = task.ReporterID; if (task.ReporterTeam != null) t.Team = task.ReporterTeam; else t.ReporterTeamID = task.ReporterTeamID; //Saves/Updates the task dataConext.Tasks.InsertOnSubmit(t); dataConext.SubmitChanges(); task.ID = t.ID; return task; } The problem is that I am sending the ID of the severity, and then, when I get this situation: DB State before calling the method: ID Name 1 high 2 medium 3 low Call the method selecting "medium" as severity DB State after calling the method: ID Name 1 high 2 medium 3 low 4 medium The point is: -It identified that the ID was related to the Medium entry (and for this reason it could populate the "Name" Column correctly), but if duplicated this entry. The problem is: Why?!! Some explanation about the code: CustomTask is almost the same as Task, but I was having problems regarding serialization as can be seen here I don't want to send the Severity property populated because I want my message to be as small as possible. Could anyone clear to my, why it recognize the entry, but creates a new entry in the DB?

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  • How to embed revision information using mercurial and maven (and svn)

    - by Zwei Steinen
    Our project had a nice hack (although I'm guessing there are better ways to do it) to embed revision information into the artifacts (jar etc.) when we used svn. Now we have migrated to mercurial, and we want to have a similar thing, but before I start working on a similar hack with mercurial, I wanted to know if there are better ways to do this. Thanks for your answers! <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>exec-maven-plugin</artifactId> <executions> <execution> <phase>process-classes</phase> <id>svninfo</id> <goals> <goal>exec</goal> </goals> <configuration> <executable>svn</executable> <arguments> <argument>info</argument> <argument>../</argument> <argument>></argument> <argument>target/some-project/META-INF/svninfo.txt</argument> </arguments> </configuration> </execution> </executions> </plugin>

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  • What is the difference between these two linq implementations?

    - by Mahesh Velaga
    I was going through Jon Skeet's Reimplemnting Linq to Objects series. In the implementation of where article, I found the following snippets, but I don't get what is the advantage that we are gettting by splitting the original method into two. Original Method: // Naive validation - broken! public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Refactored Method: public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } return WhereImpl(source, predicate); } private static IEnumerable<TSource> WhereImpl<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Jon says - Its for eager validation and then defferring for the rest of the part. But, I don't get it. Could some one please explain it in a little more detail, whats the difference between these 2 functions and why will the validations be performed in one and not in the other eagerly? Conclusion/Solution: I got confused due to my lack of understanding on which functions are determined to be iterator-generators. I assumed that, it is based on signature of a method like IEnumerable<T>. But, based on the answers, now I get it, a method is an iterator-generator if it uses yield statements.

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  • Classical task-scheduling assignment

    - by Bruno
    I am working on a flight scheduling app (disclaimer: it's for a college project, so no code answers, please). Please read this question w/ a quantum of attention before answering as it has a lot of peculiarities :( First, some terminology issues: You have planes and flights, and you have to pair them up. For simplicity's sake, we'll assume that a plane is free as soon as the flight using it prior lands. Flights are seen as tasks: They have a duration They have dependencies They have an expected date/time for beginning Planes can be seen as resources to be used by tasks (or flights, in our terminology). Flights have a specific type of plane needed. e.g. flight 200 needs a plane of type B. Planes obviously are of one and only one specific type, e.g., Plane Airforce One is of type C. A "project" is the set of all the flights by an airline in a given time period. The functionality required is: Finding the shortest possible duration for a said project The earliest and latest possible start for a task (flight) The critical tasks, with basis on provided data, complete with identifiers of preceding tasks. Automatically pair up flights and planes, so as to get all flights paired up with a plane. (Note: the duration of flights is fixed) Get a Gantt diagram with the projects scheduling, in which all flights begin as early as possible, showing all previously referred data graphically (dependencies, time info, etc.) So the questions is: How in the world do I achieve this? Particularly: We are required to use a graph. What do the graph's edges and nodes respectively symbolise? Are we required to discard tasks to achieve the critical tasks set? If you could also recommend some algorithms for us to look up, that'd be great.

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  • Can you recommend an easy to use easy to develop CMS?

    - by el_at_yahoo
    We need some easy way to manage web sites at our company, and we are evaluating some CMS tools for this purpose. We do not yet know what features the sites will need to have (but it will definitely be something with lots of functionalities), so we are looking for something with lots of features and more importantly to be easily extensible (if it does not have some feature, we at least want to be able to build-it by ourselves). We have no experience with Content Management Systems but we do with Java, so it has to be something written in Java. We evaluated some tools and from our perspective the following seem the promising of them (in no particular order): OpenCMS dotCMS (Community Edition vs Enterprise Edition) InfoGlue Alfresco (EE vs CE) Magnolia (EE vs EE Pro vs CE) Jahia (CE vs EE) Since we have no experience with either one of them, we were wondering if someone of you who have can share some information about how good they are or how easily they can be used and extended. I know similar questions have been asked on SO and I also know this is highly subjective and people will vote for closing it as soon as it is posted, but for us it is important to know what difficulties other people have been facing in using the above tools (we don’t want to walk a path that takes nowhere if other people already know it leads nowhere). Others could then vote on the posted answers if they agree or not. From your experience, which from the above mentioned CMSs is the more easily extensible, the easier to use, the easiest to learn etc? Thank you and Happy Holidays to all.

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  • Ruby: counters, counting and incrementing

    - by Shyam
    Hi, If you have seen my previous questions, you'd already know I am a big nuby when it comes to Ruby. So, I discovered this website which is intended for C programming, but I thought whatever one can do in C, must be possible in Ruby (and more readable too). The challenge is to print out a bunch of numbers. I discovered this nifty method .upto() and I used a block (and actually understanding its purpose). However, in IRb, I got some unexpected behavior. class MyCounter def run 1.upto(10) { |x| print x.to_s + " " } end end irb(main):033:0> q = MyCounter.new => #<MyCounter:0x5dca0> irb(main):034:0> q.run 1 2 3 4 5 6 7 8 9 10 => 1 I have no idea where the = 1 comes from :S Should I do this otherwise? I am expecting to have this result: 1 2 3 4 5 6 7 8 9 10 Thank you for your answers, comments and feedback!

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  • Should a programmer have mastery over C++

    - by Yogendra
    I was wondering if it is necessary for programmers to have expertise on at least 1 programming language? Programming languages like C#, java, VB.Net etc change every year or two. Should a programmer have mastery over C++, which is a stable language and rarely undergoes changes? I am a C# developer and using it for about 7 years now, I still don't have mastery on it. EDIT I think my question is being misunderstood. I am not against changes or evolution. I love the new features and abstraction provided by languages such as C#, VB, Java. And I keep waiting for new features if it makes a programmers life easy. But this fact also make this languages very difficult to master. They are continuously evolving. Languages like C++ have slow evolution cycle. So given this scenario, Is it helpful to be master of C++? This is what my original question meant. Note:- Based on the answers by friends below, I have understood that languages and framework are tools for expressing the concepts. Also it might be a good idea to express the concepts in different programming languages.

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  • Druapl & Regular PHP Integration

    - by user333128
    I'm building a new website which has one core application and many content pages. Content pages are mostly dynamic and I require a way to manage this dynamic content on a regular basis. The core application's main functionality is a 3 step process or reading user data (input page), reading data from MySQL (product page) and submitting an application to an email address (application page). Ideally I would like to build the core application in regular PHP and leverage Drupal for its content management capabilities. Can Drupal and regular PHP be integrated as I suggest easily? My feeling is that coding the core application as a Drupal module(s) will add layers of complexity that could be difficult to code from the outset and maintain later on as the system matures - so I would really like to just use regular PHP. Let me explain where dynamic content (managed by the CMS) intersects with the core application: Dynamic content such as FAQ data is used both on the 'normal' help pages and also within a mini-feed displayed within core application pages down a right hand side column. In this column, 3 random questions are pulled from the database and displayed as a feed. When users click on FAQ question they are not taken away from the core application product page but are instead shown data in a pop-up window displaying the question and answer. In addition, users can browse other questions and answers through a simple navigation menu within this popup. There are 3 such like feeds as I describe above that I require on the core application product page. So, what is the ideal solution here in terms of 'keeping things simple' for both the management of dynamic content and the ease of coding the core application? Can 'regular PHP' and Drupal co-exist 'peacefully'? If so, how is this technically possible? Because there is some content managed by Drupal contained within core application pages, can the core application still be coded in regular PHP? Any advice / suggestions? Thank you! Jim.

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  • What Test Environment Setup do Top Project Committers Use in the Ruby Community?

    - by viatropos
    Today I am going to get as far as I can setting up my testing environment and workflow. I'm looking for practical advice on how to setup the test environment from you guys who are very passionate and versed in Ruby Testing. By the end of the day (6am PST?) I would like to be able to: Type one 1-command to run test suites for ANY project I find on Github. Run autotest for ANY Github project so I can fork and make TESTABLE contributions. Build gems from the ground up with Autotest and Shoulda. For one reason or another, I hardly ever run tests for projects I clone from Github. The major reason is because unless they're using RSpec and have a Rake task to run the tests, I don't see the common pattern behind it all. I have built 3 or 4 gems writing tests with RSpec, and while I find the DSL fun, it's less than ideal because it just adds another layer/language of methods I have to learn and remember. So I'm going with Shoulda. But this isn't a question about which testing framework to choose. So the questions are: What is your, the SO reader and Github project committer, test environment setup using autotest so that whenever you git clone a gem, you can run the tests and autotest-develop them if desired? What are the guys who are writing the Paperclip Tests and Authlogic Tests doing? What is their setup? Thanks for the insight. Looking for answers that will make me a more effective tester.

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  • Html.RadioButton group defaulting to 0

    - by awrigley
    Hi A default value of 0 is creeping into a Surveys app I am developing, for no reason that I can see. The problem is as follows: I have a group of Html.RadioButtons that represent the possible values a user can choose to answer a survey question (1 == Not at all, 2 == A little, 3 == A lot). I have used a tinyint datatype, that does not allow null, to store the answer to each question. The view code looks like this: <ol class="SurveyQuestions"> <% foreach (SurveyQuestion question in Model.Questions) { string col = question.QuestionColumn; %> <li><%=question.QuestionText%> <ul style="float:right;" class="MultiChoice"> <li><%= Html.RadioButton(col, "1")%></li> <li><%= Html.RadioButton(col, "2")%></li> <li><%= Html.RadioButton(col, "3")%></li> </ul> <%= Html.ValidationMessage(col, "*") %> </li> <% } %> </ol> [Note on the above code:] Each survey has about 70 questions, so I have put the questions text in one table, and store the results in a different table. I have put the Questions into my form view model (hence Model.Questions); the questions table has a field called QuestionColumn that allows me to link up the answer table column to the question, as shown above (<%= Html.RadioButton(col, "1")%, etc) [/Note] However, when the user DOESN'T answer the question, the value 0 is getting inserted into the database column. As a result, I don't get what I expect, ie, a validation error. In no place have I stipulated a default value of 0 for the fields in the answers table. So what is happening? Any ideas?

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  • MapView EXC_BAD_ACCESS (SIGSEGV) and KERN_INVALID_ADDRESS

    - by user768113
    I'm having some 'issues' with my application... well, it crashes in an UIViewController that is presented modally, there the user enters information through UITextFields and his location is tracked by a MapView. Lets call this view controller "MapViewController" When the user submits the form, I call a different ViewController - modally again - that processes this info and a third one answers accordingly, then go back to a MenuVC using unwinding segues, which then calls MapViewController and so on. This sequence is repeated many times, but it always crashes in MapViewController. Looking at the crash log, I think that the MapView can be the problem of this or some element in the UI (because of the UIKit framework). I tried to use NSZombie in order to track a memory issue but it doesn't give me a clue about whats happening. Here is the crash log Hardware Model: iPad3,4 Process: MyApp [2253] OS Version: iOS 6.1.3 (10B329) Report Version: 104 Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x00000044 Crashed Thread: 0 Thread 0 name: Dispatch queue: com.apple.main-thread Thread 0 Crashed: 0 IMGSGX554GLDriver 0x328b9be0 0x328ac000 + 56288 1 IMGSGX554GLDriver 0x328b9b8e 0x328ac000 + 56206deallocated instance 2 IMGSGX554GLDriver 0x328bc2f2 0x328ac000 + 66290 3 IMGSGX554GLDriver 0x328baf44 0x328ac000 + 61252 4 libGPUSupportMercury.dylib 0x370f86be 0x370f6000 + 9918 5 GLEngine 0x34ce8bd2 0x34c4f000 + 629714 6 GLEngine 0x34cea30e 0x34c4f000 + 635662 7 GLEngine 0x34c8498e 0x34c4f000 + 219534 8 GLEngine 0x34c81394 0x34c4f000 + 205716 9 VectorKit 0x3957f4de 0x394c7000 + 754910 10 VectorKit 0x3955552e 0x394c7000 + 582958 11 VectorKit 0x394d056e 0x394c7000 + 38254 12 VectorKit 0x394d0416 0x394c7000 + 37910 13 VectorKit 0x394cb7ca 0x394c7000 + 18378 14 VectorKit 0x394c9804 0x394c7000 + 10244 15 VectorKit 0x394c86a2 0x394c7000 + 5794 16 QuartzCore 0x354a07a4 0x35466000 + 239524 17 QuartzCore 0x354a06fc 0x35466000 + 239356 18 IOMobileFramebuffer 0x376f8fd4 0x376f4000 + 20436 19 IOKit 0x344935aa 0x34490000 + 13738 20 CoreFoundation 0x33875888 0x337e9000 + 575624 21 CoreFoundation 0x338803e4 0x337e9000 + 619492 22 CoreFoundation 0x33880386 0x337e9000 + 619398 23 CoreFoundation 0x3387f20a 0x337e9000 + 614922 24 CoreFoundation 0x337f2238 0x337e9000 + 37432 25 CoreFoundation 0x337f20c4 0x337e9000 + 37060 26 GraphicsServices 0x373ad336 0x373a8000 + 21302 27 UIKit 0x3570e2b4 0x356b7000 + 357044 28 MyApp 0x000ea12e 0xe9000 + 4398 29 MyApp 0x000ea0e4 0xe9000 + 4324 I think thats all, additionally, I would like to ask you: if you are using unwind segues then you are releasing view controllers from the memory heap, right? Meanwhile, performing segues let you instantiate those controllers. Technically, MenuVC should be the only VC alive in the heap during the app life cycle if you understand me.

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  • Question about Multicaste Delegates?

    - by IbrarMumtaz
    I am going through some exam questions for the 70-536 exam and an actual question one developer postedon his blog has popped up in my exam questions. I cannot remember what his answer was .... but below is the question: You need to write a multicast delegate that accepts a DateTime arguement and returns a bool value. Which code segment should you use? A: public delegate int PowerDeviceOn(bool, DateTime) B: public delegate bool PowerDeviceOn(Object, EventArgs) C: public delegate void PowerDeviceOn(DateTime) D: public delegate bool PowerDeviceOn(DateTime) The answer is A. Can someone please explain why? As I already did some research into this question a while ago and so I was sure that it was C, obviously now looking back at the question its clear that I did not read properly. As i was sure I had seen the same one before so I jumped to the most obvious one. A varitation on this question: You need to write a multicast delegate that accepts a DateTime arguement. Which code segment should you use? A: public delegate int PowerDeviceOn(bool, DateTime) B: public delegate bool PowerDeviceOn(Object, EventArgs) C: public delegate void PowerDeviceOn(DateTime) D: public delegate bool PowerDeviceOn(DateTime) Now this is another variation on this quesiton, it still has the same bogus sample answers, as they still kind work in throwing the exam taker off. Notice how by simply keeping the sample asnwers the same and by removing a small portion of the question text, the answer is C and not A. The variation has no official answer as I just conjured it up using the exam question as a baseplate. The answer is definately C. This time round its easy to see why C is correctr but the very first question I have an inkiling but as you know an inkling is not good enough in passing exams. Thanks For Reading.

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  • How would a user stay logged in to a REST-based website?

    - by unforgiven3
    A year or so ago I asked this question: Can you help me understand this? “Common REST Mistakes: Sessions are irrelevant”. My question was essentially this: Okay, I get that HTTP authentication is done automatically on every message - but how? Is the username/password sent with every request? Doesn't that just increase attack surface area? I feel like I'm missing part of the puzzle. The answers I received made perfect sense in the context of a mobile (iPhone, Android, WP7) app - when talking to a REST service, the app would just send user credentials along with each request. That worked great for me. But now, I would like to better understand how one would secure a REST-like website, like StackOverflow itself or something like Reddit. How would things work if it was a user logged in via a web browser instead of logged in via an iPhone app? What happens when a user logs in? Are the credentials saved in the browser somehow? How would the browser know what credentials to send with subsequent REST requests? What if it's a JavaScript call to a webservice? How would the JavaScript call include user credentials? I'll be quite frank: my understanding of security when it comes to websites is pretty limited. I enjoyed working with REST services from an app perspective, but now I want to try and build a website that is based on REST principles, and I'm finding myself to be pretty lost. If there is anything in the above question that is unclear that you'd like me to clarify, please leave a comment and I'll address it.

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  • What to call factory-like (java) methods used with immutable objects

    - by StaxMan
    When creating classes for "immutable objects" immutable meaning that state of instances can not be changed; all fields assigned in constructor) in Java (and similar languages), it is sometimes useful to still allow creation of modified instances. That is, using an instance as base, and creating a new instance that differs by just one property value; other values coming from the base instance. To give a simple example, one could have class like: public class Circle { final double x, y; // location final double radius; public Circle(double x, double y, double r) { this.x = x; this.y = y; this.r = r; } // method for creating a new instance, moved in x-axis by specified amount public Circle withOffset(double deltaX) { return new Circle(x+deltaX, y, radius); } } So: what should method "withOffset" be called? (note: NOT what its name ought to be -- but what is this class of methods called). Technically it is kind of a factory method, but somehow that does not seem quite right to me, since often factories are just given basic properties (and are either static methods, or are not members of the result type but factory type). So I am guessing there should be a better term for such methods. Since these methods can be used to implement "fluent interface", maybe they could be "fluent factory methods"? Better suggestions? EDIT: as suggested by one of answers, java.math.BigDecimal is a good example with its 'add', 'subtract' (etc) methods. Also: I noticed that there's this question (by Jon Skeet no less) that is sort of related (although it asks about specific name for method)

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  • Importing external .jar file to Android project

    - by robintw
    I've read various answers to similar questions on StackOverflow, so I apologise if I'm repeating another question, but I can't seem to get this to work. I have a standard java project in which I've written code to parse some BBC Radio XML data from the internet. The project is called BBCSchedules and the class I'm interested in is called BBCChannel. I'm now trying to use the BBCChannel class in an android application. How should I go about doing this? I've tried various things, following various bits of advice on the internet, and the place I've got to at the moment is compiling my BBCSchedules project to a .jar file, and importing that to the Android project using the Build Path/Library/Add External Jar option. However, Eclispe still doesn't recognise the BBCChannel class, and won't let me run the application because of this. I guess I've done something silly wrong, but what is it? Cheers, Robin UPDATE: I've tried the steps listed in http://stackoverflow.com/questions/1334802/how-can-i-use-external-jars-in-an-android-project and various other StackOverflow questions I can find that seem to be related to this, but absolutely nothing seems to work. Any other ideas? UPDATE: The discussions I've had with the author of the first answer below suggest that it is something to do with how I am using Eclipse to attach the .jar file. The project he sent me with the .jar file already attached didn't work. Any other ideas anyone?

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  • How to achieve interaction between GUI class with logic class

    - by volting
    Im new to GUI programming, and haven't done much OOP. Im working on a basic calculator app to help me learn GUI design and to brush up on OOP. I understand that anything GUI related should be kept seperate from the logic, but Im unsure how to implement interaction between logic an GUI classes when needed i.e. basically passing variables back and forth... Im using TKinter and when I pass a tkinter variable to my logic it only seems to hold the string PY_VAR0. def on_equal_btn_click(self): self.entryVariable.set(self.entryVariable.get() + "=") calculator = Calc(self.entryVariable) self.entryVariable.set(calculator.calculate()) Im sure that im probably doing something fundamentally wrong and probabaly really stupid, I spent a considerable amount of time experimenting (and searching for answers online) but Im getting no where. Any help would be appreciated. Thanks, V The Full Program (well just enough to show the structure..) import Tkinter class Gui(Tkinter.Tk): def __init__(self,parent): Tkinter.Tk.__init__(self,parent) self.parent = parent self.initialize() def initialize(self): self.grid() self.create_widgets() """ grid config """ #self.grid_columnconfigure(0,weight=1,pad=0) self.resizable(False, False) def create_widgets(self): """row 0 of grid""" """Create Text Entry Box""" self.entryVariable = Tkinter.StringVar() self.entry = Tkinter.Entry(self,width=30,textvariable=self.entryVariable) self.entry.grid(column=0,row=0, columnspan = 3 ) self.entry.bind("<Return>", self.on_press_enter) """create equal button""" equal_btn = Tkinter.Button(self,text="=",width=4,command=self.on_equal_btn_click) equal_btn.grid(column=3, row=0) """row 1 of grid""" """create number 1 button""" number1_btn = Tkinter.Button(self,text="1",width=8,command=self.on_number1_btn_click) number1_btn.grid(column=0, row=1) . . . def on_equal_btn_click(self): self.entryVariable.set(self.entryVariable.get() + "=") calculator = Calc(self.entryVariable) self.entryVariable.set(calculator.calculate()) class Calc(): def __init__(self, equation): self.equation = equation def calculate(self): #TODO: parse string and calculate... return self.equation if __name__ == "__main__": app = Gui(None) app.title('Calculator') app.mainloop()

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  • Searching For A Record After A LINQ query

    - by Justin
    I'm confused to why this is happening. I'm new to LINQ so I'm clearly missing something here, that is probably pretty easy. I've looked up help on the topic, but I don't really know what to ask so I haven't found any answers that really address my question. This doesn't work It throws an EntityCommandExecutionException when the FirstOrDefault method is executed. var query = from band in context.BandsEntitySet where band.ID == 12345 select band; string venueName = "Willis Park"; foreach (var item in query) { var venue = context.VenueEntitySet.FirstOrDefault(r => r.Venue.Equals(venueName)); } This works var query = from band in context.BandsEntitySet where band.ID == 12345 select band; var bandList = query.toList(); string venueName = "Willis Park"; foreach (var item in bandList) { var venue = context.VenueEntitySet.FirstOrDefault(r => r.Venue.Equals(venueName)); } My question is simple: Why is the exception being thrown? And why does creating a list from the query allow me to use the FirstOrDefault method? Exception Message: A first chance exception of type 'System.Data.EntityCommandExecutionException' occurred in System.Data.Entity.dll I guess I am wrong in my assumption that query is a list? Then what is it exactly? I'm confused because this doesn't throw an exception: foreach (var item in query) { var area = item.VenueArea; } I'd appreciate any help on this issue. thanks, Justin

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  • drawRect gets called on UIView subclass but not on UIViewController

    - by HotFudgeSunday
    My code is working so far but I had to create a Class for the UIView. This is a bit inconvenient because I need to interact with the ViewController too. BTW, I did try [self setNeedsDisplay] on the ViewDidLoad of the UIViewController subclass file but it didn't work. Here's the code, which works on UIView Subclass but doesn't get called on a UIViewController one: - (void)drawRect:(CGRect)rect { UIColor *currentColor = [UIColor redColor]; CGContextRef context = UIGraphicsGetCurrentContext(); someNum = 1; CGContextBeginPath(context); CGContextMoveToPoint(context, 30, 40); [self addDotImageX:30 andY:40]; CGContextSetLineWidth(context, 2); CGContextSetStrokeColorWithColor(context, currentColor.CGColor); CGContextStrokePath(context); } Any ideas on what to try? BTW, this is a TabBar App. I know those can somehow block the calls to drawRect. The Tabs where created programatically, not through a Nib. Eg: NSMutableArray *listOfViewControllers = [[NSMutableArray alloc] init]; UIViewController *vc; vc = [[Education alloc] init]; vc.title = @"Education"; [listOfViewControllers addObject:vc]; vc.tabBarItem.image = [UIImage imageNamed:@"info.png"]; [vc release]; I would appreciate any ideas. I've been through the answers on this site related to setNeedsDisplay not calling drawRect and haven't found an answer for my particular case. Thanks.

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  • What is the nicest way to parse this in C++ ?

    - by ereOn
    Hi, In my program, I have a list of "server address" in the following format: host[:port] The brackets here, indicate that the port is optional. host can be a hostname, an IPv4 or IPv6 address. port, if present can be a numeric port number or a service string (like: "http" or "ssh"). If port is present and host is an IPv6 address, host must be in "bracket-enclosed" notation (Example: [::1]) Here are some valid examples: localhost localhost:11211 127.0.0.1:http [::1]:11211 ::1 [::1] And an invalid example: ::1:80 // Invalid: Is this the IPv6 address ::1:80 and a default port, or the IPv6 address ::1 and the port 80 ? ::1:http // This is not ambigous, but for simplicity sake, let's consider this is forbidden as well. My goal is to separate such entries in two parts (obviously host and port). I don't care if either the host or port are invalid as long as they don't contain a : (290.234.34.34.5 is ok for host, it will be rejected in the next process); I just want to separate the two parts, or if there is no port part, to know it somehow. I tried to do something with std::stringstream but everything I come up to seems hacky and not really elegant. How would you do this in C++ ? I don't mind answers in C but C++ is prefered. Any boost solution is welcome as well. Thank you.

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  • How to print contents from a session variable by looping in a foreach statement

    - by itsover9000
    im trying to write a code where can print and loop through the contents of my session variable by using a foreach statement here is my code <form class="form form-inline" method = "post" action="reportmaker.php"> <select name="rfield"> <option value="">--Select Field--</option> <?php $sc2=mysql_query("SELECT * from searchcolumn s left join report_fields r on s.scol_id=r.field_id where s.category != 'wh'"); foreach($sc2 as $sc){ ?> <option value="<?php echo $sc[advsearch_col]; ?>"><?php echo $sc[advsearch_name]; ?></option> <?php } ?> </select> <button type="submit" value = "submit" id="add" name="add" class="btn pull-right">Add More</button> </form> <?php if(isset($_POST['add'])) { $_SESSION['temp'][]=$_POST['rfield']; } if($_SESSION[temp][]!=""){ foreach($_SESSION[temp][] as $temp) { echo $temp; } } ?> the error that appears with this code is Fatal error: Cannot use [] for reading the line where the error is is this if($_SESSION[temp][]!=""){ i need to print the contents of the session array and this is the only way i know how is there a way to fix this? thanks =========EDIT thanks for the answers guys i finally got it

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  • Guidance required: FIrst time gonna work with real high end database (size = 50GB).

    - by claws
    I got a project of designing a Database. This is going to be my first big scale project. Good thing about it is information is mostly organized & currently stored in text files. The size of this information is 50GB. There are going to be few millions of records in each Table. Its going to have around 50 tables. I need to provide a web interface for searching & browsing. I'm going to use MySQL DBMS. I've never worked with a database more than 200MB before. So, speed & performance was never a concern but I followed things like normalization & Indexes. I never used any kind of testing/benchmarking/queryOptimization/whatever because I never had to care about them. But here the purpose of creating a database is to make it quickly searchable. So, I need to consider all possible aspects in design. I was browsing archives & found: http://stackoverflow.com/questions/1981526/what-should-every-developer-know-about-databases http://stackoverflow.com/questions/621884/database-development-mistakes-made-by-app-developers I'm gonna keep the points mentioned in above answers in mind. What else should I know? What else should I keep in mind?

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  • Are there any NOSQL-compatible CMS projects?

    - by Michael
    This question is partially related to an older question (Any CMS is Google App Engine compatible?) , but is slightly more general. It seems that in most CMS systems, the most fragile failure point is the database. Traditional database implementations scale poorly and will never be able to handle unforeseen spikes of traffic. Since Google App Engine was designed to help even small businesses overcome that problem, I had the same question that was asked earlier this year with less than satisfactory answers. But more generally, where are the CMS projects that support NOSQL databases? Looking over Wikipedia's list of CMS platforms, I see without much effort that only traditional RDBMS are supported by every single vendor on the list. I would have expected to see at least one or two projects handling CouchDB or similar engines. I understand the complexities of implementing a NOSQL solution to a problem that is typically solved using the relations cleanly expressed in any RDBMS, but there seems to be a rather wide market gap. Since databases are, today, easily outsourced to Google, Amazon, and others which use NOSQL models, I am amazed that there are not more projects actively pursuing this path. Am I simply not aware? Can someone please point me to projects that have real momentum that are developing on this path? I'm looking for two things: a CMS that has as its backbone a NOSQL database enabling easy database outsourcing (hosted MySQL clusters and similar solutions are not what I'm looking for) a project that is built to run on either a PaaS architecture like Google App Engine or an IaaS architecture like Amazon EC2 Any pointers in that direction would be most welcome.

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  • Password security; Is this safe?

    - by Camran
    I asked a question yesterday about password safety... I am new at security... I am using a mysql db, and need to store users passwords there. I have been told in answers that hashing and THEN saving the HASHED value of the password is the correct way of doing this. So basically I want to verify with you guys this is correct now. It is a classifieds website, and for each classified the user puts, he has to enter a password so that he/she can remove the classified using that password later on (when product is sold for example). In a file called "put_ad.php" I use the $_POST method to fetch the pass from a form. Then I hash it and put it into a mysql table. Then whenever the users wants to delete the ad, I check the entered password by hashing it and comparing the hashed value of the entered passw against the hashed value in the mysql db, right? BUT, what if I as an admin want to delete a classified, is there a method to "Unhash" the password easily? sha1 is used currently btw. some code is very much appreciated. Thanks

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