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  • Ruby/Rails - Add records to an object with each loop iteration / Object vs Arrays

    - by ChrisWesAllen
    I'm trying to figure out how to add records to an existing object for each iteration of a loop. I'm having a hard time discovering the difference between an object and an array. I have this @events = Event.find(1) @loops = Choices.find(:all, :limit => 5) #so loop for 5 instances of choice model for loop in @loops @events = Event.find(:all,:conditions => ["event.id = ?", loop.event_id ]) end I'm trying to add a new events to the existing @events object based on the id of whatever the loop variable is. But the ( = ) operator just creates a new instance of the @events object. I tried ( += ) and ( << ) as operators but got the error "You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil" I tried created an array events = [] events << Event.find(1) @loops = Choices.find(:all, :limit => 5) #so loop for 5 instances of choice model for loop in @loops events << Event.find(:all,:conditions => ["event.id = ?", loop.event_id ]) end But I dont know how to call that arrays attributes within the view With objects I was able do create a loop within the view and call all the attributes of that object as well... <table> <% for event in @events %> <tr> <td><%= link_to event.title, event %></td> <td><%= event.start_date %></td> <td><%= event.price %></td> </tr> <% end %> </table> How could i do this with an array set? So the questions are 1) Whats the difference between arrays and objects? 2) Is there a way to add into the existing object for each iteration? 3) If I use an array, is there a way to call the attributes for each array record within the view?

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  • self.window.rootViewController vs window addSubview

    - by Gazzer
    I've noticed a lot of examples for iPhone apps in the Application Delegate - (void)applicationDidFinishLaunching:(UIApplication *)application have [window addSubview: someController.view]; (1) as opposed to self.window.rootViewController = self.someController; (2) Is there any practical reason to use one over the other? Is one technically correct? Do controller's have the an equivalent command to number (2) like self.someController.rootController = self.someOtherController; // pseudocode

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  • One big call vs. multiple smaller TSQL calls

    - by BrokeMyLegBiking
    I have a ADO.NET/TSQL performance question. We have two options in our application: 1) One big database call with multiple result sets, then in code step through each result set and populate my objects. This results in one round trip to the database. 2) Multiple small database calls. There is much more code reuse with Option 2 which is an advantage of that option. But I would like to get some input on what the performance cost is. Are two small round trips twice as slow as one big round trip to the database, or is it just a small, say 10% performance loss? We are using C# 3.5 and Sql Server 2008 with stored procedures and ADO.NET.

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  • VS 2008 linking error

    - by AvatarBlue
    I'm using Visual Studio 2008 C++ and working on a dll project. Debug compiled and linked perfectly but when I compile the release version, it shows this: VImgPtr.obj : error LNK2001: unresolved external symbol @__security_check_cookie@4 VLibraryPtr.obj : error LNK2001: unresolved external symbol "void __cdecl operator delete[](void *)" (??_V@YAXPAX@Z) D:\Source Code\VImgLib\Release-vc9u\VImgLib-vc9u.dll : fatal error LNK1120: 2 unresolved externals If I selected Multi-threaded (/MT) in "C/C++-Code Generation tab), it linked ok. The problem is only when I choose Multi-threaded DLL (/MD). I'm releasing a dll, so should be /MD right?

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  • NSArray vs. SQLite for Complex Queries on iPhone

    - by GingerBreadMane
    Developing for iPhone, I have a collection of points that I need to make complex queries on. For example: "How many points have a y-coordinate of 10" and "Return all points with an X-coordinate between 3 and 5 and a y-coordinate of 7". Currently, I am just cycling through each element of an NSArray and checking to see if each element matches my query. It's a pain to write the queries though. SQLite would be much nicer. I'm not sure which would be more efficient though since a SQLite database resides on disk and not in memory (to my understanding). Would SQLite be as efficient or more efficient here? Or is there a better way to do it other than these methods that I haven't thought of? I would need to perform the multiple queries with multiple sets of points thousands of times, so the best performance is important.

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  • GPA and Resume and PDF vs Doc.

    - by Recursion
    As a recent graduate of a CS program, I am looking for my first job. My GPA was not above 3.0, but incredibly close. Should I still put my GPA on my resume, or is it best to leave it out? Also, is it best to submit a resume as a PDF or a DOC file?

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  • dirname(__FILE__) VS setting global variable to directories

    - by SAFAD
    what are the pros and cons of using this : $globals['server_url'] = dirname(__FILE__); $globals['mainfiles'] = dirname(__FILE__).'/main'; and the pros and cons of using this : $globals['server_url'] = '/srv/www/htdocs/somwhere/'; $globals['mainfiles'] = '/srv/www/htdocs/somwhere/main'; And what do you suggest. by the way: these are set in config.php file which is called by other files as well, to stop directory conflicts when including files we use it like this : require_once($globals['server_url'].'/test.php');

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  • NSNotifications vs delegate for multiple instances of same protocol

    - by Brent Traut
    I could use some architectural advice. I've run into the following problem a few times now and I've never found a truly elegant way to solve it. The issue, described at the highest level possible:I have a parent class that would like to act as the delegate for multiple children (all using the same protocol), but when the children call methods on the parent, the parent no longer knows which child is making the call. I would like to use loose coupling (delegates/protocols or notifications) rather than direct calls. I don't need multiple handlers, so notifications seem like they might be overkill. To illustrate the problem, let me try a super-simplified example: I start with a parent view controller (and corresponding view). I create three child views and insert each of them into the parent view. I would like the parent view controller to be notified whenever the user touches one of the children. There are a few options to notify the parent: Define a protocol. The parent implements the protocol and sets itself as the delegate to each of the children. When the user touches a child view, its view controller calls its delegate (the parent). In this case, the parent is notified that a view is touched, but it doesn't know which one. Not good enough. Same as #1, but define the methods in the protocol to also pass some sort of identifier. When the child tells its delegate that it was touched, it also passes a pointer to itself. This way, the parent know exactly which view was touched. It just seems really strange for an object to pass a reference to itself. Use NSNotifications. The parent defines a separate method for each of the three children and then subscribes to the "viewWasTouched" notification for each of the three children as the notification sender. The children don't need to attach themselves to the user dictionary, but they do need to send the notification with a pointer to themselves as the scope. Same as #4, but rather than using separate methods, the parent could just use one with a switch case or other branching along with the notification's sender to determine which path to take. Create multiple man-in-the-middle classes that act as the delegates to the child views and then call methods on the parent either with a pointer to the child or with some other differentiating factor. This approach doesn't seem scalable. Are any of these approaches considered best practice? I can't say for sure, but it feels like I'm missing something more obvious/elegant.

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  • SQL Express vs SQL Plus

    - by Bruce227
    Hi, I'm wondering what the difference is if any between SQL Express and SQL Plus. I know SQL Plus is used with Oracle but not sure if SQL Plus is a modification of SQL Express or a totally different installation. Thanks

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  • Build server polling vs. event-driven builds

    - by Daniel T.
    Why do build servers poll for changes instead of SVN firing off an event (or a post-commit step) that tells the build server to start a build? It seems terribly inefficient to poll for changes, especially when the number of projects increases and the polling period is set to a very low value (for example, 30 seconds).

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  • Managing project configurations in VS 2010

    - by Toby
    I'm working on a solution with multiple projects (class libraries, interop, web application, etc) in VS2010. For the web application, I would like to take advantage of the config transformations in VS2010, so at one point I added configurations for each of our environments: Development, Test, Production, and so on. Some time later, after having rearranged the project layout, I noticed that some projects show all of the configurations in the properties page dropdown. Some projects (added since I did that setup) show only the standard Debug & Release configurations. Once I realized that this was going to make build configurations worse, not better, I decided to remove all of the extra configurations I had added. I've removed all of the various configuration options from the solution, but the projects that had the alternate configuration options still have them, and I can't figure out how to get rid of them in individual projects. Also, now that I see that not all projects have to have the same configurations, I would like to create my environmental configurations at the solution level, and in the web application project (for the config transforms), but leave all of the class libraries with the basic Debug/Release configurations. I've been unable to find any tool in the UI, or any information on the 'Net, concerning how to set up such a thing. So, in short, what's the best/easiest way to manage configurations at the project level in VS2010?

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  • Inheritance vs specific types in Financial Modelling for cashflows

    - by BlueTrin
    Hello, I have to program some financial applications where I have to represent a schedule of flows. The flows can be of 3 types: - fee flow (just a lump payment at some date) - floating rate flow (the flow is dependant of an interest rate to be determined at a later date) - fixed rate flow (the flow is dependant of an interest rate determined when the deal is done) I need to keep the whole information and I need to represent a schedule of these flows. Originally I wanted to use inheritance and create three classes FeeFlow, FloatingFlow, FixedFlow all inheriting from ICashFlow and implement some method GetFlowType() returning an enum then I could dynamic_cast the object to the correct type. That would allow me to have only one vector to represent my schedule. What do you think of this design, should I rather use three vectors vector, vector and vector to avoid the dynamic casts ?

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  • android SQLite vs Flat Files

    - by mixm
    hi. im creating a game right now and im a bit stuck on how to implement storage of levels. i need to be able to download level files from the internet ota. im not so familiar with transferring files ota, but i have some experience with databases (mysql). what would be a better way of storing the game's level data?

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  • Python: Huge file reading by using linecache Vs normal file access open()

    - by user335223
    Hi, I am in a situation where multiple threads reading the same huge file with mutliple file pointers to same file. The file will have atleast 1 million lines. Eachline's length varies from 500 characters to 1500 characters. There won't "write" operations on the file. Each thread will start reading the same file from different lines. Which is the efficient way..? Using the Python's linecache or normal readline() or is there anyother effient way?

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  • Stored procedures vs. parameter binding

    - by Gagan
    I am using SQL server and ODBC in visual c++ for writing to the database. Currently i am using parameter binding in SQL queries ( as i fill the database with only 5 - 6 queries and same is true for retrieving data). I dont know much about stored procedures and I am wondering how much if any performance increase stored procedures have over parameter binding as in parameter binding we prepare the query only once and just execute it later in the program for diferent set of values of variables.

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  • Search relevance from XML docs (XQuery?) vs MySQL

    - by Marius
    Hello there, I have a website where documents are saved in xml documents, all with the same structure. I need a search engine where I am able to choose documents with the highest relevance according to the key words given by a searching user. I thought it could (?) be a good idea to have one using XQuery rather than having the information stored twice (in XML docs + mysql database) and querying the mysql database for relevance searches. Is XQuery any good for this, and how, and what speed can I expect on +1000 documents of about 7kb each. Thank you for your time. Kind regards

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  • Accessing property of object vs variable in javascript

    - by Samuel
    Why when I try to access a variable that don't exist, javascript throw an exception but when I try to access a property that don't exist in an object, javascript returns an undefined object? For example, this case returns an undefined object: function Foo(){ console.log(this.bar); } Foo(); But, in this other example, javascript throw an exception: function Foo(){ console.log(bar); } Foo(); ReferenceError: bar is not defined

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  • What are the pros and cons of using manual list iteration vs recursion through fail

    - by magus
    I come up against this all the time, and I'm never sure which way to attack it. Below are two methods for processing some season facts. What I'm trying to work out is whether to use method 1 or 2, and what are the pros and cons of each, especially large amounts of facts. methodone seems wasteful since the facts are available, why bother building a list of them (especially a large list). This must have memory implications too if the list is large enough ? And it doesn't take advantage of Prolog's natural backtracking feature. methodtwo takes advantage of backtracking to do the recursion for me, and I would guess would be much more memory efficient, but is it good programming practice generally to do this? It's arguably uglier to follow, and might there be any other side effects? One problem I can see is that each time fail is called, we lose the ability to pass anything back to the calling predicate, eg. if it was methodtwo(SeasonResults), since we continually fail the predicate on purpose. So methodtwo would need to assert facts to store state. Presumably(?) method 2 would be faster as it has no (large) list processing to do? I could imagine that if I had a list, then methodone would be the way to go.. or is that always true? Might it make sense in any conditions to assert the list to facts using methodone then process them using method two? Complete madness? But then again, I read that asserting facts is a very 'expensive' business, so list handling might be the way to go, even for large lists? Any thoughts? Or is it sometimes better to use one and not the other, depending on (what) situation? eg. for memory optimisation, use method 2, including asserting facts and, for speed use method 1? season(spring). season(summer). season(autumn). season(winter). % Season handling showseason(Season) :- atom_length(Season, LenSeason), write('Season Length is '), write(LenSeason), nl. % ------------------------------------------------------------- % Method 1 - Findall facts/iterate through the list and process each %-------------------------------------------------------------- % Iterate manually through a season list lenseason([]). lenseason([Season|MoreSeasons]) :- showseason(Season), lenseason(MoreSeasons). % Findall to build a list then iterate until all done methodone :- findall(Season, season(Season), AllSeasons), lenseason(AllSeasons), write('Done'). % ------------------------------------------------------------- % Method 2 - Use fail to force recursion %-------------------------------------------------------------- methodtwo :- % Get one season and show it season(Season), showseason(Season), % Force prolog to backtrack to find another season fail. % No more seasons, we have finished methodtwo :- write('Done').

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  • Android Calendar API vs Calendar Provider API

    - by John Roberts
    I'm a little bit confused about the difference between the two. An example of the Calendar API is supposedly located here: http://samples.google-api-java-client.googlecode.com/hg/calendar-android-sample/instructions.html, but the author himself suggests using the Calendar Provider API, details about which are here: http://developer.android.com/guide/topics/providers/calendar-provider.html. Can someone explain to me the difference between the two, and which would be better for me to use for a simple calendar app?

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  • assignment vs std::swap and merging and keeping duplicates in seperate object

    - by rubenvb
    Say I have two std::set<std::string>s. The first one, old_options, needs to be merged with additional options, contained in new_options. I can't just use std::merge (well, I do, but not only that) because I also check for doubles and warn the user about this accordingly. To this effect, I have void merge_options( set<string> &old_options, const set<string> &new_options ) { // find duplicates and create merged_options, a stringset containing the merged options // handle duplicated the way I want to // ... old_options = merged_options; } Is it better to use std::swap( merged_options, old_options ); or the assignment I have? Is there a better way to filter duplicates and return the merged set than consecutive calls to std::set_intersection and std::set_union to detect dupes and merge the sets? I know it's slower than one traversal and doing both at once, but these sets are small (performance is not critical) and I trust the Standard more than I trust myself.

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