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  • using KVO to update an NSTableView filtered by an NSPredicate

    - by KingRufus
    My UI is not updating when I expect it to. The application displays "projects" using a view similar to iTunes -- a source list on the left lets you filter a list (NSTableView) on the right. My filters update properly when they are examining any simple field (like name, a string), but not for arrays (like tags). I'm removing a tag from one of my objects (from an NSMutableArray field called "tags") and I expect it to disappear from the list because it no longer matches the predicate that is bound to my table's NSArrayController. ProjectBrowser.mm: self.filter = NSPredicate* srcPredicate = [NSPredicate predicateWithFormat:@"%@ IN %K", selectedTag, @"tags"]; Project.mm: [self willChangeValueForKey:@"tags"]; [tags removeAllObjects]; [self didChangeValueForKey:@"tags"]; I've also tried this, but the result is the same: [[self mutableArrayValueForKey:@"tags"] removeAllObjects]; Interface Builder setup: a ProjectBrowser object is the XIB's File Owner an NSArrayController (Project Controller) has its Content Array bound to "File's Owner".projects Project Controller's filter predicate is bound to "File's Owner".filter NSTableView's column is bound to "Project Controller".name

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  • Is there a downside to adding an anonymous empty delegate on event declaration?

    - by serg10
    I have seen a few mentions of this idiom (including on SO): // Deliberately empty subscriber public event EventHandler AskQuestion = delegate {}; The upside is clear - it avoids the need to check for null before raising the event. However, I am keen to understand if there are any downsides. For example, is it something that is in widespread use and is transparent enough that it won't cause a maintenance headache? Is there any appreciable performance hit of the empty event subscriber call?

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  • How to get all n sets of three consecutives elements in an array or arraylist with a for statement ?

    - by newba
    Hi, I'm trying to do a convex hull approach and the little problem is that I need to get all sets of three consecutive vertices, like this: private void isConvexHull(Ponto[] points) { Arrays.sort(points); for (int i = 0; i <points.length; i++) { isClockWise(points[i],points[i+1],points[i+2]); } //... } I always do something that I don't consider clean code. Could please help me find one or more ways to this? I want it to be circular, i.e., if my fisrt point of the a set is the last element in the array, the 2nd element will be the 3rd in the list and the 3rd in that set will be the the 2nd element in the list, and so on. They must be consecutive, that's all.

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  • C++ class initialisation containing class variable initialization

    - by Phil Hannent
    I noticed some code of a colleague today that initialized class variables in the initialization. However it was causing a warning, he says because of the order they are in. My question is why is it better to do variable initialization where it currently is and not within the curly brackets? DiagramScene::DiagramScene( int slideNo, QRectF screenRect, MainWindow* parent ) : QGraphicsScene( screenRect, parent ), myParent( parent ), slideUndoImageCurrentIndex(-1), nextGroupID(0), m_undoInProgress(false), m_deleteItemOnNextUndo(0) line(0), path(0) { /* Setup default brush for background */ scDetail->bgBrush.setStyle(Qt::SolidPattern); scDetail->bgBrush.setColor(Qt::white); setBackgroundBrush(scDetail->bgBrush); }

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  • Adding the sum of numbers using a loop statement

    - by Deonna
    I need serious help dividing the positive numbers and the negative numbers. I am to accumulate the total of the negative values and separately accumulate the total of the positive values. After the loop, you are then to display the sum of the negative values and the sum of the positive values. The data is suppose to look like this: -2.3 -1.9 -1.5 -1.1 -0.7 -0.3 0.1 0.5 0.9 1.3 1.7 2.1 2.5 2.9 Sum of negative values: -7.8 Sum of positive values: 12 So far I have this: int main () { int num, num2, num3, num4, num5, sum, count, sum1; int tempVariable = 0; int numCount = 100; int newlineCount = 0, newlineCount1 = 0; float numCount1 = -2.3; while (numCount <= 150) { cout << numCount << " "; numCount += 2; newlineCount ++; if(newlineCount == 6) { cout<< " " << endl; newlineCount = 0; } } **cout << "" << endl; while (numCount1 <=2.9 ) { cout << numCount1 << " "; numCount1 += 0.4; newlineCount1 ++; } while ( newlineCount1 <= 0 && newlineCount >= -2.3 ); cout << "The sum is " << newlineCount1 << endl;** return 0; }

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  • Python style: multiple-line conditions in IFs

    - by Eli Bendersky
    Hello, Sometimes I break long conditions in IFs to several lines. The most obvious way to do this is: if (cond1 == 'val1' and cond2 == 'val2' and cond3 == 'val3' and cond4 == 'val4'): do_something Isn't very very appealing visually, because the action blends with the conditions. However, it is the natural way using correct Python indentation of 4 spaces. Edit: By the way, for the moment I'm using: if ( cond1 == 'val1' and cond2 == 'val2' and cond3 == 'val3' and cond4 == 'val4'): do_something Not very pretty, I know :-) Can you recommend an alternative way ?

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  • Most readable way to write simple conditional check

    - by JRL
    What would be the most readable/best way to write a multiple conditional check such as shown below? Two possibilities that I could think of (this is Java but the language really doesn't matter here): Option 1: boolean c1 = passwordField.getPassword().length > 0; boolean c2 = !stationIDTextField.getText().trim().isEmpty(); boolean c3 = !userNameTextField.getText().trim().isEmpty(); if (c1 && c2 && c3) { okButton.setEnabled(true); } Option 2: if (passwordField.getPassword().length > 0 && !stationIDTextField.getText().trim().isEmpty() && !userNameTextField.getText().trim().isEmpty() { okButton.setEnabled(true); } What I don't like about option 2 is that the line wraps and then indentation becomes a pain. What I don't like about option 1 is that it creates variables for nothing and requires looking at two places. So what do you think? Any other options?

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  • Where to Declare Structures, etc?

    - by cam
    Should all structs and classes be declared in the header file? If I declare a struct/class in a source file, what do I need to put in the header file so that it can be used in other files? Also, are there any resources that show some standard practices of C++ out there?

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  • Use of 'super' keyword when accessing non-overridden superclass methods

    - by jonny
    I'm trying to get the hang of inheritance in Java and have learnt that when overriding methods (and hiding fields) in sub classes, they can still be accessed from the super class by using the 'super' keyword. What I want to know is, should the 'super' keyword be used for non-overridden methods? Is there any difference (for non-overridden methods / non-hidden fields)? I've put together an example below. public class Vehicle { public int tyreCost; public Vehicle(int tyreCost) { this.tyreCost = tyreCost; } public int getTyreCost() { return tyreCost; } } and public class Car extends Vehicle { public int wheelCount; public Vehicle(int tyreCost, int wheelCount) { super(tyreCost); this.wheelCount = wheelCount; } public int getTotalTyreReplacementCost() { return getTyreCost() * wheelCount; } } Specifically, given that getTyreCost() hasn't been overridden, should getTotalTyreReplacementCost() use getTyreCost(), or super.getTyreCost() ? I'm wondering whether super should be used in all instances where fields or methods of the superclass are accessed (to show in the code that you are accessing the superclass), or only in the overridden/hidden ones (so they stand out).

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  • Microsoft C++ Language Reference

    - by eSKay
    Whenever any question is asked, and a reference text is needed, I never see MSDN C++ Language Reference being referred. I was browsing through it and I personally feel that it is extremely well written. Is there some specific reason it is not used as often as a standard? Is it because it contains some VC++ specific features?

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  • Using typedefs (or #defines) on built in types - any sensible reason?

    - by jb
    Well I'm doing some Java - C integration, and throught C library werid type mappings are used (theres more of them;)): #define CHAR char /* 8 bit signed int */ #define SHORT short /* 16 bit signed int */ #define INT int /* "natural" length signed int */ #define LONG long /* 32 bit signed int */ typedef unsigned char BYTE; /* 8 bit unsigned int */ typedef unsigned char UCHAR; /* 8 bit unsigned int */ typedef unsigned short USHORT; /* 16 bit unsigned int */ typedef unsigned int UINT; /* "natural" length unsigned int*/ Is there any legitimate reason not to use them? It's not like char is going to be redefined anytime soon. I can think of: Writing platform/compiler portable code (size of type is underspecified in C/C++) Saving space and time on embedded systems - if you loop over array shorter than 255 on 8bit microprocessor writing: for(uint8_t ii = 0; ii < len; ii++) will give meaureable speedup.

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  • What's Your favorite f# use? where does f# makes life (a lot) easier (compared to c#)?

    - by luckyluke
    I've skimmed the stack and did not get the overflow as there is probably no such question. I'm just learning f# and I am A seasoned c# and .net dev. I am into financial apps and currently F# helps me a lot with maths calcs like zero finding or minimum finding (although I still want some good maths library there). I see that processing multiple items (files or smth) tends to be easier, but my GUI (web, win) are still c# based. I am in the team of 5 devs and we know that the new tool is out, we are learning it after hours (to pimp ourselves up) but maybe we shouldn't bash the door somebody already opened. So in business apps, whats Your first killer part of soft You would code in F# (if You could and would know IT would be easier, faster, more testable, easier to maintain etc.? Business rules? ImageProcessing? Data processing? hope it's not to subjective. luke

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  • How does the verbosity of identifiers affect the performance of a programmer?

    - by DR
    I always wondered: Are there any hard facts which would indicate that either shorter or longer identifiers are better? Example: clrscr() opposed to ClearScreen() Short identifiers should be faster to read because there are fewer characters but longer identifiers often better resemble natural language and therefore also should be faster to read. Are there other aspects which suggest either a short or a verbose style? EDIT: Just to clarify: I didn't ask: "What would you do in this case?". I asked for reasons to prefer one over the other, i.e. this is not a poll question. Please, if you can, add some reason on why one would prefer one style over the other.

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  • PHP if statement - select two different get variables?

    - by arsoneffect
    Below is my example script: <li><a <?php if ($_GET['page']=='photos' && $_GET['view']!=="projects"||!=="forsale") { echo ("href=\"#\" class=\"active\""); } else { echo ("href=\"/?page=photos\""); } ?>>Photos</a></li> <li><a <?php if ($_GET['view']=='projects') { echo ("href=\"#\" class=\"active\""); } else { echo ("href=\"/?page=photos&view=projects\""); } ?>>Projects</a></li> <li><a <?php if ($_GET['view']=='forsale') { echo ("href=\"#\" class=\"active\""); } else { echo ("href=\"/?page=photos&view=forsale\""); } ?>>For Sale</a></li> I want the PHP to echo the "href="#" class="active" only when it is not on the two pages: ?page=photos&view=forsale or ?page=photos&view=projects

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  • Which style of return is "better" for a method that might return None?

    - by Daenyth
    I have a method that will either return an object or None if the lookup fails. Which style of the following is better? def get_foo(needle): haystack = object_dict() if needle not in haystack: return None return haystack[needle] or, def get_foo(needle): haystack = object_dict() try: return haystack[needle] except KeyError: # Needle not found return None I'm undecided as to which is more more desirable myself. Another choice would be return haystack[needle] if needle in haystack else None, but I'm not sure that's any better.

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  • Is GOTO really as evil as we are led to believe?

    - by RoboShop
    I'm a young programmer, so all my working life I've been told GOTO is evil, don't use it, if you do, your first born son will die. Recently, I've realized that GOTO actually still exists in .NET and I was wondering, is GOTO really as bad as they say, or is it just because everyone says you shouldn't use it, so that's why you don't. I know GOTO can be used badly, but are there any legit situations where you may possibly use it. The only thing I can think of is maybe to use GOTO to break out of a bunch of nested loops. I reckon that might be better then having to "break" out of each of them but because GOTO is supposedly always bad, I would never use it and it would probably never pass a peer review. What are your views? Is GOTO always bad? Can it sometimes be good? Has anyone here actually been gutsy enough to use GOTO for a real life system?

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  • Logical value of an assignment in C

    - by Andy Shulman
    while (curr_data[1] != (unsigned int)NULL && ((curr_ptr = (void*)curr_data[1]) || 1)) Two part question. What will (curr_ptr = (void*)curr_data[1]) evaluate to, logically. TRUE? Also, I know its rather hack-ish, but is the while statement legal C? I would have to go through great contortions to put the assignment elsewhere in the code, so I'd be really nice if I could leave it there, but if it's so egregious that it makes everyone's eyeballs burst into flames, I'll change it.

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  • Resharper: how to force introducing new private fields at the bottom of the class?

    - by Igor Brejc
    Resharper offers a very useful introduce and initialize field xxx action when you specify a new parameter in a constructor like: Constructor (int parameter) The only (minor) nuisance is that it puts the new field at the beginning of the class - and I'm a fan of putting private parts as far away as possible from the prying eyes of strangers ;). If, however, you already have some private fields in the class, Resharper will put the new field "correctly" (note the quotes, I don't want to start a flame war over this issue) next to those, even if they are at the end of the class. Is there a way to force Resharper to always put new fields at the end of the class? UPDATE: OK, I forgot to mention I know about the "Type Members Layout in Options" feature, but some concrete help on how to modify the template to achieve fields placement would be nice.

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  • What is the difference between a private and public funtion?

    - by Kyle
    I am a new programmer, and I started in C and am now starting to enjoy JavaScript and a tiny bit of PHP more. Lately I've heard the terms 'private' and 'public' functions a lot. Could anybody give an explanation of the both and how they are of use to a programmer? And I'm probably totally wrong here... but is a (function(){}) in javascript a private function?

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  • Modify columns in a data frame in R more cleanly - maybe using with() or apply()?

    - by Mittenchops
    I understand the answer in R to repetitive things is usually "apply()" rather than loop. Is there a better R-design pattern for a nasty bit of code I create frequently? So, pulling tabular data from HTML, I usually need to change the data type, and end up running something like this, to convert the first column to date format (from decimal), and columns 2-4 from character strings with comma thousand separators like "2,400,000" to numeric "2400000." X[,1] <- decYY2YY(as.numeric(X[,1])) X[,2] <- as.numeric(gsub(",", "", X[,2])) X[,3] <- as.numeric(gsub(",", "", X[,3])) X[,4] <- as.numeric(gsub(",", "", X[,4])) I don't like that I have X[,number] repeated on both the left and ride sides here, or that I have basically the same statement repeated for 2-4. Is there a very R-style way of making X[,2] less repetitive but still loop-free? Something that sort of says "apply this to columns 2,3,4---a function that reassigns the current column to a modified version in place?" I don't want to create a whole, repeatable cleaning function, really, just a quick anonymous function that does this with less repetition.

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