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  • Summing up spreadsheet data when a column contains “#N/A”

    - by Doris
    I am using Goggle Spreadsheet to work up some historical stock data and I use a Google function (=googlefinance=…) to import the historical closing prices for a stock, then I work with that data further. But, in that list of data generated from the =googlefinance=… function, one of the amounts comes up as #N/A. I don’t know why, but it happens for various symbols that I have tried. When I use a max function on the array, which includes the N/A line, the max function does not come up with anything but an N/A, so the N/A throws off any further functions. I thought I’d create a second column to the right of the imported data in which I can give it an IF function, something like, If ((A1 <0), "0", A1), with the expectation that it would return 0 if cell A1 is the N/A, and the cell value if it is not N/A. However, this still returns N/A. I also tried an IS BLANK function but that resulted in the same NA. Does anyone have any suggestions for a workaround to eliminate the N/A from an array of numbers that I am trying to work with?

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  • TDWI World Conference Features Oracle and Big Data

    - by Mandy Ho
    Oracle is a Gold Sponsor at this year's TDWI World Conference Series, held at the Manchester Grand Hyatt in San Diego, California - July 31 to Aug 1. The theme of this event is Big Data Tipping Point: BI Strategies in the Era of Big Data. The conference features an educational look at how data is now being generated so quickly that organizations across all industries need new technologies to stay ahead - to understand customer behavior, detect fraud, improve processes and accelerate performance. Attendees will hear how the internet, social media and streaming data are fundamentally changing business intelligence and data warehousing. Big data is reaching critical mass - the tipping point. Oracle will be conducting the following Evening Workshop. To reserve your space, call 1.800.820.5592 ext 10775. Title...:    Integrating Big Data into Your Data Center (or A Big Data Reference Architecture) Date.:    Wed., August 1, 2012, at 7:00 p.m Venue:: Manchester Grand Hyatt, San Diego, Room Weblogs, Social Media, smart meters, senors and other devices generate high volumes of low density information that isn't readily accessible in enterprise data warehouses and business intelligence applications today. But, this data can have relevant business value, especially when analyzed alongside traditional information sources. In this session, we will outline a reference architecture for big data that will help you maximize the value of your big data implementation. You will learn: The key technologies in a big architecture, and their specific use case The integration point of the various technologies and how they fit into your existing IT environment How effectively leverage analytical sandboxes for data discovery and agile development of data driven solutions   At the end of this session you will understand the reference architecture and have the tools to implement this architecture at your company. Presenter: Jean-Pierre Dijcks, Senior Principal Product Manager Don't miss our booth and the chance to meet with our Big data experts on the exhibition floor at booth #306. 

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  • Are certain problems solved more elegantly with AOP?

    - by Winston Ewert
    I've come across the idea of Aspect Oriented Programming, and I have some concerns with it. The basic idea seems to be that we want to take cross-cutting concerns which aren't well modularized using object and modularize them. That is all very fine and well. But the implementation of AOP seems to be that of modifying code from outside of the module. So, for example, an aspect could be written that changes what happens when a particular object is passed as a parameter in a function. This seems to go directly against the idea of modules. I should not be able to modify a module's behavior from outside of that module, otherwise the whole point of modules are overturned. But aspects seem to be doing exactly that! Basically, aspects seems to be a form of code patching. It may useful for some quick hacks; but, as a general principle perhaps its not something you want to do. Aspect Oriented Programming seems to me taking a bad practice and raising to a general design principle. Is AOP a good practice? Are certain programming problems solved more elegantly with AOP?

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  • How do you encode Algebraic Data Types in a C#- or Java-like language?

    - by Jörg W Mittag
    There are some problems which are easily solved by Algebraic Data Types, for example a List type can be very succinctly expressed as: data ConsList a = Empty | ConsCell a (ConsList a) consmap f Empty = Empty consmap f (ConsCell a b) = ConsCell (f a) (consmap f b) l = ConsCell 1 (ConsCell 2 (ConsCell 3 Empty)) consmap (+1) l This particular example is in Haskell, but it would be similar in other languages with native support for Algebraic Data Types. It turns out that there is an obvious mapping to OO-style subtyping: the datatype becomes an abstract base class and every data constructor becomes a concrete subclass. Here's an example in Scala: sealed abstract class ConsList[+T] { def map[U](f: T => U): ConsList[U] } object Empty extends ConsList[Nothing] { override def map[U](f: Nothing => U) = this } final class ConsCell[T](first: T, rest: ConsList[T]) extends ConsList[T] { override def map[U](f: T => U) = new ConsCell(f(first), rest.map(f)) } val l = (new ConsCell(1, new ConsCell(2, new ConsCell(3, Empty))) l.map(1+) The only thing needed beyond naive subclassing is a way to seal classes, i.e. a way to make it impossible to add subclasses to a hierarchy. How would you approach this problem in a language like C# or Java? The two stumbling blocks I found when trying to use Algebraic Data Types in C# were: I couldn't figure out what the bottom type is called in C# (i.e. I couldn't figure out what to put into class Empty : ConsList< ??? >) I couldn't figure out a way to seal ConsList so that no subclasses can be added to the hierarchy What would be the most idiomatic way to implement Algebraic Data Types in C# and/or Java? Or, if it isn't possible, what would be the idiomatic replacement?

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  • Benefits of classic OOP over Go-like language

    - by tylerl
    I've been thinking a lot about language design and what elements would be necessary for an "ideal" programming language, and studying Google's Go has led me to question a lot of otherwise common knowledge. Specifically, Go seems to have all of the interesting benefits from object oriented programming without actually having any of the structure of an object oriented language. There are no classes, only structures; there is no class/structure inheritance -- only structure embedding. There aren't any hierarchies, no parent classes, no explicit interface implementations. Instead, type casting rules are based on a loose system similar to duck-typing, such that if a struct implements the necessary elements of a "Reader" or a "Request" or an "Encoding", then you can cast it and use it as one. Does such a system obsolete the concept of OOP? Or is there something about OOP as implemented in C++ and Java and C# that is inherently more capable, more maintainable, somehow more powerful that you have to give up when moving to a language like Go? What benefit do you have to give up to gain the simplicity that this new paradigm represents?

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  • Composing programs from small simple pieces: OOP vs Functional Programming

    - by Jay Godse
    I started programming when imperative programming languages such as C were virtually the only game in town for paid gigs. I'm not a computer scientist by training so I was only exposed to Assembler and Pascal in school, and not Lisp or Prolog. Over the 1990s, Object-Oriented Programming (OOP) became more popular because one of the marketing memes for OOP was that complex programs could be composed of loosely coupled but well-defined, well-tested, cohesive, and reusable classes and objects. And in many cases that is quite true. Once I learned object-oriented programming my C programs became better because I structured them more like classes and objects. In the last few years (2008-2014) I have programmed in Ruby, an OOP language. However, Ruby has many functional programming (FP) features such as lambdas and procs, which enable a different style of programming using recursion, currying, lazy evaluation and the like. (Through ignorance I am at a loss to explain why these techniques are so great). Very recently, I have written code to use methods from the Ruby Enumerable library, such as map(), reduce(), and select(). Apparently this is a functional style of programming. I have found that using these methods significantly reduce code volume, and make my code easier to debug. Upon reading more about FP, one of the marketing claims made by advocates is that FP enables developers to compose programs out of small well-defined, well-tested, and reusable functions, which leads to less buggy code, and low code volume. QUESTIONS: Is the composition of complex program by using FP techniques contradictory to or complementary to composition of a complex program by using OOP techniques? In which situations is OOP more effective, and when is FP more effective? Is it possible to use both techniques in the same complex program? Do the techniques overlap or contradict each other?

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  • How to REALLY start thinking in terms of objects?

    - by Mr Grieves
    I work with a team of developers who all have several years of experience with languages such as C# and Java. Most of them are young enough to have been shown OOP as a standard way to develop software in university and are very comfortable with concepts such as inheritance, abstraction, encapsulation and polymorphism. Yet, many of them, and I have to include myself, still tend to create classes which are meant to be used in a very functional fashion. The resulting software is often several smaller classes which correctly represent business objects which get passed through larger classes which only supply ways to modify and use those objects (functions). Large complex difficult-to-maintain classes named Manager are usually the result of such behaviour. I can see two theoretical reasons why people might write this type of code: It's easy to start thinking of everything in terms of the database Deep down, for me, a computer handling a web request feels more like a functional operation than an object oriented operation when you think about Request Handlers, Threads, Processes, CPU Cores and CPU operations... I want source code which is easy to read and easy to modify. I have seen excellent examples of OO code which meet these objectives. How can I start writing code like this? How I can I really start thinking in an object oriented fashion? How can I share such a mentality with my colleagues?

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  • FP for simulation and modelling

    - by heaptobesquare
    I'm about to start a simulation/modelling project. I already know that OOP is used for this kind of projects. However, studying Haskell made me consider using the FP paradigm for modelling a system of components. Let me elaborate: Let's say I have a component of type A, characterised by a set of data (a parameter like temperature or pressure,a PDE and some boundary conditions,etc.) and a component of type B, characterised by a different set of data(different or same parameter, different PDE and boundary conditions). Let's also assume that the functions/methods that are going to be applied on each component are the same (a Galerkin method for example). If I were to use an OOP approach, I would create two objects that would encapsulate each type's data, the methods for solving the PDE(inheritance would be used here for code reuse) and the solution to the PDE. On the other hand, if I were to use an FP approach, each component would be broken down to data parts and the functions that would act upon the data in order to get the solution for the PDE. This approach seems simpler to me assuming that linear operations on data would be trivial and that the parameters are constant. What if the parameters are not constant(for example, temperature increases suddenly and therefore cannot be immutable)? In OOP, the object's (mutable) state can be used. I know that Haskell has Monads for that. To conclude, would implementing the FP approach be actually simpler,less time consuming and easier to manage (add a different type of component or new method to solve the pde) compared to the OOP one? I come from a C++/Fortran background, plus I'm not a professional programmer, so correct me on anything that I've got wrong.

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  • Design pattern for parsing data that will be grouped to two different ways and flipped

    - by lewisblackfan
    I'm looking for an easily maintainable and extendable design model for a script to parse an excel workbook into two separate workbooks after pulling data from other locations like the command line, and a database. The high level details are as follows. I need to parse an excel workbook containing a sheet that lists unique question names, the only reliable information that can be parsed from the question name is the book code that identifies the title and edition of the textbook the question is associated with, the rest of the question name is not standardized well enough to be reliably parsed by computer. The general form of the question name is best described by the following regular expression. '^(\w+)\s(\w{1,2})\.(\w{1,2})\.(\w{1,3})\.(\w{1,3}\.)*$' The first sub-pattern is the book code, the second sub-pattern is 90% of the time the chapter, and the rest of the sub-patterns could be section, problem type, problem number, or question type information. There is no simple logic, at least not one I can find. There will be a minimum of three other columns in this spreadsheet; one column will be the chapter the question is associated with, the second will be the section within the chapter the question is associated with, and the third will be some kind of asset indicated by a uniform resource locator. 1 | 1 | qname1 | url | description | url | description ... 1 | 1 | qname2 | url | description 1 | 1 | qname3 | url | description | url | description | url | The asset can be indicated by a full or partial uniform resource locator, the partial url will need to be completed before it can be fed into the application. There theoretically could be no limit to the number of asset columns, the assets will be grouped in columns by type. Some times additional data will have to be retrieved from a database or combined with the book code before the asset url is complete and can be understood by the application that will be using the asset. The type is an abstraction, there are eight types right now, each with their own logic in how the uniform resource locator is handled and or completed, and I have to add a new type and its logic every three or four months. For each asset url there is the possibility of a description column, a character string for display in the application, but not always. (I've already worked out validating the description text, and squashing MSs obscure code page down to something 7-bit ascii can handle.) Now that all the details are filled-in I can get to the actual problem of parsing the file. I need to split the information in this excel workbook into two separate workbooks. The first workbook will group all the questions by section in rows. With the first cell being the section doublet and the rest of the cells in the row are the question names. 1.1 | qname1 | qname2 | qname3 | qname4 | 1.2 | qname1 | qname2 | qname3 | 1.3 | qname1 | qname2 | qname3 | qname4 | qname5 There is no set number of questions for each section as you can see from the above example. The second workbook is more complicated, there is one row per asset, and question names that have more than one asset will be duplicated. There will be four or five columns on this sheet. The first is the question name for the asset, the second is a media type used to select the correct icon for the asset in the application, the third is string representing the asset type, the four is the full and complete uniform resource locator for the asset, and the fifth columns is the optional text description for the asset. q1 | mtype1 | atype1 | url | description q1 | mtype2 | atype2 | url | description q1 | mtype2 | atype3 | url | description q2 | mtype1 | atype1 | url | description q2 | mtype2 | atype3 | url | description For the original six types I did have a script that parsed the source excel workbook into the other two excel workbooks, and I was able to add two more types until I ran aground on the implementation of the ninth type and tenth types. What broke my script was the fact that the ninth type is actually a sub-type of one of the original six, but with entirely different logic, and my mostly procedural script could not accommodate without duplicating a lot of code. I also had a lot of bugs in the script and will be writing the test first on this time around. I'm stuck with the format for the resulting two workbooks, this script is glue code, development went ahead with the project without bothering to get a complete spec from the sponsor. I work for the same company as the developers but in the editorial department, editorial is co-sponsor of the project, and am expected to fix pesky details like this (I'm foaming at the mouth as I type this). I've tried factories, I've tried different object models, but each resulting workbook is so different when I find a design that works for generating one workbook the code is not really usable for generating the other. What I would really like are ideas about a maintainable and extensible design for parsing the source workbook into both workbooks with maximum code reuse, and or sympathy.

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  • Why is my ServiceOperation method missing from my WCF Data Services client proxy code?

    - by Kev
    I have a simple WCF Data Services service and I want to expose a Service Operation as follows: [System.ServiceModel.ServiceBehavior(IncludeExceptionDetailInFaults = true)] public class ConfigurationData : DataService<ProductRepository> { // This method is called only once to initialize service-wide policies. public static void InitializeService(IDataServiceConfiguration config) { config.SetEntitySetAccessRule("*", EntitySetRights.ReadMultiple | EntitySetRights.ReadSingle); config.SetServiceOperationAccessRule("*", ServiceOperationRights.All); config.UseVerboseErrors = true; } // This operation isn't getting generated client side [WebGet] public IQueryable<Product> GetProducts() { // Simple example for testing return (new ProductRepository()).Product; } Why isn't the GetProducts method visible when I add the service reference on the client?

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  • How to Convert multiple sets of Data going from left to right to top to bottom the Pythonic way?

    - by ThinkCode
    Following is a sample of sets of contacts for each company going from left to right. ID Company ContactFirst1 ContactLast1 Title1 Email1 ContactFirst2 ContactLast2 Title2 Email2 1 ABC John Doe CEO [email protected] Steve Bern CIO [email protected] How do I get them to go top to bottom as shown? ID Company Contactfirst ContactLast Title Email 1 ABC John Doe CEO [email protected] 1 ABC Steve Bern CIO [email protected] I am hoping there is a Pythonic way of solving this task. Any pointers or samples are really appreciated! p.s : In the actual file, there are 10 sets of contacts going from left to right and there are few thousand such records. It is a CSV file and I loaded into MySQL to manipulate the data.

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  • Object oriented design of game in Java: How to handle a party of NPCs?

    - by Arvanem
    Hi folks, I'm making a very simple 2D RPG in Java. My goal is to do this in as simple code as possible. Stripped down to basics, my class structure at the moment is like this: Physical objects have an x and y dimension. Roaming objects are physical objects that can move(). Humanoid objects are roaming objects that have inventories of GameItems. The Player is a singleton humanoid object that can hire up to 4 NPC Humanoids to join his or her party, and do other actions, such as fight non-humanoid objects. NPC Humanoids can be hired by the Player object to join his or her party, and once hired can fight for the Player. So far I have given the Player class a "party" ArrayList of NPC Humanoids, and the NPC Humanoids class a "hired" Boolean. However, my fight method is clunky, using an if to check the party size before implementing combat, e.g. public class Player extends Humanoids { private ArrayList<Humanoids> party; // GETTERS AND SETTERS for party here //... public void fightEnemy(Enemy eneObj) { if (this.getParty().size() == 0) // Do combat without party issues else if (this.getParty().size() == 1) // Do combat with party of 1 else if (this.getParty().size() == 2) // Do combat with party of 2 // etc. My question is, thinking in object oriented design, am I on the right track to do this in as simple code as possible? Is there a better way?

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  • How to add data manually in core data entity

    - by pankaj
    Hi I am working on core data for the first time. I have just created an entity and attributes for that entity. I want to add some data inside the entity(u can say i want to add data in a table), earlier i when i was using sqlite, i would add data using terminal. But here in core data i am not able to find a place where i can manually add data. I just want to add data in entity and display it in a UITableView. I have gone through the the documentation of core data but it does not explain how to add data manually although it explains how i can add it programmiticaly but i dont need to do it programically. I want to do it manually. Thanks in advance

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  • What is a good approach for a Data Access Layer?

    - by Adil Mughal
    Our software is a customized Human Resource Management System (HRMS) using ASP.NET with Oracle as the database and now we are actually moving to make it a product that supports multiple tenants with their own databases. Our options: Use NHibernate to support Multiple databases and use of OO. But we concern related to NHibernate learning curve and any problem we faced. Make a generalized DAL which will continue working with Oracle using stored procedures and use tools to convert it to other databases such as SQL Server or MySql. There is a risk associated with having to support multiple database-dependent versions of a single script. Provide the software as a Service (SaaS) and maintain the way we conduct business. However there can may be clients who do not want or trust the Cloud or other SaaS business models. With this in mind, what's the best Data access layer technique?

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  • How do you verify the correct data is in a data mart?

    - by blockcipher
    I'm working on a data warehouse and I'm trying to figure out how to best verify that data from our data cleansing (normalized) database makes it into our data marts correctly. I've done some searches, but the results so far talk more about ensuring things like constraints are in place and that you need to do data validation during the ETL process (E.g. dates are valid, etc.). The dimensions were pretty easy as I could easily either leverage the primary key or write a very simple and verifiable query to get the data. The fact tables are more complex. Any thoughts? We're trying to make this very easy for a subject matter export to run a couple queries, see some data from both the data cleansing database and the data marts, and visually compare the two to ensure they are correct.

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  • How do I set default values on new properties for existing entities after light weight core data migration?

    - by Moritz
    I've successfully completed light weight migration on my core data model. My custom entity Vehicle received a new property 'tirePressure' which is an optional property of type double with the default value 0.00. When 'old' Vehicles are fetched from the store (Vehicles that were created before the migration took place) the value for their 'tirePressure' property is nil. (Is that expected behavior?) So I thought: "No problem, I'll just do this in the Vehicle class:" - (void)awakeFromFetch { [super awakeFromFetch]; if (nil == self.tirePressure) { [self willChangeValueForKey:@"tirePressure"]; self.tirePressure = [NSNumber numberWithDouble:0.0]; [self didChangeValueForKey:@"tirePressure"]; } } Since "change processing is explicitly disabled around" awakeFromFetch I thought the calls to willChangeValueForKey and didChangeValueForKey would mark 'tirePresure' as dirty. But they don't. Every time these Vehicles are fetched from the store 'tirePressure' continues to be nil despite having saved the context.

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  • Select data from three different tables with null data

    - by user3678972
    I am new in Sql. My question is how to get data from three different tables with null values. I have tried a query as below: SELECT * FROM [USER] JOIN [Location] ON ([Location].UserId = [USER].Id) JOIN [ParentChild] ON ([ParentChild].UserId = [USER].Id) WHERE ParentId=7 which I find from this link. Its working fine but, it not fetches all and each data associated with the ParentId Something like it only fetches data which are available in all tables, but also omits some data which not available in Location tables but it comes under the given ParentId. For example: UserId ParentId 1 7 8 7 For userId 8, there is data available in Location table,so it fetches all data. But there is no data for userId 1 available in Location table, so the query didn't work for this. But I want all and every data. If there is no data for userId then it can return only null columns. Is it possible ?? hope everyone can understand my problem.

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  • What's The Best Object-Relational Mapping Tool For .NET?

    - by Icono123
    I've worked on a few Java web projects and we've always used Hibernate for our data object layer. I haven't worked on a large scale ASP.NET site and I'm unsure which solution to choose. I'm tempted to try NHibernate, but I don't like the fact that they use so many third party libraries. I found this list on Wikipedia of available ORM software: http://en.wikipedia.org/wiki/List_of_object-relational_mapping_software#.NET What ORM have you used? Was it easy to use? Would you recommend using it again? Was it used on a small, medium, or large project? Would you write your own? Thanks.

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  • How does Core Data determine if an NSObjects data can be dropped?

    - by Kevin
    In the app I am working on now I was storing about 500 images in Core Data. I have since pulled those images out and store them in the file system now, but in the process I found that the app would crash on the device if I had an array of 500 objects with image data in them. An array with 500 object ids with the image data in those objects worked fine. The 500 objects without the image data also worked fine. I found that I got the best performance with both an array of object ids and image data stored on the filesystem instead of in core data. The conclusion I came to was that if I had an object in an array that told Core Data I was "using" that object and Core Data would hold on to the data. Is this correct?

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  • Is it true that in most Object Oriented Programming Languages, an "i" in an instance method always r

    - by Jian Lin
    In the following code: <script type="text/javascript"> var i = 10; function Circle(radius) { this.r = radius; this.i = radius; } Circle.i = 123; Circle.prototype.area = function() { alert(i); } var c = new Circle(1); var a = c.area(); </script> What is being alerted? The answer is at the end of this question. I found that the i in the alert call either refers to any local (if any), or the global variable. There is no way that it can be the instance variable or the class variable even when there is no local and no global defined. To refer to the instance variable i, we need this.i, and to the class variable i, we need Circle.i. Is this actually true for almost all Object oriented programming languages? Any exception? Are there cases that when there is no local and no global, it will look up the instance variable and then the class variable scope? (or in this case, are those called scope?) the answer is: 10 is being alerted.

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  • PHP Store User Data without Sessions

    - by Sev
    Is there anyway to store users data such as userid, email, etc to be accessible from all pages of a website after they have logged in, but without using sessions or cookies? For example: class User { var $userid; var $username; var $email; .. methods.. } after they login at login.php $currentUser = new User($_POST['username']) now, how do I access $currentUser from another page, such as index.php if I shouldn't use sessions or cookies at all? so that I could do the following in index.php: if ($currentUser->userid > -1) { echo "you are logged in as: " . $currentUser->username; } else { echo "click here to login"; } i asked a similar question before, here, but the answers didn't fulfill my needs.

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  • How to handle encryption key conflicts when synchronizing data?

    - by Rafael
    Assume that there is data that gets synchronized between several devices. The data is protected with a symmetric encryption algorithm and a key. The key is stored on each device and encrypted with a password. When a user changes the password only the key gets re-encrypted. Under normal circumstances, when there is a good network connection to other peers, the current key gets synchronized and all data on the new device gets encrypted with the same key. But how to handle situations where a new device doesn’t have a network connection and e.g. creates its own new, but incompatible key? How to keep the usability as high as possible under such circumstances? The application could detect that there is no network and hence refuse to start. That’s very bad usability in my opinion, because the application isn’t functional at all in this case. I don’t consider this a solution. The application could ignore the missing network connection and create a new key. But what to do when the application gains a network connection? There will be several incompatible keys and some parts of the underlying data could only be encrypted with one key and other parts with another key. The situation would get worse if there would be more keys than just two and the application would’ve to ask every time for a password when another object that should get decrypted with another key would be needed. It is very messy and time consuming to try to re-encrypt all data that is encrypted with another key with a main key. What should be the main key at all in this case? The oldest key? The key with the most encrypted objects? What if the key got synchronized but not all objects that got encrypted with this particular key? How should the user know for which particular password the application asks and why it takes probably very long to re-encrypt the data? It’s very hard to describe encryption “issues” to users. So far I didn’t find an acceptable solution, nor some kind of generic strategy. Do you have some hints about a concrete strategy or some books / papers that describe synchronization of symmetrically encrypted data with keys that could cause conflicts?

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  • How to switch from Core Data automatic lightweight migration to manual?

    - by Jaanus
    My situation is similar to this question. I am using lightweight migration with the following code, fairly vanilla from Apple docs and other SO threads. It runs upon app startup when initializing the Core Data stack. NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil]; NSError *error = nil; NSString *storeType = nil; if (USE_SQLITE) { // app configuration storeType = NSSQLiteStoreType; } else { storeType = NSBinaryStoreType; } persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; // the following line sometimes crashes on app startup if (![persistentStoreCoordinator addPersistentStoreWithType:storeType configuration:nil URL:[self persistentStoreURL] options:options error:&error]) { // handle the error } For some users, especially with slower devices, I have crashes confirmed by logs at the indicated line. I understand that a fix is to switch this to manual mapping and migration. What is the recipe to do that? The long way for me would be to go through all Apple docs, but I don't recall there being good examples and tutorials specifically for schema migration.

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  • Core data migration failing with "Can't find model for source store" but managedObjectModel for source is present

    - by Ira Cooke
    I have a cocoa application using core-data, which is now at the 4th version of its managed object model. My managed object model contains abstract entities but so far I have managed to get migration working by creating appropriate mapping models and creating my persistent store using addPersistentStoreWithType:configuration:options:error and with the NSMigratePersistentStoresAutomaticallyOption set to YES. NSDictionary *optionsDictionary = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES] forKey:NSMigratePersistentStoresAutomaticallyOption]; NSURL *url = [NSURL fileURLWithPath: [applicationSupportFolder stringByAppendingPathComponent: @"MyApp.xml"]]; NSError *error=nil; [theCoordinator addPersistentStoreWithType:NSXMLStoreType configuration:nil URL:url options:optionsDictionary error:&error] This works fine when I migrate from model version 3 to 4, which is a migration that involves adding attributes to several entities. Now when I try to add a new model version (version 5), the call to addPersistentStoreWithType returns nil and the error remains empty. The migration from 4 to 5 involves adding a single attribute. I am struggling to debug the problem and have checked all the following; The source database is in fact at version 4 and the persistentStoreCoordinator's managed object model is at version 5. The 4-5 mapping model as well as managed object models for versions 4 and 5 are present in the resources folder of my built application. I've tried various model upgrade paths. Strangely I find that upgrading from an early version 3 - 5 works .. but upgrading from 4 - 5 fails. I've tried adding a custom entity migration policy for migration of the entity whose attributes are changing ... in this case I overrode the method beginEntityMapping:manager:error: . Interestingly this method does get called when migration works (ie when I migrate from 3 to 4, or from 3 to 5 ), but it does not get called in the case that fails ( 4 to 5 ). I'm pretty much at a loss as to where to proceed. Any ideas to help debug this problem would be much appreciated.

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  • What is the best way to store site configuration data?

    - by DaveDev
    I have a question about storing site configuration data. We have a platform for web applications. The idea is that different clients can have their data hosted and displayed on their own site which sits on top of this platform. Each site has a configuration which determines which panels relevant to the client appear on which pages. The system was originally designed to keep all the configuration data for each site in a database. When the site is loaded all the configuration data is loaded into a SiteConfiguration object, and the clients panels are generated based on the content of this object. This works, but I find it very difficult to work with to apply change requests or add new sites because there is so much data to sift through and it's difficult maintain a mental model of the site and its configuration. Recently I've been tasked with developing a subset of some of the sites to be generated as PDF documents for printing. I decided to take a different approach to how I would define the configuration in that instead of storing configuration data in the database, I wrote XML files to contain the data. I find it much easier to work with because instead of reading meaningless rows of data which are related to other meaningless rows of data, I have meaningful documents with semantic, readable information with the relationships defined by visually understandable element nesting. So now with these 2 approaches to storing site configuration data, I'd like to get the opinions of people more experienced in dealing with this issue on dealing with these two approaches. What is the best way of storing site configuration data? Is there a better way than the two ways I outlined here? note: StackOverflow is telling me the question appears to be subjective and is likely to be closed. I'm not trying to be subjective. I'd like to know how best to approach this issue next time and if people with industry experience on this could provide some input.

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