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  • Should a C++ constructor do real work?

    - by Wade Williams
    I'm strugging with some advice I have in the back of my mind but for which I can't remember the reasoning. I seem to remember at some point reading some advice (can't remember the source) that C++ constructors should not do real work. Rather, they should initialize variables only. The advice when on to explain that real work should be done in some sort of init() method, to be called separately after the instance was created. The situation is I have a class that represents a hardware device. It makes logical sense to me for the constructor to call the routines that query the device in order to build up the instance variables that describe the device. In other words, once new instantiates the object, the developer receives an object which is ready to be used, no separate call to object-init() required. Is there a good reason why constructors shouldn't do real work? Obviously it could slow allocation time, but that wouldn't be any different if calling a separate method immediately after allocation. Just trying to figure out what gotchas I not currently considering that might have lead to such advice.

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  • JPA - Real primary key generated ID for references

    - by Val
    I have ~10 classes, each of them, have composite key, consist of 2-4 values. 1 of the classes is a main one (let's call it "Center") and related to other as one-to-one or one-to-many. Thinking about correct way of describing this in JPA I think I need to describe all the primary keys using @Embedded / @PrimaryKey annotations. Question #1: My concern is - does it mean that on the database level I will have # of additional columns in each table referring to the "Center" equal to number of column in "Center" PK? If yes, is it possible to avoid it by using some artificial unique key for references? Could you please give an idea how real PK and the artificial one needs to be described in this case? Note: The reason why I would like to keep the real PK and not just use the unique id as PK is - my application have some data loading functionality from external data sources and sometimes they may return records which I already have in local database. If unique ID will be used as PK - for new records I won't be able to do data update, since the unique ID will not be available for just downloaded ones. At the same time it is normal case scenario for application and it just need to update of insert new records depends on if the real composite primary key matches. Question #2: All of the 10 classes have common field "date" which I described in an abstract class which each of them extends. The "date" itself is never a key, but it always a part of composite key for each class. Composite key is different for each class. To be able to use this field as a part of PK should I describe it in each class or is there any way to use it as is? I experimented with @Embedded and @PrimaryKey annotations and always got an error that eclipselink can't find field described in an abstract class. Thank you in advance! PS. I'm using latest version of eclipselink & H2 database.

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  • 2d graph in real-time by using opencv and c++

    - by user2758510
    I have a really basic question in opencv and c++. I am trying to graph something in real time by using opencv. I am looking to find a function to draw a graph in rel-time. But still unssuccesful. I need a function that gets two arrays as an input one for x axis and one for y. I tried with this but seems not work in real-time http://www.shervinemami.info/graphs.html I just need to know if there is something available in opencv or not. Thanks in advance.

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  • Division, Remainders and only Real Numbers Allowed

    - by Senica Gonzalez
    Trying to figure out this pseudo code. The following is assumed.... I can only use unsigned and signed integers (or long). Division returns a real number with no remainder. MOD returns a real number. Fractions and decimals are not handled. INT I = 41828; INT C = 15; INT D = 0; D = (I / 65535) * C; How would you handle a fraction (or decimal value) in this situation? Is there a way to use negative value to represent the remainder? In this example I/65535 should be 0.638, however, with the limitations, I get 0 with a MOD of 638. How can I then multiply by C to get the correct answer? Hope that makes sense.

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  • hibernate show real sql

    - by tommaso
    Hi all, if I set <property name="show_sql">true</property> in my hibernate.cfg.xml configuration file in the console I can see the sql. But it's not REAL sql... Can I see the SQL code that will be passed directly to database? Example: I see select this_.code from true.employee this_ where this_.code=? Can I see select employee.code from employee where employee.code=12 the real sql? thanks!

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  • How to get real-time status notification with Facebook SDK via listener

    - by Mathias Lin
    I'm using Twitter4j and the Android Facebook SDK to fetch status messages. With Twitter4J I get real-time notifications whenever a new status has been added to the stream via StatusListener (Twitter4J). In the Facebook SDK I cannot find a similar way, I can only fetch entire streams over and over again in a fixed time interval using RequestListener (Facebook SDK) as far as I see it. Is there any way to get notified of new statuses in realtime with the Facebook SDK in a similar way as with Twitter4J? (Found a similar but unanswered question here: Facebook real-time updated application wall)

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  • problem with NSInputStream on real iPhone

    - by ThamThang
    Hi guys, I have a problem with NSInputStream. Here is my code: case NSStreamEventHasBytesAvailable: printf("BYTE AVAILABLE\n"); int len = 0; NSMutableData *data = [[NSMutableData alloc] init]; uint8_t buffer[32768]; if(stream == iStream) { printf("Receiving...\n"); len = [iStream read:buffer maxLength:32768]; [data appendBytes:buffer length:len]; } [iStream close]; I try to read small data and it works perfectly on simulator and real iPhone. If I try to read large data (more than 4kB or maybe 5kB), the real iPhone just can read 2736 bytes and stop. Why is it? Help me plz! Merci d'avance!

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  • MVC without ORM is not real MVC?

    - by ajsie
    at the moment im integrating ORM (doctrine) into a MVC framework (codeigniter). then it hit me that this was the obvious way of setting up a MVC: the controller calls the models that are representing database tables. look at this picture: MVC + ORM then i wondered, how can a MVC without ORM be real MVC? cause then the models are not real objects, rather aggregations of different functions that perform CRUD, then returning the result to the controller. and there is no need for a state (object properties) i guess so the functions would be all static? correct me if im wrong on this one. i guess a lot of people are using models without ORM. please share your thoughts. how do your models look like?

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  • Singelton on iPhone Simulator vs Singelton on real Device

    - by Helge Becker
    I am using a Singelton for some shared stuff. In the simulator, the app crashes ocasionally. Tracking the crash down shows that the the properties of my Singelton became dealocated. Those crashes never happend on a real device. Does the iPHone simulator handle memory managemend different? GC maybe? Changed the singelton to match this pattern. The iPhone Simulator dont crash now, but I am not sure about the memory handling on the real device. I assume that this solution will cause problems. What do you think?

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  • Android strace in Real device

    - by Martin Solac
    I have the following situation, I want to monitor the system calls on Android phones so I made an script to do that. With Android Emulator works perfectly (writes the traces of the application in a specific file on my Ubuntu). The problem is when I attach a real phone to analyze it, it says the following in the result file: ptrace attach failed: Operation not permitted I'm using this code to get it, but I don't understand why it works on the emulator and not in the rooted real device. This is the comand I use in perl: system("$dirTools/adb -s $Device shell strace -p $PID[1]>$dirRecordDataSet/$Date/$appName &"); Any suggestion? Thanks in advance

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  • SQLite SQLite column can't be updated to any value but zero (real type)

    - by user1065320
    Hi I'm trying to create a three fields table (date,text,real), I can insert and update the first two fields but can't set or update the last one. createSQL = @"CREATE TABLE IF NOT EXISTS ACTIVITIES (MYDATE DATETIME PRIMARY KEY, ACTIVITY TEXT , LENGTH REAL);"; try to insert char *update = "INSERT OR REPLACE INTO ACTIVITIES (MYDATE, ACTIVITY , LENGTH) VALUES (?, ? ,?);"; sqlite3_stmt *stmt; if (sqlite3_prepare_v2(database, update , -1, &stmt, nil) == SQLITE_OK) { sqlite3_bind_double(stmt, 1, valueToWrite); sqlite3_bind_text(stmt, 2, [task UTF8String], -1, NULL); sqlite3_bind_double(stmt, 3, 1.5); } if (sqlite3_step(stmt) != SQLITE_DONE) { NSAssert1(0, @"Error updating table: %s", errorMsg); } sqlite3_finalize(stmt); sqlite3_close(database); The first two values are updated but the last one remains 0 even if I'm writing a value like 1.5 or put a double variable with a different value Thanks

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  • Real pagination vs Next and Previous buttons

    - by Pablo
    By real pagination i mean something like this when in page 3: <<Previous 1 | 2 | {3} | 4 | 5 |...| 15 | Next>> By Next and Previous buttons i mean something like this when in page 3: <<previous Next>> Performance wise im sure the Previous and Next Buttons are better since unlike the real pagination it doesn't require over-querying the database. By over-querying the database i mean getting more information from the database than what you will need to display on the page. My theory is that the Previous and Next Buttons can drastically increase a site performance as it only requires the exact information you will need to display on a page, please correct me if im wrong on this. so, do users really have preference when it comes to this two options? is it just a Developer preference and its convenience? Which one do you prefer? why? *Note: Previous and Next Buttons are usually labeled Newer and older.

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  • Full GC real time is much more that user+sys times

    - by Stas
    Hi. We have a Web Java based application running on JBoss with allowed maximum heap size of about 1.2 GB (total machine physical memory is 2 GB). At some point the application stops responding (to clients) for several minutes. After some analysis we found out that the culprit is the Full GC. Here's an excerpt from the verbose GC log: 74477.402: [Full GC [PSYoungGen: 3648K-0K(332160K)] [PSOldGen: 778476K-589497K(819200K)] 782124K-589497K(1151360K) [PSPermGen: 102671K-102671K(171328K)], 646.1546860 secs] [Times: user=3.84 sys=3.72, real=646.17 secs] What I don't understand is how is it possible that the real time spent on Full GC is about 11 minutes (646 seconds), while user+sys times are just 7.5 seconds. 7.5 seconds sound to me much more logical time to spend for cleaning <200 MB from the old generation. Where does all the other time go? Thanks a lot.

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  • Real life Java Swing Project

    - by santiagobasulto
    Hi everybody! I've been working with swing for the last 2 years, but i'm still not satisfy with my own work. The apps are "fast" enough, but the development isn't enough "clean". Can you recommend me any real world project, book, or something similar that shows me how a real world swing app work. May be a framework, something structured, etc. For example, i'm thinking i may code a "window manager" that has all the window of the app in an unified resource, may be cached, etc. I think all those good ideas must be implemented already. Thanks!

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  • IE6 and IE7 Standalone: Prove they're not the real thing

    - by yar
    It's common knowledge on SO (see this question) that to run IE6 and IE7 you need a Windows box (or virtual box) with only those apps installed. I doubt this is true (they are the real versions, I think). The two browsers I'm interested in are: Standalone IE6 from the MultipleIEs install Standalone IE7 also from Tredosoft (but published elsewhere) These two plus a "real" install of IE8 give you three IE versions in one Windows install. While we all know that "You're out of luck if you're trying to run them all reliably in one VM," but can someone please show me JS, CSS, or HTML (or a plugin, etc.) that does not work on the standalone versions as it should?

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  • iPhone real memory climbs when interacting with UI

    - by Scott Gress
    I've been using the Activity Monitor to check the memory usage of my iPhone apps. I've noticed that the Real Memory climbs whenever I interact with the UI in any way, even if there's no code being called. For example, I can create a brand new View-Based application and run it, and as I click or drag in the empty window the Real Memory increases even though the app isn't responding in any way. I get that the view controller is doing some stuff in the background to interpret my interactions, but it seems like the memory should go back down after a second or so. Instead, it keeps going up and up and up as long as I keep clicking or dragging. I can wait forever and it never decreases. This is a little disturbing. Am I missing something?

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  • Very large database, very small portion most being retrieved in real time

    - by mingyeow
    Hi folks, I have an interesting database problem. I have a DB that is 150GB in size. My memory buffer is 8GB. Most of my data is rarely being retrieved, or mainly being retrieved by backend processes. I would very much prefer to keep them around because some features require them. Some of it (namely some tables, and some identifiable parts of certain tables) are used very often in a user facing manner How can I make sure that the latter is always being kept in memory? (there is more than enough space for these) More info: We are on Ruby on rails. The database is MYSQL, our tables are stored using INNODB. We are sharding the data across 2 partitions. Because we are sharding it, we store most of our data using JSON blobs, while indexing only the primary keys

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  • VPN, Tunneling to hide 'real IP' through my proxy server while showing the client IP on 'real' server side

    - by mickula
    I would like to hide my 'main server' behind the load balancer, call it 'proxy server' Although I use some closed-source software on 'main server' and it needs the client IP address to operate well. When I'm setting up some VPN connection, in that software it displays the IP address of my 'proxy server'. Is there any option to set up such tunneling or vpn to: not reveal IP of 'main server' show the IP of 'client' in 'application' on 'main server' I will be grateful for all your replies and ideas.

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  • Bridging Virtual Networking into Real LAN on a OpenNebula Cluster

    - by user101012
    I'm running Open Nebula with 1 Cluster Controller and 3 Nodes. I registered the nodes at the front-end controller and I can start an Ubuntu virtual machine on one of the nodes. However from my network I cannot ping the virtual machine. I am not quite sure if I have set up the virtual machine correctly. The Nodes all have a br0 interfaces which is bridged with eth0. The IP Address is in the 192.168.1.x range. The Template file I used for the vmnet is: NAME = "VM LAN" TYPE = RANGED BRIDGE = br0 # Replace br0 with the bridge interface from the cluster nodes NETWORK_ADDRESS = 192.168.1.128 # Replace with corresponding IP address NETWORK_SIZE = 126 NETMASK = 255.255.255.0 GATEWAY = 192.168.1.1 NS = 192.168.1.1 However, I cannot reach any of the virtual machines even though sunstone says that the virtual machine is running and onevm list also states that the vm is running. It might be helpful to know that we are using KVM as a hypervisor and I am not quite sure if the virbr0 interface which was automatically created when installing KVM might be a problem.

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