Professional Web Applications Themes

Cocoa: handling components of an NSColor - Mac Programming

I'm using some NSColors. I need to handle their components. I'm using two routines to do it (appended to this post). I can select the colours using colour wells. Most colours I select turn into components okay, with floating numbers which look right, and turn back into NSColors okay. However, sometimes even though the floating values look right when I use makeColour to put them back together into an NSColor I get a signal 10 (SIGBUS) error. The debugger tells me Program received signal: "EXC_BAD_ACCESS" This colour (r,g,b,a) is one which causes this problem: 0.102713 1.000000 0.089419 1.000000 Am I ...

  1. #1

    Default Cocoa: handling components of an NSColor

    I'm using some NSColors. I need to handle their components. I'm
    using two routines to do it (appended to this post). I can select
    the colours using colour wells. Most colours I select turn into
    components okay, with floating numbers which look right, and turn
    back into NSColors okay.

    However, sometimes even though the floating values look right
    when I use makeColour to put them back together into an NSColor
    I get a signal 10 (SIGBUS) error. The debugger tells me

    Program received signal: "EXC_BAD_ACCESS"

    This colour (r,g,b,a) is one which causes this problem:

    0.102713 1.000000 0.089419 1.000000

    Am I doing something wrong ? I don't do much with colours and
    I'm trying to feel my way. If not, any debugging tips ?

    ----------------------------

    -(NSArray *)getColourValues:(NSColor *)theColour
    {
    NSArray *theValues;
    float theRed, theGreen, theBlue, theAlpha;
    NSNumber *theRedNum, *theGreenNum, *theBlueNum, *theAlphaNum;
    NSColor *betterCSColour;

    betterCSColour = [theColour colorUsingColorSpaceName:NSCalibratedRGBColorSpace];
    [betterCSColour getRed:&theRed green:&theGreen blue:&theBlue alpha:&theAlpha];
    theRedNum = [NSNumber numberWithFloat:theRed];
    theGreenNum = [NSNumber numberWithFloat:theGreen];
    theBlueNum = [NSNumber numberWithFloat:theBlue];
    theAlphaNum = [NSNumber numberWithFloat:theAlpha];

    theValues = [[NSArray alloc] initWithObjects:theRedNum, theGreenNum, theBlueNum, theAlphaNum, nil];
    return theValues;
    }

    -(NSColor *)makeColour:(NSArray *)theValues
    {
    float theRed, theGreen, theBlue, theAlpha;
    NSColor *tempColour;

    theRed = [[theValues objectAtIndex:0] floatValue];
    theGreen = [[theValues objectAtIndex:1] floatValue];
    theBlue = [[theValues objectAtIndex:2] floatValue];
    theAlpha = [[theValues objectAtIndex:3] floatValue];

    tempColour = [NSColor colorWithCalibratedRed:theRed green:theGreen blue:theBlue alpha:theAlpha];
    return [tempColour colorUsingColorSpaceName:NSCalibratedRGBColorSpace];
    }


    Simon Guest

  2. #2

    Default Re: Cocoa: handling components of an NSColor

    In article <BBAE5B2696681D88FD0.0.0.0>,
    demon.co.uklocalhost (Simon Slavin) wrote:
     

    Odds are it's a retain/release issue. The two methods you posted have
    very different results returned (one does alloc/init while the other
    uses an autoreleased object). I'm not sure what your policy is in
    calling these, but the odds are that something calling -makeColour:
    isn't retaining what it gets back, and/or anything calling
    getColourValues: is leaking all over the place.
    Doc Guest

  3. #3

    Default Re: Cocoa: handling components of an NSColor

    In article <supernews.com>,
    Doc O'Leary <com> wrote:
     

    Ahahahah ! It works ! Thanks again, Doc. I've been
    doing this stuff throughout the program and the only place
    it didn't work was there. I reread the introduction to
    Objective-C and went through fixing everything with alloc
    and copy and it works properly.

    I've been learning Objective-C on the principle of fixing
    stuff that doesn't work. Since the stuff I used worked fine
    in other places I never realised I was doing it wrong. I
    still haven't worked-out a generalised release strategy but
    this bit now uses releases correctly and I'll figure out a
    programming style for the others next week.


    Simon Guest

  4. #4

    Default Re: Cocoa: handling components of an NSColor

    In article <0.1.2>,
    demon.co.uklocalhost (Simon Slavin) wrote:
     

    Unfortunately, memory management isn't something where you can go on the
    basis of fixing what doesn't work. An error here can cause problems in a
    totally different area of your program, or it can simply silently leak
    objects and be difficult to track down. These things can, of course, be
    debugged, but as always it's better to get it right the first time.

    A very simple rule of thumb:

    Within any pair of {}'s, the total number of alloc, copy, retain should
    equal the total number of release, autorelease.

    See this very good article for more information:

    http://www.stepwise.com/Articles/Technical/HoldMe.html

    There is also this more detailed, more complicated article from the same
    site:

    http://www.stepwise.com/Articles/Technical/MemoryManagement.html
    Michael Guest

  5. #5

    Default Re: Cocoa: handling components of an NSColor

    In article <mail-F70589.10154813102003localhost>,
    Michael Ash <com> wrote:
     

    Thanks, Michael.


    Simon Guest

Similar Threads

  1. Cocoa: how do I coerce NS objects ?
    By Simon in forum Mac Programming
    Replies: 3
    Last Post: October 8th, 11:07 PM
  2. Bit shifts in Cocoa
    By Korbin Meiser in forum Mac Programming
    Replies: 2
    Last Post: September 11th, 01:11 AM
  3. Q About Cocoa & CF Prefs..
    By David Phillip Oster in forum Mac Programming
    Replies: 2
    Last Post: July 31st, 12:04 PM
  4. Cocoa Filemaker
    By Olly Groves in forum FileMaker
    Replies: 2
    Last Post: July 25th, 01:55 AM
  5. [Cocoa] Bug with NSTableView?
    By Mark Bee in forum Mac Programming
    Replies: 1
    Last Post: July 7th, 07:38 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139