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  • Explanation of `self` usage during dealloc?

    - by Greg
    I'm trying to lock down my understanding of proper memory management within Objective-C. I've gotten into the habit of explicitly declaring self.myProperty rather than just myProperty because I was encountering occasional scenarios where a property would not be set to the reference that I intended. Now, I'm reading Apple documentation on releasing IBOutlets, and they say that all outlets should be set to nil during dealloc. So, I put this in place as follows and experienced crashes as a result: - (void)dealloc { [self.dataModel close]; [self.dataModel release], self.dataModel = nil; [super dealloc]; } So, I tried taking out the "self" references, like so: - (void)dealloc { [dataModel close]; [dataModel release], dataModel = nil; [super dealloc]; } This second system seems to work as expected. However, it has me a bit confused. Why would self cause a crash in that case, when I thought self was a fairly benign reference more used as a formality than anything else? Also, if self is not appropriate in this case, then I have to ask: when should you include self references, and when should you not?

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  • Python: Does one of these examples waste more memory?

    - by orokusaki
    In a Django view function which uses manual transaction committing, I have: context = RequestContext(request, data) transaction.commit() return render_to_response('basic.html', data, context) # Returns a Django ``HttpResponse`` object which is similar to a dictionary. I think it is a better idea to do this: context = RequestContext(request, data) response = render_to_response('basic.html', data, context) transaction.commit() return response If the page isn't rendered correctly in the second version, the transaction is rolled back. This seems like the logical way of doing it albeit there won't likely be many exceptions at that point in the function when the application is in production. But... I fear that this might cost more and this will be replete through a number of functions since the application is heavy with custom transaction handling, so now is the time to figure out. If the HttpResponse instance is in memory already (at the point of render_to_response()), then what does another reference cost? When the function ends, doesn't the reference (response variable) go away so that when Django is done converting the HttpResponse into a string for output Python can immediately garbage collect it? Is there any reason I would want to use the first version (other than "It's 1 less line of code.")?

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  • .net Attributes that handle exceptions - usage on a property accessor

    - by Mr AH
    Hi, well I know from my asp.net mvc experience that you can have attributes that handle exceptions (HandleErrorAttribute). As far as I can tell the Controller class has some OnException event which may be integral to this behaviour. However, I want to do something similar in my own code: dream example: public String MyProperty { [ExceptionBehaviour(typeof(FormatException), MyExEnum.ClearValue)] set { _thing.prop = Convert.ToThing(value); } } .... The code above obviously makes very little sense, but is close to the kind of thing I wish to do. I want the attribute on the property set accessor to catch some type of exception and then deal with this in some custom way (or even just swallow it). Any ideas guys?

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  • What really is the purpose of "base" keyword in c#?

    - by Pandiya Chendur
    Thus for used base class for some commom reusable methods in every page of my application... public class BaseClass:System.Web.UI.Page { public string GetRandomPasswordUsingGUID(int length) { string guidResult = System.Guid.NewGuid().ToString(); guidResult = guidResult.Replace("-", string.Empty); return guidResult.Substring(0, length); } } So if i want to use this method i would just do, public partial class forms_age_group : BaseClass { protected void Page_Load(object sender, EventArgs e) { //i would just call it like this string pass = GetRandomPasswordUsingGUID(10); } } It does what i want but there is a "Base" keyword that deals with base class in c# ... I really want to know when should use base keyword in my derived class.... Any good example...

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  • High precision event timer

    - by rahul jv
    #include "target.h" #include "xcp.h" #include "LocatedVars.h" #include "osek.h" /** * This task is activated every 10ms. */ long OSTICKDURATION; TASK( Task10ms ) { void XCP_FN_TYPE Xcp_CmdProcessor( void ); uint32 startTime = GetQueryPerformanceCounter(); /* Trigger DAQ for the 10ms XCP raster. */ if( XCPEVENT_DAQ_OVERLOAD & Xcp_DoDaqForEvent_10msRstr() ) { ++numDaqOverload10ms; } /* Update those variables which are modified every 10ms. */ counter16 += slope16; /* Trigger STIM for the 10ms XCP raster. */ if( enableBypass10ms ) { if( XCPEVENT_MISSING_DTO & Xcp_DoStimForEvent_10msRstr() ) { ++numMissingDto10ms; } } duration10ms = (uint32)( ( GetQueryPerformanceCounter() - startTime ) / STOPWATCH_TICKS_PER_US ); } What would be the easiest (and/or best) way to synchronise to some accurate clock to call a function at a specific time interval, with little jitter during normal circumstances, from C++? I am working on WINDOWS operating system now. The above code is for RTAS OSEK but I want to call a function at a specific time interval for windows operating system. Could anyone assist me in c++ language ??

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  • High concurrent request server in ruby

    - by WedTM
    I'm trying to write a simple server that will grab an mp3 file from rackspace cloudfiles, and stream it to a client over HTTP. The server must be able to stream to multiple clients simultaneously, however, I'm finding it difficult to come up with a viable solution. Anyone have some ideas?

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  • what exactly does system.totalMemory test in Actionscript 3.0?

    - by vasion
    before somebody screaming RTFM, let me clarify. does system.totalMemory test the memory used in movie which invokes it, or used by all movies running on the browser/system? I want to initiate garbage collaction for my app when it reaches a certain limit and i dont want the process to be initialized by the user watching funny cats youtube video.

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  • Usage of autorelease pools for fetch method

    - by Matthias
    Hi, I'm a little bit confused regarding the autorelease pools when programming for the iPhone. I've read a lot and the oppionions seem to me from "Do-NOT-use" to "No problem to use". My specific problem is, I would like to have a class which encapsulates the SQLite3 Access, so I have for example the following method: -(User*)fetchUserWithId:(NSInteger)userId Now, within this method a SQL query is done and a new user object is created with the data from the database and then returned. Within this DB Access class I don't need this object anymore, so I can do a release, but since the calling method needs it, I would do an autorelease, wouldn't I? So, is it okay to use autorelease here oder would it gain too much memory, if this method is called quite frequently? Some websites say, that the autorelease pool is released first at the end of the application, some say, at every event (e.g. user touches something). If I should not use autorelease, how can I make sure, that the object is released correctly? Can I do a release in the fetch method and hope, that the object is still there until the calling method can do a retain? Thanks for your help! Regards Matthias

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  • Appropriate high level language to deal with binary data

    - by fortran
    Hi, I need to write a small tool that parses a textual input and generates some binary encoded data. I would prefer to stay away from C and the like, in favour of a higher level, (optionally) safer, more expressive and faster to develop language. My language of choice for this kind of tasks usually is Python, but for this case dealing with binary raw data can be problematic if one isn't very careful with the numbers being promoted to bignums, sign extensions and such. Ideally I would like to have records with named bitfields that are portable to be serialised in a consistent manner. (I know that there's a strong point in doing it in a language I already master, although it isn't optimal, but I think this could be a good opportunity to learn something new). Thanks.

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  • The best alternative for String flyweight implementation in Java

    - by Dan
    My application is multithreaded with intensive String processing. We are experiencing excessive memory consumption and profiling has demonstrated that this is due to String data. I think that memory consumption would benefit greatly from using some kind of flyweight pattern implementation or even cache (I know for sure that Strings are often duplicated, although I don't have any hard data in that regard). I have looked at Java Constant Pool and String.intern, but it seems that it can provoke some PermGen problems. What would be the best alternative for implementing application-wide, multithreaded pool of Strings in java?

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  • What is the best way to find a processed memory allocations in terms of C# objects

    - by Shantaram
    I have written various C# console based applications, some of them long running some not, which can over time have a large memory foot print. When looking at the windows perofrmance monitor via the task manager, the same question keeps cropping up in my mind; how do I get a break down of the number objects by type that are contributing to this footprint; and which of those are f-reachable and those which aren't and hence can be collected. On numerous occasions I've performed a code inspection to ensure that I am not unnecessarily holding on objects longer than required and disposing of objects with the using construct. I have also recently looked at employing the CG.Collect method when I have released a large number of objects (for example held in a collection which has just been cleared). However, I am not so sure that this made that much difference, so I threw that code away. I am guessing that there are tools in sysinternals suite than can help to resolve these memory type quiestions but I am not sure which and how to use them. The alternative would be to pay for a third party profiling tool such as JetBrains dotTrace; but I need to make sure that I've explored the free options first before going cap in hand to my manager.

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  • What percent of web sites use JavaScript?

    - by Claudiu
    I'm wondering just how pervasive JavaScript is. This article states that 73% of websites they tested rely on JavaScript for important functionality, but it seems to me that the number must be larger. Have any surveys been done on this topic? Maybe a better way to phrase this question is - are there any sites that don't use JavaScript? EDIT: By 'use', I don't necessarily mean "rely on for important functionality" - that was just the statistic that one article gave.

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  • Usage of atoi in the c language

    - by maddy
    I don't understand the results of the following C code. main() { char s[] = "AAA"; advanceString(s); } void advanceString(p[3]) { int val = atoi(p); printf("The atoi val is %d\n",val); } Here the atoi val is shown as 0. But I could not figure out the exact reason. As per my understanding, it should be the summation of decimal equivalent of each values in the array.? Please correct me if I am wrong.

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  • not null usage in mysql

    - by pradeep
    Hi, I use syntax like name varchar(20) NOT NULL in mysql..i have a big confusion over here. typically does it mean that this field is mandatory? but when i store a space in this field it accepts it.is it correct. its like while insert i say '".$_POST['name']."'. even if the name does not have any value query is executed. can any1 just clarify me on this ? is NULL and blank space same ?

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  • in java, which is better - three arrays of booleans or 1 array of bytes?

    - by joe_shmoe
    I know the question sounds silly, but consider this: I have an array of items and a labelling algorithm. at any point the item is in one of three states. The current version holds these states in a byte array, where 0, 1 and 2 represent the three states. alternatively, I could have three arrays of boolean - one for each state. which is better (consumes less memory) depends on how jvm (sun's version) stores the arrays - is a boolean represented by 1 bit? (p.s. don't start with all that "this is not the way OO/Java works" - I know, but here performance comes in front. plus the algorithm is simple and perfectly readable even in such form). Thanks a lot

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  • Replacement for java.util.zip for streaming usage?

    - by evilfred
    java.util.zip sucks for stream compression. The longer you leave an Inflator/Deflator open without calling end(), the more native memory it uses up. This is a known issue: http://bugs.sun.com/view_bug.do?bug_id=4797189 which nobody seems to care about fixing. What is a good alternative? Preferably one that is free and is still actively supported by its developers.

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  • Dynamically generating high performance functions in clojure

    - by mikera
    I'm trying to use Clojure to dynamically generate functions that can be applied to large volumes of data - i.e. a requirement is that the functions be compiled to bytecode in order to execute fast, but their specification is not known until run time. e.g. suppose I specify functions with a simple DSL like: (def my-spec [:add [:multiply 2 :param0] 3]) I would like to create a function compile-spec such that: (compile-spec my-spec) Would return a compiled function of one parameter x that returns 2x+3. What is the best way to do this in Clojure?

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  • SPSS - sum of squares change radically with slight model changes in ANOVA??

    - by Pat
    I have noticed that the sum of squares in my models can change fairly radically with even the slightest adjustment to my models???? Is this normal???? I'm using SPSS 16, and both models presented below used the same data and variables with only one small change - categorizing one of the variables as either a 2 level or 3 level variable. Details - using a 2 x 2 x 6 mixed model ANOVA with the 6 being the repeated measure i get the following in the between group analysis ------------------------------------------------------------ Source | Type III SS | df | MS | F | Sig ------------------------------------------------------------ intercept | 4086.46 | 1 | 4086.46 | 104.93 | .000 X | 224.61 | 1 | 224.61 | 5.77 | .019 Y | 2.60 | 1 | 2.60 | .07 | .80 X by Y | 19.25 | 1 | 19.25 | .49 | .49 Error | 2570.40 | 66 | 38.95 | Then, when I use the exact same data but a slightly different model in which variable Y has 3 levels instead of 2 levels I get the following ------------------------------------------------------------ Source | Type III SS | df | MS | F | Sig ------------------------------------------------------------ intercept | 3603.88 | 1 | 3603.88 | 90.89 | .000 X | 171.89 | 1 | 171.89 | 4.34 | .041 Y | 19.23 | 2 | 9.62 | .24 | .79 X by Y | 17.90 | 2 | 17.90 | .80 | .80 Error | 2537.76 | 64 | 39.65 | I don't understand why variable X would have a different sum of squares simply because variable Y gets devided up into 3 levels instead of 2. This is also the case in the within groups analysis too. Please help me understand :D Thank you in advance Pat

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  • mysql stored funtion usage

    - by shikhar
    I just wrote a stored function to calculate the working days between two dates. This works select CountWeekDays('2010-03-07','2010-04-07') This doesn't work select CountWeekDays(o.order_date,o.created_date) from orders o; Any idea how to make this one work ?? function definition delimiter $$; CREATE FUNCTION CountWeekDays (sdate VARCHAR(50), edate VARCHAR(50)) RETURNS INT BEGIN DECLARE wdays, tdiff, counter, thisday smallint; DECLARE newdate DATE; SET newdate := sdate; SET wdays = 0; if DATEDIFF(edate, sdate) = 0 THEN RETURN 1; END IF; if DATEDIFF(edate, sdate) < 0 THEN RETURN 0; END IF; label1: LOOP SET thisday = DAYOFWEEK(newdate); IF thisday BETWEEN 2 AND 6 THEN SET wdays := wdays + 1; END IF; SET newdate = DATE_ADD(newdate, INTERVAL 1 DAY); IF DATEDIFF(edate, newdate) < 0 THEN LEAVE label1; END IF; END LOOP label1; RETURN wdays; END

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